WorldWideScience

Sample records for temporally variable groundwater

  1. Spatio-Temporal Variability of Groundwater Storage in India

    Science.gov (United States)

    Bhanja, Soumendra; Rodell, Matthew; Li, Bailing; Mukherjee, Abhijit

    2016-01-01

    Groundwater level measurements from 3907 monitoring wells, distributed within 22 major river basins of India, are assessed to characterize their spatial and temporal variability. Ground water storage (GWS) anomalies (relative to the long-term mean) exhibit strong seasonality, with annual maxima observed during the monsoon season and minima during pre-monsoon season. Spatial variability of GWS anomalies increases with the extent of measurements, following the power law relationship, i.e., log-(spatial variability) is linearly dependent on log-(spatial extent).In addition, the impact of well spacing on spatial variability and the power law relationship is investigated. We found that the mean GWS anomaly sampled at a 0.25 degree grid scale closes to unweighted average over all wells. The absolute error corresponding to each basin grows with increasing scale, i.e., from 0.25 degree to 1 degree. It was observed that small changes in extent could create very large changes in spatial variability at large grid scales. Spatial variability of GWS anomaly has been found to vary with climatic conditions. To our knowledge, this is the first study of the effects of well spacing on groundwater spatial variability. The results may be useful for interpreting large scale groundwater variations from unevenly spaced or sparse groundwater well observations or for siting and prioritizing wells in a network for groundwater management. The output of this study could be used to maintain a cost effective groundwater monitoring network in the study region and the approach can also be used in other parts of the globe.

  2. The spatial and temporal variability of groundwater recharge in a forested basin in northern Wisconsin

    Science.gov (United States)

    Dripps, W.R.; Bradbury, K.R.

    2010-01-01

    Recharge varies spatially and temporally as it depends on a wide variety of factors (e.g. vegetation, precipitation, climate, topography, geology, and soil type), making it one of the most difficult, complex, and uncertain hydrologic parameters to quantify. Despite its inherent variability, groundwater modellers, planners, and policy makers often ignore recharge variability and assume a single average recharge value for an entire watershed. Relatively few attempts have been made to quantify or incorporate spatial and temporal recharge variability into water resource planning or groundwater modelling efforts. In this study, a simple, daily soil-water balance model was developed and used to estimate the spatial and temporal distribution of groundwater recharge of the Trout Lake basin of northern Wisconsin for 1996-2000 as a means to quantify recharge variability. For the 5 years of study, annual recharge varied spatially by as much as 18 cm across the basin; vegetation was the predominant control on this variability. Recharge also varied temporally with a threefold annual difference over the 5-year period. Intra-annually, recharge was limited to a few isolated events each year and exhibited a distinct seasonal pattern. The results suggest that ignoring recharge variability may not only be inappropriate, but also, depending on the application, may invalidate model results and predictions for regional and local water budget calculations, water resource management, nutrient cycling, and contaminant transport studies. Recharge is spatially and temporally variable, and should be modelled as such. Copyright ?? 2009 John Wiley & Sons, Ltd.

  3. Groundwater Quality: Analysis of Its Temporal and Spatial Variability in a Karst Aquifer.

    Science.gov (United States)

    Pacheco Castro, Roger; Pacheco Ávila, Julia; Ye, Ming; Cabrera Sansores, Armando

    2017-06-15

    This study develops an approach based on hierarchical cluster analysis for investigating the spatial and temporal variation of water quality governing processes. The water quality data used in this study were collected in the karst aquifer of Yucatan, Mexico, the only source of drinking water for a population of nearly two million people. Hierarchical cluster analysis was applied to the quality data of all the sampling periods lumped together. This was motivated by the observation that, if water quality does not vary significantly in time, two samples from the same sampling site will belong to the same cluster. The resulting distribution maps of clusters and box-plots of the major chemical components reveal the spatial and temporal variability of groundwater quality. Principal component analysis was used to verify the results of cluster analysis and to derive the variables that explained most of the variation of the groundwater quality data. Results of this work increase the knowledge about how precipitation and human contamination impact groundwater quality in Yucatan. Spatial variability of groundwater quality in the study area is caused by: a) seawater intrusion and groundwater rich in sulfates at the west and in the coast, b) water rock interactions and the average annual precipitation at the middle and east zones respectively, and c) human contamination present in two localized zones. Changes in the amount and distribution of precipitation cause temporal variation by diluting groundwater in the aquifer. This approach allows to analyze the variation of groundwater quality controlling processes efficiently and simultaneously. © 2017, National Ground Water Association.

  4. Influence of temporally variable groundwater flow conditions on point measurements and contaminant mass flux estimations

    DEFF Research Database (Denmark)

    Rein, Arno; Bauer, S; Dietrich, P

    2009-01-01

    Monitoring of contaminant concentrations, e.g., for the estimation of mass discharge or contaminant degradation rates. often is based on point measurements at observation wells. In addition to the problem, that point measurements may not be spatially representative. a further complication may arise...... information representing observation wells installed along control planes using different well frequencies and configurations. Results of the scenario simulations show that temporally variable flow conditions can lead to significant temporal fluctuations of the concentration and thus are a substantial source...... is present, the concentration variability due to a fluctuating groundwater flow direction varies significantly within the control plane and between the different realizations. Determination of contaminant mass fluxes is also influenced by the temporal variability of the concentration measurement, especially...

  5. Temporal and spatial variability of groundwater recharge on Jeju Island, Korea

    Science.gov (United States)

    Mair, Alan; Hagedorn, Benjamin; Tillery, Suzanne; El-Kadi, Aly I.; Westenbroek, Stephen M.; Ha, Kyoochul; Koh, Gi-Won

    2013-01-01

    Estimates of groundwater recharge spatial and temporal variability are essential inputs to groundwater flow models that are used to test groundwater availability under different management and climate conditions. In this study, a soil water balance analysis was conducted to estimate groundwater recharge on the island of Jeju, Korea, for baseline, drought, and climate-land use change scenarios. The Soil Water Balance (SWB) computer code was used to compute groundwater recharge and other water balance components at a daily time step using a 100 m grid cell size for an 18-year baseline scenario (1992–2009). A 10-year drought scenario was selected from historical precipitation trends (1961–2009), while the climate-land use change scenario was developed using late 21st century climate projections and a change in urban land use. Mean annual recharge under the baseline, drought, and climate-land use scenarios was estimated at 884, 591, and 788 mm, respectively. Under the baseline scenario, mean annual recharge was within the range of previous estimates (825–959 mm) and only slightly lower than the mean of 902 mm. As a fraction of mean annual rainfall, mean annual recharge was computed as only 42% and less than previous estimates of 44–48%. The maximum historical reported annual pumping rate of 241 × 106 m3 equates to 15% of baseline recharge, which is within the range of 14–16% computed from earlier studies. The model does not include a mechanism to account for additional sources of groundwater recharge, such as fog drip, irrigation, and artificial recharge, and may also overestimate evapotranspiration losses. Consequently, the results presented in this study represent a conservative estimate of total recharge.

  6. Spatio-temporal variability of groundwater depth in the eghlid aquifer in southern iran

    OpenAIRE

    Delbari, Masoomeh; Bahraini Motlagh, Masoud; Amiri, Meysam

    2014-01-01

    Groundwater is the main water source for domestic and agricultural use in Eghlid, a city located in Fars province in southern Iran. Here, spatial and temporal changes in groundwater depth were monitored by using geostatistical methods at 41 observation wells in Eghlid during the wet and dry seasons of 1997, 2003 and 2010. Experimental semivariograms were calculated and modeled with the GS+ (Gamma Design Software, Plainwell, Michigan USA),and groundwater depth was inter- polated by using the o...

  7. How geomorphology and groundwater level affect the spatio-temporal variability of riverine cold water patches?

    Science.gov (United States)

    Wawrzyniak, Vincent; Piégay, Hervé; Allemand, Pascal; Vaudor, Lise; Goma, Régis; Grandjean, Philippe

    2016-04-01

    Temperature is a key factor for river ecosystems. In summer, patches of cold water are formed in the river by groundwater seepage. These patches have strong ecological significance and extend to the surface water in a well-mixed riverine system. These patches can serve as thermal refuges for some fish species during summer. In this study, the temporal variability and spatial distribution of cold water patches were explored along a 50 km river reach (the lower Ain River, France) using thermal infrared airborne remote sensing. This study examines a new range of processes acting on cold water patches at different scales that have not previously been touched upon in the literature. Three airborne campaigns were conducted during the summers of 2010, 2011 and 2014. Based on these images, a large number of cold water patches were identified using an automated method. Four types of patches were observed: tributary plumes, cold side channels (former channels or point-bar backwater channels), side seeps (located directly in the river channel) and gravel bar seeps (occurring at the downstream end of gravel bars). Logistic regression was used to analyse the longitudinal distribution of cold water patches according to geomorphologic indicators reflecting current or past fluvial process. Side seeps were found to be related to the local geology. Cold side channels were correlated to contemporary and past lateral river mobility. Gravel bar seeps were related to the current development of bars and are more prevalent in wandering reaches than in single-bed incised and paved reaches. The logistic model was subsequently used to evaluate gravel bar seep variability in the past. The model suggests larger numbers of seeps in the mid-20th century when bar surface area was higher. Interannual variability in the occurrence and spatial extent of side seeps and gravel bar seeps appear to be related to groundwater level fluctuations. Cold side channels exhibited greater interannual stability

  8. Groundwater Variability Across Temporal and Spatial Scales in the Central and Northeastern U.S.

    Science.gov (United States)

    Li, Bailing; Rodell, Matthew; Famiglietti, James S.

    2015-01-01

    Depth-to-water measurements from 181 monitoring wells in unconfined or semi-confined aquifers in nine regions of the central and northeastern U.S. were analyzed. Groundwater storage exhibited strong seasonal variations in all regions, with peaks in spring and lows in autumn, and its interannual variability was nearly unbounded, such that the impacts of droughts, floods, and excessive pumping could persist for many years. We found that the spatial variability of groundwater storage anomalies (deviations from the long term mean) increases as a power function of extent scale (square root of area). That relationship, which is linear on a log-log graph, is common to other hydrological variables but had never before been shown with groundwater data. We describe how the derived power function can be used to determine the number of wells needed to estimate regional mean groundwater storage anomalies with a desired level of accuracy, or to assess uncertainty in regional mean estimates from a set number of observations. We found that the spatial variability of groundwater storage anomalies within a region often increases with the absolute value of the regional mean anomaly, the opposite of the relationship between soil moisture spatial variability and mean. Recharge (drainage from the lowest model soil layer) simulated by the Variable Infiltration Capacity (VIC) model was compatible with observed monthly groundwater storage anomalies and month-to-month changes in groundwater storage.

  9. Spatial and temporal variability of groundwater recharge in Geba basin, Northern Ethiopia

    Science.gov (United States)

    Yenehun, Alemu; Walraevens, Kristine; Batelaan, Okke

    2017-10-01

    WetSpa, a physically based, spatially distributed watershed model, has been used to study the spatial and temporal variation of recharge in the Geba basin, Northern Ethiopia. The model covers an area of about 4, 249 km2 and integrates elevation, soil and land-use data, hydrometeorological and river discharge data. The Geba basin has a highly variable topography ranging from 1000 to 3280 m with an average slope of 12.9%. The area is characterized by a distinct wet and long dry season with a mean annual precipitation of 681 mm and temperatures ranging between 6.5 °C and 32 °C. The model was simulated on daily basis for nearly four years (January 1, 2000 to December 18, 2003). It resulted in a good agreement between measured and simulated streamflow hydrographs with Nash-Sutcliffe efficiency of almost 70% and 85% for, respectively, the calibration and validation. The water balance terms show very strong spatial and temporal variability, about 3.8% of the total precipitation is intercepted by the plant canopy; 87.5% infiltrates into the soil (of which 13% percolates, 2.7% flows laterally off and 84.2% evapotranspired from the root zone), and 7.2% is surface runoff. The mean annual recharge varies from about 45 mm (2003) to 208 mm (2001), with average of 98.6 mm/yr. On monthly basis, August has the maximum (73 mm) and December the lowest (0.1 mm) recharge. The mean annual groundwater recharge spatially varies from 0 to 371 mm; mainly controlled by the distribution of rainfall amount, followed by soil and land-use, and to a certain extent, slope. About 21% of Geba has a recharge larger than 120 mm and 1% less than 5 mm.

  10. Temporal and spatial variability of surface water and groundwater interactions in a semi-arid agricultural valley

    Science.gov (United States)

    Ochoa, C. G.; Fernald, A.; Guldan, S.; Tidwell, V. C.

    2010-12-01

    In arid and semi-arid landscape settings, an important source of groundwater supply may come from shallow aquifers. In agricultural valleys of northern New Mexico, the use of traditional surface-irrigation systems may contribute to shallow aquifer recharge. Over the last eight years, we have studied surface water and groundwater interactions occurring at different spatial and temporal scales in a 20-km agricultural valley along the Rio Grande in northern New Mexico. At the Alcalde-Velarde valley, we have conducted research trials and modeling efforts for characterizing hydrological interactions in the surface-vadose zone-aquifer continuum for representative crops and soils commonly found in this agricultural valley. Also, extensive field measurement campaigns and automated monitoring of climate variables, river and canal water flows, and shallow aquifer fluctuations are being conducted. Water budget calculations based on field-measured data showed that 33% (canal seepage 12% and irrigation percolation 21%) of the total river water diverted into one of the main irrigation canals in the valley goes to the shallow aquifer. A seasonal trend in water level fluctuations in response to these canal seepage and irrigation inputs was observed. Shallow water level measurements collected hourly from 42 monitoring wells showed the seasonal rise and decline of the water table. The water table rose 0.6 m within 3 to 5 weeks following the onset of the irrigation season and then, after temporary storage, it decreased gradually by the end of the irrigation season. A significant amount of this transient water table rise remained past the irrigation season and was considered delayed return flow. The influence of the temporal water table rise was observed in monitoring wells in the irrigated portion of the valley, but also in wells located in dry land, 800 m away from the canal source. Results from this study show the spatial and temporal variabilty of shallow aquifer recharge

  11. Controls on the spatial and temporal variability of Rn-222 in riparian groundwater in a lowland Chalk catchment.

    OpenAIRE

    Mullinger, Neil J.; Pates, Jackie M.; Binley, Andrew M.; Crook, N. P.

    2009-01-01

    Radon is a powerful tracer of stream-aquifer interactions. However, it is important to consider the source and behaviour of radon in groundwater when interpreting observations of river radon in relation to groundwater discharge. Here we characterise the variability in groundwater radon concentrations in the riparian zone of a Chalk catchment. Groundwater 222Rn (radon) concentrations were determined in riparian zone boreholes at two sites in the Lambourn catchment, Berkshire, UK, over a two ye...

  12. The spatio-temporal variability of groundwater depth in a typical ...

    Indian Academy of Sciences (India)

    depths was not significant, but the human-induced fluctuations such as intensive irrigation caused a significant increase in groundwater depth in both the farmland and the desert-oasis ecotone, seriously affecting sustainable agriculture development and the environment, in the oasis. 1. Introduction. Groundwater, which ...

  13. The spatio-temporal variability of groundwater depth in a typical ...

    Indian Academy of Sciences (India)

    Groundwater depth; annual fluctuations; inter-annual changes; influence distance; desert-oasis ecotone. ... Linze Inland River Basin Comprehensive Research Station, Chinese Ecosystem Research Network, Laboratory of Watershed Hydrology and Ecology, Cold and Arid Regions Environmental and Engineering ...

  14. The spatio-temporal variability of groundwater depth in a typical desert-oasis ecotone

    National Research Council Canada - National Science Library

    Wang, Guohua; Zhao, Wenzhi

    2015-01-01

    Eight groundwater observation wells were installed along the river plain, where the landscapes varied from floodplain, to oasis farmland, to desert-oasis ecotone to desert, in a typical desert-oasis...

  15. Modelling spatial and temporal variability of surface water-groundwater fluxes and heat exchange along a lowland river reach

    Science.gov (United States)

    Munz, Matthias; Schmidt, Christian; Fleckenstein, Jan; Oswald, Sascha

    2013-04-01

    In this study we used the deterministic, fully-integrated surface-subsurface flow and heat transport model (HydroGeoSphere) to investigate the spatial and temporal variability of surface water-groundwater (SFW-GW) interaction along a lowland river reach. The model incorporates the hydrological as well as the heat transport processes including (1) radiative fluxes warming and cooling the surface water; (2) seasonal groundwater temperature changes; (3) occasionally occurring heat inputs due to precipitation and (4) highly variable SFW-GW water advective heat exchange driven by the general relation between SFW and GW hydraulic heads and geomorphological structure of the riverbed. The study area is a 100 m long lowland river reach of the Selke river, at the boundary of the Harz mountains characterized by distinctive gravel bars. Continuous time series of hydraulic heads and temperatures at different depth in the river bank, the hyporheic zone and within the river are used to define the boundary conditions, to calibrate and to validate the numerical model. The 3D modelling results show that the water and heat exchange at the SFW-GW interface is highly variable in space with zones of daily temperature oscillations penetrating deep into the sediment and spots of daily constant temperature following the average GW temperature. To increase the understanding of evolving pattern, the observed temperature variations in space and time will be linked to dominant stream flow conditions, streambed morphology, advective and conductive heat exchange between SFW and GW and subsurface solute residence times. This study allows to analyse and quantify water and heat fluxes at the SFW-GW interface, to trace subsurface flow paths within the streambed sediments and thus improves the understanding of hyporheic zone exchange mechanisms. It is a sound basis for investigating quantitatively variations of sediment properties, boundary conditions and streambed morphology and also for subsequent

  16. Geostatistical interpolation model selection based on ArcGIS and spatio-temporal variability analysis of groundwater level in piedmont plains, northwest China.

    Science.gov (United States)

    Xiao, Yong; Gu, Xiaomin; Yin, Shiyang; Shao, Jingli; Cui, Yali; Zhang, Qiulan; Niu, Yong

    2016-01-01

    Based on the geo-statistical theory and ArcGIS geo-statistical module, datas of 30 groundwater level observation wells were used to estimate the decline of groundwater level in Beijing piedmont. Seven different interpolation methods (inverse distance weighted interpolation, global polynomial interpolation, local polynomial interpolation, tension spline interpolation, ordinary Kriging interpolation, simple Kriging interpolation and universal Kriging interpolation) were used for interpolating groundwater level between 2001 and 2013. Cross-validation, absolute error and coefficient of determination (R(2)) was applied to evaluate the accuracy of different methods. The result shows that simple Kriging method gave the best fit. The analysis of spatial and temporal variability suggest that the nugget effects from 2001 to 2013 were increasing, which means the spatial correlation weakened gradually under the influence of human activities. The spatial variability in the middle areas of the alluvial-proluvial fan is relatively higher than area in top and bottom. Since the changes of the land use, groundwater level also has a temporal variation, the average decline rate of groundwater level between 2007 and 2013 increases compared with 2001-2006. Urban development and population growth cause over-exploitation of residential and industrial areas. The decline rate of the groundwater level in residential, industrial and river areas is relatively high, while the decreasing of farmland area and development of water-saving irrigation reduce the quantity of water using by agriculture and decline rate of groundwater level in agricultural area is not significant.

  17. Spatial and Temporal Variability in Nitrate Concentration below the Root Zone in an Almond Orchard and its Implications for Potential Groundwater Contamination

    Science.gov (United States)

    Baram, S.; Couvreur, V.

    2015-12-01

    Spatial and Temporal Variability in Nitrate Concentration below the Root Zone in an Almond Orchard and its Implications for Potential Groundwater Contamination S. Baram1, M. Read1, D. Smart2, T. Harter1, J Hopmans11Department of Land, Air & Water Resources University of California Davis 2Department of Viticulture and Enology University of California Davis Estimates of water and fertilizer losses below the root zone of nitrogen (N) intensive agricultural orchard crops are major concern in groundwater protection. However, microscopic and macroscopic heterogeneity in unsaturated soils make accurate loss estimates very challenging. In this study we aimed to examine field scale variability in nitrate (NO3-) losses below the root zone (>250cm) of a 15 years old almond orchard in Madera county California. Based on a soil variability survey, tensiometers and solution samplers were installed at 17 locations around the 40 acre orchard. The hydraulic potential and the NO3- concentrations were monitored over two growing seasons. Nitrate concentrations varied spatially and temporarily, and ranged from below to more than 30 times higher than the drinking water contamination standard of >10 mg NO3--N L-1. Principal component analysis of the relations between the NO3- concentration, presence of a hard pan in the subsurface, its depth and thickness, and the fertigation and irrigation events indicated that none of these factors explained the observed variability in pore-water NO3- concentrations, with hard pan being the most dominant factor. Throughout the irrigation season minimal leaching was observed, yet post-harvest and preseason flooding events led to deep drainage. Due to the high spatial and temporal variability in the NO3- concentration and the potential for deep drainage following a wet winter or flooding event we conclude that the most efficient way to protect ground water is by transitioning to high frequency low nitrogen fertigation which would retain NO3-in the active

  18. Diffuse pollution (pesticides and nitrate) at catchment scale on two constrasted sites: mass balances and characterization of the temporal variability of groundwater quality.

    Science.gov (United States)

    Baran, N.; Gutierrez, A.

    2009-04-01

    characterizations. Notable changes in the use of pesticides generally result from the evolution of regulations. In Europe, the herbicides atrazine and isoproturon have been classified as priority substances (2455/2001/EC, OJEC 2001). The use of atrazine was forbidden in France since September 2003 following restrictions already in force since 1991. In January 2004 the maximum permitted application of isoproturon was reduced from 2500 to 1800 g ha-1. In France, two contrasted hydrogeological systems located in agricultural contexts were intensively monitored for at least a decade in order to i) characterize the spatial and temporal variability of groundwater contamination by different pesticides with varied physical and chemical characteristics (atrazine, isoproturon and their metabolites and chloroacetanilides used as atrazine substitutes) and nitrate, ii) calculate annual pesticide mass balances for a long period including years with contrasted climatic conditions and to iii) identify the different mechanisms influencing water and solute transfer. Although both sites (Brévilles and 3 Fontaines) have very different hydrogeological characteristics (4 vs. 50 sq km, sandy vs. chalky saturated zone, non karstic vs. karstic, …) the monitoring of the major springs representing the outlet of the catchments revealed similarities. For example, atrazine and its metabolite deethylatrazine have been both systematically quantified at the outlet springs despite the stop of atrazine use on the Brévilles and 3 Fontaines catchments since April1999 and September 2003, respectively. For both sites, the mass balances (comparison of inputs and outfluxes) indicated that only few percents of the applied quantity of atrazine reached the spring but led to concentrations higher than the allowed limit for drinkable water. At the opposite, isoproturon which is the pesticide applied with the highest quantities for the last decade on both sites, is detected in a very limited number of samples. The different

  19. Temporal Variability in Vertical Groundwater Fluxes and the Effect of Solar Radiation on Streambed Temperatures Based on Vertical High Resolution Distributed Temperature Sensing

    Science.gov (United States)

    Sebok, E.; Karan, S.; Engesgaard, P. K.; Duque, C.

    2013-12-01

    Due to its large spatial and temporal variability, groundwater discharge to streams is difficult to quantify. Methods using vertical streambed temperature profiles to estimate vertical fluxes are often of coarse vertical spatial resolution and neglect to account for the natural heterogeneity in thermal conductivity of streambed sediments. Here we report on a field investigation in a stream, where air, stream water and streambed sediment temperatures were measured by Distributed Temperature Sensing (DTS) with high spatial resolution to; (i) detect spatial and temporal variability in groundwater discharge based on vertical streambed temperature profiles, (ii) study the thermal regime of streambed sediments exposed to different solar radiation influence, (iii) describe the effect of solar radiation on the measured streambed temperatures. The study was carried out at a field site located along Holtum stream, in Western Denmark. The 3 m wide stream has a sandy streambed with a cobbled armour layer, a mean discharge of 200 l/s and a mean depth of 0.3 m. Streambed temperatures were measured with a high-resolution DTS system (HR-DTS). By helically wrapping the fiber optic cable around two PVC pipes of 0.05 m and 0.075 m outer diameter over 1.5 m length, temperature measurements were recorded with 5.7 mm and 3.8 mm vertical spacing, respectively. The HR-DTS systems were installed 0.7 m deep in the streambed sediments, crossing both the sediment-water and the water-air interface, thus yielding high resolution water and air temperature data as well. One of the HR-DTS systems was installed in the open stream channel with only topographical shading, while the other HR-DTS system was placed 7 m upstream, under the canopy of a tree, thus representing the shaded conditions with reduced influence of solar radiation. Temperature measurements were taken with 30 min intervals between 16 April and 25 June 2013. The thermal conductivity of streambed sediments was calibrated in a 1D flow

  20. Surface water - groundwater interactions at different spatial and temporal scales

    DEFF Research Database (Denmark)

    Sebök, Éva

    As there is a growing demand for the protection and optimal management of both the surface water and groundwater resources, the understanding of their exchange processes is of great importance. This PhD study aimed at describing the natural spatial and temporal variability of these interactions...... in lowland catchments, mainly exploring and assessing Distributed Temperature Sensing (DTS) which by detecting variability in temperatures at the Sediment-Water Interface (SWI) can indirectly map variability in groundwater discharge at several spatial and temporal scales. On the small-scale (... streambeds which were shown to influence DTS data by sedimentation and scouring processes. A new methodology was therefore developed for the long-term monitoring of surface water-groundwater exchanges in soft-bedded streams....

  1. Temporal variability in groundwater and surface water quality in humid agricultural catchments; Driving processes and consequences for regional water quality monitoring

    NARCIS (Netherlands)

    Rozemeijer, Joachim; Van Der Velde, Ype

    2014-01-01

    Considering the large temporal variability in surface water quality is essential for adequate water quality policy and management. Neglecting these dynamics may easily lead to decreased effectiveness of measures to improve water quality and to inefficient water quality monitoring. The objective of

  2. Temporal variability in groundwater and surface water quality in humid agricultural catchments; driving processes and consequences for regional water quality monitoring

    NARCIS (Netherlands)

    Rozemeijer, J.; Velde, van der Y.

    2014-01-01

    Considering the large temporal variability in surface water quality is essential for adequate water quality policy and management. Neglecting these dynamics may easily lead to decreased effectiveness of measures to improve water quality and to inefficient water quality monitoring. The objective of

  3. Application of Distributed Temperature Sensing for coupled mapping of sedimentation processes and spatio-temporal variability of groundwater discharge in soft-bedded streams

    DEFF Research Database (Denmark)

    Sebok, Eva; Duque, C; Engesgaard, Peter

    2015-01-01

    The delineation of groundwater discharge areas based on Distributed Temperature Sensing (DTS) data of the streambed can be difficult in soft-bedded streams where sedimentation and scouring processes constantly change the position of the fibre optic cable relative to the streambed. Deposition-indu...

  4. Spatial variability of groundwater recharge - I. Is it really variable?

    OpenAIRE

    De Silva, RP

    2004-01-01

    The spatial variability of recharge is an important consideration in estimating recharge especially as all methods of estimating it are 'point' estimates and in most places recharge varies in space. This paper along with the accompanying paper attempts to find a suitable answer to the question of taking this variability into account in estimating groundwater recharge. This paper attempts to determine if recharge is actually varying in space and that this is 'true' variability and that it is n...

  5. Groundwater level responses to precipitation variability in Mediterranean insular aquifers

    Science.gov (United States)

    Lorenzo-Lacruz, Jorge; Garcia, Celso; Morán-Tejeda, Enrique

    2017-09-01

    Groundwater is one of the largest and most important sources of fresh water on many regions under Mediterranean climate conditions, which are exposed to large precipitation variability that includes frequent meteorological drought episodes, and present high evapotranspiration rates and water demand during the dry season. The dependence on groundwater increases in those areas with predominant permeable lithologies, contributing to aquifer recharge and the abundance of ephemeral streams. The increasing pressure of tourism on water resources in many Mediterranean coastal areas, and uncertainty related to future precipitation and water availability, make it urgent to understand the spatio-temporal response of groundwater bodies to precipitation variability, if sustainable use of the resource is to be achieved. We present an assessment of the response of aquifers to precipitation variability based on correlations between the Standardized Precipitation Index (SPI) at various time scales and the Standardized Groundwater Index (SGI) across a Mediterranean island. We detected three main responses of aquifers to accumulated precipitation anomalies: (i) at short time scales of the SPI (24 months). The differing responses were mainly explained by differences in lithology and the percentage of highly permeable rock strata in the aquifer recharge areas. We also identified differences in the months and seasons when aquifer storages are more dependent on precipitation; these were related to climate seasonality and the degree of aquifer exploitation or underground water extraction. The recharge of some aquifers, especially in mountainous areas, is related to precipitation variability within a limited spatial extent, whereas for aquifers located in the plains, precipitation variability influence much larger areas; the topography and geological structure of the island explain these differences. Results indicate large spatial variability in the response of aquifers to precipitation in

  6. Spatial patterns and temporal variability in water quality from City of Albuquerque drinking-water supply wells and piezometer nests, with implications for the ground-water flow system

    Science.gov (United States)

    Bexfield, Laura M.; Anderholm, Scott K.

    2002-01-01

    well mixed, even in areas of large vertical gradients. Water levels in most piezometers respond to short-term variations in ground-water withdrawals and to the cumulative effect of long-term withdrawals throughout the area. In most piezometers screened below the water table, water levels respond clearly to seasonal variations in ground-water withdrawals. Water levels decline from about April through July and rise from about September through January. Water levels seem to be declining in most piezometers at a rate less than 1 foot per year. Water-quality data for unfiltered samples collected over a 10-year period from 93 City of Albuquerque drinking-water supply wells were examined for variability and temporal trends in 10 selected parameters. Variability generally was found to be greatest in the Western and Northeast water-quality regions of the study area. For the 10 parameters investigated, temporal trends were found in 5 to 57 wells. Dissolved-solids, sodium, sulfate, chloride, and silica concentrations showed more increasing than decreasing trends; calcium, bicarbonate, and arsenic concentrations, field pH, and water temperature showed more decreasing than increasing trends. The median magnitudes of most of these trends over a 1-year period were not particularly large (generally less than 1.0 milligram per liter), although the magnitudes for a few individual wells were significant. For the 10 parameters investigated, correlations with monthly pumpage volumes were found in 10 to 32 wells. Calcium and sulfate concentrations, field pH, and water temperature showed more positive than negative correlations with monthly pumpage; dissolved-solids, sodium, bicarbonate, chloride, silica, and arsenic concentrations showed more negative than positive correlations. An increase in pumpage in an individual well appears to increase the contribution

  7. Variabilidade espaço-temporal da condutividade elétrica da água subterrânea na região semiárida de Pernambuco Spatial temporal variability of electrical conductivity of groundwater in the semiarid region of Pernambuco, Brazil

    Directory of Open Access Journals (Sweden)

    Tafnes S. Andrade

    2012-05-01

    Full Text Available RESUMO Quando mal-conduzida, a irrigação pode causar degradação dos solos e da água subterrânea, por potencializar o risco de salinização. Este problema é mais evidente em regiões semiáridas, nas quais as características físico-climáticas contribuem para seu agravamento. Uma das variáveis mais utilizadas para avaliar a concentração de sais solúveis na água de irrigação e no solo, é a condutividade elétrica. Neste trabalho, buscou-se avaliar a variabilidade espacial e temporal da condutividade elétrica da água subterrânea utilizada para irrigação em um assentamento rural, no semiárido pernambucano. Técnicas estatísticas descritivas e geoestatísticas foram aplicadas para identificação dos padrões de variabilidade e dependência espacial da condutividade elétrica, visando ao mapeamento da salinidade da água subterrânea. Verificou-se que a condutividade elétrica possui variabilidade média a alta, com dependência espacial moderada, em que a textura do solo e o regime pluviométrico influenciam na variação espacial e temporal da condutividade elétrica, que vem aumentando ao longo dos anos, na área estudada.ABSTRACT Irrigation, when poorly managed, can cause soil and groundwater degradation by increasing the salinization risk. This problem is evident in semiarid regions, where the physico-climatic characteristics contribute to enhance the problem. One of the main variables used to measure the soluble salts concentration in irrigation water and soil is the electrical conductivity. This work aimed to evaluate the spatial and temporal variability of electrical conductivity of groundwater for irrigation in a semiarid rural settlement in the State of Pernambuco. Descriptive statistics and geostatistical techniques have been applied to identify patterns of variability and spatial dependence of electrical conductivity aiming to map the groundwater salinity. It was found that the electrical conductivity has medium

  8. Potential impacts of climate change and variability on groundwater ...

    African Journals Online (AJOL)

    Aizebeokhai

    This paper attempts to assess the potential impacts of climate change and variability on groundwater resources availability and sustainability in Nigeria. Key words: Climate change, variability, hydrological systems, groundwater, potential impacts, vulnerability. INTRODUCTION. All life on Earth, water and energy resources, ...

  9. Measuring and modeling spatio-temporal patterns of groundwater storage dynamics to better understand nonlinear streamflow response

    Science.gov (United States)

    Rinderer, Michael; van Meerveld, Ilja; McGlynn, Brian

    2017-04-01

    Information about the spatial and temporal variability in catchment scale groundwater storage is needed to identify runoff source area dynamics and better understand variability in streamflow. However, information on groundwater levels is typically only available at a limited number of monitoring sites and interpolation or upscaling is necessary to obtain information on catchment scale groundwater dynamics. Here we used data from 51 spatially distributed groundwater monitoring sites in a Swiss pre-alpine catchment and time series clustering to define six groundwater response clusters. Each of the clusters was distinct in terms of the groundwater rise and recession but also had distinctly different topographic site characteristics, which allowed us to assign a groundwater response cluster to all non-monitored locations. Each of them was then assigned the mean groundwater response of the monitored cluster members. A site was considered active (i.e., enabling lateral subsurface flow) when the groundwater levels rose above the groundwater response threshold which was defined based on the depth of the more transmissive soil layers (typically between 10 cm and 30 cm below the soil surface). This allowed us to create maps of the active areas across the catchment at 15 min time intervals. The mean fraction of agreement between modeled groundwater activation (based on the mean cluster member time series) and measured groundwater activation (based on the measured groundwater level time series at a monitoring site) was 0.91 (25th percentile: 0.88, median: 0.92, 75th percentile: 0.95). The fraction of agreement dropped by 10 to 15 % at the beginning of events but was never lower than 0.4. Connectivity between all active areas and the stream network was determined using a graph theory approach. During rainfall events, the simulated active and connected area extended mainly laterally and longitudinally along the channel network, which is in agreement with the variable source

  10. Potential impacts of climate change and variability on groundwater ...

    African Journals Online (AJOL)

    Aizebeokhai

    uncertainties in the characterisation of climate change induced groundwater impacts due largely to multi-scale local and ... Key words: Climate change, climate variability, hydrological systems, groundwater resources, potential impacts, vulnerability. ..... except where surface layers are of poor permeability and afford some ...

  11. Temporal variability in the deglutition literature.

    Science.gov (United States)

    Molfenter, Sonja M; Steele, Catriona M

    2012-06-01

    A literature review was conducted on temporal measures of swallowing in healthy individuals with the purpose of determining the degree of variability present in such measures within the literature. A total of 46 studies that met inclusion criteria were reviewed. The definitions and descriptive statistics for all reported temporal parameters were compiled for meta-analysis. In total, 119 different temporal parameters were found in the literature. The three most-frequently occurring durational measures were upper esophageal sphincter opening, laryngeal closure, and hyoid movement. The three most-frequently occurring interval measures were stage transition duration, pharyngeal transit time, and duration from laryngeal closure-to-UES opening. Subtle variations in operational definitions across studies were noted, making the comparison of data challenging. Analysis of forest plots compiling descriptive statistical data (means and 95% confidence intervals) across studies revealed differing degrees of variability across durations and intervals. Two parameters (UES opening duration and the laryngeal closure-to-UES opening interval) demonstrated the least variability, reflected by small ranges for mean values and tight confidence intervals. Trends emerged for factors of bolus size and participant age for some variables. Other potential sources of variability are discussed.

  12. Spatial and Temporal Scales of Surface Water-Groundwater Interactions

    Science.gov (United States)

    Boano, F.

    2016-12-01

    The interfaces between surface water and groundwater (i.e., river and lake sediments) represent hotspots for nutrient transformation in watersheds. This intense biochemical activity stems from the peculiar physicochemical properties of these interface areas. Here, the exchange of water and nutrients between surface and subsurface environments creates an ecotone region that can support the presence of different microbial species responsible for nutrient transformation. Previous studies have elucidated that water exchange between rivers and aquifers is organized in a complex system of nested flow cells. Each cell entails a range of residence timescales spanning multiple order of magnitudes, providing opportunities for different biochemical reactions to occur. Physically-bases models represent useful tools to deal with the wide range of spatial and temporal scales that characterize surface-subsurface water exchange. This contribution will present insights about how hydrodynamic processes control scale organization for surface water - groundwater interactions. The specific focus will be the influence of exchange processes on microbial activity and nutrient transformation, discussing how groundwater flow at watershed scale controls flow conditions and hence constrain microbial reactions at much smaller scales.

  13. The Safe Yield and Climatic Variability: Implications for Groundwater Management.

    Science.gov (United States)

    Loáiciga, Hugo A

    2017-05-01

    Methods for calculating the safe yield are evaluated in this paper using a high-quality and long historical data set of groundwater recharge, discharge, extraction, and precipitation in a karst aquifer. Consideration is given to the role that climatic variability has on the determination of a climatically representative period with which to evaluate the safe yield. The methods employed to estimate the safe yield are consistent with its definition as a long-term average extraction rate that avoids adverse impacts on groundwater. The safe yield is a useful baseline for groundwater planning; yet, it is herein shown that it is not an operational rule that works well under all climatic conditions. This paper shows that due to the nature of dynamic groundwater processes it may be most appropriate to use an adaptive groundwater management strategy that links groundwater extraction rates to groundwater discharge rates, thus achieving a safe yield that represents an estimated long-term sustainable yield. An example of the calculation of the safe yield of the Edwards Aquifer (Texas) demonstrates that it is about one-half of the average annual recharge. © 2016, National Ground Water Association.

  14. Determinants of Shallow Groundwater As Variability in Bangladesh

    Science.gov (United States)

    Radloff, K. A.; Zheng, Y.; Stute, M.; Rahman, M.; Mihajlov, I.; Siu, H.; Huq, M.; Choudhury, I.; Ahmed, K.; van Geen, A.

    2010-12-01

    Manually operated tube wells that tap into shallow aquifers remain a critical source of untreated drinking water in south Asia and an estimated 37 million people are still exposed to elevated levels of As in Bangladesh(1). This field effort sought to address two questions. What mechanisms control the partitioning of As between groundwater and sediment? How does groundwater transport affect the spatial variability of dissolved As? Understanding the source of groundwater variability is essential for understanding how [As] will change with time, especially as Bangladesh and its water demands develop. Arsenic mobility and transport within the shallow aquifer was investigated at a 0.5 km2 site where [As] increases from 50 μg/L in the village within the next few decades. The rapid economic development of Bangladesh could induce similar changes in groundwater flow, and thus As concentrations, elsewhere. This suggests that periodic monitoring of shallow wells low in As within regions of where the As content of groundwater is variable is particularly important. The size of the pool of As adsorbed on the sediment also indicates that current attempts to flush Bangladeshi aquifers “clean” through increased pumping will likely be ineffective. 1. BBS/UNICEF. Bangladesh: Multiple Indicator Cluster Survey, 2009. (Dhaka, Bangladesh, 2009).

  15. Stochastic modelling of aquifer level temporal fluctuations using the Kalman filter adaptation algorithm and an autoregressive exogenous variable model

    Science.gov (United States)

    Varouchakis, Emmanouil

    2017-04-01

    Reliable temporal modelling of groundwater level is significant for efficient water resources management in hydrological basins and for the prevention of possible desertification effects. In this work we propose a stochastic data driven approach of temporal monitoring and prediction that can incorporate auxiliary information. More specifically, we model the temporal (mean annual and biannual) variation of groundwater level by means of a discrete time autoregressive exogenous variable model (ARX model). The ARX model parameters and its predictions are estimated by means of the Kalman filter adaptation algorithm (KFAA). KFAA is suitable for sparsely monitored basins that do not allow for an independent estimation of the ARX model parameters. Three new modified versions of the original form of the ARX model are proposed and investigated: the first considers a larger time scale, the second a larger time delay in terms of the groundwater level input and the third considers the groundwater level difference between the last two hydrological years, which is incorporated in the model as a third input variable. We apply KFAA to time series of groundwater level values from Mires basin in the island of Crete. In addition to precipitation measurements, we use pumping data as exogenous variables. We calibrate the ARX model based on the groundwater level for the years 1981 to 2006 and use it to successfully predict the mean annual and biannual groundwater level for recent years (2007-2010).

  16. Spatial-temporal variation of groundwater and land subsidence evolution in Beijing area

    Directory of Open Access Journals (Sweden)

    K. Lei

    2015-11-01

    Full Text Available Precipitation is the main recharge source of groundwater in the plain of Beijing, China. Rapid expansion of urbanization has resulted in increased built-up area and decreased amount of effective recharge of precipitation to groundwater, indirectly leading to the long-term over-exploitation of groundwater, and induced regional land subsidence. Based on the combination of meteorological data, groundwater level data, interferometric synthetic aperture radar (InSAR; specifically persistent scatterer interferometry, PSI, geographic information system (GIS spatial analysis method and rainfall recharge theory, this paper presents a systematic analysis of spatial-temporal variation of groundwater level and land subsidence evolution. Results show that rainfall has been decreasing annually, while the exploitation of groundwater is increasing and the groundwater level is declining, which is has caused the formation and evolution of land subsidence. Seasonal and interannual variations exist in the evolution of land subsidence; the subsidence is uneven in both spatial and temporal distribution. In 2011, at the center of mapped subsidence the subsidence rate was greater than 120 mm a−1. The results revealed good correlation between the spatial distribution of groundwater level declines and subsidence. The research results show that it is beneficial to measure the evolution of land subsidence to dynamic variations of groundwater levels by combining InSAR or PSI, groundwater-level data, and GIS. This apprpach provides improved information for environmental and hydrogeologic research and a scientific basis for regional land subsidence control.

  17. Groundwater management in land administration : A spatio-temporal perspective

    NARCIS (Netherlands)

    Ghawana, T.; Hespanha, J.P.; Zevenbergen, J.A.; Van Oosterom, P.J.M.

    2010-01-01

    Although the use of land and water is intertwined, specifics for groundwater management are not effectively dealt with in the laws and other institutional mechanisms related to land. Provisions for groundwater aspects in land management are there, but with a focus on the land itself. Land rights and

  18. Temporal Variation and Scaling of Hydrological Variables in a Typical Watershed

    Science.gov (United States)

    Yang, C.; Zhang, Y. K.; Liang, X.; Liu, J.

    2016-12-01

    Temporal variations of the main hydrological variables over 16 years were systematically investigated based on the results from an integrated hydrological modeling at the Sagehen Creek Watershed in northern Sierra Nevada. Temporal scaling of these variables and damping effects of the hydrological system as well as its subsystems, i.e., the land surface, unsaturated zone, and saturated zone, were analyzed with spectral analyses. It was found that the hydrological system may act as a cascade of hierarchical fractal filters which sequentially transfer a non-fractal or less correlated fractal hydrological signal to a more correlated fractal signal. Temporal scaling of infiltration (I), actual evapotraspiration (ET), recharge (R), baseflow (BF), streamflow (SF) exist and the temporal autocorrelation of these variables increase as water moves through the system. The degree of the damping effect of the subsystems is different and is strongest in the unsaturated zone compared with that of the land surface and saturated zone. The temporal scaling of the groundwater levels (h) also exists and is strongly affected by the river: the temporal autocorrelation of h near the river is similar to that of the river stage fluctuations and increases away from the river. There is a break in the temporal scaling of h near the river at low frequencies due to the effect of the river. Temporal variations of the soil moisture (θ) is more complicated: the value of the scaling exponent (β) for θ increases with depth as water moves downwards and its high-frequency fluctuations are damped by the unsaturated zone. The temporal fluctuations of precipitation (P) and I are fractional Gauss noise (fGn), those of ET, R, BF, and SF are fractional Brownian motion (fBm), and those of h away from the river are 2nd-order fBm based on the values of β obtained in this study. Keywords: Temporal variations, Scaling, Damping effect, Hydrological system.

  19. Assessing Spatio-temporal Patterns of Groundwater Salinity in Small ...

    African Journals Online (AJOL)

    2004; Li et al., 1997; Maji & Smith, 2009;. Urish & McKenna, 2004) have shown that the oceanic tide is a factor that effectively increases the dispersion of salt in groundwater. The tide in Grande Glorieuse has a range of over 3.4 m and is undoubtedly a fundamental factor in such a significant dispersion of salinity in the water.

  20. Effect of punping on temporal changes in groundwater quality

    NARCIS (Netherlands)

    Kamra, S.K.; Khajanchi Lal,; Singh, O.P.; Boonstra, J.

    2002-01-01

    Pumping studies were conducted at five sites distributed over a 3000 ha area in the Gohana block in Haryana state of India. The project area is a part of the Indo-Gangetic plain and lies in a topographical depression susceptible to waterlogging, soil salinity and groundwater pollution from

  1. Comparison of the spatial and temporal variability of drought indices ...

    African Journals Online (AJOL)

    Comparison of the spatial and temporal variability of drought indices in Somalia and ... annual precipitation, aridity index and spatial distribution of surface water bodies. ... The lessons from the current drought in Horn of Africa are however, ...

  2. Temporal variability in soil hydraulic properties under drip irrigation

    OpenAIRE

    Mubarak, I.; Mailhol, J.C.; Angulo-Jaramillo, R.; Ruelle, P.; P. Boivin; M. R. Khaledian

    2009-01-01

    Predicting soil hydraulic properties and understanding their temporal variability during the irrigated cropping season are required to mitigate agro-environmental risks. This paper reports field measurements of soil hydraulic properties under two drip irrigation treatments, full (FT) and limited (LT). The objective was to identify the temporal variability of the hydraulic properties of field soil under high-frequency water application during a maize cropping season. Soil hydraulics were chara...

  3. Temporal relationship between climate variability, Prosopis juliflora ...

    African Journals Online (AJOL)

    Kyuma

    1Department of Land Resource Management and Agricultural Technology, University of Nairobi, Nairobi, Kenya. 2Department of Animal ... A study was conducted to determine the association of climate variability, Prosopis juliflora spread, and other ...... Pastoralists as Shrewd Managers of Risk and Resilience in the Horn of ...

  4. Temporally variable macroinvertebrate-stone relationships in streams

    DEFF Research Database (Denmark)

    Jacobsen, D.

    2005-01-01

    negatively related to density and positively related to number of families. Patterns were less clear for richness residuals. Simple linear regressions of fauna vs. stone parameters generally confirmed the results reached by the PLS analysis, although few of the regressions were significant. For all fauna......) multiple regression analyses showed high temporal variability between sampling dates in factor loadings of specific stone micro habitat variables. In spite of this, there was a clear negative effect of depth and a positive effect of current on density and number of families. Stone size was consistently...... of fauna parameter and stone variable from different sampling dates (n=9-11) were rarely correlated to any of the measures of stream stability, this study has demonstrated high temporal variability in fauna-stone relationships (CV's of regression slopes). Consequently, temporally un-replicated studies...

  5. Response of groundwater level and surface-water/groundwater interaction to climate variability: Clarence-Moreton Basin, Australia

    Science.gov (United States)

    Cui, Tao; Raiber, Matthias; Pagendam, Dan; Gilfedder, Mat; Rassam, David

    2017-08-01

    Understanding the response of groundwater levels in alluvial and sedimentary basin aquifers to climatic variability and human water-resource developments is a key step in many hydrogeological investigations. This study presents an analysis of groundwater response to climate variability from 2000 to 2012 in the Queensland part of the sedimentary Clarence-Moreton Basin, Australia. It contributes to the baseline hydrogeological understanding by identifying the primary groundwater flow pattern, water-level response to climate extremes, and the resulting dynamics of surface-water/groundwater interaction. Groundwater-level measurements from thousands of bores over several decades were analysed using Kriging and nonparametric trend analysis, together with a newly developed three-dimensional geological model. Groundwater-level contours suggest that groundwater flow in the shallow aquifers shows local variations in the close vicinity of streams, notwithstanding general conformance with topographic relief. The trend analysis reveals that climate variability can be quickly reflected in the shallow aquifers of the Clarence-Moreton Basin although the alluvial aquifers have a quicker rainfall response than the sedimentary bedrock formations. The Lockyer Valley alluvium represents the most sensitively responding alluvium in the area, with the highest declining (-0.7 m/year) and ascending (2.1 m/year) Sen's slope rates during and after the drought period, respectively. Different surface-water/groundwater interaction characteristics were observed in different catchments by studying groundwater-level fluctuations along hydrogeologic cross-sections. The findings of this study lay a foundation for future water-resource management in the study area.

  6. Recharge response to interannual and multidecadal climate variability and implications for groundwater resources of the Central Valley aquifer, California

    Science.gov (United States)

    Kuss, A. M.; Gurdak, J. J.

    2010-12-01

    Climate variability on interannual to multidecadal temporal scales has substantial implications for management and sustainability of water resources, yet are poorly understood throughout much of the United States. Climate forcings on these timescales partially control precipitation distribution, temperature fluctuations, drought occurrence and severity, streamflow, and recharge. Reliable predictions of future climate and subsequent adaptation of groundwater management strategies in vulnerable aquifers, such as the Central Valley aquifer located in central California of the United States, requires improved understanding of climate variability on interannual to multidecadal timescales and the associated responses in recharge rates. Groundwater withdrawals from the Central Valley aquifer are the second largest of all aquifers in the United States and are used to support one of the largest agricultural economies. However, the effects of the El Niño Southern Oscillation (ENSO) (2 to 6 year cycle), Pacific Decadal Oscillation (PDO) (10 to 25 year cycle), and Atlantic Multidecadal Oscillation (AMO) (50 to 80 year cycle) on recharge rates and groundwater levels in the Central Valley aquifer previously have not been quantified. In this study, singular spectrum analysis (SSA) was used to identify the principal components of groundwater level time series from selected wells in Central Valley aquifer that contribute to the greatest amount of variance in the record. In each of the time series analyzed, the PDO was the most significant contributor to groundwater level fluctuations. Wavelet analysis was also used to examine the nonstationary phase relation of multiple time series to identify significance and duration of each forcing. A consistent phase relation of multiple signals suggests possible coherence between climate forcings and groundwater levels, and also indicates the effect of the PDO on groundwater levels. These findings support the conclusion that interannual to

  7. Spatiotemporal Variability in Groundwater Depletion using GRACE Satellite and Modeling Approaches (Invited)

    Science.gov (United States)

    Scanlon, B. R.; Faunt, C.; Longuevergne, L.; Reedy, R. C.; Long, D.

    2013-12-01

    Many recent studies emphasize groundwater depletion using global models and GRACE satellite data; however, understanding spatiotemporal variability in depletion at regional scales is critical for water resources management. Here we compare groundwater depletion in the US High Plains and California Central Valley aquifers using GRACE satellite data, groundwater modeling, and water level monitoring. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ~50% of groundwater depletion in the U.S. since 1900. The GRACE satellite data provide basin scale estimates of groundwater depletion of ~ 8 km3/yr in the High Plains and up to 31 km3 during the recent three year drought (Oct 2006 - Mar 2010) in the Central Valley. Groundwater depletion is highly variable spatially with little or no depletion in the northern High Plains and northern Central Valley as shown by groundwater level monitoring and regional groundwater modeling. Groundwater recharge estimates for the High Plains based on groundwater chloride data show that groundwater depletion of ~ 330 km3 in the central and southern High Plains is most likely caused by much lower recharge in this region related to fine grained soils, with most recharge occurring during Pleistocene times within the past 13,000 yr. This fossil groundwater cannot be managed sustainably; however, reducing irrigation pumpage could extend the lifespan of the aquifer. Although the Central Valley aquifer was heavily depleted in the south in the early 20th century, north-south diversions of surface water since the 1950s has replenished much of the aquifer storage, increasing recharge by up to a factor of ~7 times. However, these diversions are regulated because of impacts on endangered species. A newly developed Central Valley Hydrologic Model shows that groundwater depletion occurs mostly in the south (Tulare Basin) and primarily during droughts. Increasing water storage through artificial recharge of excess

  8. Spatial and temporal variability of chlorophyll in Bay of Bengal.

    Science.gov (United States)

    Jutla, A.; Akanda, S.; Islam, S.

    2009-04-01

    The Bay of Bengal (BoB) receives approximately 628 km3/ year of freshwater discharge from the Ganges and Brahmaputra rivers. Freshwater discharge from rivers increases the nutrient load and thereby enhances phytoplankton production in the BoB. Cholera, an infectious water-borne disease caused by bacterium Vibrio cholerae, remains endemic in the BoB region. Phytoplankton provides favorable environment for survival of cholera bacteria. Therefore, for development of any predictive model for cholera, it is important to quantify the spatial and temporal variability of phytoplankton in the BoB. Satellite remote sensing is the most effective way to quantify this variability over a range of space and time scales. Using ten years (1998-2007) of daily, weekly and monthly SeaWiFs chlorophyll, a surrogate variable for measuring phytoplankton, imagery we explore the spatial pattern and dominant temporal variability of chlorophyll over the BoB region. We find that chlorophyll in the coastal waters has more variability, both in temporal and spatial scales, than the offshore waters. Mechanism of production and space-time variability of coastal chlorophyll is different from those of offshore chlorophyll. While coastal chlorophyll is dominated by influx of terrestrial nutrients through river discharge, chlorophyll in the offshore region is primarily controlled by oceanic processes. We will also explore issues related to dominant space and time scales of chlorophyll variations in the entire bay.

  9. Temporal Variability of Observed and Simulated Hyperspectral Earth Reflectance

    Science.gov (United States)

    Roberts, Yolanda; Pilewskie, Peter; Kindel, Bruce; Feldman, Daniel; Collins, William D.

    2012-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a climate observation system designed to study Earth's climate variability with unprecedented absolute radiometric accuracy and SI traceability. Observation System Simulation Experiments (OSSEs) were developed using GCM output and MODTRAN to simulate CLARREO reflectance measurements during the 21st century as a design tool for the CLARREO hyperspectral shortwave imager. With OSSE simulations of hyperspectral reflectance, Feldman et al. [2011a,b] found that shortwave reflectance is able to detect changes in climate variables during the 21st century and improve time-to-detection compared to broadband measurements. The OSSE has been a powerful tool in the design of the CLARREO imager and for understanding the effect of climate change on the spectral variability of reflectance, but it is important to evaluate how well the OSSE simulates the Earth's present-day spectral variability. For this evaluation we have used hyperspectral reflectance measurements from the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), a shortwave spectrometer that was operational between March 2002 and April 2012. To study the spectral variability of SCIAMACHY-measured and OSSE-simulated reflectance, we used principal component analysis (PCA), a spectral decomposition technique that identifies dominant modes of variability in a multivariate data set. Using quantitative comparisons of the OSSE and SCIAMACHY PCs, we have quantified how well the OSSE captures the spectral variability of Earth?s climate system at the beginning of the 21st century relative to SCIAMACHY measurements. These results showed that the OSSE and SCIAMACHY data sets share over 99% of their total variance in 2004. Using the PCs and the temporally distributed reflectance spectra projected onto the PCs (PC scores), we can study the temporal variability of the observed and simulated reflectance spectra. Multivariate time

  10. Partitioning and analyzing temporal variability of wash and bed ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 124; Issue 7. Partitioning and analyzing temporal variability of wash and bed material loads in a forest watershed in Iran ... Keywords. Laser particle size distribution; sand and gravel mining; sediment dynamic; suspended sediment; watershed management.

  11. Monitoring spatial-temporal variability of aerosol over Kenya ...

    African Journals Online (AJOL)

    A Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used for trajectory analysis in order to reconstruct the origins of air masses and understand the Spatial and temporal variability of aerosol concentrations. Validation of MODIS AOD using Aerosol Robotic Network (AERONET) indicated that ...

  12. Effects of Population Growth and Climate Variability on Sustainable Groundwater in Mali, West Africa

    Directory of Open Access Journals (Sweden)

    Alexandra Lutz

    2010-12-01

    Full Text Available Groundwater is increasingly relied on as a source of potable water in developing countries, but factors such as population growth, development, and climate variability, pose potential challenges for ongoing sustainable supply. The effect of these factors on the groundwater system was considered in four scenarios using a numerical model to represent the Bani area of Mali, West Africa. By 2040, population growth, climate variability, and development as urbanization, agriculture, and industry creates scenarios in which groundwater extraction is an increasingly larger percentage of the groundwater system. Consumption from agriculture and industry increases extraction rates from less than 1 to 3.8% of mean annual precipitation, which will likely affect the groundwater system. For instance, concentrated pumping in local areas may result in water level declines. The results of this study contribute to an ongoing evaluation of sustainable groundwater resources in West Africa.

  13. Potential impacts of climate change and variability on groundwater ...

    African Journals Online (AJOL)

    Such changes are known to influence subsurface hydrological systems, which could lead to changes in groundwater recharge, discharge and storage of many aquifers. Although, there are uncertainties in the characterisation of climate change induced groundwater impacts due largely to multi-scale local and regional ...

  14. Effects of temporal variability on HBV model calibration

    Directory of Open Access Journals (Sweden)

    Steven Reinaldo Rusli

    2015-10-01

    Full Text Available This study aimed to investigate the effect of temporal variability on the optimization of the Hydrologiska Byråns Vattenbalansavedlning (HBV model, as well as the calibration performance using manual optimization and average parameter values. By applying the HBV model to the Jiangwan Catchment, whose geological features include lots of cracks and gaps, simulations under various schemes were developed: short, medium-length, and long temporal calibrations. The results show that, with long temporal calibration, the objective function values of the Nash-Sutcliffe efficiency coefficient (NSE, relative error (RE, root mean square error (RMSE, and high flow ratio generally deliver a preferable simulation. Although NSE and RMSE are relatively stable with different temporal scales, significant improvements to RE and the high flow ratio are seen with longer temporal calibration. It is also noted that use of average parameter values does not lead to better simulation results compared with manual optimization. With medium-length temporal calibration, manual optimization delivers the best simulation results, with NSE, RE, RMSE, and the high flow ratio being 0.563 6, 0.122 3, 0.978 8, and 0.854 7, respectively; and calibration using average parameter values delivers NSE, RE, RMSE, and the high flow ratio of 0.481 1, 0.467 6, 1.021 0, and 2.784 0, respectively. Similar behavior is found with long temporal calibration, when NSE, RE, RMSE, and the high flow ratio using manual optimization are 0.525 3, −0.069 2, 1.058 0, and 0.980 0, respectively, as compared with 0.490 3, 0.224 8, 1.096 2, and 0.547 9, respectively, using average parameter values. This study shows that selection of longer periods of temporal calibration in hydrological analysis delivers better simulation in general for water balance analysis.

  15. Effects of temporal variability on HBV model calibration

    Directory of Open Access Journals (Sweden)

    Steven Reinaldo Rusli

    2015-10-01

    Full Text Available This study aimed to investigate the effects of temporal variability on the optimization of the Hydrologiska Byråns Vattenbalansavedlning (HBV model, as well as the calibration performance using manual optimization and average parameter values. By applying the HBV model to the Jiangwan Catchment, whose geological features include lots of cracks and gaps, simulations under various schemes were developed: short, medium-length, and long temporal calibrations. The results show that, with long temporal calibration, the objective function values of the Nash-Sutcliffe efficiency coefficient (NSE, relative error (RE, root mean square error (RMSE, and high flow ratio generally deliver a preferable simulation. Although NSE and RMSE are relatively stable with different temporal scales, significant improvements to RE and the high flow ratio are seen with longer temporal calibration. It is also noted that use of average parameter values does not lead to better simulation results compared with manual optimization. With medium-length temporal calibration, manual optimization delivers the best simulation results, with NSE, RE, RMSE, and the high flow ratio being 0.563 6, 0.122 3, 0.978 8, and 0.854 7, respectively; and calibration using average parameter values delivers NSE, RE, RMSE, and the high flow ratio of 0.481 1, 0.467 6, 1.021 0, and 2.784 0, respectively. Similar behavior is found with long temporal calibration, when NSE, RE, RMSE, and the high flow ratio using manual optimization are 0.525 3, −0.069 2, 1.058 0, and 0.980 0, respectively, as compared with 0.490 3, 0.224 8, 1.096 2, and 0.547 9, respectively, using average parameter values. This study shows that selection of longer periods of temporal calibration in hydrological analysis delivers better simulation in general for water balance analysis.

  16. Delineation of spatial-temporal patterns of groundwater/surface-water interaction along a river reach (Aa River, Belgium) with transient thermal modeling

    Science.gov (United States)

    Anibas, Christian; Tolche, Abebe Debele; Ghysels, Gert; Nossent, Jiri; Schneidewind, Uwe; Huysmans, Marijke; Batelaan, Okke

    2017-12-01

    Among the advances made in analytical and numerical analysis methods to quantify groundwater/surface-water interaction, one methodology that stands out is the use of heat as an environmental tracer. A large data set of river and riverbed temperature profiles from the Aa River in Belgium has been used to examine the spatial-temporal variations of groundwater/surface-water interaction. Exchange fluxes were calculated with the numerical heat-transport code STRIVE. The code was applied in transient mode to overcome previous limitations of steady-state analysis, and allowed for the calculation of model quality. In autumn and winter the mean exchange fluxes reached -90 mm d-1, while in spring and early summer fluxes were -42 mm d-1. Predominantly gaining conditions occurred along the river reach; however, in a few areas the direction of flow changed in time. The river banks showed elevated fluxes up to a factor of 3 compared to the center of the river. Higher fluxes were detected in the upstream section of the reach. Due to the influence of exchange fluxes along the river banks, larger temporal variations were found in the downstream section. The exchange fluxes at the river banks seemed more driven by variable local exchange flows, while the center of the river was dominated by deep and steady regional groundwater flows. These spatial and temporal differences in groundwater/surface-water exchange show the importance of long-term investigations on the driving forces of hyporheic processes across different scales.

  17. Groundwater.

    Science.gov (United States)

    Braids, Olin C.; Gillies, Nola P.

    1978-01-01

    Presents a literature review of groundwater quality covering publications of 1977. This review includes: (1) sources of groundwater contamination; and (2) management of groundwater. A list of 59 references is also presented. (HM)

  18. Exploring the spatio-temporal interrelation between groundwater and surface water by using the self-organizing maps

    Science.gov (United States)

    Chen, I.-Ting; Chang, Li-Chiu; Chang, Fi-John

    2018-01-01

    In this study, we propose a soft-computing methodology to visibly explore the spatio-temporal groundwater variations of the Kuoping River basin in southern Taiwan. The self-organizing map (SOM) is implemented to investigate the interactive mechanism between surface water and groundwater over the river basin based on large high-dimensional data sets coupled with their occurrence times. We find that extracting the occurrence time from each 30-day moving average data set in the clustered neurons of the SOM is a crucial step to learn the spatio-temporal interaction between surface water and groundwater. We design 2-D Topological Bubble Map to summarize all the groundwater values of four aquifers in a neuron, which can visibly explore the major features of the groundwater in the vertical direction. The constructed SOM topological maps nicely display that: (1) the groundwater movement, in general, extends from the eastern area to the western, where groundwater in the eastern area can be easily recharged from precipitation in wet seasons and discharged into streams during dry seasons due to the high permeability in this area; (2) the water movements in the four aquifers of the study area are quite different, and the seasonal variations of groundwater in the second and third aquifers are larger than those of the others; and (3) the spatial distribution and seasonal variations of groundwater and surface water are comprehensively linked together over the constructed maps to present groundwater characteristics and the interrelation between groundwater and surface water. The proposed modeling methodology not only can classify the large complex high-dimensional data sets into visible topological maps to effectively facilitate the quantitative status of regional groundwater resources but can also provide useful elaboration for future groundwater management.

  19. Temporal variability is a personalized feature of the human microbiome

    OpenAIRE

    Flores, Gilberto E.; Gregory Caporaso, J.; Henley, Jessica B.; Rideout, Jai Ram; Domogala, Daniel; Chase, John; Leff, Jonathan W.; Vázquez-Baeza, Yoshiki; Gonzalez, Antonio; Knight, Rob; Dunn, Robert R.; Fierer, Noah

    2014-01-01

    Background: It is now apparent that the complex microbial communities found on and in the human body (the human microbiome) vary across individuals. What has largely been missing from previous studies is an understanding of how these communities vary over time within individuals. To the extent to which it has been considered, it is often assumed that temporal variability is negligible for healthy adults. Here we address this gap in understanding by profiling the forehead, gut (fecal), palm, a...

  20. Temporal variability in epifaunal assemblages associated with temperate gorgonian gardens

    KAUST Repository

    Dias, I.M.

    2015-10-19

    The present study is one of the few that investigate the temporal variability of epifaunal assemblages associated with coral species, particularly the octocorals Eunicella gazella and Leptogorgia lusitanica in south Portugal. The results suggest time rather than colony size as a primary driver of the ecological patterns of these assemblages, which were dominated by amphipods, molluscs and polychaetes. Temporal variability was linked to changes in environmental parameters, namely temperature, chlorophyll a and particulate organic carbon. Hence, temporal variability must be taken into account for the design of future biodiversity assessment studies, as different patterns may be observed depending on the sampling time. Associated epifaunal assemblages were consistently dominated by resident species (i.e. species present in all sampling periods) and a peak of rare species was observed in the transition from spring to summer following the increase of seawater temperature. Turnover was particularly high in the transition between the spring and summer periods. In both hosts, turnover was higher in the small sized colonies, which generally harboured less diverse and less abundant assemblages which also differed from those inhabiting larger size colonies. The high levels of diversity associated with gorgonian colonies highlights the need for the conservation of this priority habitat.

  1. Comparative Spatial and Temporal Analysis of Particle Composition through the Critical Zone in the Investigation of Groundwater and Stream Chemistry

    Science.gov (United States)

    Nghiem, A.; Kim, H.; Bourne, H.; Thurnhoffer, B. M.; Bishop, J. K. B.

    2015-12-01

    Investigation into particle composition and flux of weathered material transported by rivers to the ocean basins provides insight into seasonal dynamics in chemical weathering of stream environments and on the delivery of micronutrient elements such as Fe and Mn to the coastal zone. At the headwaters of the South Fork Eel River in Northern California, the site of the Eel River Critical Zone Observatory, the temporal and spatial variability of groundwater and effects of depth and speed of water movement on stream chemistry dynamics have been examined by Kim et al. (2014). Through automated ISCO Gravity Filtration System (GFS; Kim et al. 2012, EST), samples of groundwater and stream water have been collected at frequency of one to three days since 2009 from three wells (Well 1 down-slope, Well 3 mid-slope, Well 10 up-slope) and Elder Creek and filtered through 0.45 μm diameter Supor filters. Preliminary analysis of the filters via measurements of optical density (from sample photography under controlled lighting) have served as selection aid for identifying relevant environmental phenomena such as rainstorms and wildfires in the study of reactive particulate phases. Here we investigate solubilization strategies (e.g. strong acid leaching or total digest) for sample pretreatment prior to ICP-MS analysis and the sample time series. Results from ICP analysis of particles are compared with the same temporal points taken of water samples, such as with Mn and Fe. Previous research into the fate and transport of these metals suggest that Mn exists primarily in a dissolved phase while Fe exists in colloidal phases, produced by chemical weathering in the vadose zone, which may be tested with the compositional analysis of the filter particulates. Overall, compositional analyses of filter particles and comparison with water chemistry data will complete the picture of temporal and spatial dynamics of chemical weathering.

  2. Temporal variability of spectro-temporal receptive fields in the anesthetized auditory cortex

    Directory of Open Access Journals (Sweden)

    Arne Freerk Meyer

    2014-12-01

    Full Text Available Temporal variability of neuronal response characteristics during sensory stimulation is a ubiquitous phenomenon that may reflect processes such as stimulus-driven adaptation, top-down modulation or spontaneous fluctuations. It poses a challenge to functional characterization methods such as the receptive field, since these often assume stationarity. We propose a novel method for estimation of sensory neurons' receptive fields that extends the classic static linear receptive field model to the time-varying case. Here, the long-term estimate of the static receptive field serves as the mean of a probabilistic prior distribution from which the short-term temporally localized receptive field may deviate stochastically with time-varying standard deviation. The derived corresponding generalized linear model permits robust characterization of temporal variability in receptive field structure also for highly non-Gaussian stimulus ensembles. We computed and analyzed short-term auditory spectro-temporal receptive field (STRF estimates with characteristic temporal resolution 5 s to 30 s based on model simulations and responses from in total 60 single-unit recordings in anesthetized Mongolian gerbil auditory midbrain and cortex. Stimulation was performed with short (100 ms overlapping frequency-modulated tones. Results demonstrate identification of time-varying STRFs, with obtained predictive model likelihoods exceeding those from baseline static STRF estimation. Quantitative characterization of STRF variability reveals a higher degree thereof in auditory cortex compared to midbrain. Cluster analysis indicates that significant deviations from the long-term static STRF are brief, but reliably estimated. We hypothesize that the observed variability more likely reflects spontaneous or state-dependent internal fluctuations that interact with stimulus-induced processing, rather than experimental or stimulus design.

  3. Causes of temporal variability of lead in domestic plumbing systems.

    Science.gov (United States)

    Schock, M R

    1990-07-01

    Sources of lead in drinking water are primarily lead pipe, lead/tin solder, and brass fixture materials.Lead levels in the water depend upon many solubility factors, such as pH, concentrations of substances such as inorganic carbonate, orthophosphate, chlorine, and silicate, the temperature, the nature of the pipe surface, etc. Physical factors, time, and chemical mass transfer are significant in governing lead levels in nonequilibrium systems. The diameter and length of lead pipe is extremely important, as well as the age and chemical history of the solder and brass fixtures. Analytical variability is not particularly significant relative to between-site and within-site variability. Knowledge of temporal variability at each site is necessary to define a statistically valid monitoring program. An analysis of published data covering repetitive measurements at a given site show that the variability of lead concentration at each site tends to be characterized by the frequent occurrence of 'spikes'. Variability expressed as approximate relative standard deviations tends to be of about 50 to 75% in untreated water, regardless of the mean lead concentration. The distributions are frequently nonnormal for small numbers of samples. Monitoring programs must incorporate controls for the causes of the within-site and between-site variability into their sampling design. The determination of necessary sampling frequency, sample number, and sample volume must be made with consideration of the system variability, or the results will be unrepresentative and irreproducible.

  4. The spatiotemporal variability of groundwater depth in a typical ...

    Indian Academy of Sciences (India)

    37

    degradation, soil salinization, desertification, serious drops in groundwater levels and frequent sand storms (Li et al. 2004; Gao ... typical oasis-desert ecotone at the southern edge of the Badain Jaran Desert. The area has a typical temperate desert ..... reaches of Heihe River; Inner Mongolia Meteorol. 1 38-41 (in Chinese).

  5. Spatial and temporal variability of lightings over Greece

    Science.gov (United States)

    Nastos, P. T.; Matsangouras, J. T.

    2010-09-01

    Lightings are the most powerful and spectacular natural phenomena in the lower atmosphere, being a major cause of storm related deaths. Cloud-to-ground lightning can kill and injure people by direct or indirect means. Lightning affects the many electrochemical systems in the body causing nerve damage, memory loss, personality change, and emotional problems. Besides, among the various nitrogen oxides sources, the contribution from lightning likely represents the largest uncertainty. In this study, the spatial and temporal variability of recorded lightings over Greece during the period from January 1, 2008 to December 31, 2009, were analyzed. The data for retrieving the location and time-of-occurrence of lightning were acquired from Hellenic National Meteorological Service (HNMS) archive dataset. An operational lighting detector network was established in 2007 by HNMS consisted of eight time-of-arrival sensors (TOA), spatially distributed across Greek territory. The spatial variability of lightings revealed their incidence within specific geographical sub-regions while the temporal variability concerning the seasonal, monthly and daily distributions resulted in better understanding of the time of lightings’ occurrence. All the analyses were carried out with respect to cloud to cloud, cloud to ground and ground to cloud lightings, within the examined time period.

  6. Regional mapping of depression-focussed groundwater recharge incorporating variable topography, climate, and land use

    Science.gov (United States)

    Pavlovskii, I.; Noorduijn, S. L.; Abrakhimova, P.; Bentley, L. R.; Cey, E. E.; Hayashi, M.

    2016-12-01

    In the water-deficient setting of the Northern Great Plains (or Prairie Pothole Region, PPR), groundwater recharge constitutes only a small fraction of the water budget, meaning that recharge estimates have a high degree of uncertainty. Additionally, recharge primarily occurs as focussed recharge when small topographical depressions are inundated by surface runoff, typically during spring melt while underlying soils are still frozen. This results in a high spatial and temporal variability of recharge rates, which further complicates their evaluation. As part of a major research project called Groundwater Recharge in the Prairies (GRIP), we have developed a soil water balance model to estimate recharge rates at a scale of a single depression and its catchment (recharge mapping on a regional scale in the Edmonton-Calgary corridor in Alberta, located in the north-western fringe of the PPR. The entire area (49500 km2) was divided into elements based on the proximity to one of 24 Alberta Agriculture weather stations. For each element, the model was run for a series of generic scenarios consisting of representative land use and depression catchment parameters. The latter were constructed using a high-resolution digital elevation model (DEM). The recharge value for each element was then computed using a weighted average of the generic scenario outputs. The new method has a number of benefits. Use of generic scenarios instead of real depressions dramatically reduces computational cost. Extraction of relevant parameters from DEM accounts for depressions which are only flooded sporadically and thus may be absent from the inventories of wet areas based on satellite images. If extra data on topographical parameters become available, the recharge may be recalculated without repeating the entire workflow.

  7. Natural spatial and temporal variations in groundwater chemistry in fractured, sedimentary rocks: scale and implications for solute transport

    Energy Technology Data Exchange (ETDEWEB)

    Hoven, Stephen J. van der [Department of Geography-Geology, Illinois State University, Campus Box 4400, Normal, IL 61761 (United States)]. E-mail: vanderhoven@ilstu.edu; Kip Solomon, D. [Department of Geology and Geophyics, University of Utah, 135 S. 1460 E., Room 719, Salt Lake City, UT 84112 (United States); Moline, Gerilynn R. [10 Victorian Heights, Thackeray Road, London SW8 3TD (United Kingdom)

    2005-05-15

    Natural tracers (major ions, {delta} {sup 18}O, and O{sub 2}) were monitored to evaluate groundwater flow and transport to a depth of 20 m below the surface in fractured sedimentary (primarily shale and limestone) rocks. Large temporal variations in these tracers were noted in the soil zone and the saprolite, and are driven primarily by individual storm events. During nonstorm periods, an upward flow brings water with high TDS, constant {delta} {sup 18}O, and low dissolved O{sub 2} to the water table. During storm events, low TDS, variable {delta} {sup 18}O, and high dissolved O{sub 2} water recharges through the unsaturated zone. These oscillating signals are rapidly transmitted along fracture pathways in the saprolite, with changes occurring on spatial scales of several meters and on a time scale of hours. The variations decreased markedly below the boundary between the saprolite and less weathered bedrock. Variations in the bedrock units occurred on time scales of days and spatial scales of at least 20 m. The oscillations of chemical conditions in the shallow groundwater are hypothesized to have significant implications for solute transport. Solutes and colloids that adsorb onto aquifer solids can be released into solution by decreases in ionic strength and pH. The decreases in ionic strength also cause thermodynamic undersaturation of the groundwater with respect to some mineral species and may result in mineral dissolution. Redox conditions are also changing and may result in mineral dissolution/precipitation. The net result of these chemical variations is episodic transport of a wide range of dissolved solutes or suspended particles, a phenomenon rarely considered in contaminant transport studies.

  8. Spatio-temporal variability of global soil moisture products

    Science.gov (United States)

    Rötzer, K.; Montzka, C.; Vereecken, H.

    2015-03-01

    Being an important variable for various applications, for example hydrological and weather prediction models or data assimilation, a large range of global soil moisture products from different sources, such as modeling or active and passive microwave remote sensing, are available. The diverse measurement and estimation methods can lead to differences in the characteristics of the products. This study investigates the spatial and temporal behavior of three different products: (i) the Soil Moisture and Ocean Salinity (SMOS) Level 2 product, retrieved with a physically based approach from passive microwave remote sensing brightness temperatures, (ii) the MetOp-A Advanced Scatterometer (ASCAT) product retrieved with a change detection method from radar remote sensing backscattering coefficients, and (iii) the ERA Interim product from a weather forecast model reanalysis. Results show overall similar patterns of spatial soil moisture, but high deviations in absolute values. A ranking of mean relative differences demonstrates that ASCAT and ERA Interim products show most similar spatial soil moisture patterns, while ERA and SMOS products show least similarities. For selected regions in different climate classes, time series of the ASCAT product generally show higher variability of soil moisture than SMOS, and especially than ERA products. The relationship of spatial mean and variance is, especially during wet periods, influenced by sensor and retrieval characteristics in the SMOS product, while it is determined to a larger degree by the precipitation patterns of the respective regions in the ASCAT and ERA products. The decomposition of spatial variance into temporal variant and invariant components exhibits high dependence on the retrieval methods of the respective products. The change detection retrieval method causes higher influence of temporal variant factors (e.g. precipitation, evaporation) on the ASCAT product, while SMOS and ERA products are stronger determined by

  9. Spatial and temporal trends in groundwater quantity and quality in urban area

    Science.gov (United States)

    Fejes, I.; Farsang, A.

    2012-04-01

    Nowadays one of the most important environmental problems in urban areas is groundwater contamination, since it takes effect on all parts of the urban environment. Therefore in this research the groundwater-system of Szeged (SE Hungary) was monitored and the temporal and spatial changes of heavy metals and other inorganic contaminants were examined. Water quantity and quality investigations twenty-eight sampling wells from the groundwater monitoring network of Szeged were carried out. In the course of well selection, we were about to cover complete area of the city. The water samples were collected every month from October of 2010 to September of 2011 and every second month from November 2011. Temperature, pH, total salt content, electrical conductivity, water levels and the concentrations of 12 components (copper, cadmium, cobalt, chrome, lead, nickel, zinc, arsenic, nitrate, nitrite, ammonium, orthophosphate) were measured. The water levels were strongly influenced by the extreme precipitation of the investigated period, so the maximum and minimum of groundwater levels have differed from the average. Changes of water levels followed the changes of precipitation in autumn and winter, but in spring and summer other factors, like evaporation and effects of the vegetation influenced the water regime. The relationship of different pollutants and their distribution were determined in the city. As the results show, the amount of toxic materials in the groundwater in Szeged has exceeded the limit values (according to the joint decree) in many cases. The groundwater is contaminated with lead, nickel, copper, zinc, arsenic, nitrate, ammonium and orthophosphate mainly in the downtown, close to the river Tisza, which can cause ecological and human-health risk as well. In outskirts lowest concentrations were detected. Significant statistical relationship, used Spearman's rank correlation, was determined among the siderophile (namely chrome and nickel), chalcophile elements

  10. Understanding in-stream temporal coupling of macronutrients based on high-frequency monitoring in groundwater dominated rivers

    Science.gov (United States)

    Bieroza, M. Z.; Heathwaite, A. L.

    2012-04-01

    Developments in high-frequency water quality measurements enable capturing of fine structure of temporal variations in river biogeochemistry. Understanding of the temporal variation in the nutrient source and in-stream processes is critical in restoration of the good ecological and chemical status of river ecosystems. However, to date the in-stream temporal variability of macronutrients captured by high-frequency sampling is poorly understood (Scholefield et al., 2005; Milne et al., 2009; Harris and Heathwaite, 2011). Typically, river water quality monitoring is based on coarse sampling or storm event targeting strategies that miss the low flow water quality dynamics when in-stream processes and chemical-biological interactions may be of the greatest importance. This paper investigates the temporal dynamics and interdependencies between multiple high-frequency (hourly) nutrient and water quality time series collated for the River Leith, a tributary of the River Eden (Cumbria, UK). In-stream nutrients (total phosphorus TP, soluble reactive phosphorus SRP, nitrate nitrogen NO3N) and water quality parameters (turbidity, specific conductivity, pH, temperature, dissolved oxygen, redox potential) were measured by an automated remote mobile lab. A 54 km2 catchment of the River Leith is of mixed geology with Carboniferous limestone overlain by Penrith Sandstone and glacial till deposits. Permeable riverbed deposits create an active groundwater-surface water interface with hyporheic processes potentially exerting control over nutrient cycling. The temporal variation in in-stream nutrients and water quality variables was analysed. Diurnal patterns were observed during low flow conditions for both nutrients and water quality time series. Possible physical and biogeochemical controls on nutrients short-term dynamics were discussed. Antecedent and contemporaneous interdependencies between nutrients, water quality and hydrometric time series were explored in more detail using

  11. Temporal and Spatial Variability along the Deep Western Boundary Current

    Science.gov (United States)

    Schmidtko, Sunke; Fischer, Jürgen

    2017-04-01

    The North Atlantic Deep Western Boundary Current (DWBC) connects the polar and subpolar regions, where the ocean is ventilated to greater depth, with the tropical oceans and beyond. It is part of the global ocean circulation as the deep branch of the Atlantic meridional overturning circulation (AMOC). It has a core depth between 1500-4500m with water mass properties varying by origin and decade. We analyze all publically available CTD data from Porcupine Abyssal Plain along Denmark Straight, Labrador Sea, Cape Cod, Cape Hatteras and Bahamas to the equator. The spatial and temporal development is analyzed for the past five decades. Waters originating from the overflow regions between Greenland and Scotland and from the Labrador Sea merge along the pathway but show distinct temporal variability and trends. We distinguish between local and large-scale variability and relate our results with the atmospheric forcing of the North Atlantic. This gives insight into new key aspects to be validated with state of the art ocean circulation models.

  12. Spatial and temporal variability in urban fine particulate matter concentrations.

    Science.gov (United States)

    Levy, Jonathan I; Hanna, Steven R

    2011-01-01

    Identification of hot spots for urban fine particulate matter (PM(2.5)) concentrations is complicated by the significant contributions from regional atmospheric transport and the dependence of spatial and temporal variability on averaging time. We focus on PM(2.5) patterns in New York City, which includes significant local sources, street canyons, and upwind contributions to concentrations. A literature synthesis demonstrates that long-term (e.g., one-year) average PM(2.5) concentrations at a small number of widely-distributed monitoring sites would not show substantial variability, whereas short-term (e.g., 1-h) average measurements with high spatial density would show significant variability. Statistical analyses of ambient monitoring data as a function of wind speed and direction reinforce the significance of regional transport but show evidence of local contributions. We conclude that current monitor siting may not adequately capture PM(2.5) variability in an urban area, especially in a mega-city, reinforcing the necessity of dispersion modeling and methods for analyzing high-resolution monitoring observations. Copyright © 2010 Elsevier Ltd. All rights reserved.

  13. Rapid groundwater-related land subsidence in Yemen observed by multi-temporal InSAR

    Science.gov (United States)

    Abdullin, Ayrat; Xu, Wenbin; Kosmicki, Maximillian; Jonsson, Sigurjon

    2015-04-01

    Several basins in Yemen are suffering from a rapid drawdown of groundwater, which is the most important water source for agricultural irrigation, industry and domestic use. However, detailed geodetic measurements in the region have been lacking and the extent and magnitude of groundwater-related land subsidence has been poorly known. We used 13 ascending ALOS and 15 descending Envisat images to study land subsidence of several basins in Yemen, with a special focus on the Sana'a and Mabar basins. From multitemporal synthetic aperture radar interferometric analysis (persistent scatterers (PS) and small baseline subsets (SBAS)) we examined the spatio-temporal behavior of the subsidence induced by depletion of groundwater aquifer systems from November 2003 to February 2011. In the interferometric data processing, we carefully chose interferogram pairs to minimize spatial and temporal decorrelation, because of high subsidence rates and the type of land cover. Our results show that the spatial pattern of subsidence remained quite stable during the observation period in both the Sana'a and Mabar basins. In the Sana'a basin, the maximum subsidence rate exceeded 14 cm/year in the radar line-of-sight (LOS) direction between 2003 and 2008 in an agricultural area just north of Sana'a city, where water wells have been drying up according to the well data. The subsidence rate was lower in the urban areas, or approximately 1 cm/year, exhibiting annual variations. The main subsidence was found in the center and southern parts of the city, while deformation in the northern part is less obvious. For the Mabar basin, the subsidence rate exceeded 30 cm/year in the agricultural area north of the town of Mabar during 2007 - 2011. The southern part of the Mabar basin also experienced high subsidence rates, although somewhat lower than to the north. Excessive water pumping is the main cause of the ground subsidence and it has already led to extensive ground fracturing at the edge of some

  14. Rapid groundwater-related land subsidence in Yemen observed by multi-temporal InSAR

    KAUST Repository

    Abdullin, Ayrat

    2015-04-01

    Several basins in Yemen are suffering from a rapid drawdown of groundwater, which is the most important water source for agricultural irrigation, industry and domestic use. However, detailed geodetic measurements in the region have been lacking and the extent and magnitude of groundwater-related land subsidence has been poorly known. We used 13 ascending ALOS and 15 descending Envisat images to study land subsidence of several basins in Yemen, with a special focus on the Sana\\'a and Mabar basins. From multitemporal synthetic aperture radar interferometric analysis (persistent scatterers (PS) and small baseline subsets (SBAS)) we examined the spatio-temporal behavior of the subsidence induced by depletion of groundwater aquifer systems from November 2003 to February 2011. In the interferometric data processing, we carefully chose interferogram pairs to minimize spatial and temporal decorrelation, because of high subsidence rates and the type of land cover. Our results show that the spatial pattern of subsidence remained quite stable during the observation period in both the Sana\\'a and Mabar basins. In the Sana\\'a basin, the maximum subsidence rate exceeded 14 cm/year in the radar line-of-sight (LOS) direction between 2003 and 2008 in an agricultural area just north of Sana\\'a city, where water wells have been drying up according to the well data. The subsidence rate was lower in the urban areas, or approximately 1 cm/year, exhibiting annual variations. The main subsidence was found in the center and southern parts of the city, while deformation in the northern part is less obvious. For the Mabar basin, the subsidence rate exceeded 30 cm/year in the agricultural area north of the town of Mabar during 2007 - 2011. The southern part of the Mabar basin also experienced high subsidence rates, although somewhat lower than to the north. Excessive water pumping is the main cause of the ground subsidence and it has already led to extensive ground fracturing at the edge

  15. Monitoring of the temporal and spatial variation of groundwater storage in the Three Gorges area based on the CORS network

    Science.gov (United States)

    Wang, Wei; Zhang, Chuanyin; Liang, Shiming; Yang, Qiang; Hu, MinZhang; Feng, Wei

    2017-11-01

    The variation of groundwater storage is not well understood due to the complex hydrodynamic environment in the Three Gorges area. The variation of monthly groundwater storage from January 2011 to June 2015 was directly inverted in the Three Gorges area of China based on 26 Continuously Operating Reference Station (CORS) and eight gravity stations with a resolution of 2‧ × 2‧ using the Earth's gravity field and the load deformation theory. The results were then compared with the water level from groundwater monitoring wells. The comparison indicates that it is possible to calculate the temporal and spatial variation of groundwater with high precision based on the continuous observation data of CORS and a small amount of gravity stations. Our analysis shows that the groundwater storage was consistent in the Three Gorges area from 2011 to 2014. The Three Gorges Reservoir has a large impact on the variation of groundwater storage. The variation of the groundwater storage derived from CORS agrees well with that of the groundwater monitoring wells. The new data are important references for the research of hydrodynamic environmental change in the Three Gorges area and for the analysis of the impact of water impoundment and drainage in the Three Gorges Reservoir.

  16. Long-term spatio-temporal drought variability in Turkey

    Science.gov (United States)

    Dabanlı, İsmail; Mishra, Ashok K.; Şen, Zekai

    2017-09-01

    The spatio-temporal variability of drought is presented by evaluating homogeneously distributed 250 station records from 1931 to 2010 for 80 years' duration in Turkey. The drought analysis is implemented using Standardized Precipitation Index (SPI) in terms of SPI-1, SPI-3, SPI-6, SPI-6AS (SPI-6 April to September) and SPI-12. The principle component analysis (PCA) is applied to SPI time series to identify spatial and temporal drought patterns. SPI time series are classified into two groups (1st group: SPI-1, SPI-3, SPI-6AS; and 2nd group: SPI-6 and SPI-12) according to the similarity in spatial drought patterns. SPI-3 and SPI-12 are selected as representative members of each group for spatio-temporal analysis. A relationship among correlation area (An), correlation coefficient (CC), principle component numbers (Fn) and total variances explained (Vexp) are investigated for identifying four well-defined drought vulnerable homogeneous regions over Turkey mainland. Mean percentages of extreme, severe, and moderate drought areas are calculated as 3.13% (2.81%), 3.75% (4.06%) and 7.19% (7.50%) for SPI-3 (SPI-12) based on 80 years in all drought vulnerable regions. Spectral characteristics of drought are also investigated based on fast Fourier transform (FFT) method. It is observed that while southeastern and western parts of Turkey are more stable due to the highly-correlated variances of spatial patterns; central parts and few pockets in northern areas of Turkey are less stable regions because of the low-correlated variance scores (below 10%). Furthermore, the impact of extreme phases of the ENSO (El Nino/La Nina) on droughts in four drought regions over Turkey is discussed.

  17. Spatial variability of groundwater recharge and its effect on shallow groundwater quality in southern New Jersey

    Science.gov (United States)

    Nolan, Bernard T.; Baehr, Arthur L.; Kauffman, Leon J.

    2003-01-01

    Point estimates of groundwater recharge at 48 sediment-coring locations vary substantially (−18.5–1840 cm yr−1) in a 930-km2 area of southern New Jersey. Darcian estimates of steady, long-term recharge made at depth in the unsaturated zone were estimated using pedotransfer functions of soil texture and interpolated (mapped) with nonparametric methods to assess aquifer vulnerability in the area. The probability of exceeding the median recharge (29.1 cm yr−1) is low in the southwestern and northeastern portions of the study area and high in the eastern and southeastern portions. Estimated recharge is inversely related to measured percentage clay and positively related to the percentage of well-drained soils near wells. Spatial patterns of recharge estimates, exceedance probabilities, and clay content indicate that sediment texture controls recharge in the study area. Relations with land elevation and a topographic wetness index were statistically insignificant. Nitrate concentration and atrazine (6-chloro-N 2-ethyl-N 4-isopropyl-1,3,5-triazine-2,4-diamine) percentage detection in samples of shallow groundwater (typically 29.1 cm yr−1) in agricultural and urban areas. Differences between high and low recharge sites in these areas are highly significant for NO3 concentration, but not for atrazine concentration.

  18. Temporal variations of groundwater tables and implications for submarine groundwater discharge: a 3-decade case study in central Japan

    Directory of Open Access Journals (Sweden)

    B. Zhang

    2017-07-01

    Full Text Available Fresh submarine groundwater discharge (SGD is the key pathway of flux and nutrients for the groundwater from land to the ocean. SGD flux is a current issue of discussion and a means to clarify the coastal marine system under climate change. SGD flux accounts for about one-quarter of the river runoff in the Katakai alluvial fan in Uozu, Toyama, Japan, which is an ideal area to study SGD flux considering the need for a rapid response to climate change and the prior research on SGD there. In this paper, the monthly groundwater table's condition over 30 years is analyzed using monthly rainfall, snowfall, and the climate change index. Rainfall has been on an upward trend, but the snowfall has decreased over 40 years. Furthermore, the groundwater table at monitoring wells in the coastal area increased, as a result of the increased rainfall. However, the relationship between snowfall and groundwater is negative. As expected by Darcy's law, SGD flux was controlled by the hydraulic gradient of the coastal groundwater. The estimated historic SGD flux by groundwater table variation shows an upward trend of SGD. Considering the increase in precipitation and the groundwater table, SGD flux may increase under climate change.

  19. Spatial and temporal study of nitrate concentration in groundwater by means of coregionalization

    Science.gov (United States)

    D'Agostino, V.; Greene, E.A.; Passarella, G.; Vurro, M.

    1998-01-01

    Spatial and temporal behavior of hydrochemical parameters in groundwater can be studied using tools provided by geostatistics. The cross-variogram can be used to measure the spatial increments between observations at two given times as a function of distance (spatial structure). Taking into account the existence of such a spatial structure, two different data sets (sampled at two different times), representing concentrations of the same hydrochemical parameter, can be analyzed by cokriging in order to reduce the uncertainty of the estimation. In particular, if one of the two data sets is a subset of the other (that is, an undersampled set), cokriging allows us to study the spatial distribution of the hydrochemical parameter at that time, while also considering the statistical characteristics of the full data set established at a different time. This paper presents an application of cokriging by using temporal subsets to study the spatial distribution of nitrate concentration in the aquifer of the Lucca Plain, central Italy. Three data sets of nitrate concentration in groundwater were collected during three different periods in 1991. The first set was from 47 wells, but the second and the third are undersampled and represent 28 and 27 wells, respectively. Comparing the result of cokriging with ordinary kriging showed an improvement of the uncertainty in terms of reducing the estimation variance. The application of cokriging to the undersampled data sets reduced the uncertainty in estimating nitrate concentration and at the same time decreased the cost of the field sampling and laboratory analysis.Spatial and temporal behavior of hydrochemical parameters in groundwater can be studied using tools provided by geostatistics. The cross-variogram can be used to measure the spatial increments between observations at two given times as a function of distance (spatial structure). Taking into account the existence of such a spatial structure, two different data sets (sampled

  20. A reconnaissance spatial and temporal assessment of methane and inorganic constituents in groundwater in bedrock aquifers, Pike County, Pennsylvania, 2012-13

    Science.gov (United States)

    Senior, Lisa A.

    2014-01-01

    Pike County in northeastern Pennsylvania is underlain by the Devonian-age Marcellus Shale and other shales, formations that have potential for natural gas development. During 2012–13, the U.S. Geological Survey in cooperation with the Pike County Conservation District conducted a reconnaissance study to assess baseline shallow groundwater quality in bedrock aquifers prior to possible shale-gas development in the county. For the spatial component of the assessment, 20 wells were sampled in summer 2012 to provide data on the occurrence of methane and other aspects of existing groundwater quality throughout the county, including concentrations of inorganic constituents commonly present at low levels in shallow, fresh groundwater but elevated in brines. For the temporal component of the assessment, 4 of the 20 wells sampled in summer 2012 were sampled monthly from July 2012 through June 2013 to provide data on seasonal variability in groundwater quality. All water samples were analyzed for major ions, nutrients, selected inorganic trace constituents (including metals and other elements), stable isotopes of water, radon-222, gross alpha- and gross beta-particle activity, dissolved gases (methane, ethane, and ethene), and, if possible, isotopic composition of methane. Additional analyses for boron and strontium isotopes, age-dating of water, and radium-226 were done on water samples collected from six wells in June 2013.

  1. Bacteriophage Distributions and Temporal Variability in the Ocean's Interior.

    Science.gov (United States)

    Luo, Elaine; Aylward, Frank O; Mende, Daniel R; DeLong, Edward F

    2017-11-28

    productivity. To better understand these viral assemblages, we conducted genomic analyses of planktonic viruses over a seasonal cycle to ocean depths of 1,000 m. We identified 172,385 different viral gene families and 129 unique virus genotypes in this open-ocean setting. The spatiotemporal distributions of the most abundant open-ocean viruses that we report here provide new insights into viral temporal variability, life history, and virus-host-environment interactions throughout the water column. Copyright © 2017 Luo et al.

  2. Assessing variability of water quality in a groundwater-fed perennial ...

    Indian Academy of Sciences (India)

    Assessing variability of water quality in a groundwater-fed perennial lake of Kashmir Himalayas using linear geostatistics. S Sarah1,∗, Gh Jeelani2 and Shakeel Ahmed1. 1IFCGR, National Geophysical Research Institute, CSIR, Hyderabad 500 606, India. 2Department of Geology and Geophysics, University of Kashmir, ...

  3. Temporal analysis of text data using latent variable models

    DEFF Research Database (Denmark)

    Mølgaard, Lasse Lohilahti; Larsen, Jan; Goutte, Cyril

    2009-01-01

    Detecting and tracking of temporal data is an important task in multiple applications. In this paper we study temporal text mining methods for Music Information Retrieval. We compare two ways of detecting the temporal latent semantics of a corpus extracted from Wikipedia, using a stepwise...

  4. The active liquid Earth - importance of temporal and spatial variability

    Science.gov (United States)

    Arheimer, Berit

    2016-04-01

    The Planet Earth is indeed liquid and active - 71 percent of its surface is water-covered and this water never rests. Thanks to the water cycle, our planet's water supply is constantly moving from one place to another and from one form to another. Only 2.5% of the water is freshwater and it exists in the air as water vapor; it hits the ground as rain and snow; it flows on the surface from higher to lower altitudes in rivers, lakes, and glaciers; and it flows in the ground in soil, aquifers, and in all living organisms until it reaches the sea. On its way over the Earth's crust, some returns quickly to vapor again, while some is trapped and exposed to many "fill and spill" situations for a long journey. The variability in the water balance is crucial for hydrological understanding and modelling. The water cycle may appear simple, but magnitudes and rates in fluxes are very different from one place to another, resulting from variable drivers such as solar energy, precipitation and gravity in co-evolution with geology, soil, vegetation and fauna. The historical evolution, the temporal fluxes and diversity in space continue to fascinate hydrological scientists. Specific physical processes may be well known, but their boundary conditions, interactions and rate often remain unknown at a specific site and are difficult to monitor in nature. This results in mysterious features where trends in drivers do not match runoff, like the Sahelian Paradox or discharge to the Arctic Ocean. Humans have always interfered with the water cycle and engineering is fundamental for water regulation and re-allocation. Some 80% of the river flow from the northern part of the Earth is affected by fragmentation of the river channels by dams. In water management, there is always a tradeoff between upstream and downstream activities, not only regarding total water quantities but also for temporal patterns and water quality aspects. Sharing a water resource can generate conflicts but geopolitical

  5. Enhanced Groundwater Recharge Rates and Altered Recharge Sensitivity to Climate Variability Through Subsurface Heterogeneity

    Science.gov (United States)

    Hartmann, Andreas; Gleeson, Tom; Wada, Yoshihide; Wagener, Thorsten

    2017-01-01

    Our environment is heterogeneous. In hydrological sciences, the heterogeneity of subsurface properties, such as hydraulic conductivities or porosities, exerts an important control on water balance. This notably includes groundwater recharge, which is an important variable for efficient and sustainable groundwater resources management. Current large-scale hydrological models do not adequately consider this subsurface heterogeneity. Here we show that regions with strong subsurface heterogeneity have enhanced present and future recharge rates due to a different sensitivity of recharge to climate variability compared with regions with homogeneous subsurface properties. Our study domain comprises the carbonate rock regions of Europe, Northern Africa, and the Middle East, which cover 25 of the total land area. We compare the simulations of two large-scale hydrological models, one of them accounting for subsurface heterogeneity. Carbonate rock regions strongly exhibit karstification, which is known to produce particularly strong subsurface heterogeneity. Aquifers from these regions contribute up to half of the drinking water supply for some European countries. Our results suggest that water management for these regions cannot rely on most of the presently available projections of groundwater recharge because spatially variable storages and spatial concentration of recharge result in actual recharge rates that are up to four times larger for present conditions and changes up to five times larger for potential future conditions than previously estimated. These differences in recharge rates for strongly heterogeneous regions suggest a need for groundwater management strategies that are adapted to the fast transit of water from the surface to the aquifers.

  6. Spatial and temporal variability of Mediterranean drought events

    Science.gov (United States)

    Trigo, R.; Sousa, P.; Nieto, R.; Gimeno, L.

    2009-04-01

    The original Palmer Drought Severity Index (PDSI) and a recent adaptation to European soil characteristics, the Self Calibrated PDSI (or scPDSI) proposed by Schrier et al (2005) were used. We have computed monthly, seasonal and annual trends between 1901 and 2000 but also for the first and second halves of the 20th century. Results were represented only when achieving a minimum level of statistical significance (either 5% or 10% using a Mann-Kendall test) and confirm that the majority of the western and central Mediterranean is getting drier in the last decades of the 20th century while Turkey is generally getting wetter (Trigo et al., 2006). The spatio-temporal variability of these indices was evaluated with an EOF analysis, in order to reduce the large dimensionality of the fields under analysis. Spatial representation of the first EOF patterns shows that EOF 1 covers the entire Mediterranean basin (16.4% of EV), while EOF2 is dominated by a W-E dipole (10% EV). The following EOF patterns present smaller scale features, and explain smaller amounts of variance. The EOF patterns have also facilitated the definition of four sub-regions with large socio-economic relevance: 1) Iberia, 2) Italian Peninsula, 3) Balkans and 4) Turkey. The inter-annual variability of the regional spatial droughts indices for each region was analyzed separately. We have also performed an evaluation of their eventual links with large-scale atmospheric circulation indices that affect the Mediterranean basin, namely the NAO, EA, and SCAND. Finally we have evaluated the main sources of moisture affecting two drought prone areas in the western (Iberia) and eastern (Balkans) Mediterranean. This analysis was performed by means of backward tracking the air masses that ultimately reach these two regions using the Lagrangian particle dispersion model FLEXPART (Stohl et al., 1998) and meteorological analysis data from the ECMWF to track atmospheric moisture. This was done for a five-year period (2000

  7. Monitoring studies should consider temporal variability to reveal relations between cyanobacterial abundance and environmental variables

    Directory of Open Access Journals (Sweden)

    JULIANA WOJCIECHOWSKI

    2015-09-01

    Full Text Available One of the main goals of monitoring cyanobacteria blooms in aquatic environments is to reveal the relationship between cyanobacterial abundance and environmental variables. Studies typically correlate data that were simultaneously sampled. However, samplings occur sparsely over time and may not reveal the short-term responses of cyanobacterial abundance to environmental changes. In this study, we tested the hypothesis that stronger cyanobacteria x environment relationships in monitoring are found when the temporal variability of sampling points is incorporated in the statistical analyses. To this end, we investigated relationships between cyanobacteria and seven environmental variables that were sampled twice yearly for three years across 11 reservoirs, and data from an intensive monitoring in one of these reservoirs. Poor correlations were obtained when correlating data simultaneously sampled. In fact, the 'highly recurrent' role of phosphorus in cyanobacteria blooms is not properly observed in all sampling periods. On the other hand, the strongest correlation values for the total phosphorus x cyanobacteria relationship were observed when we used the variation of sampling points. We have also shown that environment variables better explain cyanobacteria when a time lag is considered. We conclude that, in cyanobacteria monitoring, the best approach to reveal determinants of cyanobacteria blooms is to consider environmental variability.

  8. Long-term trends and spatial variability of shallow groundwater temperatures beneath Bratislava

    Science.gov (United States)

    Krcmar, David; Benz, Susanne A.; Bayer, Peter; Blum, Philipp; Stankova, Hana

    2017-04-01

    Shallow groundwater temperatures are closely linked to surface temperatures. In recent years several studies have shown that the effects from atmospheric warming can be observed in rural groundwater temperature measurements. However, urban groundwater temperatures are different. Especially shallow aquifers show temperatures that change with the evolution of a city. Temperatures are locally variable and regionally higher when compared to undisturbed rural environments. For several cities, particularly in cold and temperate climate zones, pronounced subsurface urban heat islands have been reported with groundwater temperatures that are increased by several degrees compared to their rural surrounding. Heat release from basements and other urban infrastructure has been identified as a major heat source, superposing the effects from atmospheric warming. A major challenge still is to distinguish between the anthropogenic urban effects and the influence from climate change. In our study, we focus on the conditions in the city of Bratislava in Slovakia, where productive aquifers are hosted by the sediments in the Danube river valley. At selected wells, long-term groundwater temperature measurements have been recorded since the year 2002. These temperature time series are measured in shallow depth and therefore show substantial seasonal variations. Each temperature time series is compared to satellite-derived land surface temperature trends, and a clear correlation is found that supports the strong coupling between atmospheric, land surface and groundwater temperatures. Additionally, it is now possible to analyze the main differences between these two temperature trends for all selected wells and relate them to location specific cases of urban infrastructure that influence groundwater temperatures but not land surface temperatures.

  9. Do we need a spatially and temporally variable observation error?

    Science.gov (United States)

    Mladenova, I. E.; Bolten, J. D.; Crow, W. T.; de Jeu, R. A. M.; Cosh, M. H.; Walker, J. P.

    2016-12-01

    It is well known that the accuracy of hydrologic models is highly dependent on the quality of the precipitation data used to force the model. Data assimilation (DA) enables us to address this limitation through the integration of independent observations derived from satellite-based systems into the model. In a way, DA can be regarded as a merging technique where the model predictions and the satellite observations are combined through a set of error parameters that inform the system how much weight should be put on the observations. For example, a small observation error would put less weight to the model forecast and make the analysis to draw closer to the observation. There are a number of ways to model the observation error. The simplest approach is to assume a global average, which results into a temporally and spatially stable value. However, the accuracy of passive-based soil moisture (SM) retrievals is variable in space and time and strongly depends on the density of the overlying canopy layer. Thus, conceptually, a more appropriate approach is to model the observation error as a function of some vegetation-related parameter. Here we explore a new methodology modeling the observation error as a function of vegetation optical depth data (VOD), which provides information on not only the spatial, but also the seasonal and possibly the inter-annual variability of the observation error. Thus, our objectives are (1) to evaluate the potential to use VOD to model the observation error and (2) to examine the benefit of dynamically adjusting the error in both space and time scales consistent with the SM observations. The analysis was done using Land Parameter Retrieval Model-based SM and VOD retrievals obtained from the Advanced Microwave Scanning Radiometer 2 (AMSR2) mission (C-/X-band) and the Soil Moisture Ocean Salinity (SMOS) instrument (L-band; theoretically it should offer higher sensitivity to soil moisture as compared to C-/X-band). Thus, an additional

  10. Interests of long-term hydrogeological observatories for characterizing and modelling heterogeneous groundwater systems at multiple temporal and spatial scales: the example of Ploemeur, a crystalline rock aquifer (Brittany).

    Science.gov (United States)

    Bour, Olivier; Longuervergne, Laurent; Le Borgne, Tanguy; Lavenant, Nicolas; de Dreuzy, Jean-Raynald; Schuite, Jonathan; Labasque, Thierry; Aquilina, Luc; Davy, Philippe

    2017-04-01

    Characterizing groundwater flows and surface interactions in heterogeneous groundwater systems such as crystalline fractured rock is often extremely complex. In particular, hydraulic properties are highly variable while groundwater chemical properties may vary both in space and time, especially due to the impact of groundwater abstraction. Here, we show the interest of hydrological observatories and long-term monitoring for characterizing hydrological processes occurring in a crystalline rock aquifer. We present results from the site of Ploemeur (French Brittany) that belongs to the network of hydrogeological sites H+ and the research infrastructure OZCAR, and where interdisciplinary and integrated research at multiple temporal and spatial scales has been developed for almost twenty years. This outstandingly heterogeneous crystalline rock aquifer is also used for groundwater supply since 1991. In particular, we show how cross-borehole flowmeter tests, pumping tests and a frequency domain analysis of groundwater levels allow quantifying the hydraulic properties of the aquifer at different scales. In addition, groundwater temperature evolution was used as an excellent tracer for characterizing groundwater flow. At the site scale, measurements of ground surface deformation through long-base tiltmeters provide robust estimates of aquifer storage and allow identifying the active structures, including those acting during recharge process. Finally, a numerical model of the watershed scale that combines hydraulic data and groundwater ages confirms the geometry of this complex aquifer and the consistency of the different datasets. In parallel, this hydrological observatory is also used for developing hydrogeophysical methods and to characterize groundwater transport and biogeochemical reactivity in the sub-surface. The Ploemeur hydrogeological observatory is a good example of the interest of focusing research activities on a site during long-term as it provides a thorough

  11. Assessing Climate Change Impacts on Large-Scale Soil Moisture, its Temporal Variability and Associated Drought-Flood Risks

    Science.gov (United States)

    Destouni, G.; Verrot, L.

    2015-12-01

    Soil moisture is a dynamic variable of great importance for water cycling and climate, as well as for ecosystems and societal sectors such as agriculture. Model representation of soil moisture and its temporal variability is, for instance, central for assessing the impacts of hydro-climatic change on drought and flood risks. However, our ability to assess such impacts and guide appropriate mitigation and adaptation measures is challenged by the need to link data and modeling across a range of spatiotemporal scales of relevance for the variability and change of soil moisture in long-term time series. This paper synthesizes recent advances for meeting this challenge by a relatively simple, analytical, data-driven approach to modeling the variability and change of large-scale soil moisture under long-term hydro-climatic change. Model application to two major Swedish drainage basins, and model-data comparison for ten study catchments across the United States shows the model ability to reproduce variability dynamics in long-term data series of the key soil-moisture variables: unsaturated water content and groundwater table position. The Swedish application shows that human-driven hydro-climatic shifts may imply increased risk for hydrological drought (runoff-related) and agricultural drought (soil moisture-related), even though meteorological drought risk (precipitation-related) is unchanged or lowered. The direct model-data comparison for ten U.S. catchments further shows good model representation of seasonal and longer-term fluctuation timings and frequencies for water content and groundwater level, along with physically reasonable model tendency to underestimate the local fluctuation magnitudes. Overall, the tested modeling approach can fulfill its main aim of screening long-term time series of large-scale hydro-climatic data (historic or projected for the future by climate modeling) for relatively simple, unexaggerated assessment of variability and change in key

  12. Temporal dynamics of groundwater-surface water interaction under the effects of climate change: A case study in the Kiskatinaw River Watershed, Canada

    Science.gov (United States)

    Saha, Gopal Chandra; Li, Jianbing; Thring, Ronald W.; Hirshfield, Faye; Paul, Siddhartho Shekhar

    2017-08-01

    Groundwater-surface water (GW-SW) interaction plays a vital role in the functioning of riparian ecosystem, as well as sustainable water resources management. In this study, temporal dynamics of GW-SW interaction were investigated under climate change. A case study was chosen for a study area along the Kiskatinaw River in Mainstem sub-watershed of the Kiskatinaw River Watershed, British Columbia, Canada. A physically based and distributed GW-SW interaction model, Gridded Surface Subsurface Hydrologic Analysis (GSSHA), was used. Two different greenhouse gas (GHG) emission scenarios (i.e., A2: heterogeneous world with self-reliance and preservation of local identities, and B1: more integrated and environmental friendly world) of SRES (Special Report on Emissions Scenarios) from Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) were used for climate change study for 2020-2040. The simulation results showed that climate change influences significantly the temporal patterns of GW-SW interaction by generating variable temporal mean groundwater contributions to streamflow. Due to precipitation variability, these contributions varied monthly, seasonally, and annually. The mean annual groundwater contribution to streamflow during 2020-2040 under the A2 and B1 scenarios is expected to be 74.5% (σ = 2%) and 75.6% (σ = 3%), respectively. As compared to that during the base modeling period (2007-2011), the mean annual groundwater contribution to streamflow during 2020-2040 under the A2 and B1 scenarios is expected to decrease by 5.5% and 4.4%, respectively, due to the increased precipitation (on average 6.7% in the A2 and 4.8% in the B1 scenarios) and temperature (on average 0.83 °C in the A2 and 0.64 °C in the B1 scenarios). The results obtained from this study will provide useful information in the long-term seasonal and annual water extractions from the river for future water supply, as well as for evaluating the ecological conditions of the

  13. Spatial-temporal variability in GHG fluxes and their functional interpretation in RusFluxNet

    Science.gov (United States)

    Vasenev, Ivan; Meshalkina, Julia; Sarzhanov, Dmitriy; Mazirov, Ilia; Yaroslavtsev, Alex; Komarova, Tatiana; Tikhonova, Maria

    2016-04-01

    different meso- or micro-relief forms, natural or man-made succession studies, topsoil texture or organic matter state, subsoil or perched groundwater features. Zonal, seasonal and functional subdividing the monitoring data allows essentially increase the regression links between GHG fluxes and air or soil temperature and moisture (to 0.75-0.87) that is very important for their modeling and prediction. In taiga and mix-forest zones usually there is stronger effect on GHG fluxes by air temperature than soil one due to comparatively thin (from 3 till 10 cm) layer of principal soil organic and/or humus-accumulative horizons with maximum biological activity that usually determines the total rate of GHG soil fluxes. Unfavorable seasonal conditions (dry season or low temperature) determine essential (in 1.5-2 times) decreasing not only in soil GHG fluxes but in level of their spatial variability, intraseasonal and daily dynamics too. These trends are most obvious in case of more open and sensitive to the external factors ecosystems, for example in case of industrial area lawns or at the first stages of the windthrow or fallow-forest successions. Understanding the principal regional and land-use-determined regularities of spatial and temporal changes in ecosystem and soil GHG fluxes help better modeling them in the process of spatial intra- and extrapolations, seasonal and interseasonal predictions, taking into attention basic and current principal ecological factors limiting GHG fluxes and balances. Their introduction in the ecological or agroecological models and land-use decision support systems allows improve the quality of environmental/agroecological monitoring and control not only for GHG emission but also for soil organic matter conservation, manure and nitrogen fertilizer application that is often crucially important for sustainable rural development and profitable farming.

  14. Radon hazard in shallow groundwaters: Amplification and long term variability induced by rainfall

    Energy Technology Data Exchange (ETDEWEB)

    De Francesco, S., E-mail: stefano.defrancesco@unina2.it [Department of Environmental Sciences, Second University of Naples, Via Vivaldi, 43, 81100 Caserta (Italy); Tommasone, F. Pascale [Office of Civil Protection, Meteorology, Climatology and Natural Hazards, Piazza Municipio, 81051 Pietramelara, Caserta (Italy); Cuoco, E.; Verrengia, G. [Department of Environmental Sciences, Second University of Naples, Via Vivaldi, 43, 81100 Caserta (Italy); Tedesco, D. [Department of Environmental Sciences, Second University of Naples, Via Vivaldi, 43, 81100 Caserta (Italy); C.N.R. (Italian Council for Research), Institute of Environmental Geology and Geological Engineering, Piazzale Aldo Moro, 00100 Roma (Italy)

    2010-01-15

    {sup 222}Rn concentrations have been determined with a RAD7 radon detector in shallow groundwaters of the Pietramelara Plain, north-western Campania, southern Italy, where pyroclastic deposits, along with recent stream alluvial sediments, come in contact with Mesozoic carbonate reservoirs. The aim of this study has been to study the annual variation of {sup 222}Rn concentration in the shallow groundwaters, scarcely considered in the literature and of obvious relevance for radon hazard evaluation. Our results definitely show that {sup 222}Rn levels are characterized by a clear annual periodicity, strictly related to rainfall and water table levels, with a pronounced difference between the dry and the wet season. In this last case with concentrations increasing up to two orders of magnitude (up to two times the lower threshold given in the Recommendation 2001/928/EURATOM for public waters). In relation to this, experimental field data will be presented to demonstrate that this variability is due to purely hydrological mechanisms, mainly rinse out and discharge that control leaching efficiency. The detected cycle (Radon Hydrological Amplification Cycle, RHAC) has been generalized for the Mediterranean Tyrrhenian climate. The marked and seasonally persistent amplification in {sup 222}Rn levels poses the problem of evaluating the epidemiological risk brought up by this previously not yet reported mechanism. This mechanism, occurring in shallow groundwaters, very likely should strongly influence indoor radon levels via groundwater-soil-building exchange.

  15. Documentation for the State Variables Package for the Groundwater-Management Process of MODFLOW-2005 (GWM-2005)

    Science.gov (United States)

    Ahlfeld, David P.; Barlow, Paul M.; Baker, Kristine M.

    2011-01-01

    Many groundwater-management problems are concerned with the control of one or more variables that reflect the state of a groundwater-flow system or a coupled groundwater/surface-water system. These system state variables include the distribution of heads within an aquifer, streamflow rates within a hydraulically connected stream, and flow rates into or out of aquifer storage. This report documents the new State Variables Package for the Groundwater-Management Process of MODFLOW-2005 (GWM-2005). The new package provides a means to explicitly represent heads, streamflows, and changes in aquifer storage as state variables in a GWM-2005 simulation. The availability of these state variables makes it possible to include system state in the objective function and enhances existing capabilities for constructing constraint sets for a groundwater-management formulation. The new package can be used to address groundwater-management problems such as the determination of withdrawal strategies that meet water-supply demands while simultaneously maximizing heads or streamflows, or minimizing changes in aquifer storage. Four sample problems are provided to demonstrate use of the new package for typical groundwater-management applications.

  16. MODELING OF RELATIONSHIP BETWEEN GROUNDWATER FLOW AND OTHER METEOROLOGICAL VARIABLES USING FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    Şaban YURTÇU

    2006-02-01

    Full Text Available In this study, modeling of the effect of rainfall, flow and evaporation as independent variables on the change of underground water levels as dependent variables were investigated by fuzzy logic (FL. In the study, total 396 values taken from six observation stations belong to Afyon inferior basin in Akarçay from 1977 to 1989 years were used. Using the monthly average values of stations, the change of underground water level was modeled by FL. It is observed that the results obtained from FL and the observations are compatible with each other. This shows FL modeling can be used to estimate groundwater levels from the appropriate meteorological value.

  17. Enhanced groundwater recharge rates and altered recharge sensitivity to climate variability through subsurface heterogeneity

    Science.gov (United States)

    Hartmann, Andreas; Gleeson, Tom; Wagener, Thorsten

    2017-01-01

    Our environment is heterogeneous. In hydrological sciences, the heterogeneity of subsurface properties, such as hydraulic conductivities or porosities, exerts an important control on water balance. This notably includes groundwater recharge, which is an important variable for efficient and sustainable groundwater resources management. Current large-scale hydrological models do not adequately consider this subsurface heterogeneity. Here we show that regions with strong subsurface heterogeneity have enhanced present and future recharge rates due to a different sensitivity of recharge to climate variability compared with regions with homogeneous subsurface properties. Our study domain comprises the carbonate rock regions of Europe, Northern Africa, and the Middle East, which cover ∼25% of the total land area. We compare the simulations of two large-scale hydrological models, one of them accounting for subsurface heterogeneity. Carbonate rock regions strongly exhibit “karstification,” which is known to produce particularly strong subsurface heterogeneity. Aquifers from these regions contribute up to half of the drinking water supply for some European countries. Our results suggest that water management for these regions cannot rely on most of the presently available projections of groundwater recharge because spatially variable storages and spatial concentration of recharge result in actual recharge rates that are up to four times larger for present conditions and changes up to five times larger for potential future conditions than previously estimated. These differences in recharge rates for strongly heterogeneous regions suggest a need for groundwater management strategies that are adapted to the fast transit of water from the surface to the aquifers. PMID:28242703

  18. Spatial and temporal variability in recruitment of intertidal mussels ...

    African Journals Online (AJOL)

    IntenSity of intertidal mussel recruitment was compared across a range of different spatial and temporal scales around the coast of southern Africa between June 1995 and October 1996. Comparison of the east and west coasts revealed significantly higher recruit densities on the west coast, corresponding to larger adult ...

  19. Spatial and temporal variability in recruitment of intertidal mussels ...

    African Journals Online (AJOL)

    Intensity of intertidal mussel recruitment was compared across a range of different spatial and temporal scales around the coast of southern Africa between June 1995 and October 1996. Comparison of the east and west coasts revealed significantly higher recruit densities on the west coast, corresponding to larger adult ...

  20. Temporal and Spatial variability in Reef fish Density and Biomass ...

    African Journals Online (AJOL)

    Underwater Visual Census (UVC) techniques were used for the assessment of reef fish density and biomass, and line intercept transect (LIT) was used for the estimation of benthic cover. Results showed that there was a significant seasonal and temporal variation in fish density and biomass at both Mbundya and Bongoyo ...

  1. Regional variability of nitrate fluxes in the unsaturated zone and groundwater, Wisconsin, USA

    Science.gov (United States)

    Green, Christopher T.; Liao, Lixia; Nolan, Bernard T.; Juckem, Paul F.; Shope, Christopher L.; Tesoriero, Anthony J.; Jurgens, Bryant

    2018-01-01

    Process-based modeling of regional NO3− fluxes to groundwater is critical for understanding and managing water quality, but the complexity of NO3− reactive transport processes make implementation a challenge. This study introduces a regional vertical flux method (VFM) for efficient estimation of reactive transport of NO3− in the vadose zone and groundwater. The regional VFM was applied to 443 well samples in central-eastern Wisconsin. Chemical measurements included O2, NO3−, N2 from denitrification, and atmospheric tracers of groundwater age including carbon-14, chlorofluorocarbons, tritium, and tritiogenic helium. VFM results were consistent with observed chemistry, and calibrated parameters were in-line with estimates from previous studies. Results indicated that (1) unsaturated zone travel times were a substantial portion of the transit time to wells and streams (2) since 1945 fractions of applied N leached to groundwater have increased for manure-N, possibly due to increased injection of liquid manure, and decreased for fertilizer-N, and (3) under current practices and conditions, approximately 60% of the shallow aquifer will eventually be affected by downward migration of NO3−, with denitrification protecting the remaining 40%. Recharge variability strongly affected the unsaturated zone lag times and the eventual depth of the NO3− front. Principal components regression demonstrated that VFM parameters and predictions were significantly correlated with hydrogeochemical landscape features. The diverse and sometimes conflicting aspects of N management (e.g. limiting N volatilization versus limiting N losses to groundwater) warrant continued development of large-scale holistic strategies to manage water quality and quantity.

  2. Groundwater Depletion in Dhaka City, Bangladesh: A Spatio-temporal Analysis

    Science.gov (United States)

    Jerin, T.; Ishtiaque, A.

    2015-12-01

    Dhaka city, having a population of more than fifteen million, exclusively depends on groundwater as a source of quality drinking water. In recent decades the city is encountering groundwater diminution and the declining scenario is dissimilar in different parts of the city. This paper aims to discuss the groundwater depletion in different parts of Dhaka city from 1990 to 2012 along with the causes and consequences. Groundwater level data of different locations of Dhaka city were collected from Bangladesh Water Development Board (BWDB). The data were processed and analyzed using SPSS and Excel Worksheet; a contour map was generated using ArcGIS 10.0 to outline the contemporary groundwater scenario of Dhaka city and the spatial analyst tool, Inverse Distance Weighted (IDW) was used to prepare the map. In addition, experts' opinions were collected using an in-depth interview strategy in order to provide a better understanding of the causes and consequences of groundwater depletion. The research results show that groundwater in Dhaka city is depleting at an alarming rate; the central part has the worst situation followed by the south-western part. In contrast, northern part has relatively better groundwater condition. Moreover, the peripheral zone exhibits a better condition because of the existence of rivers and wetlands. The interviews reveal that population density and overexploitation are mainly responsible for groundwater depletion; however, various other factors such as the deliberate establishment of deep tube wells, reduction of recharge capacity due to rapid growth of urban structures altogether results in huge drop of water level throughout the city. Rapid decline in groundwater augments the city's exposure towards multiple risks including land subsidence, groundwater pollution and most importantly, paucity of available fresh water that might ultimately results into an urban disaster. Potential solutions to ameliorate this situation include urban greening

  3. Spatial and temporal variability of N2O emissions in a subtropical forest catchment in China

    Directory of Open Access Journals (Sweden)

    J. Zhu

    2013-03-01

    Full Text Available Subtropical forests in southern China have received chronically large amounts of atmogenic nitrogen (N, causing N saturation. Recent studies suggest that a significant proportion of the N input is returned to the atmosphere, in part as nitrous oxide (N2O. We measured N2O emission fluxes by closed chamber technique throughout two years in a Masson pine-dominated headwater catchment with acrisols (pH ~ 4 at Tieshanping (Chongqing, SW China and assessed the spatial and temporal variability in two landscape elements typical for this region: a mesic forested hillslope (HS and a hydrologically connected, terraced groundwater discharge zone (GDZ in the valley bottom. High emission rates of up to 1800 μg N2O-N m−2 h−1 were recorded on the HS shortly after rain storms during monsoonal summer, whereas emission fluxes during the dry winter season were generally low. Overall, N2O emission was lower in GDZ than on HS, rendering the mesic HS the dominant source of N2O in this landscape. Temporal variability of N2O emissions on HS was largely explained by soil temperature (ST and moisture, pointing at denitrification as a major process for N removal and N2O production. The concentration of nitrate (NO3− in pore water on HS was high even in the rainy season, apparently never limiting denitrification and N2O production. The concentration of NO3− decreased along the terraced GDZ, indicating efficient N removal, but with moderate N2O-N loss. The extrapolated annual N2O fluxes from soils on HS (0.54 and 0.43 g N2O-N m−2 yr−1 for a year with a wet and a dry summer, respectively are among the highest N2O fluxes reported from subtropical forests so far. Annual N2O-N emissions amounted to 8–10% of the annual atmogenic N deposition, suggesting that forests on acid soils in southern China are an important, hitherto overlooked component of the anthropogenic N2O budget.

  4. Cation exchange in a temporally fluctuating thin freshwater lens on top of saline groundwater

    NARCIS (Netherlands)

    Eeman, S.; Louw, de P.G.B.; Zee, van der S.E.A.T.M.

    2017-01-01

    In coastal-zone fields with a high groundwater level and sufficient rainfall, freshwater lenses are formed on top of saline or brackish groundwater. The fresh and the saline water meet at shallow depth, where a transition zone is found. This study investigates the mixing zone that is characterized

  5. Spatial and temporal small-scale variation in groundwater quality of a shallow sandy aquifer

    DEFF Research Database (Denmark)

    Bjerg, Poul Løgstrup; Christensen, Thomas Højlund

    1992-01-01

    The groundwater quality of a shallow unconfined sandy aquifer has been characterized for pH, alkalinity, chloride, nitrate, sulfate, calcium, magnesium, sodium and potassium in terms of vertical and horizontal variations (350 groundwater samples). The test area is located within a farmland lot...

  6. Irrigation as an Adaptation Strategy to Climate Change: The Relative Influence of Groundwater and Canal Irrigation on Winter Crop Production and its Sensitivity to Weather Variability in India

    Science.gov (United States)

    Jain, M.; Fishman, R.; Mondal, P.; Galford, G. L.; Naeem, S.; Modi, V.; DeFries, R. S.

    2014-12-01

    India is a hotspot for food security issues over the upcoming decades, due to increasing population pressures, groundwater depletion, and climate change. Investing in additional irrigation infrastructure may bolster food security, however, the relative influence of different types of irrigation (e.g. groundwater versus canal) on agricultural production remains unclear. One reason that the relative impact of different irrigation strategies on agricultural production has not been analyzed across India is because national-scale data on crop production and the types of irrigation technologies used are typically available at too coarse of spatial and temporal resolutions to answer this question adequately. Thus, we develop a novel algorithm to map cropped area across India at a 1 x 1 km scale using MODIS satellite data, and link these high-resolution cropped area maps with village-level data (n = 600,000) on irrigation. This allowed us to assess the relative impact of groundwater (i.e. dug, shallow, and deep wells) and canal irrigation (i.e. surface lift and flow canals) on winter cropped area and its sensitivity to rainfall across India at the village-scale from 2000 to 2006. We find that deep well irrigation is both associated with the greatest amount of winter cropped area, and is also the least sensitive to monsoon and winter rainfall variability. However, the effectiveness of deep well irrigation varies across India, with the greatest benefits seen in the regions that are most at risk for losing groundwater as a possible source of irrigation over the upcoming decades (e.g. Northwest India). This work highlights the need to develop ways to use remaining groundwater more efficiently (e.g. drip irrigation, less water-intensive crops) given that canal irrigation is not an adequate substitute, particularly in the regions that are facing the greatest levels of groundwater depletion.

  7. Exploring the Effects of Climate Variability and Land Use Change on Groundwater-Surface Water Interactions

    Science.gov (United States)

    Duncan, L. L.; Hornberger, G. M.

    2013-12-01

    Locke Island is a 3.5-km long and 375-m wide differentially cemented sand and gravel, mid-channel island located in the Hanford Reach of the Columbia River. Across the eastern channel of the Columbia River from the island is the large Locke Island landslide complex, originating from the White Bluffs. There is evidence that landslides occurred along the White Bluffs in prehistoric times, within the last 11,000 years or so, and evidence of younger landslides, active in the last several hundred years. Irrigation of the land adjacent to the bluffs, and subsequent creation of unlined irrigation wastewater ponds behind the bluffs, is one of the hypotheses concerning the major cause of modern landsliding in this area, which began in the late 1960s. The estimated eight-fold increase in water delivered to the semi-arid area over the course of a decade resulted in an increase in the annual flow through the groundwater system. Similar to land use impacts, changes in the flow through groundwater systems as a result of variations in climate can alter groundwater-surface water exchange processes and connectivity too. We use a vertical two-dimensional finite element model to simulate variably saturated and unsaturated flow in the subsurface porous media along a cross-section of the hillslope-river-island continuum. Our work characterizes the hydraulic gradients and quantifies the outflows at the toe of the landslide and along the banks of the island, in response to creation of ponds behind the bluffs and decadal to multi-decadal changes in patterns of dryness. Understanding the effects of climate variability and land use change on groundwater-surface water exchanges, both separately and in combination, provides insight to the relative importance of these different mechanisms in landslide activity.

  8. Temporal abiotic variability structures invertebrate communities in agricultural drainage ditches

    NARCIS (Netherlands)

    Whatley, M.H.; Vonk, J.A.; van der Geest, H.G.; Admiraal, W.

    2015-01-01

    Abiotic variability is known to structure lotic invertebrate communities, yet its influence on lentic invertebrates is not clear. This study tests the hypothesis that variability of nutrients and macro-ions are structuring invertebrate communities in agricultural drainage ditches. This was

  9. Effects of temporal changes in climate variables on crop production ...

    African Journals Online (AJOL)

    Administrator

    Key words: Climate variability, crop yield and production, regional climate projections, South-western Nigeria. INTRODUCTION. The variability of the ... continuously facing an immediate risk of increased crop failure and loss of livestock. ... ral productivity may assist in proffering management strategies for a sustainable and ...

  10. Temporal analysis of groundwater nitrate concentrations from wells in Prince Edward Island, Canada: application of a linear mixed effects model

    Science.gov (United States)

    Benson, Victoria S.; Vanleeuwen, John A.; Stryhn, Henrik; Somers, George H.

    2007-08-01

    Changes in nitrate concentration in groundwater from wells in Prince Edward Island, Canada were investigated over time using two datasets. Temporal trends in groundwater nitrate concentrations were assessed annually during 1981-1996 (1,299 observations), and both seasonally and monthly during 1988-1991 (1,868 observations). Data were analysed using linear mixed models with random effects and correlation structures. The average nitrate concentration in the monthly dataset was 3.99 mg/L as NO3-N, with January, May, and November concentrations being higher ( p = 0.018). A seasonal effect was present when season was combined with land use type in an interaction term ( p = 0.004). Wells located in agricultural areas had greater nitrate concentrations than urban areas, which in turn, had greater values than low human-impact areas. Row-cropped areas had higher groundwater nitrate concentrations in the summer, whereas manure storage areas were higher in the spring and autumn. Nitrate in groundwater in areas with low human impact and with centralized sewage disposal infrastructure remained relatively low and stable throughout the seasons. There was no significant annual trend ( p = 0.954), but for individual sites, 9.6% significantly increased in nitrate concentration over time, and 6.6% significantly decreased over time.

  11. Evaluation of groundwater discharge into small lakes based on the temporal distribution of radon-222

    Science.gov (United States)

    Dimova, N.T.; Burnett, W.C.

    2011-01-01

    In order to evaluate groundwater discharge into small lakes we constructed a model that is based on the budget of 222Rn (radon t1/2 5 3.8 d) as a tracer. The main assumptions in our model are that the lake's waters are wellmixed horizontally and vertically; the only significant 222Rn source is via groundwater discharge; and the only losses are due to decay and atmospheric evasion. In order to evaluate the groundwater-derived 222Rn flux, we monitored the 222Rn concentration in lake water over periods long enough (usually 1-3 d) to observe changes likely caused by variations in atmospheric exchange (primarily a function of wind speed and temperature). We then attempt to reproduce the observed record by accounting for decay and atmospheric losses and by estimating the total 222Rn input flux using an iterative approach. Our methodology was tested in two lakes in central Florida: one of which is thought to have significant groundwater inputs (Lake Haines) and another that is known not to have any groundwater inflows but requires daily groundwater augmentation from a deep aquifer (Round Lake). Model results were consistent with independent seepage meter data at both Lake Haines (positive seepage of ??? 1.6 ?? 104 m3 d-1 in Mar 2008) and at Round Lake (no net groundwater seepage). ?? 2011, by the American Society of Limnology and Oceanography, Inc.

  12. Variability in clinical assessment of neuroimaging in temporal lobe epilepsy.

    Science.gov (United States)

    Struck, Aaron F; Westover, Michael B

    2015-08-01

    Neuroimaging is critical in deciding candidacy for epilepsy surgery. Currently imaging is primarily assessed qualitatively, which may affect patient selection and outcomes. The epilepsy surgery database at MGH was reviewed for temporal lobectomy patients from the last 10 years. Radiology reports for MRI and FDG-PET were compared to the epilepsy conference consensus. First, specific findings of ipsi/contra hippocampal atrophy and T2 signal changes were directly compared. Next the overall impression of presence of hippocampal sclerosis (HS) for MRI and temporal hypometabolism for PET was used for sensitivity/specificity analysis. To assess predictive power of imaging findings logistic regression was used. 104 subjects were identified. 70% of subjects were ILAE class I at 1-year. Radiology reports and the conference consensus differed in 31% of FDG-PET studies and 41% of MRIs. For PET most disagreement (50%) stemmed for discrepancy regarding contralateral temporal hypometabolism. For MRI discrepancy in ipsilateral hippocampal atrophy/T2 signal accounted for 59% of disagreements. When overall impression of the image was used the overall reliability between groups was high with only MRI sensitivity to detect HS (0.75 radiology, 0.91 conference, p=0.02) was significantly different between groups. On logistic regression MRI was a significant predictor of HS, but still 36% of patients with normal MRI as read by both groups had HS on pathology. Despite some difference in specific radiologic findings, overall accuracy for MRI and PET is similar in clinical practice between radiology and conference; nonetheless there are still cases of hippocampal pathology not detected by standard imaging methods. Copyright © 2015 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

  13. Comparison of stochastic and deterministic methods for mapping groundwater level spatial variability in sparsely monitored basins.

    Science.gov (United States)

    Varouchakis, Epsilon A; Hristopulos, D T

    2013-01-01

    In sparsely monitored basins, accurate mapping of the spatial variability of groundwater level requires the interpolation of scattered data. This paper presents a comparison of deterministic interpolation methods, i.e. inverse distance weight (IDW) and minimum curvature (MC), with stochastic methods, i.e. ordinary kriging (OK), universal kriging (UK) and kriging with Delaunay triangulation (DK). The study area is the Mires Basin of Mesara Valley in Crete (Greece). This sparsely sampled basin has limited groundwater resources which are vital for the island's economy; spatial variations of the groundwater level are important for developing management and monitoring strategies. We evaluate the performance of the interpolation methods with respect to different statistical measures. The Spartan variogram family is applied for the first time to hydrological data and is shown to be optimal with respect to stochastic interpolation of this dataset. The three stochastic methods (OK, DK and UK) perform overall better than the deterministic counterparts (IDW and MC). DK, which is herein for the first time applied to hydrological data, yields the most accurate cross-validation estimate for the lowest value in the dataset. OK and UK lead to smooth isolevel contours, whilst DK and IDW generate more edges. The stochastic methods deliver estimates of prediction uncertainty which becomes highest near the southeastern border of the basin.

  14. Temporal variability of mass transport across Canary Islands Channels

    Science.gov (United States)

    Marrero-Díaz, Ángeles; Rodríguez-Santana, Ángel; José Machín, Francisco; García-Weil, Luis; Sangrà, Pablo; Vélez-Belchí, Pedro; Fraile-Nuez, Eugenio

    2014-05-01

    The equatorward flowing Canary Current (CC) is the main feature of the circulation in the Canary Islands region. The CC flow perturbation by the Canary Islands originate the Canary Eddy Corridor which is the major pathway for long lived eddies in the subtropical North Atlantic (Sangrà et al., 2009, DSR). Therefore the variability of the CC passing through the Canary Archipelago will have both local and regional importance. Past studies on the CC variability trough the Canary Islands point out a clearly seasonal variability (Fraile-Nuez et al, 2010 (JGR); Hernández-Guerra et al, 2002 (DSR)). However those studies where focused on the eastern islands channels missing the variability through the western island channels which are the main source of long lived eddies. In order to fill this gap from November 2012 until September 2013 we conducted trimonthly surveys crossing the whole islands channels using opportunity ships (Naviera Armas Ferries). XBT and XCTD where launched along the cross channels transects. Additionally a closed box circling the Archipelago was performed on October 2013 as part of the cruise RAPROCAN-2013 (IEO) using also XBT and XCTD. Dynamical variables where derived inferring salinity from S(T,p) analytical relationships for the region updated with new XCTD data. High resolution, vertical sections of temperature, potential density, geostrophic velocity and transport where obtained. Our preliminary results suggest that the CC suffer a noticeable acceleration in those islands channels where eddy shedding is more frequent. They also indicate a clearly seasonal variability of the flows passing the islands channels. With this regard we observed significant differences on the obtained seasonal variability with respect the cited past studies on the eastern islands channel (Lanzarote / Fuerteventura - Africa coast). This work was co-funded by Canary Government (TRAMIC project: PROID20100092) and the European Union (FEDER).

  15. Spatial and temporal variability of biophysical variables in southwestern France from airborne L-band radiometry

    Directory of Open Access Journals (Sweden)

    E. Zakharova

    2012-06-01

    Full Text Available In 2009 and 2010 the L-band microwave Cooperative Airborne Radiometer for Ocean and Land Studies (CAROLS campaign was performed in southwestern France to support the calibration and validation of the new Soil Moisture and Ocean Salinity (SMOS satellite mission. The L-band Microwave Emission of the Biosphere (L-MEB model was used to retrieve surface soil moisture (SSM and the vegetation optical depth (VOD from the CAROLS brightness temperature measurements. The CAROLS SSM was compared with in situ observations at 11 sites of the SMOSMANIA (Soil Moisture Observing System-Meteorological Automatic Network Integrated Application network of Météo-France. For eight of them, significant correlations were observed (0.51 ≤ r ≤ 0.82, with standard deviation of differences ranging from 0.039 m3 m−3 to 0.141 m3 m−3. Also, the CAROLS SSM was compared with SSM values simulated by the A-gs version of the Interactions between Soil, Biosphere and Atmosphere (ISBA-A-gs model along 20 flight lines, at a resolution of 8 km × 8 km. A significant spatial correlation between these two datasets was observed for all the flights (0.36 ≤ r ≤ 0.85. The CAROLS VOD presented significant spatial correlations with the vegetation water content (VWC derived from the spatial distribution of vegetation types used in ISBA-A-gs and from the Leaf Area Index (LAI simulated for low vegetation. On the other hand, the CAROLS VOD presented little temporal changes, and no temporal correlation was observed with the simulated LAI. For low vegetation, the ratio of VOD to VWC tended to decrease, from springtime to summertime. The ISBA-A-gs grid cells (8 km × 8 km were sampled every 5 m by CAROLS observations, at a spatial resolution of about 2 km. For 83% of the grid cells, the standard deviation of the sub-grid CAROLS SSM was lower than 0.05 m3 m−3. The presence of small water bodies within the

  16. GROUNDWATER RESPONSE TO WEATHER VARIABILITY IN A POOR AQUIFER UNIT: AN EXAMPLE FROM TROPICAL BASEMENT COMPLEX ROCK OF NIGERIA

    Directory of Open Access Journals (Sweden)

    Eniola D. Ashaolu

    2015-01-01

    Full Text Available More than 50 % of Nigeria is underlain by basement complex rock which is a poor aquifer unit and evidences abound that the climate of Nigeria is changing. The posing question is how this poor aquifer will respond to the vagaries of climate variability and change. However, understanding the response of groundwater to climate variability and change in Nigeria will be hampered by dearth of data, because the nature of change in groundwater is not monitored. On this basis, the study tried to understand how groundwater responds to weather variability in a poor aquifer unit of Ilara-mokin and its environs in the tropical area of Nigeria. Rainfall and temperature data for forty years (1973-2012 were collected from NIMET and groundwater level were monitored in the area for two years (2012-2014.The general trends in rainfall and temperature received in the last forty years were examined using regression analysis and moving average. The dry and wet episodes were also examined using Standard Rainfall Anomalies Index (SAI. Also, the percentage changes in the rainfall and temperature received were determined using reduction pattern analysis. The response of groundwater to weather variability was however established using Pearson Moment Correlation and multiple regression analysis. The results of the analyses revealed an average of six years dry episode every decade in the last 40 years. The temperature of the study area is increasing in the last 20 years. Groundwater responded negatively to temperature but positively to rainfall in the area. Rainfall and temperature accounted for 67 % of variability in monthly groundwater level. This study is a good starting point in understanding groundwater response to climate in poor aquifer units of Nigeria despite the dearth of data.

  17. Monitoring spatial-temporal variability of aerosol over Kenya ...

    African Journals Online (AJOL)

    Validation of MODIS AOD using Aerosol Robotic Network (AERONET) indicated that MODIS overestimated the aerosol loading over the study region. Space time variability of MODIS AOD measurements over Kenya showed a decreasing trend in aerosol loading with a long term mean of between 0.02 and 0.56.

  18. Rainfall–runoff temporal variability in Kermanshah province, Iran ...

    Indian Academy of Sciences (India)

    Investigation of changes in rainfall and runoff patterns in various regions and determining their relationship in the sense of hydrology and climatology are of great importance, considering those patterns efficiently reveal the human and natural factors in this variability. One of the mathematical methods to recognise and model ...

  19. Partitioning and analyzing temporal variability of wash and bed ...

    Indian Academy of Sciences (India)

    southern Arizona, the wash load concentration could be predicted by rainfall better than water discharge. Gellis (2013) studied the significant characteristics controlling the variability in storm generated suspended sediment loads and concen- trations in four watersheds with different land uses in humid-tropical Puerto Rico.

  20. Effects of temporal changes in climate variables on crop production ...

    African Journals Online (AJOL)

    Climate variability and change have been implicated to have significant impacts on global and regional food production particularly the common stable food crops performance in tropical sub-humid climatic zone. However, the extent and nature of these impacts still remain uncertain. In this study, records of crop yields and ...

  1. Temporal and spatial variability of rainfall distribution and ...

    African Journals Online (AJOL)

    Analysis of rainfall variability is made by the rainfall anomaly index, coefficient of variance and precipitation concentration index. The FAO-56 reference ET (ETo) approach was used to determine the amount of evapotranspiration. Estimation of the onset, end of growing season and length of growing period was done using ...

  2. The Trade-Off between Spatial and Temporal Variabilities in Reciprocal Upper-Limb Aiming Movements of Different Durations

    NARCIS (Netherlands)

    Danion, Frederic; Bongers, Raoul M.; Bootsma, Reinoud J.

    2014-01-01

    The spatial and temporal aspects of movement variability have typically been studied separately. As a result the relationship between spatial and temporal variabilities remains largely unknown. In two experiments we examined the evolution and covariation of spatial and temporal variabilities over

  3. Addressing Groundwater Declines with Precision Agriculture: An Economic Comparison of Monitoring Methods for Variable-Rate Irrigation

    OpenAIRE

    Grant H. West; Kent Kovacs

    2017-01-01

    Irrigated row-crop agriculture is contributing to declining groundwater in areas such as the Mississippi Delta region of eastern Arkansas. There is a need to move toward sustainable levels of groundwater withdrawal. Recent improvements in remote monitoring technologies such as wireless soil moisture sensors and unmanned aerial vehicles offer the potential for farmers to effectively practice site-specific variable-rate irrigation management for the purpose of applying water more efficiently, r...

  4. Spatial and temporal variability of precipitation and drought in Portugal

    Directory of Open Access Journals (Sweden)

    D. S. Martins

    2012-05-01

    Full Text Available The spatial variability of precipitation and drought are investigated for Portugal using monthly precipitation from 74 stations and minimum and maximum temperature from 27 stations, covering the common period of 1941–2006. Seasonal precipitation and the corresponding percentages in the year, as well as the precipitation concentration index (PCI, was computed for all 74 stations and then used as an input matrix for an R-mode principal component analysis to identify the precipitation patterns. The standardized precipitation index at 3 and 12 month time scales were computed for all stations, whereas the Palmer Drought Severity Index (PDSI and the modified PDSI for Mediterranean conditions (MedPDSI were computed for the stations with temperature data. The spatial patterns of drought over Portugal were identified by applying the S-mode principal component analysis coupled with varimax rotation to the drought indices matrices. The result revealed two distinct sub-regions in the country relative to both precipitation regimes and drought variability. The analysis of time variability of the PC scores of all drought indices allowed verifying that there is no linear trend indicating drought aggravation or decrease. In addition, the analysis shows that results for SPI-3, SPI-12, PDSI and MedPDSI are coherent among them.

  5. Spatial and temporal variability of rainfall erosivity factor for Switzerland

    Directory of Open Access Journals (Sweden)

    K. Meusburger

    2012-01-01

    Full Text Available Rainfall erosivity, considering rainfall amount and intensity, is an important parameter for soil erosion risk assessment under future land use and climate change. Despite its importance, rainfall erosivity is usually implemented in models with a low spatial and temporal resolution. The purpose of this study is to assess the temporal- and spatial distribution of rainfall erosivity in form of the (Revised Universal Soil Loss Equation R-factor for Switzerland. Time series of 22 yr for rainfall (10 min resolution and temperature (1 h resolution data were analysed for 71 automatic gauging stations distributed throughout Switzerland. Regression-kriging was used to interpolate the rainfall erosivity values of single stations and to generate a map for Switzerland. Latitude, longitude, average annual precipitation, biogeographic units (Jura, Midland, etc., aspect and elevation were used as covariates, of which average annual precipitation, elevation and the biographic unit (Western Central Alps were significant (p<0.01 predictors. The mean value of long-term rainfall erosivity is 1330 MJ mm ha−1 h−1 yr−1 with a range of lowest values of 124 MJ mm ha−1 h−1 yr−1 at an elevated station in Grisons to highest values of 5611 MJ mm ha−1 h−1 yr−1 in Ticino. All stations have highest erosivity values from July to August and lowest values in the winter months. Swiss-wide the month May to October show significantly increasing trends of rainfall erosivity for the observed period (p<0.005. Only in February a significantly decreasing trend of rainfall erosivity is found (p<0.01. The increasing trends of rainfall erosivity in May, September and October when vegetation cover is scarce are likely to enhance soil erosion risk for certain agricultural crops and alpine grasslands in Switzerland.

  6. Temporal Variability of Microplastic Concentrations in Freshwater Streams

    Science.gov (United States)

    Watkins, L.; Walter, M. T.

    2016-12-01

    Plastic pollution, specifically the size fraction less than 5mm known as microplastics, is an emerging contaminant in waterways worldwide. The ability of microplastics to adsorb and transport contaminants and microbes, as well as be ingested by organisms, makes them a concern in both freshwater and marine ecosystems. Recent efforts to determine the extent of microplastic pollution are increasingly focused on freshwater systems, but most studies have reported concentrations at a single time-point; few have begun to uncover how plastic concentrations in riverine systems may change through time. We hypothesize the time of day and season of sampling influences the concentrations of microplastics in water samples and more specifically, that daytime stormflow samples contain the highest microplastic concentrations due to maximized runoff and wastewater discharge. In order to test this hypothesis, we sampled in two similar streams in Ithaca, New York using a 333µm mesh net deployed within the thalweg. Repeat samples were collected to identify diurnal patterns as well as monthly variation. Samples were processed in the laboratory following the NOAA wet peroxide oxidation protocol. This work improves our ability to interpret existing single-time-point survey results by providing information on how microplastic concentrations change over time and whether concentrations in existing stream studies are likely representative of their location. Additionally, these results will inform future studies by providing insight into representative sample timing and capturing temporal trends for the purposes of modeling and of developing regulations for microplastic pollution.

  7. Spatial-temporal pattern recognition of groundwater head variations for recharge zone identification

    Science.gov (United States)

    Tsai, Jui-Pin; Chang, Liang-Cheng; Chang, Ping-Yu; Lin, Yuan-Chien; Chen, You-Cheng; Wu, Meng-Ting; Yu, Hwa-Lung

    2017-06-01

    The delineation of groundwater recharge zones is crucial for the conservation of groundwater quality and quantity. To objectively estimate groundwater recharge zones, many field surveys are required that are costly in both time and money. To facilitate the assessment of recharge zones with high efficiency and low expense, this study proposes a 'fast-filter' approach based on empirical orthogonal function analysis and applies it in a synthetic case study and to Taiwan's Yilan Plain. In the synthetic case study, we demonstrate that the proposed method can effectively identify the recharge area by considering the head variations driven by rainfall recharge. For the case of Yilan Plain application, the field investigations (i.e., collected wellbore logs and electrical resistivity tomography [ERT] surveys) and a groundwater simulation model support the recharge zones estimated by the proposed method. The study results show that within the estimated recharge zone, all of the collected wellbore logs consist of coarse grains, and thick and continuous high resistivity zones were shown in the ERT profile images. Moreover, the groundwater model indicates that the recharge within the estimated recharge zone is 57.6% of the total recharge despite that the area of the estimated zone is only 26.8% of the study area. Therefore, the proposed method is shown to delineate recharge zones at low cost.

  8. Representing spatial and temporal complexity in ecohydrological models: a meta-analysis focusing on groundwater - surface water interactions

    Science.gov (United States)

    McDonald, Karlie; Mika, Sarah; Kolbe, Tamara; Abbott, Ben; Ciocca, Francesco; Marruedo, Amaia; Hannah, David; Schmidt, Christian; Fleckenstein, Jan; Karuse, Stefan

    2016-04-01

    Sub-surface hydrologic processes are highly dynamic, varying spatially and temporally with strong links to the geomorphology and hydrogeologic properties of an area. This spatial and temporal complexity is a critical regulator of biogeochemical and ecological processes within the interface groundwater - surface water (GW-SW) ecohydrological interface and adjacent ecosystems. Many GW-SW models have attempted to capture this spatial and temporal complexity with varying degrees of success. The incorporation of spatial and temporal complexity within GW-SW model configuration is important to investigate interactions with transient storage and subsurface geology, infiltration and recharge, and mass balance of exchange fluxes at the GW-SW ecohydrological interface. Additionally, characterising spatial and temporal complexity in GW-SW models is essential to derive predictions using realistic environmental conditions. In this paper we conduct a systematic Web of Science meta-analysis of conceptual, hydrodynamic, and reactive and heat transport models of the GW-SW ecohydrological interface since 2004 to explore how these models handled spatial and temporal complexity. The freshwater - groundwater ecohydrological interface was the most commonly represented in publications between 2004 and 2014 with 91% of papers followed by marine 6% and estuarine systems with 3% of papers. Of the GW-SW models published since 2004, the 52% have focused on hydrodynamic processes and heat and reactive transport). Within the hydrodynamic subset, 25% of models focused on a vertical depth of concepts that underpin these current modelling approaches is critical for scientists to develop measures to derive predictions from realistic environmental conditions at management relevant scales and establish best-practice modelling approaches for improving the scientific understanding and management of the GW-SW interface. Additionally, the assessment of current modelling approaches informs our proposed

  9. Spatial and temporal variability of the Black Sea suboxic zone

    Science.gov (United States)

    Glazer, Brian T.; Luther, George W.; Konovalov, Sergey K.; Friederich, Gernot E.; Trouwborst, Robert E.; Romanov, Alexander S.

    2006-08-01

    We coupled an in situ electrochemical analyzer to a CTD to conduct high-resolution, real-time profiling of redox species across the oxic-anoxic transition zone of the Black Sea water column. Voltammetry was performed using gold-amalgam working electrodes to measure simultaneously soluble oxygen and sulfur species (H 2S/HS -, Sx2-, S 8) at a resolution of greater than one measurement per meter. In situ data agreed with measurements made in an on-deck voltammetry flow cell coupled to a pump profiling system, and from water samples collected with conventional CTD rosette bottle casts. In situ voltammetric analyses provided rapid redox information, thus enabling more accurate targeting of specific geochemical features by the CTD rosette package. We observed much less lateral oxygen injection from the Bosphorus in 2003 (less than 95 km from Bosphorus) than in 2001 (up to 150 km). This difference can be attributed to variability in physical processes including seasonal temperature and wind variations between winter conditions (2003) and early summer conditions (2001). Furthermore, suboxic zone thickness varied basin-wide, exhibiting changes in the depth of oxygen extinction (minimum detection limit=3 μM) and sulfide onset (minimum detection limit=30 nM). The density surface for oxygen extinction was more variable than the density for the onset of sulfide. Vertical shifts in oxygen extinction and sulfide onset also were observed at the western central gyre station for seven profiles measured over 21 days in 2003.

  10. Spatial and temporal variability in seasonal snow density

    KAUST Repository

    Bormann, Kathryn J.

    2013-03-01

    Snow density is a fundamental physical property of snowpacks used in many aspects of snow research. As an integral component in the remote sensing of snow water equivalent and parameterisation of snow models, snow density may be used to describe many important features of snowpack behaviour. The present study draws on a significant dataset of snow density and climate observations from the United States, Australia and the former Soviet Union and uses regression-based techniques to identify the dominant climatological drivers for snow densification rates, characterise densification rate variability and estimate spring snow densities from more readily available climate data. Total winter precipitation was shown to be the most prominent driver of snow densification rates, with mean air temperature and melt-refreeze events also found to be locally significant. Densification rate variance is very high at Australian sites, very low throughout the former Soviet Union and between these extremes throughout much of the US. Spring snow densities were estimated using a statistical model with climate variable inputs and best results were achieved when snow types were treated differently. Given the importance of snow density information in many snow-related research disciplines, this work has implications for current methods of converting snow depths to snow water equivalent, the representation of snow dynamics in snow models and remote sensing applications globally. © 2013 Elsevier B.V.

  11. Coastal upwelling south of Madagascar: Temporal and spatial variability

    Science.gov (United States)

    Ramanantsoa, Juliano D.; Krug, M.; Penven, P.; Rouault, M.; Gula, J.

    2018-02-01

    Madagascar's southern coastal marine zone is a region of high biological productivity which supports a wide range of marine ecosystems, including fisheries. This high biological productivity is attributed to coastal upwelling. This paper provides new insights on the structure, variability and drivers of the coastal upwelling south of Madagascar. Satellite remote sensing is used to characterize the spatial extent and strength of the coastal upwelling. A front detection algorithm is applied to thirteen years of Multi-scale Ultra-high Resolution (MUR) Sea Surface Temperatures (SST) and an upwelling index is calculated. The influence of winds and ocean currents as drivers of the upwelling is investigated using satellite, in-situ observations, and a numerical model. Results reveal the presence of two well-defined upwelling cells. The first cell (Core 1) is located in the southeastern corner of Madagascar, and the second cell (Core 2) is west of the southern tip of Madagascar. These two cores are characterized by different seasonal variability, different intensities, different upwelled water mass origins, and distinct forcing mechanisms. Core 1 is associated with a dynamical upwelling forced by the detachment of the East Madagascar Current (EMC), which is reinforced by upwelling favourable winds. Core 2 appears to be primarily forced by upwelling favourable winds, but is also influenced by a poleward eastern boundary flow coming from the Mozambique Channel. The intrusion of Mozambique Channel warm waters could result in an asynchronicity in seasonality between upwelling surface signature and upwelling favourables winds.

  12. Joint propagation of variability and imprecision in assessing the risk of groundwater contamination

    Science.gov (United States)

    Baudrit, Cédric; Guyonnet, Dominique; Dubois, Didier

    2007-08-01

    Estimating risks of groundwater contamination often require schemes for representing and propagating uncertainties relative to model input parameters. The most popular method is the Monte Carlo method whereby cumulative probability distributions are randomly sampled in an iterative fashion. The shortcoming of the approach, however, arises when probability distributions are arbitrarily selected in situations where available information is incomplete or imprecise. In such situations, alternative modes of information representation can be used, for example the nested intervals known as "possibility distributions". In practical situations of groundwater risk assessment, it is common that certain model parameters may be represented by single probability distributions (representing variability) because there are data to justify these distributions, while others are more faithfully represented by possibility distributions (representing imprecision) due to the partial nature of available information. This paper applies two recent methods, designed for the joint-propagation of variability and imprecision, to a groundwater contamination risk assessment. Results of the joint-propagation methods are compared to those obtained using both interval analysis and the Monte Carlo method with a hypothesis of stochastic independence between model parameters. The two joint-propagation methods provide results in the form of families of cumulative distributions of the probability of exceeding a certain value of groundwater concentration. These families are delimited by an upper cumulative distribution and a lower distribution respectively called Plausibility and Belief after evidence theory. Slight differences between the results of the two joint-propagation methods are explained by the different assumptions regarding parameter dependencies. Results highlight the point that non-conservative results may be obtained if single cumulative probability distributions are arbitrarily selected

  13. Temporal variability and stability in infant-directed sung speech: evidence for language-specific patterns.

    Science.gov (United States)

    Falk, Simone

    2011-06-01

    In this paper, sung speech is used as a methodological tool to explore temporal variability in the timing of word-internal consonants and vowels. It is hypothesized that temporal variability/stability becomes clearer under the varying rhythmical conditions induced by song.This is explored crosslinguistically in German - a language that exhibits a potential vocalic quantity distinction - and the non-quantity languages French and Russian. Songs by non-professional singers, i.e. parents that sang to their infants aged 2 to 13 months in a non-laboratory setting, were recorded and analyzed.Vowel and consonant durations at syllable contacts of trochaic word types with CVCV or CV:CV structure were measured under varying rhythmical conditions. Evidence is provided that in German non-professional singing, the two syllable structures can be differentiated by two distinct temporal variability patterns: vocalic variability (and consonantal stability) was found to be dominant in CV:CV structures whereas consonantal variability (and vocalic stability) was characteristic for CVCV structures. In French and Russian, however, only vocalic variability seemed to apply.Additionally, findings suggest that the different temporal patterns found in German were also supported by the stability pattern at the tonal level. These results point to subtle (supra) segmental timing mechanisms in sung speech that affect temporal targets according to the specific prosodic nature of the language in question.

  14. Spatial and temporal variability of winds in the Northern European Seas

    DEFF Research Database (Denmark)

    Karagali, Ioanna; Badger, Merete; Hahmann, Andrea N.

    2013-01-01

    the spatial and temporal variability of the near-surface wind field, including the inter- and intra-annual variability for resource assessment purposes. This study demonstrates the applicability of satellite observations as the means to provide information useful for selecting areas to perform higher...

  15. Multi-technique assessment of spatial and temporal variability of methane fluxes in a peat meadow

    NARCIS (Netherlands)

    Hendriks, D.M.D.; van Huissteden, J.; Dolman, A.J.

    2010-01-01

    Methane fluxes measured in a eutrophic peat meadow in The Netherlands dominated by vascular plants showed high spatial and temporal variability. To elucidate this variability as well as the underlying processes, various measurement techniques were used: soil gradients of methane concentrations, the

  16. Spatial and temporal variability of guinea grass (Megathyrsus maximus) fuel loads and moisture on Oahu, Hawaii

    Science.gov (United States)

    Lisa M. Ellsworth; Creighton M. Litton; Andrew D. Taylor; J. Boone Kauffman

    2013-01-01

    Frequent wildfires in tropical landscapes dominated by non-native invasive grasses threaten surrounding ecosystems and developed areas. To better manage fire, accurate estimates of the spatial and temporal variability in fuels are urgently needed. We quantified the spatial variability in live and dead fine fuel loads and moistures at four guinea grass (...

  17. Characterization of oral and gut microbiome temporal variability in hospitalized cancer patients.

    Science.gov (United States)

    Galloway-Peña, Jessica R; Smith, Daniel P; Sahasrabhojane, Pranoti; Wadsworth, W Duncan; Fellman, Bryan M; Ajami, Nadim J; Shpall, Elizabeth J; Daver, Naval; Guindani, Michele; Petrosino, Joseph F; Kontoyiannis, Dimitrios P; Shelburne, Samuel A

    2017-02-28

    Understanding longitudinal variability of the microbiome in ill patients is critical to moving microbiome-based measurements and therapeutics into clinical practice. However, the vast majority of data regarding microbiome stability are derived from healthy subjects. Herein, we sought to determine intra-patient temporal microbiota variability, the factors driving such variability, and its clinical impact in an extensive longitudinal cohort of hospitalized cancer patients during chemotherapy. The stool (n = 365) and oral (n = 483) samples of 59 patients with acute myeloid leukemia (AML) undergoing induction chemotherapy (IC) were sampled from initiation of chemotherapy until neutrophil recovery. Microbiome characterization was performed via analysis of 16S rRNA gene sequencing. Temporal variability was determined using coefficients of variation (CV) of the Shannon diversity index (SDI) and unweighted and weighted UniFrac distances per patient, per site. Measurements of intra-patient temporal variability and patient stability categories were analyzed for their correlations with genera abundances. Groups of patients were analyzed to determine if patients with adverse outcomes had significantly different levels of microbiome temporal variability. Potential clinical drivers of microbiome temporal instability were determined using multivariable regression analyses. Our cohort evidenced a high degree of intra-patient temporal instability of stool and oral microbial diversity based on SDI CV. We identified statistically significant differences in the relative abundance of multiple taxa amongst individuals with different levels of microbiota temporal stability. Increased intra-patient temporal variability of the oral SDI was correlated with increased risk of infection during IC (P = 0.02), and higher stool SDI CVs were correlated with increased risk of infection 90 days post-IC (P = 0.04). Total days on antibiotics was significantly associated with increased

  18. On the Temporal Causal Relationship Between Macroeconomic Variables

    Directory of Open Access Journals (Sweden)

    Srinivasan Palamalai

    2014-02-01

    Full Text Available The present study examines the dynamic interactions among macroeconomic variables such as real output, prices, money supply, interest rate (IR, and exchange rate (EXR in India during the pre-economic crisis and economic crisis periods, using the autoregressive distributed lag (ARDL bounds test for cointegration, Johansen and Juselius multivariate cointegration test, Granger causality/Block exogeneity Wald test based on Vector Error Correction Model, variance decomposition analysis and impulse response functions. The empirical results reveal a stronger long-run bilateral relationship between real output, price level, IR, and EXR during the pre-crisis sample period. Moreover, the empirical results confirm a unidirectional short-run causality running from price level to EXR, IR to price level, and real output to money supply during the pre-crisis period. Also, it is evident from the test results that there exist short-run bidirectional relationships running between real output and EXR, price level and IR, and IR and EXR in the pre-crisis era, respectively. Most importantly, long-run bidirectional causality is found between real output, EXR, and IR during the economic crisis period. And the study results indicate short-run bidirectional causality between money supply and EXR, IR and price level, and IR and output in India during the crisis era. Also, a short-run unidirectional causality runs from prices to real output in the crisis period.

  19. Eastern Mediterranean Sea Spatial and Temporal Variability of Thermohaline Structure and Circulation Identified from Observational (T, S) Profiles

    Science.gov (United States)

    2015-12-01

    MEDITERRANEAN SEA SPATIAL AND TEMPORAL VARIABILITY OF THERMOHALINE STRUCTURE AND CIRCULATION IDENTIFIED FROM OBSERVATIONAL (T, S) PROFILES by Nuri...MEDITERRANEAN SEA SPATIAL AND TEMPORAL VARIABILITY OF THERMOHALINE STRUCTURE AND CIRCULATION IDENTIFIED FROM OBSERVATIONAL (T, S) PROFILES 5. FUNDING NUMBERS...variability of thermohaline structure and circulation were investigated. Surface depth shows high seasonal temperature variability through the year

  20. Application of water quality index to evaluate groundwater quality (temporal and spatial variation) of an intensively exploited aquifer (Puebla valley, Mexico).

    Science.gov (United States)

    Salcedo-Sánchez, Edith R; Garrido Hoyos, Sofía E; Esteller Alberich, Ma Vicenta; Martínez Morales, Manuel

    2016-10-01

    The spatial and temporal variation of water quality in the urban area of the Puebla Valley aquifer was evaluated using historical and present data obtained during this investigation. The current study assessed water quality based on the Water Quality Index developed by the Canadian Council of Ministers of the Environment (CCME-WQI), which provides a mathematical framework to evaluate the quality of water in combination with a set of conditions representing quality criteria, or limits. This index is flexible regarding the type and number of variables used by the evaluation given that the variables of interest are selected according to the characteristics and objectives of development, conservation and compliance with regulations. The CCME-WQI was calculated using several variables that assess the main use of the wells in the urban area that is public supply, according to criteria for human use and consumption established by Mexican law and international standards proposed by the World Health Organization. The assessment of the index shows a gradual deterioration in the quality of the aquifer over time, as the amount of wells with excellent quality have decreased and those with lower index values (poor quality) have increased throughout the urban area of the Puebla Valley aquifer. The parameters affecting groundwater quality are: total dissolved solids, sulfate, calcium, magnesium and total hardness.

  1. Variable thickness transient ground-water flow model. Volume 3. Program listings

    Energy Technology Data Exchange (ETDEWEB)

    Reisenauer, A.E.

    1979-12-01

    The Assessment of Effectiveness of Geologic Isolation Systems (AEGIS) Program is developing and applying the methodology for assessing the far-field, long-term post-closure safety of deep geologic nuclear waste repositories. AEGIS is being performed by Pacific Northwest Laboratory (PNL) under contract with the Office of Nuclear Waste Isolation (OWNI) for the Department of Energy (DOE). One task within AEGIS is the development of methodology for analysis of the consequences (water pathway) from loss of repository containment as defined by various release scenarios. Analysis of the long-term, far-field consequences of release scenarios requires the application of numerical codes which simulate the hydrologic systems, model the transport of released radionuclides through the hydrologic systems to the biosphere, and, where applicable, assess the radiological dose to humans. Hydrologic and transport models are available at several levels of complexity or sophistication. Model selection and use are determined by the quantity and quality of input data. Model development under AEGIS and related programs provides three levels of hydrologic models, two levels of transport models, and one level of dose models (with several separate models). This is the third of 3 volumes of the description of the VTT (Variable Thickness Transient) Groundwater Hydrologic Model - second level (intermediate complexity) two-dimensional saturated groundwater flow.

  2. Spatial and temporal variability of consanguinity in the French Cerdagne

    Directory of Open Access Journals (Sweden)

    Vigo, Marta

    1993-12-01

    Full Text Available In this paper we have studied consanguinity in the population of the French Cerdagne (a Pyrenean valley from 1836 until 1990. Calculation of consanguineous marriage frequencies and of the coefficient a reveals that consanguinity in this population is slightly lower than in other Pyrenean populations. Analysis of variability over time shows a decrease in the consanguinity levels during the above-mentioned period. The consanguinity pattern is similar in all parts of the area considered.

    [es] En este trabajo se ha estudiado la consanguinidad de la comarca pirenaica de la Cerdaña francesa desde 1836 a 1990. El cálculo de las frecuencias de matrimonios consanguíneos y del coeficiente a muestra que la consanguinidad de esta población es inferior, aunque no excesivamente, a la de otras poblaciones pirenaicas. El análisis de la evolución a lo largo del tiempo muestra un descenso de los niveles de consanguinidad durante todo el período estudiado. El modelo de consanguinidad es parecido en todas las zonas del área estudiada.
    [fr] Dans ce travail nous avons étudié la consanguinité de la région de la Cerdagne française dans les Pyrénées depuis 1836 jusqu'à 1990. Le calcule de la fréquence des mariages consanguins et de le coefficient a montrent que la consanguinité de cette population est inférieure, quoique pas excessivement, à celle d'autres populations des Pyrénées. L'analyse de l'évolution à travers le temps a démontré une réduction des niveaux de consanguinité pendant la période étudiée. Ce modèle de consanguinité est semblable dans toutes les zones de la région étudiée.

  3. Temporally variable dispersal and demography can accelerate the spread of invading species.

    Science.gov (United States)

    Ellner, Stephen P; Schreiber, Sebastian J

    2012-12-01

    We analyze how temporal variability in local demography and dispersal combine to affect the rate of spread of an invading species. Our model combines state-structured local demography (specified by an integral or matrix projection model) with general dispersal distributions that may depend on the state of the individual or its parent. It allows very general patterns of stationary temporal variation in both local demography and in the frequency and distribution of dispersal distances. We show that expressions for the asymptotic spread rate and its sensitivity to parameters, which have been derived previously for less general models, continue to hold. Using these results we show that random temporal variability in dispersal can accelerate population spread. Demographic variability can further accelerate spread if it is positively correlated with dispersal variability, for example if high-fecundity years are also years in which juveniles tend to settle further away from their parents. A simple model for the growth and spread of patches of an invasive plant (perennial pepperweed, Lepidium latifolium) illustrates these effects and shows that they can have substantial impacts on the predicted speed of an invasion wave. Temporal variability in dispersal has received very little attention in both the theoretical and empirical literature on invasive species spread. Our results suggest that this needs to change.

  4. Nitrate isotopic composition and ancillary variables (land use, redox, excess N2, age, water isotopics) in California groundwater

    Science.gov (United States)

    Veale, Nathan; Moran, Jean; Visser, Ate; Singleton, Michael; Esser, Bradley

    2017-04-01

    Nitrate is a critical water quality issue in California, the United States and the world. Lawrence Livermore National Laboratory (LLNL) has compiled a large, unique database of California groundwater nitrate isotopic compositions (δ15N-NO3 and δ18O-NO3), acquired largely through more than a decade of coordination with the State of California Groundwater Ambient Monitoring and Assessment (GAMA) program. The water samples are predominantly from shallow aquifers accessed by domestic and monitoring wells. The database of >1,300 nitrate isotopic compositions includes a number of important ancillary parameters: DO, ORP and DOC (measured for 18% of samples); excess air and dissolved N2 (24%); water isotopic composition (δ18O-H2O and δD-H2O) (43%); and tritium/3He groundwater age (27%). Methods used at LLNL include sample preparation by the denitrifier method (for δ15N-NO3 and δ18O-NO3) and Isotope Ratio Mass Spectrometry with (δ15N-NO3 and δ18O-NO3 and δ18O-H2O and δD-H2O), Noble Gas Mass Spectrometry (NGMS; for excess air and groundwater age), and Membrane Inlet Mass Spectrometry (MIMS; for major dissolved gases and excess N2). Redox indicators (DO, ORP and DOC) in conjunction with excess N2, groundwater age, and nitrate isotopic composition are used to assess the presence or absence, and potentially the rate of, saturated-zone denitrification. Comparison of δ18O-NO3 to δ18O-H2O isotopic composition is used to distinguish synthetic nitrate from nitrification of reduced forms of nitrogen as a source of groundwater nitrate. Groundwater age is used to discern timing and temporal trends in groundwater nitrate isotopic composition. The relationship of nitrate isotopic composition to ancillary parameters (redox, excess N2, water isotopic composition and groundwater age) is explored, along with its relationship to well location, screened interval, and land use, with a focus on the extent of saturated-zone denitrification and the significance of synthetic nitrate as

  5. Characteristics, processes, and causes of the spatio-temporal variabilities of the East Asian monsoon system

    Science.gov (United States)

    Huang, Ronghui; Chen, Jilong; Wang, Lin; Lin, Zhongda

    2012-09-01

    Recent advances in the study of the characteristics, processes, and causes of spatio-temporal variabilities of the East Asian monsoon (EAM) system are reviewed in this paper. The understanding of the EAM system has improved in many aspects: the basic characteristics of horizontal and vertical structures, the annual cycle of the East Asian summer monsoon (EASM) system and the East Asian winter monsoon (EAWM) system, the characteristics of the spatio-temporal variabilities of the EASM system and the EAWM system, and especially the multiple modes of the EAM system and their spatio-temporal variabilities. Some new results have also been achieved in understanding the atmosphere-ocean interaction and atmosphere-land interaction processes that affect the variability of the EAM system. Based on recent studies, the EAM system can be seen as more than a circulation system, it can be viewed as an atmosphere-ocean-land coupled system, namely, the EAM climate system. In addition, further progress has been made in diagnosing the internal physical mechanisms of EAM climate system variability, especially regarding the characteristics and properties of the East Asia-Pacific (EAP) teleconnection over East Asia and the North Pacific, the "Silk Road" teleconnection along the westerly jet stream in the upper troposphere over the Asian continent, and the dynamical effects of quasi-stationary planetary wave activity on EAM system variability. At the end of the paper, some scientific problems regarding understanding the EAM system variability are proposed for further study.

  6. Relations of hydrogeologic factors, groundwater reduction-oxidation conditions, and temporal and spatial distributions of nitrate, Central-Eastside San Joaquin Valley, California, USA

    Science.gov (United States)

    Landon, Matthew K.; Green, Christopher T.; Belitz, Kenneth; Singleton, Michael J.; Esser, Bradley K.

    2011-01-01

    In a 2,700-km2 area in the eastern San Joaquin Valley, California (USA), data from multiple sources were used to determine interrelations among hydrogeologic factors, reduction-oxidation (redox) conditions, and temporal and spatial distributions of nitrate (NO3), a widely detected groundwater contaminant. Groundwater is predominantly modern, or mixtures of modern water, with detectable NO3 and oxic redox conditions, but some zones have anoxic or mixed redox conditions. Anoxic conditions were associated with long residence times that occurred near the valley trough and in areas of historical groundwater discharge with shallow depth to water. Anoxic conditions also were associated with interactions of shallow, modern groundwater with soils. NO3 concentrations were significantly lower in anoxic than oxic or mixed redox groundwater, primarily because residence times of anoxic waters exceed the duration of increased pumping and fertilizer use associated with modern agriculture. Effects of redox reactions on NO3 concentrations were relatively minor. Dissolved N2 gas data indicated that denitrification has eliminated >5 mg/L NO3–N in about 10% of 39 wells. Increasing NO3 concentrations over time were slightly less prevalent in anoxic than oxic or mixed redox groundwater. Spatial and temporal trends of NO3 are primarily controlled by water and NO3 fluxes of modern land use.

  7. Identification of temporal and small-scale spatial variations of phosphate concentration in the near-shore groundwater of an oligotrophic lake

    Science.gov (United States)

    Pöschke, Franziska; Schlichting, Hendrik; Lewandowski, Jörg

    2016-04-01

    Lake Stechlin is one of the last oligotrophic lakes in the German North-Eastern Lake District. In recent years there was some worry over a small but continuous increase of phosphate concentrations in the open water body. The reasons remain unclear. Since the lake obtains its water only from groundwater and precipitation there is the assumption that the former can be a significant source of phosphate inputs into the lake. In the present study, three different groundwater sampling settings on different scales in time and space were used to investigate the phosphate concentration in the near-shore groundwater. A multi-level sampling grid of twelve samplers and 60 sampling ports was installed to study the temporal small-scale fluctuations of P concentration in the groundwater and the interstitial water. Furthermore, a one-time sampling campaign of shallow near-shore groundwater was conducted every 500 m along the lake shore. Additionally, nests of permanent groundwater wells were sampled monthly for one year to identify concentration patterns in the deeper aquifer. The results indicate a large spatial and small temporal heterogeneity of P concentrations. The range of P concentration is catchment belongs since 1938 to a natural protected area other anthropogenic impacts are quite unlikely. Hence, the main source for phosphate is probably the decomposition of naturally present organic material under anaerobic and warm conditions.

  8. Temporal Variability of Canopy Light Use Efficiency and its Environmental Controls in a Subtropical Mangrove Wetland

    Science.gov (United States)

    Zhu, X.

    2016-12-01

    Mangrove wetlands play an important role in global carbon cycle due to their strong carbon sequestration resulting from high plant carbon assimilation and low soil respiration. However, temporal variability of carbon sequestration in mangrove wetlands is less understood since carbon processes of mangrove wetlands are influenced by many complicated and concurrent environmental controls including tidal activities, site climate and soil conditions. Canopy light use efficiency (LUE), is the most important plant physiological parameter that can be used to describe the temporal dynamics of canopy photosynthesis, and therefore a better characterization of temporal variability of canopy LUE will improve our understanding in mangrove photosynthesis and carbon balance. One of our aims is to study the temporal variability of canopy LUE and its environmental controls in a subtropical mangrove wetland. Half-hourly canopy LUE is derived from eddy covariance (EC) carbon flux and photosynthesis active radiation observations, and half-hourly environmental controls we measure include temperature, humidity, precipitation, radiation, tidal height, salinity, etc. Another aim is to explore the links between canopy LUE and spectral indices derived from near-surface tower-based remote sensing (normalized difference vegetation index, enhanced vegetation index, photochemical reflectance index, solar-induced chlorophyll fluorescence, etc.), and then identify potential quantitative relationships for developing remote sensing-based estimation methods of canopy LUE. At present, some instruments in our in-situ observation system have not yet been installed (planned in next months) and therefore we don't have enough measurements to support our analysis. However, a preliminary analysis of our historical EC and climate observations in past several years indicates that canopy LUE shows strong temporal variability and is greatly affected by environmental factors such as tidal activity. Detailed and

  9. Interpersonal variability in timing strategy and temporal accuracy in rapid interception task with variable time-to-contact.

    Science.gov (United States)

    Ijiri, Tetsuya; Shinya, Masahiro; Nakazawa, Kimitaka

    2015-01-01

    In rapid interceptive actions such as hitting a baseball, cricket ball or tennis ball, ball speed varies between trials, and players have to compensate the time lag by controlling the moment of movement onset and movement duration. Previous studies have found that these two variables can flexibly co-vary and are robustly influenced by target speed (i.e. velocity-coupling effect: faster movement for faster target). However, some studies reported an interpersonal variability in the timing control strategy and the relationship between the strategy and temporal accuracy in rapid interception is unclear. We used a baseball-simulated rapid interceptive task to assess this issue. Under relatively easy time constraints, there was a large interpersonal variability, and participants were distinctively divided into two groups: those who mainly modulated their movement duration and those who mainly controlled their movement onset. When the time constraint became severe, the second strategy shifted to the first strategy in most of the second group participants. In the both cases, being able to mainly control movement onset resulted in higher temporal accuracy. These results suggest that minimising the velocity-coupling effect is an important factor to achieve high temporal accuracy in rapid interception.

  10. Temporal variability in discharge and benthic macroinvertebrate assemblages in a tropical glacier-fed stream

    DEFF Research Database (Denmark)

    Jacobsen, Dean; Andino, Patricio; Calvez, Roger

    2014-01-01

    -pronounced diel variability in discharge that tracks a year-round diurnal melting–nocturnal freezing cycle of glaciers. Consequently, qualitative and quantitative differences in temporal variability of macrobenthos communities should be expected between high-latitude and tropical glacier-fed streams. We explored...... and sampled fauna at approximately quarterly intervals over 30 mo. Temporal variability in the fauna was aseasonal. However, the overall magnitude of the coefficient of variability (CV) at the 3 sites was not lower than the CV at temperate latitudes. The explanatory power of flow did not differ among......, possibly because of differences among sites in physical characteristics (e.g., refugia space), which moderated the effect of disturbances, and taxonomic composition of communities. Our study is the first to show a close link between hydrological and biological fluctuations in an equatorial glacier...

  11. Spatial and temporal variability of mean daily wind speeds in the Czech Republic, 1961-2015

    Czech Academy of Sciences Publication Activity Database

    Brázdil, Rudolf; Zahradníček, Pavel; Řezníčková, Ladislava; Tolasz, R.; Štěpánek, Petr; Dobrovolný, Petr

    2017-01-01

    Roč. 72 (2017), s. 197-216 ISSN 0936-577X R&D Projects: GA MŠk(CZ) LO1415; GA ČR(CZ) GA15-11805S Institutional support: RVO:67179843 Keywords : mean daily wind speed * spatial variability * temporal variability * wind stilling * Czech Republic Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.578, year: 2016

  12. Spatial variability of shallow groundwater level, electrical conductivity and nitrate concentration, and risk assessment of nitrate contamination in North China Plain.

    Science.gov (United States)

    Hu, Kelin; Huang, Yuangfang; Li, Hong; Li, Baoguo; Chen, Deli; White, Robert Edlin

    2005-08-01

    In recent years, nitrate (NO3) contamination of groundwater has become a growing concern for people in rural areas in North China Plain (NCP) where groundwater is used as drinking water. The objective of this study was to evaluate groundwater resource level, to determine groundwater quality and to assess the risk of NO3 pollution in groundwater in Quzhou County in the NCP. Ordinary Kriging (OK) method was used to analyze the spatial variability of shallow groundwater level, groundwater electrical conductivity (EC) and NO3-N concentrations, and Indictor Kriging (IK) method was used to analyze the data with NO3-N concentrations equal or greater than the groundwater NO3 pollution threshold (20 mg L(-1)). The results indicated that groundwater level averaged 9.81 m, a level 6 m lower than in 1990. The spatial correlation distances for groundwater level, EC and NO3-N concentration were 21.93, 2.19 and 3.55 km, respectively. The contour map showed that shallow groundwater level areas extended from north to south across the County. Groundwater EC was above 3 dS m(-1) in the most part of the northern county. Groundwater NO3 pollution (NO3-N> or =20 mg L(-1)) mainly occurred in the County Seat areas due to wastewater irrigation and excessive fertilizer leaching from agricultural fields. At Henantuang town, besides suburban of the County Seat, groundwater was also contaminated by NO3 shown by the map generated using the IK method, which was not reflected in the map generated using the OK method. The map generated using the OK method could not reflect correctly the groundwater NO3 pollution status. The IK method is useful to assess the risk of NO3 pollution by giving the conditional probability of NO3 concentration exceeding the threshold value. It is suggested that risk assessment of NO3 pollution is useful for better managing groundwater resource, preventing soil salinization and minimizing NO3 pollution in groundwater.

  13. Spatio-temporal variability of hyporheic exchange through a pool-riffle-pool sequence

    Science.gov (United States)

    Frank P. Gariglio; Daniele Tonina; Charles H. Luce

    2013-01-01

    Stream water enters and exits the streambed sediment due to hyporheic fluxes, which stem primarily from the interaction between surface water hydraulics and streambed morphology. These fluxes sustain a rich ecotone, whose habitat quality depends on their direction and magnitude. The spatio-temporal variability of hyporheic fluxes is not well understood over several...

  14. Spatial and Temporal Variability of Soil CO2 Flux in Sugarcane Green Harvest Systems

    Directory of Open Access Journals (Sweden)

    Rose Luiza Moraes Tavares

    2016-01-01

    Full Text Available ABSTRACT The sugarcane green harvest system, characterized by mechanized harvesting and the absence of crop burning, affects soil quality by increasing crop residue on the soil surface after harvest; thus, it contributes to improving the physical, chemical, and microbiological properties and influences the soil carbon content and CO2 flux (FCO2. This study aimed to evaluate the spatial and temporal variability of soil FCO2 in sugarcane green harvest systems. The experiment was conducted in two areas of sugarcane in São Paulo, Brazil: the first had a 5-year history of sugarcane green harvest (SG-5 and the second had a longer history of 10 years (SG-10. The temporal FCO2 were evaluated in the dry and rainy periods, and spatial variability in the dry period, and related to soil chemical and physical properties, including organic C porosity, bulk density, soil penetration resistance, mean weight diameter of soil aggregates, clay, P, S, Ca, Mg and Fe. The temporal variability indicated no differences between the dry and rainy periods in SG-10, while in SG-5 soil moisture was increased by 33 % in the rainy period. The spatial variability indicated a different pattern from the temporal one, where FCO2 in SG-10 was correlated with soil temperature, air-filled pore space, total porosity, soil moisture, and the Ca and Mg contents; in the SG-5 area, FCO2 was correlated with soil mean weight diameter of soil aggregates and the sulfur content.

  15. A descriptive analysis of temporal and spatial patterns of variability in Puget Sound oceanographic properties

    Science.gov (United States)

    Stephanie Moore; Nathan J. Mantua; Jan A. Newton; Mitsuhiro Kawase; Mark J. Warner; Jonathan P. Kellogg

    2008-01-01

    Temporal and spatial patterns of variability in Puget Sound's oceanographic properties are determined using continuous vertical profile data from two long-term monitoring programs; monthly observations at 16 stations from 1993 to 2002, and biannual observations at 40 stations from 1998 to 2003. Climatological monthly means of temperature, salinity, and density...

  16. Temporal variability of fish larvae assemblages: influence of natural and anthropogenic disturbances

    Directory of Open Access Journals (Sweden)

    David A. Reynalte-Tataje

    Full Text Available Natural and induced disturbances greatly influence the temporal distribution of ichthyoplankton abundance. This study assesses and compares the temporal variability of fish larvae assemblages in controlled and free environments to determine the influence of environment variables on the main taxa in these systems. The study was conducted at the Chapecó (without dam impact and Ligeiro (with dam impact river mouths, which are located in the upper Uruguay River. Samples were made between October 2001 and March 2004 during three reproductive periods. The larvae assemblages were composed of small and medium-sized Characiformes and Siluriformes. The variation in the distribution of larvae was mainly temporal (>85%. When the three reproductive periods were compared, it was observed in the second period, characterized by a larger water flow and a lower temperature, that there was a reduction in abundance, a lower number of taxa, an absence of stages in post-flexion and a high dissimilarity in larvae assemblage structure. In general, the environmental variables of water flow and temperature most influenced the distribution of egg and larvae abundance. In the studied area, a smaller temporal variability was observed in the structure of larvae assemblages at the sampling sites in the Chapecó River mouth than in in the Ligeiro River mouth under the influence of dams.

  17. Temporal and spatial variability of urban heat island and thermal comfort within the Rotterdam agglomeration

    NARCIS (Netherlands)

    Hove, van B.; Jacobs, C.M.J.; Heusinkveld, B.G.; Elbers, J.A.; Driel, van B.L.; Holtslag, A.A.M.

    2015-01-01

    This paper reports on temporal and spatial variability of local climate and outdoor human thermal comfort within the Rotterdam agglomeration. We analyse three years of meteorological observations (2010–2012) from a monitoring network. Focus is on the atmospheric urban heat island (UHI); the

  18. Impact of spatial-temporal variations of climatic variables onsummer maize yield in North China Plain

    NARCIS (Netherlands)

    Wu, D.; Yu, Q.; Wang, E.; Hengsdijk, H.

    2008-01-01

    Summer maize (Zea mays L.) is one of the dominant crops in the North China Plain (NCP). Itsgrowth is greatly influenced by the spatial-temporal variation of climatic variables, especially solar radiation, temperature and rainfall. The WOFOST (version 7.1) model was applied to evaluate the impact of

  19. SEAWAT: A Computer Program for Simulation of Variable-Density Groundwater Flow and Multi-Species Solute and Heat Transport

    Science.gov (United States)

    Langevin, Christian D.

    2009-01-01

    SEAWAT is a MODFLOW-based computer program designed to simulate variable-density groundwater flow coupled with multi-species solute and heat transport. The program has been used for a wide variety of groundwater studies including saltwater intrusion in coastal aquifers, aquifer storage and recovery in brackish limestone aquifers, and brine migration within continental aquifers. SEAWAT is relatively easy to apply because it uses the familiar MODFLOW structure. Thus, most commonly used pre- and post-processors can be used to create datasets and visualize results. SEAWAT is a public domain computer program distributed free of charge by the U.S. Geological Survey.

  20. Dryland Precipitation Variability and Desertification Processes: An Assessment of Spatial and Temporal Rain Variability within the Grand Canyon, Arizona

    Science.gov (United States)

    Caster, J.; Sankey, J. B.; Draut, A.; Fairley, H.; Collins, B. D.; Bedford, D.

    2014-12-01

    In drylands, spatial and temporal rain variability can result from natural climatic cycles, weather patterns, and physiographic factors. In these environments, minor differences in rainfall distribution can invoke significant ecosystem response. The Grand Canyon, Arizona is an iconic dryland environment that receives less than 430 mm of annual rainfall. Recent monitoring of desertification processes at culturally sensitive landscapes in Grand Canyon has examined variability in vegetation, soil crusts, and runoff induced erosion, and identified a lack of knowledge about the nature, drivers and effects of local rainfall variability. We examine rainfall variability using five years of high resolution data collected from 11 weather stations distributed along the Colorado River within Grand Canyon, coupled with 60 years of lower resolution data from National Weather Service Cooperative Observer (NOAA COOP) stations. We characterize spatial and temporal variability in 10-minute rainfall intensity, an important predictor of soil erosion, and daily rainfall depth, an important predictor of biotic cover. We quantify the intensity-daily depth relationship to infer long-term variability in rainfall intensity from the NOAA COOP data that only record rainfall depth. Results confirm findings from previous studies showing a bi-seasonally rainfall pattern with longer duration-lower intensity storms in the cool season and shorter duration-higher intensity storms during the North American Monsoon (NAM).Seasonal differences in rainfall intensity-depth relationships are significant, and suggest NAM storms have greater potential to produce erosion-generating intensities. As NAM rainfall is spatially and inter-annually more variable than cool season rain, yearly rain depths are strongly influenced by NAM fluctuations. These findings will be useful in future efforts to track desertification processes in this and other drylands characterized by complex topography and extreme rainfall

  1. Spatial and temporal variability in VOC levels within a commercial retail building.

    Science.gov (United States)

    Eklund, B M; Burkes, S; Morris, P; Mosconi, L

    2008-10-01

    A study was performed to characterize the concentration of dozens of volatile organic compounds (VOCs) at 10 locations within a single large building and track these concentrations over a 2-year period. The study was performed at a shopping center (strip mall) in New Jersey. A total of 130 indoor air samples were collected from 10 retail stores within the shopping center and analyzed for 60 VOCs by US EPA Method TO-15. Indoor concentrations of up to 55,100 microg/m(3) were measured for individual VOCs. The indoor/outdoor ratio (I/O) was as high as 1500 for acetone and exceeded 100 at times for various compounds, indicating that significant indoor air sources were present. A large degree of spatial variability was observed between stores within the building, with concentrations varying by three to four orders of magnitude for some compounds. The spatial variability was dependent on the proximity of the sampling locations to the indoor sources. A large degree of temporal variability also was observed for compounds emitted from indoor sources, but the temporal variability generally did not exceed two standard deviations (sigma). For compounds not emitted from indoor sources at significant rates, both the spatial and temporal variability tended to range within an order of magnitude at each location. Many cross-sectional studies have been published where the levels of volatile organic compounds (VOCs) were measured in indoor air at one or two locations for houses or offices. This study provides longitudinal data for a commercial retail building and also addresses spatial variability within the building. The data suggest that spatial and temporal variability are important considerations for compounds emitted from indoor sources. Elevated concentrations were found in retail spaces with no apparent emission sources due to their proximity to other retail spaces with emission sources.

  2. Capturing temporal and spatial variability in the chemistry of shallow permafrost ponds

    Science.gov (United States)

    Morison, Matthew Q.; Macrae, Merrin L.; Petrone, Richard M.; Fishback, LeeAnn

    2017-12-01

    Across the circumpolar north, the fate of small freshwater ponds and lakes (climates through sediment records. A changing climate has implications for the capacity of ponds and lakes to support organisms and store carbon, which in turn has important feedbacks to climate change. Thus, an improved understanding of pond biogeochemistry is needed. To characterize spatial and temporal patterns in water column chemistry, a suite of tundra ponds were examined to answer the following research questions: (1) does temporal variability exceed spatial variability? (2) If temporal variability exists, do all ponds (or groups of ponds) behave in a similar temporal pattern, linked to seasonal hydrologic drivers or precipitation events? Six shallow ponds located in the Hudson Bay Lowlands region were monitored between May and October 2015 (inclusive, spanning the entire open-water period). The ponds span a range of biophysical conditions including pond area, perimeter, depth, and shoreline development. Water samples were collected regularly, both bimonthly over the ice-free season and intensively during and following a large summer storm event. Samples were analysed for nitrogen speciation (NO3-, NH4+, dissolved organic nitrogen) and major ions (Cl-, SO42-, K+, Ca2+, Mg2+, Na+). Across all ponds, temporal variability (across the season and within a single rain event) exceeded spatial variability (variation among ponds) in concentrations of several major species (Cl-, SO42-, K+, Ca2+, Na+). Evapoconcentration and dilution of pond water with precipitation and runoff inputs were the dominant processes influencing a set of chemical species which are hydrologically driven (Cl-, Na+, K+, Mg2+, dissolved organic nitrogen), whereas the dissolved inorganic nitrogen species were likely mediated by processes within ponds. This work demonstrates the importance of understanding hydrologically driven chemodynamics in permafrost ponds on multiple scales (seasonal and event scale).

  3. A Monte Carlo approach for improved estimation of groundwater level spatial variability in poorly gauged basins

    Science.gov (United States)

    Varouchakis, Emmanouil; Hristopulos, Dionissios

    2013-04-01

    Groundwater level is an important source of information in hydrological modelling. In many aquifers the boreholes monitored are scarce and/or sparse in space. In both cases, geostatistical methods can help to visualize the free surface of an aquifer, whereas the use of auxiliary information improves the accuracy of level estimates and maximizes the information gain for the quantification of groundwater level spatial variability. In addition, they allow the exploitation of datasets that cannot otherwise be efficiently used in catchment models. In this presentation, we demonstrate an approach for incorporating auxiliary information in interpolation approaches using a specific case study. In particular, the study area is located on the island of Crete (Greece). The available data consist of 70 hydraulic head measurements for the wet period of the hydrological year 2002-2003, the average pumping rates at the 70 wells, and 10 piezometer readings measured in the preceding hydrological year. We present a groundwater level trend model based on the generalized Thiem's equation for multiple wells. We use the drift term to incorporate secondary information in Residual Kriging (RK) (Varouchakis and Hristopulos 2013). The residuals are then interpolated using Ordinary Kriging and then are added to the drift model. Thiem's equation describes the relationship between the steady-state radial inflow into a pumping well and the drawdown. The generalized form of the equation includes the influence of a number of pumping wells. It incorporates the estimated hydraulic head, the initial hydraulic head before abstraction, the number of wells, the pumping rate, the distance of the estimation point from each well, and the well's radius of influence. We assume that the initial hydraulic head follows a linear trend, which we model based on the preceding hydrological year measurements. The hydraulic conductivity in the study basin varies between 0.0014 and 0.00014 m/s according to geological

  4. Triennial changes in groundwater quality in aquifers used for public supply in California: Utility as indicators of temporal trends

    Science.gov (United States)

    Kent, Robert; Landon, Matthew K.

    2016-01-01

    From 2004 to 2011, the U.S. Geological Survey collected samples from 1686 wells across the State of California as part of the California State Water Resources Control Board’s Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project (PBP). From 2007 to 2013, 224 of these wells were resampled to assess temporal trends in water quality. The samples were analyzed for 216 water-quality constituents, including inorganic and organic compounds as well as isotopic tracers. The resampled wells were grouped into five hydrogeologic zones. A nonparametric hypothesis test was used to test the differences between initial sampling and resampling results to evaluate possible step trends in water-quality, statewide, and within each hydrogeologic zone. The hypothesis tests were performed on the 79 constituents that were detected in more than 5 % of the samples collected during either sampling period in at least one hydrogeologic zone. Step trends were detected for 17 constituents. Increasing trends were detected for alkalinity, aluminum, beryllium, boron, lithium, orthophosphate, perchlorate, sodium, and specific conductance. Decreasing trends were detected for atrazine, cobalt, dissolved oxygen, lead, nickel, pH, simazine, and tritium. Tritium was expected to decrease due to decreasing values in precipitation, and the detection of decreases indicates that the method is capable of resolving temporal trends.

  5. Spatial and temporal variability of mobile macro-invertebrate assemblages associated to coralligenous habitat

    Directory of Open Access Journals (Sweden)

    R. BEDINI

    2014-03-01

    Full Text Available The study aimed to investigate patterns of spatial and temporal variability of mobile macroinvertebrate assemblages associated to coralligenous habitat. A multi-factorial sampling design was used to test the hypotheses that the structure of assemblages and their spatial and temporal variability changed in relation to substrate inclination. Moreover, macroalgae and sessile macro-invertebrates were also investigated in order to detect eventual relationship between sessile and mobile assemblages. A total of 236 mobile macro-invertebrate taxa were identified, among them 2 Platyhelminthes, 4 Sipuncula, 6 Nemertea, 27 Mollusca, 86 Annelida, 103 Arthropoda, 8 Echinodermata. Results of the study showed that mobile macro-invertebrate assemblages of coralligenous habitat were little influenced by the inclination of substrate and by the morphology of sessile organisms, as patterns of variation were different between the two assemblages. Mobile macro-invertebrate assemblages changed among sampling dates within one year period and they showed high variability at the spatial scale examined.

  6. Addressing Groundwater Declines with Precision Agriculture: An Economic Comparison of Monitoring Methods for Variable-Rate Irrigation

    Directory of Open Access Journals (Sweden)

    Grant H. West

    2017-01-01

    Full Text Available Irrigated row-crop agriculture is contributing to declining groundwater in areas such as the Mississippi Delta region of eastern Arkansas. There is a need to move toward sustainable levels of groundwater withdrawal. Recent improvements in remote monitoring technologies such as wireless soil moisture sensors and unmanned aerial vehicles offer the potential for farmers to effectively practice site-specific variable-rate irrigation management for the purpose of applying water more efficiently, reducing pumping costs, and retaining groundwater. Soil moisture sensors and unmanned aerial vehicles are compared here in terms of their net returns per acre-foot and cost-effectiveness of aquifer retention. Soil moisture sensors ($9.09 per acre-foot offer slightly more net returns to producers than unmanned aerial vehicles ($7.69 per acre-foot, though costs associated with unmanned aerial vehicles continue to drop as more manufacturers enter the market and regulations become clear.

  7. Space Technology 5 Multipoint Observations of Temporal and Spatial Variability of Field-Aligned Currents

    Science.gov (United States)

    Le, G.; Wang, Y.; Slavin, J. A.; Strangeway, R. L.

    2009-01-01

    Space Technology 5 (ST5) is a constellation mission consisting of three microsatellites. It provides the first multipoint magnetic field measurements in low Earth orbit, which enables us to separate spatial and temporal variations. In this paper, we present a study of the temporal variability of field-aligned currents using the ST5 data. We examine the field-aligned current observations during and after a geomagnetic storm and compare the magnetic field profiles at the three spacecraft. The multipoint data demonstrate that mesoscale current structures, commonly embedded within large-scale current sheets, are very dynamic with highly variable current density and/or polarity in approx.10 min time scales. On the other hand, the data also show that the time scales for the currents to be relatively stable are approx.1 min for mesoscale currents and approx.10 min for large-scale currents. These temporal features are very likely associated with dynamic variations of their charge carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of mesoscale field-aligned currents are found to be consistent with those of auroral parallel electric field.

  8. Temporal scaling phenomena in groundwater-floodplain systems using robust detrended fluctuation analysis

    Science.gov (United States)

    Habib, Abrar; Sorensen, James P. R.; Bloomfield, John P.; Muchan, Katie; Newell, Andrew J.; Butler, Adrian P.

    2017-06-01

    In order to determine objectively the fractal behaviour of a time series, and to facilitate potential future attempts to assess model performance by incorporating fractal behaviour, a multi-order robust detrended fluctuation analysis (r-DFAn) procedure is developed herein. The r-DFAn procedure allows for robust and automated quantification of mono-fractal behaviour. The fractal behaviour is quantified with three parts: a global scaling exponent, crossovers, and local scaling exponents. The robustness of the r-DFAn procedure is established by the systematic use of robust regression, piecewise linear regression, Analysis of Covariance (ANCOVA) and Multiple Comparison Procedure to determine statistically significant scaling exponents and optimum crossover locations. The MATLAB code implementing the r-DFAn procedure has also been open sourced to enable reproducible results. r-DFAn will be illustrated on a synthetic signal after which is used to analyse high-resolution hydrologic data; although the r-DFAn procedure is not limited to hydrological or geophysical time series. The hydrological data are 4 year-long datasets (January 2012 to January 2016) of 1-min groundwater level, river stage, groundwater and river temperature, and 15-min precipitation and air temperature, at Wallingford, UK. The datasets are analysed in both time and fractal domains. The study area is a shallow riparian aquifer in hydraulic connection to River Thames, which traverses the site. The unusually high resolution datasets, along with the responsive nature of the aquifer, enable detailed examination of the various data and their interconnections in both time- and fractal-domains.

  9. Impact of multi-purpose aquifer utilisation on a variable-density groundwater flow system in the Gippsland Basin, Australia

    Science.gov (United States)

    Varma, Sunil; Michael, Karsten

    2012-02-01

    The Latrobe aquifer in the Gippsland Basin in southeastern Australia is a prime example for emerging resource conflicts in Australian sedimentary basins. The Latrobe Group forms a major freshwater aquifer in the onshore Gippsland Basin, and is an important reservoir for oil and gas in both onshore and offshore parts of the basin. The Latrobe Group and overlying formations contain substantial coal resources that are being mined in the onshore part of the basin. These may have coal-seam-gas potential and, in addition, the basin is considered prospective for its geothermal energy and CO2 storage potential. The impacts of groundwater extraction related to coal-mine dewatering, public water supply, and petroleum production on the flow of variable-density formation water has been assessed using freshwater hydraulic heads and impelling force vectors. Groundwater flows from the northern and western edges towards the central part of the basin. Groundwater discharge occurs mainly offshore along the southern margin. Post-stress hydraulic heads show significant declines near the petroleum fields and in the coal mining areas. A hydrodynamic model of the Latrobe aquifer was used to simulate groundwater recovery in the Latrobe aquifer from different scenarios of cessation of groundwater and other fluid extractions.

  10. An innovative procedure to assess multi-scale temporal trends in groundwater quality: Example of the nitrate in the Seine-Normandy basin, France

    Science.gov (United States)

    Lopez, Benjamin; Baran, Nicole; Bourgine, Bernard

    2015-03-01

    The European Water Framework Directive (WFD) asks Member States to identify trends in contaminant concentrations in groundwater and to take measures to reach a good chemical status by 2015. In this study, carried out in a large hydrological basin (95,300 km2), an innovative procedure is described for the assessment of recent trends in groundwater nitrate concentrations both at sampling point and regional scales. Temporal variograms of piezometric and nitrate concentration time series are automatically calculated and fitted in order to classify groundwater according to their temporal pattern. These results are then coupled with aquifer lithology to map spatial units within which the modes of diffuse transport of contaminants towards groundwater are assumed to be the same at all points. These spatial units are suitable for evaluating regional trends. The stability over time of the time series is tested based on the cumulative sum principle, to determine the time period during which the trend should be sought. The Mann-Kendall and Regional-Kendall nonparametric tests for monotonic trends, coupled with the Sen-slope test, are applied to the periods following the point breaks thus determined at both the sampling point or regional scales. This novel procedure is robust and enables rapid processing of large databases of raw data. It would therefore be useful for managing groundwater quality in compliance with the aims of the WFD.

  11. Spatial and temporal variability in summer snow pack in Dronning Maud Land, Antarctica

    Directory of Open Access Journals (Sweden)

    T. Vihma

    2011-03-01

    Full Text Available To quantify the spatial and temporal variability in the snow pack, field measurements were carried out during four summers in Dronning Maud Land, Antarctica. Data from a 310-km-long transect revealed the largest horizontal gradients in snow density, temperature, and hardness in the escarpment region. On the local scale, day-to-day temporal variability dominated the standard deviation of snow temperature, while the diurnal cycle was of second significance, and horizontal variability on the scale of 0.4 to 10 m was least important. In the uppermost 0.2 m, the snow temperature was correlated with the air temperature over the previous 6–12 h, whereas at the depths of 0.3 to 0.5 m the most important time scale was 3 days. Cloud cover and radiative fluxes affected the snow temperature in the uppermost 0.30 m and the snow density in the uppermost 0.10 m. Both on the intra-pit and transect scales, the ratio of horizontal to temporal variability increased with depth. The horizontal standard deviation of snow density increased rapidly between the scales of 0.4 and 2 m, and more gradually from 10 to 100 m. Inter-annual variations in snow temperature and density were due to inter-annual differences in air temperature and the timing of the precipitation events.

  12. Cross-scale impact of climate temporal variability on ecosystem water and carbon fluxes

    Science.gov (United States)

    Paschalis, Athanasios; Fatichi, Simone; Katul, Gabriel G.; Ivanov, Valeriy Y.

    2015-09-01

    While the importance of ecosystem functioning is undisputed in the context of climate change and Earth system modeling, the role of short-scale temporal variability of hydrometeorological forcing (~1 h) on the related ecosystem processes remains to be fully understood. Various impacts of meteorological forcing variability on water and carbon fluxes across a range of scales are explored here using numerical simulations. Synthetic meteorological drivers that highlight dynamic features of the short temporal scale in series of precipitation, temperature, and radiation are constructed. These drivers force a mechanistic ecohydrological model that propagates information content into the dynamics of water and carbon fluxes for an ensemble of representative ecosystems. The focus of the analysis is on a cross-scale effect of the short-scale forcing variability on the modeled evapotranspiration and ecosystem carbon assimilation. Interannual variability of water and carbon fluxes is emphasized in the analysis. The main study inferences are summarized as follows: (a) short-scale variability of meteorological input does affect water and carbon fluxes across a wide range of time scales, spanning from the hourly to the annual and longer scales; (b) different ecosystems respond to the various characteristics of the short-scale variability of the climate forcing in various ways, depending on dominant factors limiting system productivity; (c) whenever short-scale variability of meteorological forcing influences primarily fast processes such as photosynthesis, its impact on the slow-scale variability of water and carbon fluxes is small; and (d) whenever short-scale variability of the meteorological forcing impacts slow processes such as movement and storage of water in the soil, the effects of the variability can propagate to annual and longer time scales.

  13. TEMPORALLY VARIABLE GEOGRAPHICAL DISTANCE EFFECTS CONTRIBUTE TO THE ASSEMBLY OF ROOT-ASSOCIATED FUNGAL COMMUNITIES

    Directory of Open Access Journals (Sweden)

    Christopher James Barnes

    2016-02-01

    Full Text Available Root-associated fungi are key contributors to ecosystem functioning, however the factors which determine community assembly are still relatively poorly understood. This study simultaneously quantified the roles of geographical distance, environmental heterogeneity and time in determining root-associated fungal community composition at the local scale within a short rotation coppice (SRC willow plantation. Culture independent molecular analyses of the root-associated fungal community suggested a strong but temporally variable effect of geographical distance between fungal communities on composition at the local geographical level. Whilst these distance effects were most prevalent on October communities, soil pH had an effect on structuring of the communities throughout the sampling period. Given the temporal variation in the effects of geographical distance and the environment for shaping root-associated fungal communities, there is clearly need for a temporal component to sampling strategies in future investigations of fungal biogeography.

  14. Temporally Variable Geographical Distance Effects Contribute to the Assembly of Root-Associated Fungal Communities.

    Science.gov (United States)

    Barnes, Christopher J; van der Gast, Christopher J; Burns, Caitlin A; McNamara, Niall P; Bending, Gary D

    2016-01-01

    Root-associated fungi are key contributors to ecosystem functioning, however, the factors which determine community assembly are still relatively poorly understood. This study simultaneously quantified the roles of geographical distance, environmental heterogeneity and time in determining root-associated fungal community composition at the local scale within a short rotation coppice (SRC) willow plantation. Culture independent molecular analyses of the root-associated fungal community suggested a strong but temporally variable effect of geographical distance among fungal communities in terms of composition at the local geographical level. Whilst these distance effects were most prevalent on October communities, soil pH had an effect on structuring of the communities throughout the sampling period. Given the temporal variation in the effects of geographical distance and the environment for shaping root-associated fungal communities, there is clearly need for a temporal component to sampling strategies in future investigations of fungal ecology.

  15. Tracing fecal pollution sources in karst groundwater by Bacteroidales genetic biomarkers, bacterial indicators, and environmental variables.

    Science.gov (United States)

    Zhang, Ya; Kelly, Walton R; Panno, Samuel V; Liu, Wen-Tso

    2014-08-15

    Fecal contamination in Midwestern karst regions was evaluated by simultaneously measuring traditional bacterial indicators (coliforms and Escherichia coli), Bacteroidales-based biomarkers, and environmental variables. Water samples from springs and wells were collected from karst regions in Illinois (IL), Wisconsin (WI), Kentucky (KY), and Missouri (MO). Quantitative PCR (Q-PCR) with seven primer sets targeting different members of Bacteroidales was used to determine the origin of fecal contamination (i.e., from human waste, livestock waste, or both). Most samples were contaminated by both human and animal waste, with a few samples showing pollution solely by one or the other. Spring water tended to have higher levels of contamination than well water, and higher concentrations of fecal biomarkers were detected in urban springs compared to rural spring systems. However, there were discrepancies on contamination profile determined by Bacteroidales-based biomarkers and by traditional bacterial indicators. Among all the environmental parameters examined, E. coli, sulfate, total dissolved solids (TDS), and silicon were significantly correlated (p<0.05) with the level of Bacteroidales-based fecal indicators. A rapid screening method using total nitrogen (TN) and chloride (Cl(-)) concentrations to determine fecal contamination was shown to be effective and correlated well with Bacteroidales-based MST. The results suggest that human and livestock feces co-contaminated a large portion of karst groundwater systems in Midwestern regions, and the inclusion of traditional bacterial indicators, environmental variables, and Bacteroidales-based MST is an effective approach for identifying fecal contamination in karst regions. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Understanding flood-induced water chemistry variability extracting temporal patterns with the LDA method

    Science.gov (United States)

    Aubert, A. H.; Tavenard, R.; Emonet, R.; De Lavenne, A.; Malinowski, S.; Guyet, T.; Quiniou, R.; Odobez, J.; Merot, P.; Gascuel-odoux, C.

    2013-12-01

    Studying floods has been a major issue in hydrological research for years, both in quantitative and qualitative hydrology. Stream chemistry is a mix of solutes, often used as tracers, as they originate from various sources in the catchment and reach the stream by various flow pathways. Previous studies (for instance (1)) hypothesized that stream chemistry reaction to a rainfall event is not unique but varies seasonally, and according to the yearly meteorological conditions. Identifying a typology of flood temporal chemical patterns is a way to better understand catchment processes at the flood and seasonal time scale. We applied a probabilistic model (Latent Dirichlet Allocation or LDA (2)) mining recurrent sequential patterns from a dataset of floods. A set of 472 floods was automatically extracted from a daily 12-year long record of nitrate, dissolved organic carbon, sulfate and chloride concentrations. Rainfall, discharge, water table depth and temperature are also considered. Data comes from a long-term hydrological observatory (AgrHys, western France) located at Kervidy-Naizin. From each flood, a document has been generated that is made of a set of "hydrological words". Each hydrological word corresponds to a measurement: it is a triplet made of the considered variable, the time at which the measurement is made (relative to the beginning of the flood), and its magnitude (that can be low, medium or high). The documents and the number of pattern to be mined are used as input data to the LDA algorithm. LDA relies on spotting co-occurrences (as an alternative to the more traditional study of correlation) between words that appear within the flood documents. It has two nice properties that are its ability to easily deal with missing data and its additive property that allows a document to be seen as a mixture of several flood patterns. The output of LDA is a set of patterns easily represented in graphics. These patterns correspond to typical reactions to rainfall

  17. Estimation of natural direct groundwater recharge in southwest Ghana using water balance simulations

    OpenAIRE

    Darko, Philip K.

    2002-01-01

    The Sacramento soil moisture-accounting model has been used to simulate the discharges of a major catchment (Pra river basin) in southern Ghana. Through the simulation it was possible to assess the temporal variability of evapotranspiratio, base flow proportions and groundwater in storage, as well as the average groundwater recharge to the weathered aquifers. Groundwater recharge was estimated by considering the measured discharge of groundwater across the boundary of the basin over periods o...

  18. Variability of pesticides and nitrates concentrations along a river transect: chemical and isotopic evidence of groundwater - surface water interconnections

    Science.gov (United States)

    Baran, Nicole; Petelet-Giraud, Emmanuelle; Saplairoles, Maritxu

    2015-04-01

    concentration. Finally, downstream the quantified pesticides were different from those observed in the upper part of the Crieu but similar to those observed in groundwater. Sr isotopes together with major elements and Sr concentrations allow to identify 3 distinct end-members to explain the river quality evolution : 1) surface water, 2) groundwater and 3) sub-surface water. On this basis, we first demonstrate that the contribution of the different end-members to the river flow is highly variable from upstream to downstream. Secondly, we evidence water exchanges between the river and the groundwater compartment and vice-versa. The combination of the isotopic and geochemical approaches was essential to understand the complex relations and exchanges between surface and ground-waters occurring in few kilometers along the Crieu River. This understanding allows the comprehension of spatial variability of surface water quality. This is of primary importance when to help water managers to select relevant sampling points to be monitored in the framework of the WFD. Amalric L., et al. (2013). International Journal of Environmental Analytical Chemistry, 93: 1660-1675 Loos R. et al. (2010). Water Research, 44: 4115-4126 Stuart M. et al. (2012). Science of the Total Environment, 416: 1-21.

  19. Time Series Analysis: A New Methodology for Comparing the Temporal Variability of Air Temperature

    Directory of Open Access Journals (Sweden)

    Piia Post

    2013-01-01

    Full Text Available Temporal variability of three different temperature time series was compared by the use of statistical modeling of time series. The three temperature time series represent the same physical process, but are at different levels of spatial averaging: temperatures from point measurements, from regional Baltan65+, and from global ERA-40 reanalyses. The first order integrated average model IMA(0, 1, 1 is used to compare the temporal variability of the time series. The applied IMA(0, 1, 1 model is divisible into a sum of random walk and white noise component, where the variances for both white noises (one of them serving as a generator of the random walk are computable from the parameters of the fitted model. This approach enables us to compare the models fitted independently to the original and restored series using two new parameters. This operation adds a certain new method to the analysis of nonstationary series.

  20. Spatial-temporal gait variability poststroke: variations in measurement and implications for measuring change.

    Science.gov (United States)

    Chisholm, Amanda E; Makepeace, Shelley; Inness, Elizabeth L; Perry, Stephen D; McIlroy, William E; Mansfield, Avril

    2014-07-01

    To determine the responsiveness to change of spatial-temporal gait parameters among stroke survivors for 3 different variability measures: SD, coefficient of variation (CV), and median absolute deviation (MAD). Retrospective chart review. Clinical laboratory in a Canadian hospital. Stroke survivors (N=74) receiving inpatient rehabilitation. Not applicable. Spatial-temporal gait variability was calculated for step length, step width, stance time, swing time, and double support time. Responsiveness to change was determined by comparing (1) trials without versus trials with a concurrent cognitive task and (2) admission to discharge from rehabilitation. Variability estimators (SD, CV, and MAD) increased with the addition of a cognitive task and decreased from admission to discharge of rehabilitation. However, these changes were not statistically significant when change in gait velocity was included as a covariate. The effect size values were similar for all variability estimators with a trend toward a greater SD response to temporal parameters. The CV displayed a larger response to change for step length than did the SD and MAD. Although gait variability decreased between admission and discharge, the effect size was larger for the condition without the cognitive task than for the condition with the cognitive task. Our results show that gait variability estimators demonstrate a similar responsiveness to a concurrent cognitive task and improved walking ability with recovery from stroke. Future work may focus on evaluating the clinical utility of these measures in relation to informing therapy and response to gait-specific training protocols. Copyright © 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  1. A Study of the Groundwater Level Spatial Variability in the Messara Valley of Crete

    Science.gov (United States)

    Varouchakis, E. A.; Hristopulos, D. T.; Karatzas, G. P.

    2009-04-01

    The island of Crete (Greece) has a dry sub-humid climate and marginal groundwater resources, which are extensively used for agricultural activities and human consumption. The Messara valley is located in the south of the Heraklion prefecture, it covers an area of 398 km2, and it is the largest and most productive valley of the island. Over-exploitation during the past thirty (30) years has led to a dramatic decrease of thirty five (35) meters in the groundwater level. Possible future climatic changes in the Mediterranean region, potential desertification, population increase, and extensive agricultural activity generate concern over the sustainability of the water resources of the area. The accurate estimation of the water table depth is important for an integrated groundwater resource management plan. This study focuses on the Mires basin of the Messara valley for reasons of hydro-geological data availability and geological homogeneity. The research goal is to model and map the spatial variability of the basin's groundwater level accurately. The data used in this study consist of seventy (70) piezometric head measurements for the hydrological year 2001-2002. These are unevenly distributed and mostly concentrated along a temporary river that crosses the basin. The range of piezometric heads varies from an extreme low value of 9.4 meters above sea level (masl) to 62 masl, for the wet period of the year (October to April). An initial goal of the study is to develop spatial models for the accurate generation of static maps of groundwater level. At a second stage, these maps should extend the models to dynamic (space-time) situations for the prediction of future water levels. Preliminary data analysis shows that the piezometric head variations are not normally distributed. Several methods including Box-Cox transformation and a modified version of it, transgaussian Kriging, and Gaussian anamorphosis have been used to obtain a spatial model for the piezometric head. A

  2. Geostatistical methods in evaluating spatial variability of groundwater quality in Al-Kharj Region, Saudi Arabia

    Science.gov (United States)

    Al-Omran, Abdulrasoul M.; Aly, Anwar A.; Al-Wabel, Mohammad I.; Al-Shayaa, Mohammad S.; Sallam, Abdulazeam S.; Nadeem, Mahmoud E.

    2017-11-01

    The analyses of 180 groundwater samples of Al-Kharj, Saudi Arabia, recorded that most groundwaters are unsuitable for drinking uses due to high salinity; however, they can be used for irrigation with some restriction. The electric conductivity of studied groundwater ranged between 1.05 and 10.15 dS m-1 with an average of 3.0 dS m-1. Nitrate was also found in high concentration in some groundwater. Piper diagrams revealed that the majority of water samples are magnesium-calcium/sulfate-chloride water type. The Gibbs's diagram revealed that the chemical weathering of rock-forming minerals and evaporation are influencing the groundwater chemistry. A kriging method was used for predicting spatial distribution of salinity (EC dS m-1) and NO3 - (mg L-1) in Al-Kharj's groundwater using data of 180 different locations. After normalization of data, variogram was drawn, for selecting suitable model for fitness on experimental variogram, less residual sum of squares value was used. Then cross-validation and root mean square error were used to select the best method for interpolation. The kriging method was found suitable methods for groundwater interpolation and management using either GS+ or ArcGIS.

  3. Temporal and spatial variability in the Guadalquivir estuary: a challenge for real-time telemetry

    Science.gov (United States)

    Navarro, Gabriel; Gutiérrez, Francisco Javier; Díez-Minguito, Manuel; Losada, Miguel Angel; Ruiz, Javier

    2011-06-01

    Meteorological, hydrological, and hydrodynamic data for 3 years (2008-2010) have been used to document and explain the temporal and spatial variability of the physical-biogeochemical interactions in the Guadalquivir River Estuary. A real-time, remote monitoring network has been deployed along the course of the river between its mouth and Seville to study a broad range of temporal scales (semidiurnal, diurnal, fortnightly, and seasonal). This network consists of eight hydrological monitoring stations capable of measuring temperature, conductivity, dissolved oxygen, turbidity, and chlorophyll fluorescence at four depths. In addition, six stations have been deployed to study hydrodynamics, obtaining 20-cell water column current profiles, and there is a meteorological station at the river mouth providing data for understanding atmospheric interactions. Completing this data-gathering network, there are several moorings (tide gauges, current/wave sensors, and a thermistor chain) deployed in the estuary and river mouth. Various sources of physical forcing, such as wind, tide-associated currents, and river discharge, are responsible for the particular temporal and spatial patterns of turbidity and salinity found in the estuary. These variables force the distribution of biogeochemical variables, such as dissolved oxygen and chlorophyll fluorescence. In particular, episodes of elevated turbidity (when suspended particle matter concentration >3,000 mg/l) have been detected by the network, together with episodes of declining values of salinity and dissolved oxygen. All these patterns are related to river discharge and tidal dynamics (spring/neap and high/low tide).

  4. Modeling the Spatial and Temporal Variability of Precipitation in Northwest Iran

    Directory of Open Access Journals (Sweden)

    Mohammad Arab Amiri

    2017-12-01

    Full Text Available Spatial and temporal variability analysis of precipitation is an important task in water resources planning and management. This study aims to analyze the spatial and temporal variability of precipitation in the northeastern corner of Iran using data from 24 well-distributed weather stations between 1991 and 2015. The mean annual rainfall, precipitation concentration index (PCI, and their coefficients of variation were mapped to examine the spatial variability of rainfall. An artificial neural network (ANN in association with the inverse distance weighted (IDW method was proposed as a hybrid interpolation method to map the spatial distribution of the detected trends of mean annual rainfall and PCI over the study region. In addition, principal component analysis (PCA was applied to annual precipitation time series in order to verify the results of the analysis using the mean annual rainfall and PCI data sets. Results show high variation in inter-annual precipitation in the west, and a moderate to high intra-annual variability over the whole region. Irregular year-to-year precipitation concentration is also observed in the northeastern and northwestern parts. All in all, the highest variations in inter-annual and intra-annual precipitation occurred over the western and northern parts, while the lowest variability was observed in the eastern part (i.e., the coastal region.

  5. Spatial Variability of Ground-Water Recharge Estimates in the Glassboro Area, New Jersey

    Science.gov (United States)

    Nolan, B. T.; Baehr, A. L.

    2001-12-01

    The spatial variability of ground-water recharge estimates in the Glassboro area, NJ, was evaluated using geostatistical methods as a preliminarily assessment of aquifer vulnerability. Recharge was estimated using Darcy's law, based on parameters obtained from pedotransfer functions applied to measured soil texture values. The recharge estimates correspond to sediments overlying the Kirkwood-Cohansey aquifer, which comprises highly permeable unconsolidated sands and gravels. Knowing which areas receive greater recharge would indicate areas of greater vulnerability, depending on overlying land use. Recharge varied from -7.3 to 722 in/yr in the study area and the median was 12.1 in/yr. Experimental variograms of untransformed recharge data were erratic and related kriged maps were dominated by extreme values (250-722 in/yr) in the data set. An indicator transform stabilized the variograms. Indicator kriging (IK) reduced the influence of extreme values in the data set and yielded maps showing the probability of exceeding threshold values of recharge in the study area. The probability of exceeding the median recharge rate of 12.1 in/yr was 0.9 in the southern portion of the study area and might represent an area of focused recharge. As a check of model fit, probabilities predicted with IK were compared with the original recharge estimates and found to be strongly related. IK predictions corresponding to quintiles of recharge were used to estimate cumulative distribution functions (cdfs) for specific locations in the study area. The cdfs indicate the probability of exceeding any recharge rate at a particular location, and are shaped differently depending on location in the study area. The IK technique estimates cdfs with a single sampling realization (i.e., without a mean and variance at a given location). Additional variables were analyzed with regression to add a deterministic aspect to the analysis and to improve predictions. These variables included land slope

  6. Capturing temporal variation in phosphorus dynamics in groundwater dominated rivers using automated high-frequency sampling

    Science.gov (United States)

    Bieroza, M. Z.; Heathwaite, A. L.; Mullinger, N. J.; Keenan, P. O.

    2012-04-01

    High-frequency river water quality monitoring provides detailed hydrochemical information on the time scale of hydrologic response. Several studies (Kirchner et al., 2004; Johnes, 2007; Cassidy and Jordan, 2011) have shown previously that coarse sampling approaches fail to quantify nutrient and sediment loads and to capture the fine structure of water quality dynamics correctly. A robust analysis of high-frequency nutrient and water quality time series can present a complex conceptual, analytical and computational problem. High-frequency nutrient monitoring provides new evidence of processes and patterns that could not be observed previously using standard coarse resolution sampling schemes. However, to fully utilise the wealth of information contained in high-frequency nutrient data, we need to address the following questions: how to detect complex coupling patterns and processes in high-resolution flow-nutrients data, how do these patterns and processes change throughout the period of observation, and how to distinguish noise signals from an evidence of real processes (Harris and Heathwaite, 2005). Here, hourly measurements of total phosphorus (TP), soluble reactive phosphorus (SRP) and turbidity were carried out using bank side analysers to study the biogeochemical response of a 54 km2 catchment of the River Leith, a tributary of the River Eden (Cumbria, UK). A remote automated mobile lab facilitates real-time high-frequency nutrient and water quality monitoring, with no time delay between collection and analysis of the reactive elements. The objectives of this study were two-fold: first to investigate the intrinsic complexity of the temporal relationship between phosphorus fractions (SRP, TP), turbidity and continuous hydrometric time series and secondly to investigate the possibilities of missing high-frequency phosphorus data infilling using continuous hydrometric time series. Complex non-linear relationships between flow, TP and SRP, turbidity were observed

  7. Stream Temperature Spatial and Temporal Response to Large Dam Removal and Groundwater Pumping under Varying Climate Conditions

    Science.gov (United States)

    Risley, J. C.; Constantz, J. E.; Essaid, H.; Rounds, S. A.

    2016-12-01

    We simulated the effects of large upstream dam removal and in-reach groundwater pumping on stream temperature spatial and temporal patterns in a hypothetical river basin under varying climate conditions. A MODFLOW-2000 model, with options for stream-aquifer interaction and grid-block rewetting, was constructed to simulate monthly streamflows for 12 watershed scenarios described below. For each scenario, streamflow output became input into a stream temperature simulation model. Stream temperatures were simulated using the CE-QUAL-W2 water quality model over a 110 km model grid, with the presence and removal of a dam at the top of the reach and pumping in the lower 60 km of the reach. Measured meteorological data from three locations in Oregon and California representing the three meteorological conditions were used as model input to simulate the impact of varying climate conditions on streamflows and stream temperature. For each climate condition, four hypothetical watershed scenarios were modeled: (1) natural (no dam or pumping), (2) large upstream dam present, (3) dam with in-reach pumping, and (4) no dam with pumping continued, resulting in 12 cases. If a transition from a humid to more arid environment occurs under future climate change, the simulations showed that decreased streamflow, increased solar radiation, and increased air temperatures would result in overall increased stream temperatures as expected. From March to August, the presence of a dam caused monthly mean stream temperatures to decrease on average by approximately 3.0°C, 2.5°C, and 2.0°C for the humid, semiarid, and arid conditions, respectively; however, stream temperatures generally increased from September to February. Pumping caused stream temperatures to warm in summer and cool in winter by generally less than 0.5°C. Though dam removal led to greater changes in stream temperature than pumping, ephemeral conditions were increased both temporally and spatially by pumping.

  8. Investigation of Hillslope-Scale Soil Moisture Spatial and Temporal Variability

    Science.gov (United States)

    Martini, E.; Kögler, S.; Wollschlaeger, U.; Zacharias, S.; Werban, U.; Dietrich, P.

    2013-12-01

    Soil moisture is a key state variable that controls hydrological and energy fluxes at various spatial and temporal scales. Understanding and characterizing this variability is one of the major challenges within hydrological sciences. Understanding soil moisture dynamics at the hillslope scale is important to link point- and catchment-scale studies, and for up- and down-scaling of hydrological processes. Nevertheless, deriving generalizable process understanding is not trivial, because of the non-linearity of hillslope response to rainfall. The overall aim of this work was to describe the soil moisture variability at different spatial and temporal scales within a hillslope area with varying topography and soil type but homogeneous land use. Recent developments of wireless sensor technology allow for the long-term monitoring of soil water content with high spatial and temporal resolution, hence facilitate a better understanding of soil moisture spatial variability and the related hydrological processes. Geophysical techniques such as electromagnetic induction (EMI) methods have been widely used during the last decades to map soil properties at the field scale, because of their suitability for fast and precise mapping of soil apparent electrical conductivity (ECa) over large areas. In the Harz Mountains (Central Germany), a 2.5 ha hillslope area was permanently instrumented with a wireless soil moisture and soil temperature monitoring network (SoilNet). It comprises 40 measurement nodes, and 30 of them were located according to a geostatitstical sampling strategy based on ancillary information. At each of the network nodes, 6 sensors measure hourly the soil water content and soil temperature at three depths within the vadose zone. Time-lapse EMI measurements were carried out to map spatial patterns of ECa over several depths. The one-year high-resolution SoilNet time-series is described, and the soil moisture spatial variability is discussed.

  9. Spatial and temporal scales of satellite sea surface salinity variability in the Tropical Atlantic

    Science.gov (United States)

    Tzortzi, E.

    2016-02-01

    Taking advantage of the different coverage of satellite-derived sea surface salinity (SSS), concurrent SMOS and Aquarius observations are used for the first time for the quantification of the spatial and temporal decorrelation scales of SSS in the Tropical Atlantic. Different 7-10 days composite SSS products from the two missions are used to examine any potential effects of varying resolution, bias corrections and averaging characteristics. Given the dominance of the seasonal cycle in SSS variability in the region, the scales are calculated both for the mean and anomaly SSS fields. With the seasonal cycle retained, homogeneous SSS variations are strongly anisotropic, with the longest zonal scales in the Tropics reaching over 2000 km and long temporal scales of up to 70-80 days, as seen by both SMOS and Aquarius. The longest meridional scales of over 1000 km occur in the South Atlantic ( 10°-25°S), most discernible in Aquarius data. SSS variability has the longest persistence in time of up to 150-200 days at the Southern Sargasso Sea in the N.W. Atlantic. The removal of the seasonal cycle decreases noticeably the spatio-temporal scales over most of the basin. Overall, with the exception of differences in the S. Atlantic, there is good consistency between the spatio-temporal scales of SSS from the two satellites and different products, despite their individual calibration and resolution characteristics. The new estimates of decorrelation scales of SSS improve our knowledge of the processes and mechanisms controlling the Tropical Atlantic SSS variability, and represent a powerful new investigative tool equally applicable to other regions, SSS products and other ocean geophysical properties. This work has also important applications for the evaluation of the impact of satellite SSS in assimilation systems, the development of optimally interpolated products, as well as the definition of appropriate validation procedures of the various satellite SSS products.

  10. Seasonal and Spatial Variability of Anthropogenic and Natural Factors Influencing Groundwater Quality Based on Source Apportionment.

    Science.gov (United States)

    Guo, Xueru; Zuo, Rui; Meng, Li; Wang, Jinsheng; Teng, Yanguo; Liu, Xin; Chen, Minhua

    2018-02-06

    Globally, groundwater resources are being deteriorated by rapid social development. Thus, there is an urgent need to assess the combined impacts of natural and enhanced anthropogenic sources on groundwater chemistry. The aim of this study was to identify seasonal characteristics and spatial variations in anthropogenic and natural effects, to improve the understanding of major hydrogeochemical processes based on source apportionment. 34 groundwater points located in a riverside groundwater resource area in northeast China were sampled during the wet and dry seasons in 2015. Using principal component analysis and factor analysis, 4 principal components (PCs) were extracted from 16 groundwater parameters. Three of the PCs were water-rock interaction (PC₁), geogenic Fe and Mn (PC₂), and agricultural pollution (PC₃). A remarkable difference (PC₄) was organic pollution originating from negative anthropogenic effects during the wet season, and geogenic F enrichment during the dry season. Groundwater exploitation resulted in dramatic depression cone with higher hydraulic gradient around the water source area. It not only intensified dissolution of calcite, dolomite, gypsum, Fe, Mn and fluorine minerals, but also induced more surface water recharge for the water source area. The spatial distribution of the PCs also suggested the center of the study area was extremely vulnerable to contamination by Fe, Mn, COD, and F - .

  11. Temporal and Spatial prediction of groundwater levels using Artificial Neural Networks, Fuzzy logic and Kriging interpolation.

    Science.gov (United States)

    Tapoglou, Evdokia; Karatzas, George P.; Trichakis, Ioannis C.; Varouchakis, Emmanouil A.

    2014-05-01

    The purpose of this study is to examine the use of Artificial Neural Networks (ANN) combined with kriging interpolation method, in order to simulate the hydraulic head both spatially and temporally. Initially, ANNs are used for the temporal simulation of the hydraulic head change. The results of the most appropriate ANNs, determined through a fuzzy logic system, are used as an input for the kriging algorithm where the spatial simulation is conducted. The proposed algorithm is tested in an area located across Isar River in Bayern, Germany and covers an area of approximately 7800 km2. The available data extend to a time period from 1/11/2008 to 31/10/2012 (1460 days) and include the hydraulic head at 64 wells, temperature and rainfall at 7 weather stations and surface water elevation at 5 monitoring stations. One feedforward ANN was trained for each of the 64 wells, where hydraulic head data are available, using a backpropagation algorithm. The most appropriate input parameters for each wells' ANN are determined considering their proximity to the measuring station, as well as their statistical characteristics. For the rainfall, the data for two consecutive time lags for best correlated weather station, as well as a third and fourth input from the second best correlated weather station, are used as an input. The surface water monitoring stations with the three best correlations for each well are also used in every case. Finally, the temperature for the best correlated weather station is used. Two different architectures are considered and the one with the best results is used henceforward. The output of the ANNs corresponds to the hydraulic head change per time step. These predictions are used in the kriging interpolation algorithm. However, not all 64 simulated values should be used. The appropriate neighborhood for each prediction point is constructed based not only on the distance between known and prediction points, but also on the training and testing error of

  12. On the Temporal Variability of Low-Mode Internal Tides in the Deep Ocean

    Science.gov (United States)

    Ray, Richard D.; Zaron, E. D.

    2010-01-01

    In situ measurements of internal tides are typically characterized by high temporal variability, with strong dependence on stratification, mesoscale eddies, and background currents commonly observed. Thus, it is surprising to find phase-locked internal tides detectable by satellite altimetry. An important question is how much tidal variability is missed by altimetry. We address this question in several ways. We subset the altimetry by season and find only very small changes -- an important exception being internal tides in the South China Sea where we observe strong seasonal dependence. A wavenumber-domain analysis confirms that throughout most of the global ocean there is little temporal variability in altimetric internal-tide signals, at least in the first baroclinic mode, which is the mode that dominates surface elevation. The analysis shows higher order modes to be significantly more variable. The results of this study have important practical implications for the anticipated SWOT wide-swath altimeter mission, for which removal of internal tide signals is critical for observing non-tidal submesoscale phenomena.

  13. Spatial and temporal variability of snow depth and ablation rates in a small mountain catchment

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    T. Grünewald

    2010-05-01

    Full Text Available The spatio-temporal variability of the mountain snow cover determines the avalanche danger, snow water storage, permafrost distribution and the local distribution of fauna and flora. Using a new type of terrestrial laser scanner, which is particularly suited for measurements of snow covered surfaces, snow depth was monitored in a high alpine catchment during an ablation period. From these measurements snow water equivalents and ablation rates were calculated. This allowed us for the first time to obtain a high resolution (2.5 m cell size picture of spatial variability of the snow cover and its temporal development. A very high variability of the snow cover with snow depths between 0–9 m at the end of the accumulation season was observed. This variability decreased during the ablation phase, while the dominant snow deposition features remained intact. The average daily ablation rate was between 15 mm/d snow water equivalent at the beginning of the ablation period and 30 mm/d at the end. The spatial variation of ablation rates increased during the ablation season and could not be explained in a simple manner by geographical or meteorological parameters, which suggests significant lateral energy fluxes contributing to observed melt. It is qualitatively shown that the effect of the lateral energy transport must increase as the fraction of snow free surfaces increases during the ablation period.

  14. Assessing temporal uncertainties in integrated groundwater management: an opportunity for change?

    Science.gov (United States)

    Anglade, J. A.; Billen, G.; Garnier, J.

    2013-12-01

    aquifer of about 25 years. Uncertainties about the time delay for positive results created a shock among the involved actors that motivated them to re-launch the dialogue, and enter into a new phase of the iterative decision making process to determine up to date long term strategies. Secondly, a diagnostic of recommended solutions in the existing agreements based on the soil surface balance method has raised alert about the inefficiency of agricultural best practices set up to deliver sub-root water concentration meeting the European drinking standard. According to the scientific committee, only a shift to organic farming could reconcile water and food production, with the pre-condition that this agricultural transition takes place in a territorial project which goes beyond the catchment borders. This proposal offers possibilities for re-structuring the issue for the different sides. This example underlines that integrated groundwater management could impose a time delay of several decades to cope with complex biophysical processes, construct coordination and modify individual practices. This time needed to build collaborative agreement is all the more difficult to control as part of an evolving regulatory framework.

  15. Spatio-temporal variability of faunal and floral assemblages in Mediterranean temporary wetlands.

    Science.gov (United States)

    Rouissi, Maya; Boix, Dani; Muller, Serge D; Gascón, Stéphanie; Ruhí, Albert; Sala, Jordi; Bouattour, Ali; Ben Haj Jilani, Imtinen; Ghrabi-Gammar, Zeineb; Ben Saad-Limam, Samia; Daoud-Bouattour, Amina

    2014-12-01

    Six temporary wetlands in the region of Sejenane (Mogods, NW Tunisia) were studied in order to characterize the aquatic flora and fauna and to quantify their spatio-temporal variability. Samplings of aquatic fauna, phytosociological relevés, and measurements of the physicochemical parameters of water were taken during four different field visits carried out during the four seasons of the year (November 2009-July 2010). Despite the strong anthropic pressures on them, these temporary wetlands are home to rich and diversified biodiversity, including rare and endangered species. Spatial and temporal variations affect fauna and flora differently, as temporal variability influences the fauna rather more than the plants, which are relatively more dependent on spatial factors. These results demonstrate the interest of small water bodies for maintaining biodiversity at the regional level, and thus underscore the conservation issues of Mediterranean temporary wetlands that are declining on an ongoing basis currently. Copyright © 2014 Académie des sciences. Published by Elsevier SAS. All rights reserved.

  16. Spatio-temporal analysis of the relationship between WNV dissemination and environmental variables in Indianapolis, USA

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    Gaines David

    2008-12-01

    Full Text Available Abstract Background This study developed a multi-temporal analysis on the relationship between West Nile Virus (WNV dissemination and environmental variables by using an integrated approach of remote sensing, GIS, and statistical techniques. WNV mosquito cases in seven months (April-October of the six years (2002–2007 were collected in Indianapolis, USA. Epidemic curves were plotted to identify the temporal outbreaks of WNV. Spatial-temporal analysis and k-mean cluster analysis were further applied to determine the high-risk areas. Finally, the relationship between environmental variables and WNV outbreaks were examined by using Discriminant Analysis. Results The results show that the WNV epidemic curve reached its peak in August for all years in the study area except in 2007, where the peak was reached in July. WNV dissemination started from the central longitudinal corridor of the city and spread out to the east and west. Different years and seasons had different high-risk areas, but the southwest and southeast corners show the highest risk for WNV infection due to their high percentages of agriculture and water sources. Conclusion Major environmental factors contributing to the outbreak of WNV in Indianapolis were the percentages of agriculture and water, total length of streams, and total size of wetlands. This study provides important information for urban public health prevention and management. It also contributes to the optimization of mosquito control and arrangement of future sampling efforts.

  17. Temporal variability in macroinvertebrates diversity patterns and their relation with environmental factors

    Directory of Open Access Journals (Sweden)

    MOHAMMAD HASAN GERAMI

    2016-05-01

    Full Text Available Abstract. Gerami MH, Patimar R, Negarestan H, Jafarian H, Mortazavi MS. 2015. Temporal variability in macroinvertebrates diversity patterns and their relation with environmental factors. Biodiversitas 17: 36-43. Seasonal changes are the most important factor in temporal variability of macroinvertebrates communities in marine benthic zone. Realizing the pattern of these changes are the key attributes to maintain benthic resources. For this purpose this study aimed to investigate temporal variability of macroinvertebrates diversity patterns in different seasons in Hormozgan province waters, Persian Gulf. Five sites were identified and sampling was carried out randomly at three places with three replicate in each site from autumn 2014 to spring 2015. Physiochemical properties of water were recorded in each sampling site. Total of 19 macroinvertebrate orders were identified form four seasons in all sites. Results showed that Polychaeta were dominant taxa in all seasons and maximum diversity of benthic macroinvertebrates exhibited in winter. According to evenness index (E1, abundances of species were most balanced in spring. Analysis of weight and density revealed that the species diversity and mean weight of macroinvertebrates had maximum in winter and minimum in summer. Macroinvertebrate community structure was similar in the spring and summer and partly discriminated from remaining two seasons. SIMPER analysis confirmed these dissimilarities and revealed that Foraminifera, Gastropoda and Polychaeta have three major contributions in dissimilarities between seasons. According to BIO-ENV analysis, oxygen and chlorophyll a were the best variables (r = 0.7143 explaining changes in the abundance over time of the benthic fauna under study. On the contrary, eight orders (Amphipoda, Secernentea, Cumacea, Euphausiacea, Gastropoda, Isopoda, Anthozoa and Sagittoidea did not show any convergence with environmental factors in this study.

  18. Hydroclimate temporal variability in a coastal Mediterranean watershed: the Tafna basin, North-West Algeria

    Science.gov (United States)

    Boulariah, Ouafik; Longobardi, Antonia; Meddi, Mohamed

    2017-04-01

    One of the major challenges scientists, practitioners and stakeholders are nowadays involved in, is to provide the worldwide population with reliable water supplies, protecting, at the same time, the freshwater ecosystems quality and quantity. Climate and land use changes undermine the balance between water demand and water availability, causing alteration of rivers flow regime. Knowledge of hydro-climate variables temporal and spatial variability is clearly helpful to plan drought and flood hazard mitigation strategies but also to adapt them to future environmental scenarios. The present study relates to the coastal semi-arid Tafna catchment, located in the North-West of Algeria, within the Mediterranean basin. The aim is the investigation of streamflow and rainfall indices temporal variability in six sub-basins of the large catchment Tafna, attempting to relate streamflow and rainfall changes. Rainfall and streamflow time series have been preliminary tested for data quality and homogeneity, through the coupled application of two-tailed t test, Pettitt test and Cumsum tests (significance level of 0.1, 0.05 and 0.01). Subsequently maximum annual daily rainfall and streamflow and average daily annual rainfall and streamflow time series have been derived and tested for temporal variability, through the application of the Mann Kendall and Sen's test. Overall maximum annual daily streamflow time series exhibit a negative trend which is however significant for only 30% of the station. Maximum annual daily rainfall also e exhibit a negative trend which is intend significant for the 80% of the stations. In the case of average daily annual streamflow and rainfall, the tendency for decrease in time is unclear and, in both cases, appear significant for 60% of stations.

  19. Spatial and temporal CH4 flux variability in a shallow tropical floodplain lake, Pantanal, South America

    Science.gov (United States)

    Peixoto, R.; Enrich Prast, A.; Silva, E. C.; Pontual, L.; Marotta, H.; Pinho, L.; Bastviken, D.

    2012-04-01

    Spatial and temporal CH4 flux variability in a shallow tropical floodplain lake, Pantanal, South America Peixoto, R, Enrich-Prast, A., Silva, E. C., Pontual, L., Marotta, H., Pinho, L. Q. and Bastviken, D. Methane (CH4) is an important greenhouse gas produced during anaerobic decomposition of organic matter (OM). It can play a significant role in carbon emissions from tropical aquatic ecosystems to the atmosphere and have a substantial participation in greenhouse gas balances. However, most studies report low numbers of short-term (≤ 24h) measurements in each system and the spatial and temporal variability is poorly understood. In this study we analyzed the temporal and spatial variability of CH4 emissions from a shallow Pantanal lake. Pantanal is the world's largest savanna tropical floodplain with a significant input of organic matter from the drainage area around and an annual inundation pulse. Methane fluxes were measured in September 2008 with floating chambers over 24 hour periods for five consecutive days. We used > 20 chambers along transects from the marginal vegetated regions of the lake to the central parts of the lake. Methane fluxes were determined as described by Bastviken et al. 2010 (doi: 10.1021/es1005048). There was no significant difference of methane fluxes among sampling days. Methane fluxes at the vegetated area and the margin were significantly higher than at central parts of the lake showing clearly the importance of different compartments within lakes. This study indicates that a) 24 hour measurements may be representative for time perspectives of a week given similar weather conditions, while b) spatial variability within lakes must be considered to correctly evaluate CH4 emissions from aquatic systems.

  20. Simulating Salt Movement and Transformation using a Coupled Reactive Transport Model in Variably-Saturated Groundwater Systems

    Science.gov (United States)

    Tavakoli Kivi, S.; Bailey, R. T.; Gates, T.

    2016-12-01

    Salinization is one of the major concerns in irrigated agricultural landscapes. Increasing salinity concentrations are due principally to evaporative concentration; dissolution of salts from weathered minerals and bedrock; and a high water table that results from excessive irrigation, canal seepage, and a lack of efficient drainage systems; leading to decreasing crop yield. High groundwater salinity loading to nearby river systems also impacts downstream areas, with saline river water diverted for application on irrigated fields. In this study, a solute transport model coupled with equilibrium chemistry reactions has been developed to simulate transport of individual salt ions in regional-scale aquifer systems and thereby investigate strategies for salinity remediation. The physically-based numerical model is based on the UZF-RT3D variably-saturated, multi-species groundwater reactive transport modeling code, and accounts for advection, dispersion, carbon and nitrogen cycling, oxidation-reduction reactions, and salt ion equilibrium chemistry reactions such as complexation, ion exchange, and precipitation/dissolution. Each major salt ion (sulfate, chloride, bicarbonate, calcium, sodium, magnesium, potassium) is included. The model has been tested against measured soil salinity at a small scale (soil profile) and against soil salinity, groundwater salinity, and groundwater salinity loading to surface water at the regional scale (500 km2) in the Lower Arkansas River Valley (LARV) in southeastern Colorado, an area acutely affected by salinization for many decades and greatly influenced by gypsum deposits. Preliminary results of using the model in scenario analysis suggest that increasing irrigation efficiency, sealing earthen canals, and rotational fallowing of land can decrease the groundwater salt load to the Arkansas River by 50 to 70% and substantially lower soil salinity in the root zone.

  1. Improvement of groundwater level prediction in sparsely gauged basins using physical laws and local geographic features as auxiliary variables

    Science.gov (United States)

    Varouchakis, E. A.; Hristopulos, D. T.

    2013-02-01

    This work aims to present new modeling tools that help to better monitor and predict the groundwater level in sparsely gauged basins. The working area is the Mires basin of Mesara valley in the island of Crete (Greece). Efficient groundwater management in the basin is crucial in light of regional climate change model estimates showing a substantial risk of desertification for Crete. We propose that the prediction of the hydraulic head spatial variability in Mires basin can be improved by incorporating in the trend the distance of the prediction points from a temporary river crossing the basin and a component based on the generalized Thiem's equation for multiple wells as well as using the flexible Spartan semivariogram family to perform Residual Kriging. Our proposal is supported by the results of cross validation analysis. Our results are applicable to other unconfined aquifers.

  2. McMaster Mesonet soil moisture dataset: description and spatio-temporal variability analysis

    Directory of Open Access Journals (Sweden)

    K. C. Kornelsen

    2013-04-01

    Full Text Available This paper introduces and describes the hourly, high-resolution soil moisture dataset continuously recorded by the McMaster Mesonet located in the Hamilton-Halton Watershed in Southern Ontario, Canada. The McMaster Mesonet consists of a network of time domain reflectometer (TDR probes collecting hourly soil moisture data at six depths between 10 cm and 100 cm at nine locations per site, spread across four sites in the 1250 km2 watershed. The sites for the soil moisture arrays are designed to further improve understanding of soil moisture dynamics in a seasonal climate and to capture soil moisture transitions in areas that have different topography, soil and land cover. The McMaster Mesonet soil moisture constitutes a unique database in Canada because of its high spatio-temporal resolution. In order to provide some insight into the dominant processes at the McMaster Mesonet sites, a spatio-temporal and temporal stability analysis were conducted to identify spatio-temporal patterns in the data and to suggest some physical interpretation of soil moisture variability. It was found that the seasonal climate of the Great Lakes Basin causes a transition in soil moisture patterns at seasonal timescales. During winter and early spring months, and at the meadow sites, soil moisture distribution is governed by topographic redistribution, whereas following efflorescence in the spring and summer, soil moisture spatial distribution at the forested site was also controlled by vegetation canopy. Analysis of short-term temporal stability revealed that the relative difference between sites was maintained unless there was significant rainfall (> 20 mm or wet conditions a priori. Following a disturbance in the spatial soil moisture distribution due to wetting, the relative soil moisture pattern re-emerged in 18 to 24 h. Access to the McMaster Mesonet data can be provided by visiting www.hydrology.mcmaster.ca/mesonet.

  3. Spatial variability and long-term analysis of groundwater quality of Faisalabad industrial zone

    Science.gov (United States)

    Nasir, Muhammad Salman; Nasir, Abdul; Rashid, Haroon; Shah, Syed Hamid Hussain

    2017-10-01

    Water is the basic necessity of life and is essential for healthy society. In this study, groundwater quality analysis was carried out for the industrial zone of Faisalabad city. Sixty samples of groundwater were collected from the study area. The quality maps of deliberately analyzed results were prepared in GIS. The collected samples were analyzed for chemical parameters and heavy metals, such as total hardness, alkalinity, cadmium, arsenic, nickel, lead, and fluoride, and then, the results were compared with the WHO guidelines. The values of these results were represented by a mapping of quality parameters using the ArcView GIS v9.3, and IDW was used for raster interpolation. The long-term analysis of these parameters has been carried out using the `R Statistical' software. It was concluded that water is partially not fit for drinking, and direct use of this groundwater may cause health issues.

  4. Short-term spatial and temporal variability in greenhouse gas fluxes in riparian zones.

    Science.gov (United States)

    Vidon, P; Marchese, S; Welsh, M; McMillan, S

    2015-08-01

    Recent research indicates that riparian zones have the potential to contribute significant amounts of greenhouse gases (GHG: N2O, CO2, CH4) to the atmosphere. Yet, the short-term spatial and temporal variability in GHG emission in these systems is poorly understood. Using two transects of three static chambers at two North Carolina agricultural riparian zones (one restored, one unrestored), we show that estimates of the average GHG flux at the site scale can vary by one order of magnitude depending on whether the mean or the median is used as a measure of central tendency. Because the median tends to mute the effect of outlier points (hot spots and hot moments), we propose that both must be reported or that other more advanced spatial averaging techniques (e.g., kriging, area-weighted average) should be used to estimate GHG fluxes at the site scale. Results also indicate that short-term temporal variability in GHG fluxes (a few days) under seemingly constant temperature and hydrological conditions can be as large as spatial variability at the site scale, suggesting that the scientific community should rethink sampling protocols for GHG at the soil-atmosphere interface to include repeated measures over short periods of time at select chambers to estimate GHG emissions in the field. Although recent advances in technology provide tools to address these challenges, their cost is often too high for widespread implementation. Until technology improves, sampling design strategies will need to be carefully considered to balance cost, time, and spatial and temporal representativeness of measurements.

  5. The trade-off between spatial and temporal variabilities in reciprocal upper-limb aiming movements of different durations.

    Science.gov (United States)

    Danion, Frederic; Bongers, Raoul M; Bootsma, Reinoud J

    2014-01-01

    The spatial and temporal aspects of movement variability have typically been studied separately. As a result the relationship between spatial and temporal variabilities remains largely unknown. In two experiments we examined the evolution and covariation of spatial and temporal variabilities over variations in the duration of reciprocal aiming movements. Experiments differed in settings: In Experiment 1 participants moved unperturbed whereas in Experiment 2 they were confronted with an elastic force field. Different movement durations-for a constant inter-target distance-were either evoked by imposing spatial accuracy constraints while requiring participants to move as fast as possible, or prescribed by means of an auditory metronome while requiring participants to maximize spatial accuracy. Analyses focused on absolute and relative variabilities, respectively captured by the standard deviation (SD) and the coefficient of variation (CV = SD/mean). Spatial variability (both SDspace and CVspace) decreased with movement duration, while temporal variability (both SDtime and CVtime) increased with movement duration. We found strong negative correlations between spatial and temporal variabilities over variations in movement duration, whether the variability examined was absolute or relative. These findings observed at the level of the full movement contrasted with the findings observed at the level of the separate acceleration and deceleration phases of movement. During the separate acceleration and deceleration phases both spatial and temporal variabilities (SD and CV) were found to increase with their respective durations, leading to positive correlations between them. Moreover, variability was generally larger at the level of the constituent movement phases than at the level of the full movement. The general pattern of results was robust, as it emerged in both tasks in each of the two experiments. We conclude that feedback mechanisms operating to maximize task

  6. Understanding the Temporal and Spatial Variability of New Generation Gridded TMYs

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, Anthony

    2017-04-26

    Presentation at ASHRAE about the spatial and temporal variability of gridded TMYs, discussing advanced GIS and Web services that allow for direct access to data, surface-based observations for thousands of stations, climate reanalysis data, and products derived from satellite data; new developments in NREL's solar databases based on both observed data and satellite-derived gridded data, status of TMY3 weather files, and NREL's plans for the next-generation TMY weather files; and also covers what is new and different in the Climatic Design Conditions Table in the 2013 ASHRAE Handbook of Fundamentals.

  7. Spatial and Temporal Variability of Channel Retention in a Lowland Temperate Forest Stream Settled by European Beaver (Castor fiber

    Directory of Open Access Journals (Sweden)

    Mateusz Grygoruk

    2014-09-01

    Full Text Available Beaver ponds remain a challenge for forest management in those countries where expansion of beaver (Castor fiber is observed. Despite undoubted economic losses generated in forests by beaver, their influence on hydrology of forest streams especially in terms of increasing channel retention (amount of water stored in the river channel, is considered a positive aspect of their activity. In our study, we compared water storage capacities of a lowland forest stream settled by beaver in order to unravel the possible temporal variability of beaver’s influence on channel retention. We compared distribution, total damming height, volumes and areas of beaver ponds in the valley of Krzemianka (Northeast Poland in the years 2006 (when a high construction activity of beaver was observed and in 2013 (when the activity of beaver decreased significantly. The study revealed a significant decrease of channel retention of beaver ponds from over 15,000 m3 in 2006 to 7000 m3 in 2013. The total damming height of the cascade of beaver ponds decreased from 6.6 to 5.6 m. Abandoned beaver ponds that transferred into wetlands, where lost channel retention was replaced by soil and groundwater retention, were more constant over time and less vulnerable to the external disturbance means of water storage than channel retention. We concluded that abandoned beaver ponds played an active role in increasing channel retention of the river analyzed for approximately 5 years. We also concluded that if the construction activity of beaver was used as a tool (ecosystem service in increasing channel retention of the river valley, the permanent presence of beaver in the riparian zone of forest streams should have been assured.

  8. Temporal variability in taxonomic and trait compositions of invertebrate assemblages in two climatic regions with contrasting flow regimes.

    Science.gov (United States)

    Dolédec, Sylvain; Tilbian, Jessica; Bonada, Núria

    2017-12-01

    Understanding natural temporal changes in Mediterranean rivers with contrasting flow regimes in relation to those of temperate rivers may prove helpful in predicting effects of climate change on aquatic biodiversity. We aimed to compare temporal variability in taxonomic and trait compositions of nearly natural rivers in two climatic regions with varying flow regimes to address the effects of future climate changes on aquatic biodiversity in reference conditions. We analysed taxonomic and biological trait compositions using the Foucard multivariate method to compare within-site temporal variability levels and the evolution of within-date spatial variability patterns. In addition, we assessed the effects of temporal variability levels on taxonomic and functional diversity and on community specialization. Our results reveal (i) highly fluctuating environments of the Mediterranean region, particularly in intermittent rivers, which lead to higher levels of temporal variability in both taxonomic and trait compositions of benthic invertebrate assemblages, with marked synchrony in Mediterranean streams linked to contrasting flow characteristics; (ii) higher degrees of taxonomic richness associated with higher levels of functional diversity in Mediterranean rivers relative to temperate rivers, (iii) higher temporal stability for functional diversity and trait compositions of benthic invertebrate assemblages than for taxonomic richness and compositions; and (iv) a recovery of all diversity metrics following drying events in intermittent sites. This study offers insight into a rarely addressed question concerning the temporal variability of trait compositions in benthic invertebrate assemblages among rivers differing in terms of flow regimes. It suggests that temperate rivers will experience higher levels of temporal variability in terms of taxonomic and trait compositions under future climatic change scenarios, even in sites that will remain perennial, resulting in higher

  9. Temporal Variability and Trends of Rainfall and Streamflow in Tana River Basin, Kenya

    Directory of Open Access Journals (Sweden)

    Philip Kibet Langat

    2017-10-01

    Full Text Available This study investigated temporal variabilities and trends of rainfall and discharges in Tana River Basin in Kenya using Mann–Kendall non-parametric test. Monthly rainfall data from ten stations spanning from 1967 to 2016 and daily streamflow data time series of observations from 1941 to 2016 (75 years were analyzed with the aim of capturing and detecting multiannual and seasonal variabilities and monotonic trends. The results for the datasets suggested that the streamflow is largely dependent on increasing rainfall at the highlands. The rainfall trends seemed to have been influenced by altitudinal factors. The coefficient of variation of the ten rainfall stations ranged from 12% to 17% but 70% of rainfall stations showed negative monotonic trends and 30% show significant trends. The streamflow showed statistically significant upward monotonic trend and seasonal variability indicating a substantial change in the streamflow regime. Although the increasing trend of the streamflow during this period may not pose future risks and vulnerability of energy and irrigated agricultural production systems across the basin, variability observed indicates the need for enhanced alternative water management strategies during the low flow seasons. The trends and time series data indicate the potential evidence of climate and land use change and their impacts on the availability of water and sustainability of ecology and energy and agricultural production systems across the basin. Variability and trends of rainfall and streamflow are useful for planning studies, hydrological modeling and climate change impacts assessment within Tana River Basin.

  10. Temporal and Spatial Variability of Droughts in Southwest China from 1961 to 2012

    Directory of Open Access Journals (Sweden)

    Yaohuan Huang

    2015-10-01

    Full Text Available Southwest China (SC has suffered a series of super extreme droughts in the last decade. This study analyzed the temporal and spatial variations of drought in SC from 1961 to 2012. Based on precipitation anomaly index (PAI that was derived from 1 km gridded precipitation data, three time scales (month, year and decade for the drought frequency (DF and drought area were applied to estimate the spatio-temporal structure of droughts. A time-series analysis showed that winter droughts and spring droughts occurred frequently for almost half of the year from November to March. Summer droughts occasionally occurred in severe drought decades: the 1960s, 1980s and 2000s. During the period of observation, the percent of drought area in SC increased from the 1960s (<5% to the 2000s (>25%. A total of 57% of the area was affected by drought in 2011, when the area experienced its most severe drought both in terms of area and severity. The spatial analysis, which benefitted from the gridded data, detailed that all of SC is at drought risk except for the central Sichuan Basin. The area at high risk for severe and extreme droughts was localized in the mountains of the junction of Sichuan and Yunnan. The temporal and spatial variability can be prerequisites for drought resistance planning and drought risk management of SC.

  11. Implications of temporal variability for uncertainty in spatial interpretations of stream geochemistry data

    Science.gov (United States)

    Bearcock, Jenny; Lark, Murray

    2016-04-01

    Stream water is a key medium for regional geochemical survey. Stream water geochemical data have many potential applications, including mineral exploration, environmental monitoring and protection, catchment management and modelling potential impacts of climate or land use changes. However, stream waters are transient, and measurements are susceptible to various sources of temporal variation. In a regional geochemical survey stream water data comprise "snapshots" of the state of the medium at a sample time. For this reason the British Geological Survey (BGS) has included monitoring streams in its regional geochemical baseline surveys (GBASE) at which daily stream water samples are collected to supplement the spatial data collected in once-off sampling events. In this study we present results from spatio-temporal analysis of spatial stream water surveys and the associated monitoring stream data. We show how the interpretation of the temporal variability as a source of uncertainty depends on how the spatial data are interpreted (as estimates of a summer-time mean concentration, or as point measurements), and explore the implications of this uncertainty in the interpretation of stream water data in a regulatory context.

  12. Temporal variability of marine debris deposition at Tern Island in the Northwestern Hawaiian Islands.

    Science.gov (United States)

    Agustin, Alyssa E; Merrifield, Mark A; Potemra, James T; Morishige, Carey

    2015-12-15

    A twenty-two year record of marine debris collected on Tern Island is used to characterize the temporal variability of debris deposition at a coral atoll in the Northwestern Hawaiian Islands. Debris deposition tends to be episodic, without a significant relationship to local forcing processes associated with winds, sea level, waves, and proximity to the Subtropical Convergence Zone. The General NOAA Operational Modeling Environment is used to estimate likely debris pathways for Tern Island. The majority of modeled arrivals come from the northeast following prevailing trade winds and surface currents, with trajectories indicating the importance of the convergence zone, or garbage patch, in the North Pacific High region. Although debris deposition does not generally exhibit a significant seasonal cycle, some debris types contain considerable 3 cycle/yr variability that is coherent with wind and surface pressure over a broad region north of Tern. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Temporal Variability and Environmental Drivers of Harmful Algal Blooms (HABs) in Western Lake Erie

    Science.gov (United States)

    Liang, S.; Tian, D.; Xie, G.; Tian, J.; Tseng, K. S.; Shum, C. K.; Lee, J.

    2014-12-01

    Understanding temporal variability and environmental drivers of harmful algal blooms (HABs) is important for guiding HABs impact mitigation plans in Lake Erie. The objective of this study is to characterize temporal variability and explore environmental driving factors of chlorophyll a (Chl-a) and phycocyanin (PC), which are determinants of HABs, in western Lake Erie. Ten years' (2002 to 2012) biweekly estimates of Chl-a and PC over western Lake Erie were retrieved from remote sensing-based measurements of water color with Medium Resolution Imaging Spectrometer ( MERIS). Nine environmental factors, including water quality and hydrometeorological variables, for the same period were also collected. While Chl-a and PC showed different predictabilities and differences in importance of environmental drivers at different locations and seasons using the Multivariate Adaptive Regression Splines (MARS) with the Variance Inflation Factor (VIF) method, hydrometeorological variables consistently showed great influences on Chl-a and PC in all four seasons. For Chl-a, the most significant environmental drivers are solar radiation and wind speed (spring); water temperature, solar radiation, and total Kjeldahl nitrogen concentration (summer); wind speed (fall); and water temperature and streamflow (winter). For PC, the most important environmental drivers are solar radiation and wind speed (spring); precipitation, water temperature, wind speed, and total Kjeldahl nitrogen concentration (summer); wind speed (fall); precipitation, water temperature, and streamflow ( winter). Wavelet analysis suggested that Chl-a and PC showed strong seasonal and inter-annual pattern - the 0.5- and 1-year periods are the dominant modes for both Chl-a and PC series. These findings offer insights into possible mechanisms underlying the dynamics of the HABs.

  14. Heterogeneity of gaseous emissions in soils-spatial vs temporal variability

    Science.gov (United States)

    Cardenas, Laura; Chadwick, David; Misselbrook, Tom; Donovan, Neil; Dunn, Rob; Griffith, Bruce; Orr, Robert; Smith, Keith; Rees, Robert M.; Bell, Madeleine; Watson, Catherine; McGeough, Karen; McNeill, Gavin; Williams, John; Cloy, Joanna; Thorman, Rachel; Dhanoa, Dan

    2015-04-01

    Nitrous oxide (N2O) plays a dual role in the atmosphere as a greenhouse gas and via its influence on stratospheric ozone chemistry. The main source of N2O is agricultural soil, with an estimated 96 kt emitted from this source in the UK in 2012 (ca. 83% of the total UK N2O emissions). Microbial transformations such as nitrification, denitrification and chemodenitrification are responsible for these emissions. Soil texture and structure and land management practices (including presence of livestock) -- soil wetness, aeration, temperature and mineral N content -- influence the magnitude of the emissions. Heterogeneity in nutrient distribution and moisture, i.e. hot spots, create spatial variations in the main drivers of these transformations. Studies at laboratory scale are aimed to minimize the variability encountered in the field but although they provide important information on the controlling factors of the soil processes, they are not useful for real quantification. Daily and seasonal variation (temporal) in soil conditions (chemistry, physics and biology) and thus in emissions also occurs. This variability makes it a difficult challenge to quantify emissions and currently makes the soil source the largest contributor to the overall uncertainty of the UK greenhouse gas inventory. Here we present results of a statistical study on the variability of N2O emissions from measurements using the static chamber technique for a variety of N sources. Results from measurements using automated chambers are also presented. Part of the work was funded by the UK government to improve the quantification of this source by measuring emissions from sites with contrasting soil, climate and land management combinations. We also include results from measurements carried out with automated chambers on the UK National Capability Farm Platform in the South West of England. The results show that spatial variability largely contributes to the uncertainty of emissions but temporal

  15. Simulation of groundwater flow in the glacial aquifer system of northeastern Wisconsin with variable model complexity

    Science.gov (United States)

    Juckem, Paul F.; Clark, Brian R.; Feinstein, Daniel T.

    2017-05-04

    The U.S. Geological Survey, National Water-Quality Assessment seeks to map estimated intrinsic susceptibility of the glacial aquifer system of the conterminous United States. Improved understanding of the hydrogeologic characteristics that explain spatial patterns of intrinsic susceptibility, commonly inferred from estimates of groundwater age distributions, is sought so that methods used for the estimation process are properly equipped. An important step beyond identifying relevant hydrogeologic datasets, such as glacial geology maps, is to evaluate how incorporation of these resources into process-based models using differing levels of detail could affect resulting simulations of groundwater age distributions and, thus, estimates of intrinsic susceptibility.This report describes the construction and calibration of three groundwater-flow models of northeastern Wisconsin that were developed with differing levels of complexity to provide a framework for subsequent evaluations of the effects of process-based model complexity on estimations of groundwater age distributions for withdrawal wells and streams. Preliminary assessments, which focused on the effects of model complexity on simulated water levels and base flows in the glacial aquifer system, illustrate that simulation of vertical gradients using multiple model layers improves simulated heads more in low-permeability units than in high-permeability units. Moreover, simulation of heterogeneous hydraulic conductivity fields in coarse-grained and some fine-grained glacial materials produced a larger improvement in simulated water levels in the glacial aquifer system compared with simulation of uniform hydraulic conductivity within zones. The relation between base flows and model complexity was less clear; however, the relation generally seemed to follow a similar pattern as water levels. Although increased model complexity resulted in improved calibrations, future application of the models using simulated particle

  16. Spatial and temporal variability in the ratio of trace gases emitted from biomass burning

    Directory of Open Access Journals (Sweden)

    T. T. van Leeuwen

    2011-04-01

    Full Text Available Fires are a major source of trace gases and aerosols to the atmosphere. The amount of biomass burned is becoming better known, most importantly due to improved burned area datasets and a better representation of fuel consumption. The spatial and temporal variability in the partitioning of biomass burned into emitted trace gases and aerosols, however, has received relatively little attention. To convert estimates of biomass burned to trace gas and aerosol emissions, most studies have used emission ratios (or emission factors (EFs based on the arithmetic mean of field measurement outcomes, stratified by biome. However, EFs vary substantially in time and space, even within a single biome. In addition, it is unknown whether the available field measurement locations provide a representative sample for the various biomes. Here we used the available body of EF literature in combination with satellite-derived information on vegetation characteristics and climatic conditions to better understand the spatio-temporal variability in EFs. While focusing on CO, CH4, and CO2, our findings are also applicable to other trace gases and aerosols. We explored relations between EFs and different measurements of environmental variables that may correlate with part of the variability in EFs (tree cover density, vegetation greenness, temperature, precipitation, and the length of the dry season. Although reasonable correlations were found for specific case studies, correlations based on the full suite of available measurements were lower and explained about 33%, 38%, 19%, and 34% of the variability for respectively CO, CH4, CO2, and the Modified Combustion Efficiency (MCE. This may be partly due to uncertainties in the environmental variables, differences in measurement techniques for EFs, assumptions on the ratio between flaming and smoldering combustion, and incomplete information on the location and timing of EF

  17. Higher temporal variability of forest breeding bird communities in fragmented landscapes

    Science.gov (United States)

    Boulinier, T.; Nichols, J.D.; Hines, J.E.; Sauer, J.R.; Flather, C.H.; Pollock, K.H.

    1998-01-01

    Understanding the relationship between animal community dynamics and landscape structure has become a priority for biodiversity conservation. In particular, predicting the effects of habitat destruction that confine species to networks of small patches is an important prerequisite to conservation plan development. Theoretical models that predict the occurrence of species in fragmented landscapes, and relationships between stability and diversity do exist. However, reliable empirical investigations of the dynamics of biodiversity have been prevented by differences in species detection probabilities among landscapes. Using long-term data sampled at a large spatial scale in conjunction with a capture-recapture approach, we developed estimates of parameters of community changes over a 22-year period for forest breeding birds in selected areas of the eastern United States. We show that forest fragmentation was associated not only with a reduced number of forest bird species, but also with increased temporal variability in the number of species. This higher temporal variability was associated with higher local extinction and turnover rates. These results have major conservation implications. Moreover, the approach used provides a practical tool for the study of the dynamics of biodiversity.

  18. Evolution of dispersal in spatially and temporally variable environments: The importance of life cycles.

    Science.gov (United States)

    Massol, François; Débarre, Florence

    2015-07-01

    Spatiotemporal variability of the environment is bound to affect the evolution of dispersal, and yet model predictions strongly differ on this particular effect. Recent studies on the evolution of local adaptation have shown that the life cycle chosen to model the selective effects of spatiotemporal variability of the environment is a critical factor determining evolutionary outcomes. Here, we investigate the effect of the order of events in the life cycle on the evolution of unconditional dispersal in a spatially heterogeneous, temporally varying landscape. Our results show that the occurrence of intermediate singular strategies and disruptive selection are conditioned by the temporal autocorrelation of the environment and by the life cycle. Life cycles with dispersal of adults versus dispersal of juveniles, local versus global density regulation, give radically different evolutionary outcomes that include selection for total philopatry, evolutionary bistability, selection for intermediate stable states, and evolutionary branching points. Our results highlight the importance of accounting for life-cycle specifics when predicting the effects of the environment on evolutionarily selected trait values, such as dispersal, as well as the need to check the robustness of model conclusions against modifications of the life cycle. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

  19. A simple daily soil-water balance model for estimating the spatial and temporal distribution of groundwater recharge in temperate humid areas

    Science.gov (United States)

    Dripps, W.R.; Bradbury, K.R.

    2007-01-01

    Quantifying the spatial and temporal distribution of natural groundwater recharge is usually a prerequisite for effective groundwater modeling and management. As flow models become increasingly utilized for management decisions, there is an increased need for simple, practical methods to delineate recharge zones and quantify recharge rates. Existing models for estimating recharge distributions are data intensive, require extensive parameterization, and take a significant investment of time in order to establish. The Wisconsin Geological and Natural History Survey (WGNHS) has developed a simple daily soil-water balance (SWB) model that uses readily available soil, land cover, topographic, and climatic data in conjunction with a geographic information system (GIS) to estimate the temporal and spatial distribution of groundwater recharge at the watershed scale for temperate humid areas. To demonstrate the methodology and the applicability and performance of the model, two case studies are presented: one for the forested Trout Lake watershed of north central Wisconsin, USA and the other for the urban-agricultural Pheasant Branch Creek watershed of south central Wisconsin, USA. Overall, the SWB model performs well and presents modelers and planners with a practical tool for providing recharge estimates for modeling and water resource planning purposes in humid areas. ?? Springer-Verlag 2007.

  20. Temporal variability of CO2 and CH4 fluxes of a rewetted fen in NE Germany

    Science.gov (United States)

    Franz, Daniela; Larmanou, Eric; Koebsch, Franziska; Augustin, Jürgen; Sachs, Torsten

    2015-04-01

    During the last 20 years, restoring degraded peatlands became common practice in the context of climate protection, as it is expected to reduce their greenhouse gas (GHG) contribution to the atmosphere in the long term. However, suboptimal management decisions can even impair the GHG budget beyond the "restoration effect" during the first years of the rewetting. To improve future restoration management, the GHG dynamics following rewetting have to be quantified and understood. Apart from this, knowledge on the variability of the gas exchange and the respective drivers over different time scales is still lacking, though especially important for process understanding and advancement of estimations. Using the eddy covariance (EC) technique we investigate CH4 and CO2 flux dynamics between the atmosphere and a highly degraded minerotrophic fen grassland flooded in 2004/2005. The study site is located in the Peene River valley (53°52'N, 12°52'E), NE Germany. It is part of the Terrestrial Environmental Observatories Network (TERENO) spanning across Germany. In the course of flooding, a shallow lake (30-80 cm depth) developed in the centre of the rewetted area and persisted until now. The footprint of the EC measurements covers both the shallow lake and non-permanently inundated parts surrounding the lake. We will present CO2 and CH4 flux data covering one year since the system was newly established. We applied wavelet analysis and wavelet coherence to detect the multi-scale temporal variability of ecosystem gas exchange and the respective drivers by splitting time series into spectral and temporal components. Thus, transitions of ecosystem processes during the observation period are considered. Both methods are performed on continuous EC data over one year in case of CO2 and shorter measurement periods in the course of the growing season for CH4, due to data gaps. The addressed scales of temporal variation range from hour to week and season for CH4 and CO2, respectively.

  1. Temporal Variability of Soil Respiration in Experimental Tree Plantations in Lowland Costa Rica

    Directory of Open Access Journals (Sweden)

    James W. Raich

    2017-02-01

    Full Text Available The principal objective of this study was to determine if there is consistent temporal variability in soil respiration from different forest plantations in a lowland tropical rainforest environment. Soil respiration was measured regularly over 2004 to 2010 in replicated plantations of 15- to 20-year-old evergreen tropical trees in lowland Costa Rica. Statistically significant but small differences in soil respiration were observed among hours of the day; daytime measurements were suitable for determining mean fluxes in this study. Fluxes varied more substantially among months, with the highest average emissions (5.9 μmol·m−2·s−1 occurring in September and low emissions (3.7 μmol·m−2·s−1 occurring in January. Three of the six tree species had significantly increasing rates of soil respiration across 2004–2010, with fluxes increasing at an average of 0.09 μmol·m−2·s−1 per year: the three other species had no long-term trends. It was hypothesized that there would be a tradeoff between carbon allocation aboveground, to produce new leaves, and belowground, to sustain roots and mycorrhizae, but the relationship between canopy leaf fall—a surrogate for canopy leaf flushing—and soil respiration was significantly positive. The similarities observed among temporal trends across plantation types, and significant relationships between soil respiration, soil water content and soil temperature, suggest that the physical environment largely controlled the temporal variability of soil respiration, but differences in flux magnitude among tree species were substantial and consistent across years.

  2. Sulfur dioxide in the Venus Atmosphere: II. Spatial and temporal variability

    Science.gov (United States)

    Vandaele, A. C.; Korablev, O.; Belyaev, D.; Chamberlain, S.; Evdokimova, D.; Encrenaz, Th.; Esposito, L.; Jessup, K. L.; Lefèvre, F.; Limaye, S.; Mahieux, A.; Marcq, E.; Mills, F. P.; Montmessin, F.; Parkinson, C. D.; Robert, S.; Roman, T.; Sandor, B.; Stolzenbach, A.; Wilson, C.; Wilquet, V.

    2017-10-01

    The vertical distribution of sulfur species in the Venus atmosphere has been investigated and discussed in Part I of this series of papers dealing with the variability of SO2 on Venus. In this second part, we focus our attention on the spatial (horizontal) and temporal variability exhibited by SO2. Appropriate data sets - SPICAV/UV nadir observations from Venus Express, ground-based ALMA and TEXES, as well as UV observation on the Hubble Space Telescope - have been considered for this analysis. High variability both on short-term and short-scale are observed. The long-term trend observed by these instruments shows a succession of rapid increases followed by slow decreases in the SO2 abundance at the cloud top level, implying that the transport of air from lower altitudes plays an important role. The origins of the larger amplitude short-scale, short-term variability observed at the cloud tops are not yet known but are likely also connected to variations in vertical transport of SO2 and possibly to variations in the abundance and production and loss of H2O, H2SO4, and Sx.

  3. Spatial variability in groundwater N2 and N2O in the San Joaquin River

    Science.gov (United States)

    Hinshaw, S.; Dahlgren, R. A.

    2010-12-01

    The San Joaquin River is surrounded by nearly 2 million acres of irrigated agricultural land. Groundwater inputs from agricultural areas can have severe negative effects on water quality with high nitrate concentrations being a major concern. Riparian zones are important ecological habitats that mitigate nitrogen loading from groundwater discharging into rivers primarily by denitrification. Denitrification is a permanent removal of nitrate by anaerobic microbial communities via the reduction to NO, N2O and N2. However, previous studies have shown that these areas can be source of N2O emissions. Although removal of nitrate through denitrification is advantageous from a water quality perspective, N2O is a harmful greenhouse gas. This study aimed to investigate nitrogen dynamics and dissolved N gases in surface and groundwater of the riparian zones of the San Joaquin River. Excess N2 and N2O concentrations were measured in surface and groundwater at 4 locations along a 33 km reach of the river. Samples were collected within bank sediments and 5 transect points across the river at depth intervals between 2-3 cm and 150 cm. Dissolved N2 and Ar were measured by membrane inlet mass spectrometry and used to estimate excess dissolved N2 concentrations. Dissolved N2O concentrations were measured using the headspace equilibrium technique and analyzed with a gas chromatograph. Both N2 uptake and excess N2 were present, ranging from -3.40 to 8.65 N2 mg/L with a median concentration of 1.20 N2 mg/L. Significantly lower concentrations of N2O were present ranging from 0.0 to 0.12 N2O mg/L. Deeper groundwater sites had significantly higher N2 and N2O concentrations coinciding with decreased O2. The presence of excess N2 and low N2O concentrations documents the importance of denitrification in removing nitrate from groundwater. Further investigation will examine N2O emissions from riparian soils and benthic sediments using static chambers and focus on nitrogen pathways that

  4. Assessing scales of spatial & temporal variability in radiocarbon contents of soil organic carbon

    Science.gov (United States)

    van der Voort, Tessa Sophia; Feng, Xiaojuan; Hagedorn, Frank; Eglinton, Timothy

    2014-05-01

    Soil organic matter (SOM) forms the largest terrestrial reservoir of carbon outside of sedimentary rocks and it provides the fundamental reservoir for nutrients that sustains vegetation and the microbial communities. With ongoing changes in land-use and climate, SOM is also subject to change, with potentially major consequences for soil as a resource and for global biogeochemical cycles. Radiocarbon is a powerful tool for assessing SOM dynamics and is increasingly used in studies of carbon turnover. However, due to the nature of the measurement, comprehensive 14C studies of soils systems are rare. In particular, information on spatial variability in the radiocarbon contents of soils is limited. The present study aims to develop and apply a comprehensive four-dimensional approach to explore heterogeneity in bulk SOM 14C, with a broader goal of assessing controls on organic matter stability and vulnerability in soils across Switzerland. Focusing on range of Swiss soil types, we examine lateral variability in 14C over plot (decimeter to meter) to regional scales, vertical variability from surface to deeper soil horizons, and temporal variability by comparing present-day with archived (legacy) samples. Preliminary results show that there are large differences in SOM 14C age across small lateral and vertical distances within soil systems. Ultimately, studies of bulk variability will be followed up with analyses of SOM sub-fractions, including 14C measurements at the molecular level. Investigating 14C variability over various space and time domains may shed light on the scales of processes that dictate the composition and vulnerability of SOM, and provide valuable constraints on models of SOM turnover.

  5. Regional and temporal variation in minor ions in groundwater of a part of a large river delta, southern India.

    Science.gov (United States)

    Elumalai, Vetrimurugan; Brindha, K; Elango, L

    2017-07-01

    Impact of agricultural activities on groundwater can be determined from the concentration of nutrients present in groundwater. This study was carried out with the aim to assess the minor ions content of groundwater and to identify its sources, spatial, and seasonal variations in a part of the Cauvery River basin, southern India. Groundwater samples were collected from July 2007 to September 2009 and were analyzed for minor ions. These ions were in the order of dominance of nitrate> phosphate> bromide> fluoride> ammonium= nitrite> lithium. The concentration of ions tends to increase towards the coast except for fluoride. Increased concentration of ions identified in shallow wells than in deep wells with an exception of few locations indicates the impact of human activities. Relatively high concentration of agriculture-sourced nitrate was identified which pose a threat to groundwater suitability for agriculture and domestic usage. Combined influence of use of agrochemicals, improper sewage disposal, aquaculture activities, seawater intrusion due to heavy pumping near the coast, and natural weathering of aquifer materials are the major sources. Also, fine grain sediments of this area aid in poor flushing of the ions towards the sea resulting in accumulation of higher concentration of ions. A sustainable management strategy is essential to control the concentration of these ions, especially nitrate. Reduced use of fertilizers, increasing the rainfall recharge for diluting the pollutants in groundwater and maintaining the river flow for sufficiently longer period to reduce dependence on groundwater for irrigation can help to improve the situation.

  6. Spatial and Temporal Variability of Surface Energy Fluxes During Autumn Ice Advance: Observations and Model Validation

    Science.gov (United States)

    Persson, O. P. G.; Blomquist, B.; Grachev, A. A.; Guest, P. S.; Stammerjohn, S. E.; Solomon, A.; Cox, C. J.; Capotondi, A.; Fairall, C. W.; Intrieri, J. M.

    2016-12-01

    From Oct 4 to Nov 5, 2015, the Office of Naval Research - sponsored Sea State cruise in the Beaufort Sea with the new National Science Foundation R/V Sikuliaq obtained extensive in-situ and remote sensing observations of the lower troposphere, the advancing sea ice, wave state, and upper ocean conditions. In addition, a coupled atmosphere, sea ice, upper-ocean model, based on the RASM model, was run at NOAA/PSD in a hindcast mode for this same time period, providing a 10-day simulation of the atmosphere/ice/ocean evolution. Surface energy fluxes quantitatively represent the air-ice, air-ocean, and ice-ocean interaction processes, determining the cooling (warming) rate of the upper ocean and the growth (melting) rate of sea ice. These fluxes also impact the stratification of the lower troposphere and the upper ocean. In this presentation, both direct and indirect measurements of the energy fluxes during Sea State will be used to explore the spatial and temporal variability of these fluxes and the impacts of this variability on the upper ocean, ice, and lower atmosphere during the autumn ice advance. Analyses have suggested that these fluxes are impacted by atmospheric synoptic evolution, proximity to existing ice, ice-relative wind direction, ice thickness and snow depth. In turn, these fluxes impact upper-ocean heat loss and timing of ice formation, as well as stability in the lower troposphere and upper ocean, and hence heat transport to the free troposphere and ocean mixed-layer. Therefore, the atmospheric structure over the advancing first-year ice differs from that over the nearby open water. Finally, these observational analyses will be used to provide a preliminary validation of the spatial and temporal variability of the surface energy fluxes and the associated lower-tropospheric and upper-ocean structures in the simulations.

  7. Characterizing the spatiotemporal variability of groundwater levels of alluvial aquifers in different settings using drought indices

    Science.gov (United States)

    Haas, Johannes Christoph; Birk, Steffen

    2017-05-01

    To improve the understanding of how aquifers in different alluvial settings respond to extreme events in a changing environment, we analyze standardized time series of groundwater levels (Standardized Groundwater level Index - SGI), precipitation (Standardized Precipitation Index - SPI), and river stages of three subregions within the catchment of the river Mur (Austria). Using correlation matrices, differences and similarities between the subregions, ranging from the Alpine upstream part of the catchment to its shallow foreland basin, are identified and visualized. Generally, river stages exhibit the highest correlations with groundwater levels, frequently affecting not only the wells closest to the river, but also more distant parts of the alluvial aquifer. As a result, human impacts on the river are transferred to the aquifer, thus affecting the behavior of groundwater levels. Hence, to avoid misinterpretation of groundwater levels in this type of setting, it is important to account for the river and human impacts on it. While the river is a controlling factor in all of the subregions, an influence of precipitation is evident too. Except for deep wells found in an upstream Alpine basin, groundwater levels show the highest correlation with a precipitation accumulation period of 6 months (SPI6). The correlation in the foreland is generally higher than that in the Alpine subregions, thus corresponding to a trend from deeper wells in the Alpine parts of the catchment towards more shallow wells in the foreland. Extreme events are found to affect the aquifer in different ways. As shown with the well-known European 2003 drought and the local 2009 floods, correlations are reduced under flood conditions, but increased under drought. Thus, precipitation, groundwater levels and river stages tend to exhibit uniform behavior under drought conditions, whereas they may show irregular behavior during floods. Similarly, correlations are found to be weaker in years with little

  8. Impact of radionuclide spatial variability on groundwater quality downstream from a shallow waste burial in the Chernobyl Exclusion Zone

    Science.gov (United States)

    Nguyen, H. L.; de Fouquet, C.; Courbet, C.; Simonucci, C. A.

    2016-12-01

    The effects of spatial variability of hydraulic parameters and initial groundwater plume localization on the possible extent of groundwater pollution plumes have already been broadly studied. However, only a few studies, such as Kjeldsen et al. (1995), take into account the effect of source term spatial variability. We explore this question with the 90Sr migration modeling from a shallow waste burial located in the Chernobyl Exclusion Zone to the underlying sand aquifer. Our work is based upon groundwater sampled once or twice a year since 1995 until 2015 from about 60 piezometers and more than 3,000 137Cs soil activity measurements. These measurements were taken in 1999 from one of the trenches dug after the explosion of the Chernobyl nuclear power plant, the so-called "T22 Trench", where radioactive waste was buried in 1987. The geostatistical analysis of 137Cs activity data in soils from Bugai et al. (2005) is first reconsidered to delimit the trench borders using georadar data as a covariable and to perform geostatistical simulations in order to evaluate the uncertainties of this inventory. 90Sr activity in soils is derived from 137Cs/154Eu and 90Sr/154Eu activity ratios in Chernobyl hot fuel particles (Bugai et al., 2003). Meanwhile, a coupled 1D non saturated/3D saturated transient transport model is constructed under the MELODIE software (IRSN, 2009). The previous 90Sr transport model developed by Bugai et al. (2012) did not take into account the effect of water table fluctuations highlighted by Van Meir et al. (2007) which may cause some discrepancies between model predictions and field observations. They are thus reproduced on a 1D vertical non saturated model. The equiprobable radionuclide localization maps produced by the geostatistical simulations are selected to illustrate different heterogeneities in the radionuclide inventory and are implemented in the 1D model. The obtained activity fluxes from all the 1D vertical models are then injected in a 3D

  9. Spatial and temporal variability of greenhouse gas emissions from a small and shallow temperate lake

    Science.gov (United States)

    Praetzel, Leandra; Schmiedeskamp, Marcel; Broder, Tanja; Hüttemann, Caroline; Jansen, Laura; Metzelder, Ulrike; Wallis, Ronya; Knorr, Klaus-Holger; Blodau, Christian

    2017-04-01

    Small inland waters (lakes. They are further expected to be susceptible to changing climate conditions. So far, little is known about the spatial and temporal variability of carbon dioxide (CO2) and methane (CH4) emissions and in-lake dynamics of CH4 production and oxidation in small, epilimnetic lakes in the temperate zone. Of particular interest is the potential occurrence of "hot spots" and "hot moments" that could contribute significantly to total emissions. To address this knowledge gap, we determined CO2 and CH4 emissions and dynamics to identify their controlling environmental factors in a polymictic small (1.4 ha) and shallow (max. depth approx. 1.5 m) crater lake ("Windsborn") in the Eifel uplands in south-west Germany. As Lake Windsborn has a small catchment area (8 ha) and no surficial inflows, it serves well as a model system for the identification of factors and processes controlling emissions. In 2015, 2016 and 2017 we measured CO2 and CH4 gas fluxes with different techniques across the sediment/water and water/atmosphere interface. Atmospheric exchange was measured using mini-chambers equipped with CO2 sensors and with an infra-red greenhouse gas analyzer for high temporal resolution flux measurements. Ebullition of CH4 was quantified with funnel traps. Sediment properties were examined using pore-water peepers. All measurements were carried out along a transect covering both littoral and central parts of the lake. Moreover, a weather station on a floating platform in the center of the lake recorded meteorological data as well as CO2 concentration in different depths of the water column. So far, Lake Windsborn seems to be a source for both CO2 and CH4 on an annual scale. CO2 emissions generally increased from spring to summer. Even though CO2 uptake could be observed during some periods in spring and fall, CO2 emissions in the summer exceeded the uptake. CO2 and CH4 emissions also appeared to be spatially variable between littoral areas and the inner

  10. Evaluating the role of soil variability on groundwater pollution and recharge at regional scale by integrating a process-based vadose zone model in a stochastic approach

    Science.gov (United States)

    Coppola, Antonio; Comegna, Alessandro; Dragonetti, Giovanna; Lamaddalena, Nicola; Zdruli, Pandi

    2013-04-01

    the lack of information on vertical variability of soil properties. It is our opinion that, with sufficient information on soil horizonation and with an appropriate horizontal resolution, it may be demonstrated that model outputs may be largely sensitive to the vertical variability of stream tubes, even at applicative scales. Horizon differentiation is one of the main observations made by pedologists while describing soils and most analytical data are given according to soil horizons. Over the last decades, soil horizonation has been subjected to regular monitoring for mapping soil variation at regional scales. Accordingly, this study mainly aims to developing a regional-scale simulation approach for vadose zone flow and transport that use real soil profiles data based on information on vertical variability of soils. As to the methodology, the parallel column concept was applied to account for the effect of vertical heterogeneity on variability of water flow and solute transport in the vadose zone. Even if the stream tube approach was mainly introduced for (unrealistic) vertically homogeneous soils, we extended their use to real vertically variable soils. The approach relies on available datasets coming from different sources and offers quantitative answers to soil and groundwater vulnerability to non-point source of chemicals and pathogens at regional scale within a defined confidence interval. This result will be pursued through the design and building up of a spatial database containing 1). Detailed pedological information, 2). Hydrological properties mainly measured in the investigated area in different soil horizons, 3). Water table depth, 4). Spatially distributed climatic temporal series, and 5). Land use. The area of interest for the study is located in the sub-basin of Metaponto agricultural site, located in southern Basilicata Region in Italy, covering approximately 11,698 hectares, crossed by two main rivers, Sinni and Agri and from many secondary water

  11. Spatial and temporal precipitation variability across scales: regional to global, decadal to centennial scales and beyond

    Science.gov (United States)

    de Lima, Isabel; Lovejoy, Shaun

    2017-04-01

    The investigation of changes in precipitation variability in the Anthropocene requires both data with adequate resolution and length as well as an appropriate theoretical framework, because wide ranges of scales should be explored. We suggest several ways forward to characterize precipitation variability across scales based on the systematic application of scaling fluctuation analysis to characterizing different precipitation scaling regimes (weather, macroweather, climate - from higher to lower frequencies). Our study uses three qualitatively different global scale precipitation products (from gauges, reanalyses and a satellite and gauge hybrid) that allow to investigate precipitation from monthly to centennial scales and in space from planetary down to 5°x5° scales. The information gathered this way on the fundamental nature of centennial and multicentennial precipitation variability is impossible to derive from proxy data. The key finding from our study is that, in macroweather, precipitation - similarly to other atmospheric fields - have scaling properties characterized by negative temporal fluctuation exponents, which implies - contrary to the weather and climate regimes - that fluctuations tend to cancel each other out. In the pre-industrial period and the Anthropocene, the macroweather regime spans different ranges of time scales: the lower limit is about a month, but whereas the upper limit is up to ≈20-30 years in the industrial period, this limit is believed to extend to centuries or longer in the pre-industrial epoch, although it is yet not well established. The improved understanding of monthly to centennial scale precipitation variability opens new perspectives to separating natural and anthropogenic precipitation variability, and quantifying anthropogenic changes in precipitation. These techniques can be applied to temperature and other climatological data.

  12. Hydrological variables play a remarkable role in temporal dynamics of daily sampled diatom community in a German lowland river

    Science.gov (United States)

    Sun, Xiuming; Wu, Naicheng; Faber, Claas; Fohrer, Nicola

    2017-04-01

    Temporal dynamics of diatom community with relation to abiotic factors is an important part of water quality monitoring and water resource management. However, the contribution of hydrological variables to temporal diatom variation has been rarely reported, especially at a short-interval sampling scale. Based on daily riverine diatom samples over a 1-year period (25 April 2013 - 30 April 2014) at the outlet of a German lowland river, we aimed to examine the temporal variation patterns of diatom community and to compare the relative importance between chemical and hydrological variables of affecting the temporal diatom community variation. Among the 339 samples, a total of 113 diatom taxa from 45 genera were identified. Sampling dates with similar species composition and structure were classified into five clusters by a Kohonen Self-Organizing Map (SOM) method within Matlab software. These five groups were distinct with respect to species composition, density, richness, and indicator species, as well as environmental variables. Redundancy analysis (RDA) and variance partitioning techniques were used to explain the relationships between environmental variables and diatom community dynamics. For the whole dataset, chemical and hydrological variables could jointly explain 50.17% of the diatom community variation including chemical variables with 36.45% and hydrological variables with 12.89%. The most important chemical variables were Phosphate-Phosphorus (PO4-P) and Silicon (Si) concentrations, while the most significant hydrological variable was antecedent precipitation index (API), indicating the importance of nutrient and hydrological factor in shaping diatom structure. In general, the relative importance of chemical and hydrological factors to diatom communities varied among seasons (or SOM clusters). Partial RDAs revealed that 3.60%, 11.96%, 7.10%, 10.4% and 7.11% of diatom variation can be explained by hydrological variables from cluster 1 to 5, while 52.71%, 47

  13. Spatial and temporal variability of rainfall and their effects on hydrological response in urban areas - A review

    NARCIS (Netherlands)

    Cristiano, E.; ten Veldhuis, J.A.E.; van de Giesen, N.C.

    2017-01-01

    In urban areas, hydrological processes are characterized by high variability in space and time, making them sensitive to small-scale temporal and spatial rainfall variability. In the last decades new instruments, techniques, and methods have been developed to capture rainfall and hydrological

  14. Temporal and spatial variability of wind resources in the United States as derived from the Climate Forecast System Reanalysis

    Science.gov (United States)

    Lejiang Yu; Shiyuan Zhong; Xindi Bian; Warren E. Heilman

    2015-01-01

    This study examines the spatial and temporal variability of wind speed at 80m above ground (the average hub height of most modern wind turbines) in the contiguous United States using Climate Forecast System Reanalysis (CFSR) data from 1979 to 2011. The mean 80-m wind exhibits strong seasonality and large spatial variability, with higher (lower) wind speeds in the...

  15. Temporal and spatial characteristics of sea surface height variability in the North Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    D. Cromwell

    2006-01-01

    Full Text Available We investigate the spatial and temporal variability of sea surface height (SSH in the North Atlantic basin using satellite altimeter data from October 1992–January 2004. Our primary aim is to provide a detailed description of such variability, including that associated with propagating signals. We also investigate possible correlations between SSH variability and atmospheric pressure changes as represented by climate indices. We first investigate interannual SSH variations by deriving the complex empirical orthogonal functions (CEOFs of altimeter data lowpass-filtered at 18 months. We determine the spatial structure of the leading four modes (both in amplitude and phase and also the associated principal component (PC time series. Using wavelet analysis we derive the time-varying spectral density of the PCs, revealing when particular modes were strongest between 1992–2004. The spatial pattern of the leading CEOF, comprising 30% of the total variability, displays a 5-year periodicity in phase; signal propagation is particularly marked in the Labrador Sea. The second mode, with a dominant 3-year signal, has strong variability in the eastern basin. Secondly, we focus on the Azores subtropical frontal zone. The leading mode (35% is strong in the south and east of this region with strong variations at 3- and 5-year periods. The second mode (21% has a near-zonal band of low variance between  22°–27° N, sandwiched between two regions of high variance. Thirdly, we lowpass filter the altimeter data at a cutoff of 30 days, instead of 18 months, in order to retain signals associated with propagating baroclinic Rossby waves and/or eddies. The leading mode is the annual steric signal, around 46% of the SSH variability. The third and fourth CEOFs,  11% of the remaining variability, are associated with westward propagation which is particularly dominant in a "waveband" between 32°–36° N. For all three cases considered above, no significant cross

  16. Spatio-temporal Distribution of North African Dust Sources: Controling Mechanism and Interannual Variability

    Science.gov (United States)

    Schepanski, K.; Feuerstein, S.

    2016-12-01

    Mineral dust aerosol emitted from arid and semi-arid areas impacts on the weather and climate system by e.g. altering the atmospheric radiation budget and affecting nutrient cycles which ultimately changes the carbon cycle. To estimate the effect of dust in the Earth system, detailed knowledge on the spatio-temporal distribution of active dust sources is necessary. Furthermore, the understanding on the natural variablity of dust source activity has to be improved for a better representation of dust-related processes in numerical models and climate change projections. We discuss the atmospheric dust life-cycle over North Africa with regard to mechanisms both controlling dust uplift and transport pathways. Results from a four-year satellite-based study analysing the spatio-temporal distribution of dust source activations inferred from 15-minute Meteosat Second Generation (MSG) SEVIRI infra-red observations are linked to atmospheric conditions and dust source characteristics. The predominance of dust sources located in desert valleys illustrates the importance of alluvial sediments for the atmospheric dust life-cycle. With focus on alluvial dust sources, Landsat and Sentinel-2 data are analysed to identify changes in surface sediments caused by flash floodings which possibly generate fresh layers of sediments that are prone to wind erosion. Classification algorithms applied to the remote sensing data highlight an increase of alluvial sediments downstream of ephemeral channels and in mountain foothill regions subsequent to events of strong precipitation and a decrease in sediment coverage for long periods of rain absence and the occurrence of wind erosion (dust emission). Altogether, the presented and discussed results (1) illustrate the spatio-temporal distribution of dust sources over North Africa, (2) identify atmospheric controlling mechanism on dust source activation, and (3) investigate alluvial sediments as dust source. In summary, the outcomes contribute to the

  17. Temporal changes in spatial variability of plant available water at the watershed scale

    Science.gov (United States)

    de Alwis, D. A.; Gerard-Merchant, P.; Philpot, W. D.; Steenhuis, T. S.

    2004-05-01

    Identification of soil moisture distribution patterns by remote-sensing at the basin scale has become a major challenge for variable source hydrology. On time scales of a few days, water uptake from plants and evaporation can change significantly as a result of soil moisture dynamics, while on a time scales of a few weeks vegetation dynamics may represent a strong relationship with soil moisture. This study explores the relationship between vegetation dynamics and soil water content/ subsurface storage. Multi-temporal, multi-spectral Remotely Sensed Landsat images are used to identify spatial differences and temporal changes of vegetative cover over a subbasin of the Cannonsville reservoir, in the Catskills mountains region of New York state. Vegetation indices are processed and compared for six months (April,May June, July, September and October) in 2001. For each month, three classes of vegetation indices were determined from the frequency distribution of indices over the study area. The histogram of the vegetation indices revealed hypothetical Gaussians corresponding with generic land uses (forest, open grass/shrublands, pasture/crops and plowed land), and were well correlated with land uses estimated by from other sources. Comparison from one month to another of the actual position in the landscape of these three index classes led to the identification of different zones sharing the same index distribution. These zones were also seen to follow the temporal growth curve characteristic of its particular vegetation types. The spatial variations patterns of vegetation indices within each land use zone were then compared with the patterns of soil moisture distribution, as output by a fully distributed hydrological model, SMDR.

  18. Groundwater vulnerability to climate variability: modelling experience and field observations in the lower Magra Valley (Liguria, Italy)

    Science.gov (United States)

    Menichini, Matia; Doveri, Marco; El Mansoury, Bouabid; El Mezouary, Lhoussaine; Lelli, Matteo; Raco, Brunella; Scozzari, Andrea; Soldovieri, Francesco

    2016-04-01

    The aquifer of the Lower Magra Valley (SE Liguria, Italy) extends in a flat plain, where two main rivers (Magra and Vara) flow. These rivers are characterized by a wide variation of water level and water chemical composition (TDS, Cl and SO4) due to the combination of rainfall regime and the presence of thermal springs in the inner part of the catchment area. Groundwater flow is apparently controlled by stream water infiltration, which affects both water levels and water quality. In particular, the wide range of variation of some particular chemical species in the stream water influences the groundwater chemistry on a seasonal basis. In the area of interest, there is an important well-field, which supplies most of the drinking water to the nearby city of La Spezia. In this context, the groundwater system is exposed to a high degree of vulnerability, both in terms of quality and quantity. This study is aimed to develop a predictive flow and transport model in order to assess the vulnerability s.l. of the Magra Valley aquifer system and to evaluate its behaviour in awaited climate scenarios. A flow and transport model was developed by using MODFLOW and MT3DMS codes, and it's been calibrated in both steady state and transient conditions. The model confirmed the importance of the Magra river in the water balance and chemical composition of the extracted groundwater. In addition, a data-driven modelling approach was applied in order to determine boundary conditions (e.g. rivers and constant head or general head boundaries) of the physical model under hypothetic future climate scenarios. For this purpose, fully synthetic datasets have been generated as a training set of the data-driven scheme, with input variables inspired by selected climate models and input/output relationships estimated by past observations. An experimental run of the flow-transport model for 30 years ahead was performed, based on such hypothetic scenarios. This approach highlighted how the

  19. Temporal variability of neustonic ichthyoplankton assemblages of the eastern Pacific warm pool: Can community structure be linked to climate variability?

    Science.gov (United States)

    Ignacio Vilchis, L.; Ballance, Lisa T.; Watson, William

    2009-01-01

    Considerable evidence exists, showing an accelerated warming trend on earth during the past 40-50 years, attributed mainly to anthropogenic factors. Much of this excess heat is stored in the world's oceans, likely resulting in increased environmental variability felt by marine ecosystems. The long-term effects of this phenomenon on oceanic tropical ecosystems are largely unknown, and our understanding of its effects could be facilitated by long-term studies of how species compositions change with time. Ichthyoplankton, in particular, can integrate physical, environmental and ecological factors making them excellent model taxa to address this question. While on eight (1987-1990, 1992 and 1998-2000) NOAA Fisheries cruises to the eastern Pacific warm pool, we characterized the thermal and phytoplankton pigment structure of the water column, as well as the neustonic ichthyoplankton community using CTD casts and Manta (surface) net tows. Over the 13-year period, 852 CTD and Manta tow stations were completed. We divided the study area into three regions based on regional oceanography, thermocline depth and productivity, as well as a longitudinal gradient in species composition among stations. We then analyzed temporal trends of ichthyoplankton species composition within each region by pooling stations by region and year and making pairwise comparisons of community similarity between all combinations of the eight cruises within each region. We also identified environment-specific species assemblages and station groupings using hierarchical clustering and non-metric multi-dimensional scaling (MDS). Our analyses revealed a longitudinal gradient in community structure and temporal stability of ichthyoplankton species composition. Over the 13 years ichthyoplankton assemblages in the two westernmost regions varied less than in the eastern region. MDS and cluster analyses identified five ichthyoplankton assemblages that corresponded to oceanographic habitats and a gradient in

  20. SATELLITE-MEASURED SPATIAL AND TEMPORAL CHLOROPHYLL-A VARIABILITY IN THE GULF OF TOMINI, SULAWESI

    Directory of Open Access Journals (Sweden)

    I Nyoman Radiarta

    2009-12-01

    Full Text Available Chlorophyll-a concentration, an index of phytoplankton biomass, is an important parameter for fisheries resources and marine aquaculture development. Spatial and temporal variability of surface cholophyll-a (chl-a concentration and water condition in the Gulf of Tomini were investigated using monthly climatologies the Sea-viewing Wide Field-of-view sensor (SeaWiFS, sea surface temperature (SST, and wind data from January 2000 to December 2007. The results showed seasonal variation of chla and SST in the Gulf of Tomini. High chl-a concentrations located in the eastern part of the gulf were observed during the southeast monsoon in August. During the northwest monsoon, chl-a concentrations were relatively low ( 28oC during the northwest monsoon, but low during the southeast monsoon. High wind speed was coincided with high chl-a concentrations. Local forcing such as sea surface heating and wind condition are the mechanisms that controlled the spatial and temporal variations of chlorophyll concentrations.

  1. LRO/LAMP Observations of Temporal Variability of Lunar Exospheric Helium During June and July 2012

    Science.gov (United States)

    Feldman, P. D.; Hurley, D. M.; Retherford, K. D.; Gladstone, R.; Stern, S. A.; Pryor, W. R.; Parker, J.

    2012-12-01

    We have previously reported on observations of the lunar helium exosphere made in January 2012 with the Lyman Alpha Mapping Project (LAMP) ultraviolet spectrograph on NASA's Lunar Reconnaissance Orbiter Mission. Those observations, of resonantly scattered He I emission at 584 Å from illuminated atmosphere against the dark lunar surface, were made over the night side of the Moon within 30 degrees of the dawn terminator. During June-July 2012 these observations were repeated, this time including both the dusk and dawn terminators. We find temporal variability of the derived surface He density as well as a strong dawn/dusk asymmetry with the He density on the dawn side approximately a factor of three higher than at corresponding longitudes on the dusk side. We again observe a factor of two decrease in surface density during the passage of the Moon through the Earth's magnetotail.

  2. Reconstruction of groundwater circulation after seashore reclamation

    Science.gov (United States)

    Zhang, Xiaoying; Hu, Bill; Yang, Lei; Chen, Junbing

    2017-04-01

    In recent years, the effects of land reclamation on the coastal groundwater system have received increasing attention in China as extensive reclamation activities have altered the original groundwater dynamics and salinity distribution in the coastal subsurface. Previous studies focused on either the steady-state groundwater flow or the large scale numerical simulation after land reclamation, however the short-period variation of groundwater flow and its impacts on hydrogeochemical system have not often been considered. Furthermore, a permeable coastal boundary assumed exclusively in previous work is often not the case in contemporary engineering practice, and an impermeable coastal boundary with dikes has been adopted in this study. We investigate the temporal variation of groundwater levels in the un-reclaimed clay layer and reclaimed layer based on the continuous observation of 14 monitoring wells in Zhoushan island, China. We use the morphological wave analysis method to study the effect of nonstationary tidal signals on groundwater level fluctuations. The results indicate that the method of continuous wavelet transform is suitable for analyzing the groundwater flow pattern, where short period groundwater level fluctuations are affected by tidal activities through pipes built in the reclamation dike. In particular, the method of discrete wavelet transform (DWT) is proved effective in extracting tidal signals from groundwater level time series. The approximation term in the multi-resolution analysis is well in agreement with original groundwater level data, demonstrating the advantages of the DWT method in obtaining the change trends of geological, hydrological, and climate variables. Additionally, an examination of groundwater samples indicates that saltwater exists in entire reclamation regions. Our study reveals some different groundwater features in reclamation regions where the coastal boundary is impermeable, which could provide significant implications

  3. Temporal variability of tidal and gravity waves during a record long 10-day continuous lidar sounding

    Science.gov (United States)

    Baumgarten, Kathrin; Gerding, Michael; Baumgarten, Gerd; Lübken, Franz-Josef

    2018-01-01

    Gravity waves (GWs) as well as solar tides are a key driving mechanism for the circulation in the Earth's atmosphere. The propagation of gravity waves is strongly affected by tidal waves as they modulate the mean background wind field and vice versa, which is not yet fully understood and not adequately implemented in many circulation models. The daylight-capable Rayleigh-Mie-Raman (RMR) lidar at Kühlungsborn (54° N, 12° E) typically provides temperature data to investigate both wave phenomena during one full day or several consecutive days in the middle atmosphere between 30 and 75 km altitude. Outstanding weather conditions in May 2016 allowed for an unprecedented 10-day continuous lidar measurement, which shows a large variability of gravity waves and tides on timescales of days. Using a one-dimensional spectral filtering technique, gravity and tidal waves are separated according to their specific periods or vertical wavelengths, and their temporal evolution is studied. During the measurement period a strong 24 h wave occurs only between 40 and 60 km and vanishes after a few days. The disappearance is related to an enhancement of gravity waves with periods of 4-8 h. Wind data provided by ECMWF are used to analyze the meteorological situation at our site. The local wind structure changes during the observation period, which leads to different propagation conditions for gravity waves in the last days of the measurement period and therefore a strong GW activity. The analysis indicates a further change in wave-wave interaction resulting in a minimum of the 24 h tide. The observed variability of tides and gravity waves on timescales of a few days clearly demonstrates the importance of continuous measurements with high temporal and spatial resolution to detect interaction phenomena, which can help to improve parametrization schemes of GWs in general circulation models.

  4. Temporal variability and coloured noise of SLR translations with respect to the ITRF2014 origin

    Science.gov (United States)

    Riddell, Anna; King, Matt; Watson, Christopher; Rietbroek, Roelof; Sun, Yu; Riva, Riccardo

    2017-04-01

    Inferring large-scale environmental change, such as of sea-level change, glacial isostatic adjustment or ice sheet volume change (i.e. from altimetry), requires a geodetic reference frame stable to 0.1 mm/yr. Since 1988, each iterative improvement in the precision of the International Terrestrial Reference Frame (ITRF) has enabled significant advancement of scientific and technical research in the Earth sciences. We demonstrate the occurrence of coloured noise in the translation components between the SLR network and the long-term ITRF2014 origin from 1993.0 to 2015.0 with power law spectral indices close to -1, where white-noise-only linear trend uncertainties are underestimated by a factor of five in contrast to power-law linear trend uncertainties. The observed geocentre motion is expected to be influenced by the SLR observing network, known as the "network effect". Temporal translations in the SLR network may not necessarily average out over long time periods and therefore have the potential to shift the computed reference frame origin from the true long term centre of mass. Comparison with geophysical loading models demonstrates that the variability cannot be fully accounted for by surface mass transport such as changes in atmospheric, hydrologic or glacial loading. Our results demonstrate that the proportion of variance explained by geophysical surface loading is less than 50% in each translational component. Evidence of temporal variability in both the SLR amplitude and trend of the annual signal suggest that a different coloured noise model be considered in place of, or as an extension of, the traditional linear and white-noise-only model to represent the long-term average centre of mass.

  5. Spatio-temporal variability of the North Sea cod recruitment in relation to temperature and zooplankton.

    Directory of Open Access Journals (Sweden)

    Delphine Nicolas

    Full Text Available The North Sea cod (Gadus morhua, L. stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature and/or indirect (i.e. changes in the quantity and quality of zooplankton prey effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability.

  6. Surface radiation over the pan-Arctic land region: temporal variability and trends

    Science.gov (United States)

    Shi, X.; Wild, M.; Lettenmaier, D. P.

    2009-12-01

    Surface radiation fluxes are not only a major component of the surface energy balance, but also control a diverse set of physical-biological processes, including the land surface hydrological cycle and plant photosynthesis. Past studies of the pan-Arctic region have identified changes in land surface hydrological fluxes, but less attention has been focused on the energy inputs to the system. Recent satellite data and atmospheric model reanalysis products have provided several data sets that predict most or all terms in the surface energy budget, and provide the opportunity to investigate spatial and temporal variations in surface radiation fluxes. We analyzed surface downward shortwave and longwave fluxes and albedo from (1) Off-line simulations with the Variable Infiltration Capacity (VIC) model, (2) International Satellite Cloud Climatology Project (ISCCP-FD) products, (3) European Centre for Medium-Range Weather Forecast 40-Year Reanalysis (ERA-40), and (4) European Centre for Medium-Range Weather Forecast Interim Reanalysis (ERA-Interim) for the period 1984 to 2006. In addition, diurnal and mean seasonal cycles were compared at 35 sites with in situ measurements from the Global Energy Balance Archive (GEBA), the Asian Automatic Weather Station Network (AAN), the Baseline Surface Radiation Network (BSRN), the Boreal Ecosystem-Atmosphere Study (BOREAS), and the National Solar Radiation Data Base (NSRDB). At the regional scale, the consistency of dominant spatial, temporal and latitudinal variability of these surface parameters across different data sets was examined. Also, for a small number of GEBA stations with records spanning the period from the 1950s and 1960s to post-2000, we analyzed long-term trends in surface downward shortwave radiation.

  7. Spatial distribution and temporal variability of solar radiant over southern Thailand

    Energy Technology Data Exchange (ETDEWEB)

    Waewsak, J.; Chancham, C. [Thaksin Univ., Phatthalung (Thailand). Dept. of Physics, Renewable Energy System Research and Demonstration Center, Solar and Wind Energy Research Lab

    2009-07-01

    The potential for solar energy in Thailand has been estimated at over 50,000 MW for power generation. However, existing power plants in the country produce only 32 MW. Most the the systems have been installed in rural areas, islands and other off-grid sites. The availability and variability of global solar radiant intensity and its spatial distribution are key parameters for designing and testing outdoor solar energy systems. These parameters must be well understood in order to evaluate system efficiency at specific locations. Therefore, this study examined the spatial distribution and temporal variability of solar radiant over southern Thailand using the Surfer computer program. The incident of solar radiation on a horizontal plane was estimated at 14 synoptic stations using the Angstrom's correlation which was obtained from meteorological data. Rainfall quantity at 3 main meteorological stations was used to correlate the hours of sunshine and to predict them in meteorological stations where sunshine recorders were absent but where rainfall data were present. The 3 stations were at the Surat Thani, Phuket and Hat Yai airports. Angstrom's correlation coefficients were obtained using the correlation between the hours of sunshine and day length. The solar radiant was obtained once the extraterrestrial solar radiation was known. The study showed that the solar radiant over southern Thailand varies between 12.51 to 24.54 MJ per m{sup 2} per day. It was concluded that the temporal variation of solar radiant over southern Thailand is highly influenced by the North-East and South-West monsoons. 16 refs., 1 tab., 17 figs.

  8. Spatial variability of groundwater quality of Sabour block, Bhagalpur district (Bihar, India)

    Science.gov (United States)

    Verma, D. K.; Bhunia, Gouri Sankar; Shit, Pravat Kumar; Kumar, S.; Mandal, Jajati; Padbhushan, Rajeev

    2017-07-01

    This paper examines the quality of groundwater of Sabour block, Bhagalpur district of Bihar state, which lies on the southern region of Indo-Gangetic plains in India. Fifty-nine samples from different sources of water in the block have been collected to determine its suitability for drinking and irrigational purposes. From the samples electrical conductivity (EC), pH and concentrations of Calcium (Ca2+), Magnesium (Mg2+), Sodium (Na+), Potassium (K+), carbonate ion (CO 3 2- ), Bicarbonate ion (HCO 3 - ), Chloride ion (Cl-), and Fluoride (F-) were determined. Surface maps of all the groundwater quality parameters have been prepared using radial basis function (RBF) method. RBF model was used to interpolate data points in a group of multi-dimensional space. Root Mean Square Error (RMSE) is employed to scrutinize the best fit of the model to compare the obtained value. The mean value of pH, EC, Ca2+, Mg2+, Na+, K+, HCO3 -, Cl-, and F- are found to be 7.26, 0.69, 38.98, 34.20, 16.92, 1.19, 0.02, and 0.28, respectively. Distribution of calcium concentration is increasing to the eastern part and K+ concentrations raise to the downstream area in the southwestern part. Low pH concentrations (less than 6.71) occur in eastern part of the block. Spatial variations of hardness in Sabour block portraying maximum concentration in the western part and maximum SAR (more than 4.23) were recorded in the southern part. These results are not exceeding for drinking and irrigation uses recommended by World Health Organization. Therefore, the majority of groundwater samples are found to be safe for drinking and irrigation management practices.

  9. Spatial and Temporal Variability of Macronutrients in a Lime-amended Acid Paddy Field

    Science.gov (United States)

    Vidal Vázquez, E.; Morales, L. A.; Paz González, A.

    2012-04-01

    tillering could be also attributed to lime addition, but a negative effect of liming on P availability was observed during flowering. Mehlich I extractable K was in general low to very low and decreased from sowing to flowering, irrespective of lime treatment. Semivariogram analysis showed a rather strong spatial dependence of NH4+, P and K concentrations and this all over the three study periods and for the three lime treatments. Empirical semivariograms could be adjusted quite well by a nugget component (C0) plus a spatial structure (C1), which was described by spherical or exponential models with a correlation range between 40 and 85 m. Geostatistical analysis provided insight into possible processes responsible of the observed spatial variability patterns within the rice soil. Kriging was useful in mapping macronutrient variability allowing identifying microrregions with high or low values of the target soil properties clearly showing the presence of small scale variability for the study soil attributes within each liming treatment and during each of the three sampling dates. Also the position of patches with maxima and minima values changed between successive sampling dates illustrating the lack of temporal stability of the pattern of spatial distribution for the study soil attributes. Results illustrate the potential for applying the principles of precision agriculture to control spatiotemporal variability in rice fields.

  10. Short-term temporal variability in fish community structure at two western Mediterranean slope locations

    Science.gov (United States)

    Moranta, Joan; Massutí, Enric; Stefanescu, Constantí; Palmer, Miquel; Morales-Nin, Beatriz

    2008-07-01

    Short-term temporal variability in deep-sea demersal fish assemblages is described for two slope areas characterised by different oceanographic conditions, which are situated north (Balearic sub-basin, BsB) and south (Algerian sub-basin, AsB) of the Balearic Islands (western Mediterranean). A total of 75 hauls were analysed from six bottom trawl surveys carried out in the two sub-basins. At BsB, surveys were designed for sampling different slope habitats during April 1991, December 1991, March 1992 and July 1992: (i) a submarine canyon at a depth of around 450 m, (ii) the upper slope at a depth of 600-650 m, and (iii) the middle slope at a depth of around 1200 m. At AsB, surveys were carried out during October 1996 and May 1998, along a continuous transect on the upper, middle and lower slope. The taxonomic composition, ecological parameters (number of species, abundance and biomass) and biomass spectra of the assemblages, as well as the length frequency distribution of the main species, were compared for different seasons and bathymetric ranges. Forty-four demersal species were captured in BsB and 38 in AsB. Helicolenus dactylopterus and Trachyrinchus scabrus were more abundant in BsB, and Hoplostethus mediterraneus, Galeus melastomus and Centroscymnus coelolepis in AsB. Depth was the determinant factor in all the analyses. Species-specific densities (abundance and biomass) showed significant differences between surveys, depth strata and their interaction in BsB. However, survey and its interaction with depth, were not significant in AsB. We also found significant differences in relation to depth and season for the three ecological parameters tested in BsB, but only significant differences in relation to depth in AsB. Biomass spectra showed large differences in relation to depth but only slight between-survey differences, which mainly occurred in the upper slope. The length frequency distributions of single species presented short-term temporal variations, mainly

  11. East Sea Spatial and Temporal Variability of Thermohaline Structure and Circulation Identified From Observational (T, S) Profiles

    Science.gov (United States)

    2015-12-01

    VARIABILITY OF THERMOHALINE STRUCTURE AND CIRCULATION IDENTIFIED FROM OBSERVATIONAL (T, S) PROFILES by Hyewon Choi December 2015 Thesis Advisor...the gridded data, seasonal and inter-annual variability of thermohaline structure and circulation of the East Sea were analyzed. Found was a low...unlimited EAST SEA SPATIAL AND TEMPORAL VARIABILITY OF THERMOHALINE STRUCTURE AND CIRCULATION IDENTIFIED FROM OBSERVATIONAL (T, S) PROFILES Hyewon Choi

  12. Composition and temporal variability of particle fluxes in an insular canyon of the northwestern Mediterranean Sea

    Science.gov (United States)

    Grinyó, Jordi; Isla, Enrique; Peral, Laura; Gili, Josep-Maria

    2017-12-01

    Particle fluxes have been widely studied in canyons located in continental margins; conversely, particle fluxes in canyons in sediment starved margins incising small island margins have received very little attention and remain poorly understood. The Menorca Canyon is the largest canyon system in the Balearic Archipelago. Despite the high oligotrophic conditions of the Balearic Archipelago the canyon and surrounding areas host diverse communities dominated by benthic suspension feeders. Understanding the magnitude and variability of environmental factors influencing these communities thus remain crucial. In order to characterize the temporal variability of particle fluxes, analyze its geochemical and macroscopic composition and identify the main processes that modulate particle fluxes in the Menorca Canyon, one instrumented line with a sediment trap and a current meter was deployed at 430 m water depth from September 2010 to October 2012. Particle fluxes ranged between 190 and 2300 mg m2 d-1 being one of the lowest ever registered in a Mediterranean submarine canyon's head. The CaCO3 fraction was the major constituent contrasting with the general trend observed in other Mediterranean canyons. Macroscopic constituents (fecal pellets, Posidonia oceanica detritus and pelagic and benthic foraminifera) presented a wide variability throughout the sampling period and were not significantly correlated with the total mass flux. The low magnitude of the registered fluxes and the lack of correlation with the observed environmental variables (e.g., currents, winds, wave height, chlorophyll-a biomass) suggest that there is no evident controlling mechanism. However, we could infer that resuspension processes and the presence of different hydrodynamic features (e.g., eddies, interchange of water masses) condition the magnitude and composition of particle fluxes.

  13. On the intrinsic timescales of temporal variability in measurements of the surface solar radiation

    Science.gov (United States)

    Bengulescu, Marc; Blanc, Philippe; Wald, Lucien

    2018-01-01

    This study is concerned with the intrinsic temporal scales of the variability in the surface solar irradiance (SSI). The data consist of decennial time series of daily means of the SSI obtained from high-quality measurements of the broadband solar radiation impinging on a horizontal plane at ground level, issued from different Baseline Surface Radiation Network (BSRN) ground stations around the world. First, embedded oscillations sorted in terms of increasing timescales of the data are extracted by empirical mode decomposition (EMD). Next, Hilbert spectral analysis is applied to obtain an amplitude-modulation-frequency-modulation (AM-FM) representation of the data. The time-varying nature of the characteristic timescales of variability, along with the variations in the signal intensity, are thus revealed. A novel, adaptive null hypothesis based on the general statistical characteristics of noise is employed in order to discriminate between the different features of the data, those that have a deterministic origin and those being realizations of various stochastic processes. The data have a significant spectral peak corresponding to the yearly variability cycle and feature quasi-stochastic high-frequency variability components, irrespective of the geographical location or of the local climate. Moreover, the amplitude of this latter feature is shown to be modulated by variations in the yearly cycle, which is indicative of nonlinear multiplicative cross-scale couplings. The study has possible implications on the modeling and the forecast of the surface solar radiation, by clearly discriminating the deterministic from the quasi-stochastic character of the data, at different local timescales.

  14. Advances in catchment scale bank erosion modelling - quantifying the improved representation of temporal and spatial variability

    Science.gov (United States)

    Janes, Victoria; Holman, Ian; O'Donnell, Greg; Birkinshaw, Stephen; Kilsby, Chris

    2015-04-01

    Channel bank erosion processes are influenced by numerous factors resulting in high spatial and temporal variability of sediment production. The representation of channel bank erosion is overly simplistic within most catchment models, despite its significance to catchment sediment budgets. Within this study, the physically-based distributed SHETRAN model is modified to incorporate bank vegetation and channel sinuosity factors that influence spatial and temporal bank erosion rates. The modified model simulates the temporal variation of bank erosion in response to high magnitude events with the potential to remove bank vegetation and de-stabilise banks, thereby increasing erodibility. As vegetation re-establishes, simulated bank erodibility decreases. During the recovery period, banks have increased vulnerability to further high magnitude events that will result in increased bank erosion. This enables the model to represent the impact of flood clustering on sediment generation. The modified model also represents the spatial variation of bank erosion as a result of varying channel planform. Channel geometry has also been linked to bank erosion rates as a result of flow circulation within channels. Channel sinuosity shows a non-linear relationship with bank erosion, with bank erosion increasing up to a threshold value of sinuosity and decreasing as sinuosity increases above this point. The original and modified models have been applied to the Eden catchment in north east England. Bank erosion data derived from a GIS overlay methodology covering 150 years has been used to validate the models, indicating annual sediment generation from bank erosion processes within the catchment is 410-4500 t yr-1, equivalent to 2-11% of the catchment sediment budget. Comparison of the original and modified models highlights the improved ability of the modified model to simulate annual variation of bank eroded sediment production; annual sediment production from the original model ranged

  15. High temporal and spatial variability of atmospheric-methane oxidation in Alpine glacier-forefield soils.

    Science.gov (United States)

    Chiri, Eleonora; Nauer, Philipp A; Rainer, Edda-Marie; Zeyer, Josef; Schroth, Martin H

    2017-07-07

    Glacier-forefield soils can provide a substantial sink for atmospheric CH4, facilitated by aerobic methane-oxidizing bacteria (MOB). However, MOB activity, abundance, and community structure may be affected by soil age, location in different forefield landforms, and temporal fluctuations in soil-physical parameters. We assessed spatial and temporal variability of atmospheric CH4 oxidation in an Alpine glacier forefield during the snow-free season 2013. We quantified CH4 flux in soils of increasing age and in different landforms (sandhill, terrace, floodplain) using soil-gas-profile and static flux-chamber methods. To determine MOB abundance and community structure, we employed pmoA-gene-based quantitative PCR and targeted-amplicon sequencing. Uptake of CH4 increased in magnitude and decreased in variability with increasing soil age. Sandhill soils exhibited CH4 uptake ranging from -0.03- -3.7 mg CH4 m-2 d-1 Floodplain and terrace soils exhibited smaller uptake and even intermittent CH4 emissions. Linear mixed-effect models indicated that soil age and landform were dominating factors shaping CH4 flux, followed by cumulative rainfall (weighted sum ≤ 4 d prior to sampling). Of 31 MOB operational taxonomic units retrieved, ∼30% were potentially novel, and ∼50% were affiliated with Upland Soil Clusters gamma and alpha. The MOB community structures in floodplain and terrace soils were nearly identical, but differed significantly from highly variable sandhill-soil communities. We conclude that soil age and landform modulate the soil CH4 sink strength in glacier forefields, and recent rainfall affects its short-term variability. This should be taken into account when including this environment in future CH4 inventories.Importance Oxidation of methane (CH4) in well-drained, "upland" soils is an important mechanism for the removal of this potent greenhouse gas from the atmosphere. It is largely mediated by aerobic, methane-oxidizing bacteria (MOB). Whereas there is

  16. Spatio-temporal variability in western Baltic cod early life stage survival mediated by egg buoyancy, hydrography and hydrodynamics

    DEFF Research Database (Denmark)

    Hinrichsen, H-H.; Hüssy, K.; Huwer, B.

    2012-01-01

    spatial (within and between different spawning areas) and temporal (interannual and seasonal) dynamics. A spatially and temporally highly-resolved biophysical model of the Baltic Sea was used to describe mortalities and survival success of eggs and yolk-sac larvae—represented by individual, virtual......Spatio-temporal variability in western Baltic cod early life stage survival mediated by egg buoyancy, hydrography and hydrodynamics. – ICES Journal of Marine Science, 69: 1744–1752.To disentangle the effects of different drivers on recruitment variability of marine fish, a spatially and temporally...... drifters—as predicted proportions of drifters that either died due to bottom contact or lethal temperatures, or that survived up to the end of the yolk-sac larval stage. The environmental conditions allowing survival of cod and yolk-sac larvae indicate that favourable conditions predominately occurred...

  17. Spatio-temporal analysis reveals active control of both task-relevant and task-irrelevant variables.

    Science.gov (United States)

    Rácz, Kornelius; Valero-Cuevas, Francisco J

    2013-01-01

    The Uncontrolled Manifold (UCM) hypothesis and Minimal Intervention principle propose that the observed differential variability across task relevant (i.e., task goals) vs. irrelevant (i.e., in the null space of those goals) variables is evidence of a separation of task variables for efficient neural control, ranked by their respective variabilities (sometimes referred to as hierarchy of control). Support for this comes from spatial domain analyses (i.e., structure of) of kinematic, kinetic, and EMG variability. While proponents admit the possibility of preferential as opposed to strictly uncontrolled variables, such distinctions have only begun to be quantified or considered in the temporal domain when inferring control action. Here we extend the study of task variability during tripod static grasp to the temporal domain by applying diffusion analysis. We show that both task-relevant and task-irrelevant parameters show corrective action at some time scales; and conversely, that task-relevant parameters do not show corrective action at other time scales. That is, the spatial fluctuations of fingertip forces show, as expected, greater ranges of variability in task-irrelevant variables (>98% associated with changes in total grasp force; vs. only acceleration of the object). But at some time scales, however, temporal fluctuations of task-irrelevant variables exhibit negative correlations clearly indicative of corrective action (scaling exponents spatial and temporal features of all task variables when inferring control action and understanding how the CNS confronts task redundancy. Instead of a dichotomy of presence vs. absence of control, we should speak of a continuum of weaker to stronger-and potentially different-control strategies in specific spatiotemporal domains, indicated here by the magnitude of deviation from the 0.5 scaling exponent. Moreover, these results are counter examples to the UCM hypothesis and the Minimal Intervention principle, and the similar

  18. Stable Associations Masked by Temporal Variability in the Marine Copepod Microbiome.

    Directory of Open Access Journals (Sweden)

    Pia H Moisander

    Full Text Available Copepod-bacteria interactions include permanent and transient epi- and endobiotic associations that may play roles in copepod health, transfer of elements in the food web, and biogeochemical cycling. Microbiomes of three temperate copepod species (Acartia longiremis, Centropages hamatus, and Calanus finmarchicus from the Gulf of Maine were investigated during the early summer season using high throughput amplicon sequencing. The most prominent stable component of the microbiome included several taxa within Gammaproteobacteria, with Pseudoalteromonas spp. especially abundant across copepod species. These Gammaproteobacteria appear to be promoted by the copepod association, likely benefitting from nutrient enriched microenvironments on copepods, and forming a more important part of the copepod-associated community than Vibrio spp. during the cold-water season in this temperate system. Taxon-specific associations included an elevated relative abundance of Piscirickettsiaceae and Colwelliaceae on Calanus, and Marinomonas sp. in Centropages. The communities in full and voided gut copepods had distinct characteristics, thus the presence of a food-associated microbiome was evident, including higher abundance of Rhodobacteraceae and chloroplast sequences in the transient communities. The observed variability was partially explained by collection date that may be linked to factors such as variable time since molting, gender differences, and changes in food availability and type over the study period. While some taxon-specific and stable associations were identified, temporal changes in environmental conditions, including food type, appear to be key in controlling the composition of bacterial communities associated with copepods in this temperate coastal system during the early summer.

  19. Spatial and temporal variability in a stratified hypersaline microbial mat community.

    Science.gov (United States)

    Dillon, Jesse G; Miller, Scott; Bebout, Brad; Hullar, Meredith; Pinel, Nicolás; Stahl, David A

    2009-04-01

    Hypersaline microbial mat communities have recently been shown to be more diverse than once thought. The variability in community composition of hypersaline mats, both in terms of spatial and temporal dimensions, is still poorly understood. Because this information is essential to understanding the complex biotic and abiotic interactions within these communities, terminal restriction fragment analysis and 16S rRNA gene sequencing were used to characterize the near-surface community of a hypersaline microbial mat in Guerrero Negro, Mexico. Core samples were analyzed to assay community variability over large regional scales (centimeter to kilometer) and to track depth-related changes in population distribution at 250-microm intervals over a diel period. Significant changes in total species diversity were observed at increasing distances across the mat surface; however, key species (e.g. Microcoleus sp.) were identified throughout the mat. The vertical position and abundance of >50% of the 60 peaks detected varied dramatically over a diel cycle, including Beggiatoa sp., cyanobacteria, Chloroflexus sp., Halochromatium sp., Bacteroidetes sp. and several as-yet-identified bacteria. Many of these migrations correlated strongly with diel changes in redox conditions within the mat, contributing to strong day-night community structure differences.

  20. Integrating spatial and temporal variability into the analysis of fish food web linkages in Tijuana Estuary.

    Energy Technology Data Exchange (ETDEWEB)

    West, Janelle M.; Williams, Greg D.; Madon, Sharook P.; Zedler, Joy B.

    2003-05-14

    Our understanding of fish feeding interactions at Tijuana Estuary was improved by incorporating estimates of spatial and temporal variability into diet analyses. We examined the stomach contents of 7 dominant species (n=579 total fish) collected between 1994 and 1999. General feeding patterns pooled over time produced a basic food web consisting of 3 major trophic levels: (1) primary consumers (Atherinops affinis, Mugil cephalus) that ingested substantial amounts of plant material and detritus; (2) benthic carnivores (Clevelandia ios, Hypsopsetta guttulata, Gillichthys mirabilis, and Fundulus parvipinnis) that ingested high numbers of calanoid copepods and exotic amphipods (Grandidierella japonica); and (3) piscivores (Paralichthys californicus and Leptocottus armatus) that often preyed on smaller gobiids. Similarity-based groupings of individual species' diets were identified using nonmetric multidimensional scaling to characterize their variability within and between species, and in s pace and time. This allowed us to identify major shifts and recognize events (i.e., modified prey abundance during 1997-98 El Nino floods) that likely caused these shifts.

  1. Temporal variability of urinary di(2-ethylhexyl) phthalate metabolites during a dietary intervention study.

    Science.gov (United States)

    Ackerman, Janet M; Dodson, Robin E; Engel, Connie L; Gray, Janet M; Rudel, Ruthann A

    2014-11-01

    Exposure to di(2-ethylhexyl) phthalate (DEHP) may be related to adverse health effects including developmental and reproductive disorders, prompting interest in strategies for reducing human exposure. We previously reported a reduction of DEHP metabolite levels in composite urine samples by more than 50% (geometric means) during a 3-day dietary intervention avoiding plastics in food packaging, preparation, and storage. In the present study, we analyzed individual spot urine samples before compositing in order to evaluate temporal variability. There were no meaningful changes in any of the previous findings when using individual rather than composited samples. Individual urine samples, like the composites, showed significant decreases of ≥50% in all three measured DEHP metabolites during the intervention. Compositing urine samples provided sufficient information to observe the effect of the intervention, whereas reducing analytical expenses compared with analyzing multiple samples individually. Low intraclass correlations (ICCs) for samples collected from the same person before the intervention indicate the importance of collecting multiple samples per exposure condition. Substantially larger ICCs during and after the intervention suggest that much of the variability observed in DEHP metabolite levels originates from dietary exposure.

  2. Dying like rabbits: general determinants of spatio-temporal variability in survival.

    Science.gov (United States)

    Tablado, Zulima; Revilla, Eloy; Palomares, Francisco

    2012-01-01

    1. Identifying general patterns of how and why survival rates vary across space and time is necessary to truly understand population dynamics of a species. However, this is not an easy task given the complexity and interactions of processes involved, and the interpopulation differences in main survival determinants. 2. Here, using European rabbits (Oryctolagus cuniculus) as a model and information from local studies, we investigated whether we could make inferences about trends and drivers of survival of a species that are generalizable to large spatio-temporal scales. To do this, we first focused on overall survival and then examined cause-specific mortalities, mainly predation and diseases, which may lead to those patterns. 3. Our results show that within the large-scale variability in rabbit survival, there exist general patterns that are explained by the integration of factors previously known to be important at the local level (i.e. age, climate, diseases, predation or density dependence). We found that both inter- and intrastudy survival rates increased in magnitude and decreased in variability as rabbits grow old, although this tendency was less pronounced in populations with epidemic diseases. Some causes leading to these higher mortalities in young rabbits could be the stronger effect of rainfall at those ages, as well as, other death sources like malnutrition or infanticide. 4. Predation is also greater for newborns and juveniles, especially in population without diseases. Apart from the effect of diseases, predation patterns also depended on factors, such as, density, season, and type and density of predators. Finally, we observed that infectious diseases also showed general relationships with climate, breeding (i.e. new susceptible rabbits) and age, although the association type varied between myxomatosis and rabbit haemorrhagic disease. 5. In conclusion, large-scale patterns of spatio-temporal variability in rabbit survival emerge from the combination

  3. Temporal variability of trace metals in new jersey pinelands streams: relationships to discharge and pH

    Science.gov (United States)

    Sherrell, Robert M.; Ross, James M.

    1999-10-01

    Dissolved and particulate trace metal (Al, Cd, Cu, Pb, and Zn) concentrations were determined over a 21 month time period at four streamwater sites in the Pinelands (New Jersey, USA), a coastal plain region characterized by low-pH waters and highly weathered soils. Al and Zn were also determined at two sites over a 5 day period following a major precipitation event. In the Batsto River (pH 4.4-6.3), a representative Pinelands stream draining a largely forested watershed moderately impacted by agriculture, discharge-weighted mean concentrations of dissolved metals were (in nM): Al = 4610; Cd = 0.39; Cu = 4.6; Pb = 1.0; and Zn = 149. Dissolved Cd, Cu, and Zn in the undeveloped Bass River (pH 4.1-4.8) are in a similar range, but Pb concentration is 2-3 times greater. Dissolved metals show highly significant positive correlations to discharge, and weaker inverse relationships to pH over both the long- and short-term time series. Overall, seasonal and short-term variability in dissolved metal concentrations is most consistent with control by hydrologic flow path changes during high discharge, when shallow groundwaters mobilize anthropogenic metals stored in near-surface soil horizons and bypass potential metal removal processes in bordering wetlands. The data also suggest that in-stream metal removal driven by summertime biological productivity may further reduce low-discharge metal concentrations, as a secondary effect. For these metals, the particulate fraction is generally minor, and variations in solution/particle partitioning are unimportant to spatial/temporal variations dissolved concentrations, except for Pb. Estimates of atmospheric input can account for riverine fluxes of these metals, and suggest that Zn retention is minimal in this system, while Pb, Cu and Cd are more strongly retained. The positive relationship between discharge and metals concentration, and the unusually high concentrations in Pinelands streams compared to other world rivers, suggest that

  4. Dynamics and spatio-temporal variability of environmental factors in Eastern Australia using functional principal component analysis

    Science.gov (United States)

    Szabo, J.K.; Fedriani, E.M.; Segovia-Gonzalez, M. M.; Astheimer, L.B.; Hooper, M.J.

    2010-01-01

    This paper introduces a new technique in ecology to analyze spatial and temporal variability in environmental variables. By using simple statistics, we explore the relations between abiotic and biotic variables that influence animal distributions. However, spatial and temporal variability in rainfall, a key variable in ecological studies, can cause difficulties to any basic model including time evolution. The study was of a landscape scale (three million square kilometers in eastern Australia), mainly over the period of 19982004. We simultaneously considered qualitative spatial (soil and habitat types) and quantitative temporal (rainfall) variables in a Geographical Information System environment. In addition to some techniques commonly used in ecology, we applied a new method, Functional Principal Component Analysis, which proved to be very suitable for this case, as it explained more than 97% of the total variance of the rainfall data, providing us with substitute variables that are easier to manage and are even able to explain rainfall patterns. The main variable came from a habitat classification that showed strong correlations with rainfall values and soil types. ?? 2010 World Scientific Publishing Company.

  5. Temporal variability of the Circumpolar Deep Water inflow onto the Ross Sea continental shelf

    Science.gov (United States)

    Castagno, Pasquale; Falco, Pierpaolo; Dinniman, Michael S.; Spezie, Giancarlo; Budillon, Giorgio

    2017-02-01

    The intrusion of Circumpolar Deep Water (CDW) is the primary source of heat, salt and nutrients onto Antarctica's continental shelves and plays a major role in the shelf physical and biological processes. Different studies have analyzed the processes responsible for the transport of CDW across the Ross Sea shelf break, but until now, there are no continuous observations that investigate the timing of the intrusions. Also, few works have focused on the effect of the tides that control these intrusions. In the Ross Sea, the CDW intrudes onto the shelf in several locations, but mostly along the troughs. We use hydrographic observations and a mooring placed on the outer shelf in the middle of the Drygalski Trough in order to characterize the spatial and temporal variability of CDW inflow onto the shelf. Our data span from 2004 to the beginning of 2014. In the Drygalski Trough, the CDW enters as a 150 m thick layer between 250 and 400 m, and moves upward towards the south. At the mooring location, about 50 km from the shelf break, two main CDW cores can be observed: one on the east side of the trough spreading along the west slope of Mawson Bank from about 200 m to the bottom and the other one in the central-west side from 200 m to about 350 m depth. A signature of this lighter and relatively warm water is detected by the instruments on the mooring at bottom of the Drygalski Trough. High frequency periodic CDW intrusion at the bottom of the trough is related to the diurnal and spring/neap tidal cycles. At lower frequency, a seasonal variability of the CDW intrusion is noticed. A strong inflow of CDW is observed every year at the end of December, while the CDW inflow is at its seasonal minimum during the beginning of the austral fall. In addition an interannual variability is also evident. A change of the CDW intrusion before and after 2010 is observed.

  6. Spatial distribution and temporal variability of Harmattan dust haze in sub-Sahel West Africa

    Science.gov (United States)

    Anuforom, Anthony C.

    The distributions of frequency of occurrence (FOO) of 'thick dust haze' (TDH) and of 'light dust haze' (LDH) with respect to latitude, longitude, elevation and distance from source during Harmattan season (from November to February) are investigated, using 30-year visibility data collected from 27 synoptic stations located in Nigeria between the West African Sahel and the coasts of Gulf of Guinea. This region lies along the Harmattan season trajectory of Saharan dust. Also investigated is the temporal variability of TDH and LDH on intra-seasonal and inter-annual timescales spanning three decades from 1971 to 2000. Dust haze distribution over the region is found to correlate with the four geographical variables to different extents, with latitude, distance from source and elevation showing strong correlations with both TDH and LDH. The investigation also shows that while FOO of TDH days increases with latitude (correlation coefficient, rlat,FOO_TDH=0.88), FOO of LDH days decreases with latitude over the region (correlation coefficient, rlat,FOO_LDH=-0.74). The correlation coefficients with longitude over the region are rlon,FOO_TDH=0.44 and rlon,FOO_LDH=-0.25, respectively, indicating weaker dependence of TDH and LDH on longitude. The average number of TDH days per month during the Harmattan season in the region ranges from about 0.5 in the humid coastal zone near the Gulf of Guinea in the south, to approximately 6 in the dry semi-arid zone near the West African Sahel. An empirical equation which shows that FOO of TDH increases exponentially with latitude over the region is derived. The FOO of TDH is found to be most variable in or near the Sahel zone and decreases southwards towards the Gulf of Guinea. The average of the standard deviations is 1.13 for the six northernmost synoptic stations and decreases to 0.51 over the six coastal and southernmost locations. In contrast, the FOO of LDH is most variable in the south (with standard deviation of 2.11 (over the six

  7. Epibacterial community patterns on marine macroalgae are host-specific but temporally variable.

    Science.gov (United States)

    Lachnit, Tim; Meske, Diana; Wahl, Martin; Harder, Tilmann; Schmitz, Ruth

    2011-03-01

    Marine macroalgae are constantly exposed to epibacterial colonizers. The epiphytic bacterial patterns and their temporal and spatial variability on host algae are poorly understood. To investigate the interaction between marine macroalgae and epiphytic bacteria, this study tested if the composition of epibacterial communities on different macroalgae was specific and persisted under varying biotic and abiotic environmental conditions over a 2-year observation time frame. Epibacterial communities on the co-occurring macroalgae Fucus vesiculosus, Gracilaria vermiculophylla and Ulva intestinalis were repeatedly sampled in summer and winter of 2007 and 2008. The epibacterial community composition was analysed by denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene libraries. Epibacterial community profiles did not only differ significantly at each sampling interval among algal species, but also showed consistent seasonal differences on each algal species at a bacterial phylum level. These compositional patterns re-occurred at the same season of two consecutive years. Within replicates of the same algal species, the composition of bacterial phyla was subject to shifts at the bacterial species level, both within the same season but at different years and between different seasons. However, 7-16% of sequences were identified as species specific to the host alga. These findings demonstrate that marine macroalgae harbour species-specific and temporally adapted epiphytic bacterial biofilms on their surfaces. Since several algal host-specific bacteria were highly similar to other bacteria known to either avoid subsequent colonization by eukaryotic larvae or to exhibit potent antibacterial activities, algal host-specific bacterial associations are expected to play an important role for marine macroalgae. © 2010 Society for Applied Microbiology and Blackwell Publishing Ltd.

  8. Spatial and temporal variability of trace element concentrations in an urban subtropical watershed, Honolulu, Hawaii

    Energy Technology Data Exchange (ETDEWEB)

    Heinen de Carlo, E. [University of Hawaii, Honolulu, HI (United States). Dept. of Oceanography; U.S. Geological Survey, Honolulu, HI (United States); Anthony, S.S. [U.S. Geological Survey, Honolulu, HI (United States)

    2002-07-01

    Trace metal concentrations in soils and in stream and estuarine sediments from a subtropical urban watershed in Hawaii are presented. The results are placed in the context of historical studies of environmental quality (water, soils, and sediment) in Hawaii to elucidate sources of trace elements and the processes responsible for their distribution. This work builds on earlier studies on sediments of Ala Wai Canal of urban Honolulu by examining spatial and temporal variations in the trace elements throughout the watershed. Natural processes and anthropogenic activity in urban Honolulu contribute to spatial and temporal variations of trace element concentrations throughout the watershed. Enrichment of trace elements in watershed soils result, in some cases, from contributions attributed to the weathering of volcanic rocks, as well as to a more variable anthropogenic input that reflects changes in land use in Honolulu. Varying concentrations of As, Cd, Cu, Pb and Zn in sediments reflect about 60 a of anthropogenic activity in Honolulu. Land use has a strong impact on the spatial distribution and abundance of selected trace elements in soils and stream sediments. As noted in continental US settings, the phasing out of Pb-alkyl fuel additives has decreased Pb inputs to recently deposited estuarine sediments. Yet, a substantial historical anthropogenic Pb inventory remains in soils of the watershed and erosion of surface soils continues to contribute to its enrichment in estuarine sediments. Concentrations of other elements (e.g., Cu, Zn, Cd), however, have not decreased with time, suggesting continued active inputs. Concentrations of Ba, Co, Cr, Ni, V and U, although elevated in some cases, typically reflect greater proportions attributed to natural sources rather than anthropogenic input. (author)

  9. Temporal and Regional Variability in the Skin Microbiome of Humpback Whales along the Western Antarctic Peninsula.

    Science.gov (United States)

    Bierlich, K C; Miller, Carolyn; DeForce, Emelia; Friedlaender, Ari S; Johnston, David W; Apprill, Amy

    2018-03-01

    The skin is the first line of defense between an animal and its environment, and disruptions in skin-associated microorganisms can be linked to an animal's health and nutritional state. To better understand the skin microbiome of large whales, high-throughput sequencing of partial small subunit rRNA genes was used to study the skin-associated bacteria of 89 seemingly healthy humpback whales ( Megaptera novaeangliae ) sampled along the Western Antarctic Peninsula (WAP) during early (2010) and late (2013) austral summers. Six core groups of bacteria were present in 93% or more of all humpback skin samples. A shift was observed in the average relative abundances of these core bacteria over time, with the emergence of four additional core groups of bacteria that corresponded to a decrease in water temperature, possibly caused by season- or foraging-related changes in skin biochemistry that influenced microbial growth, or other temporal factors. The skin microbiome differed between whales sampled at several regional locations along the WAP, suggesting that environmental factors or population may also influence the whale skin microbiome. Overall, the skin microbiome of humpback whales appears to provide insight into animal- and environment-related factors and may serve as a useful indicator for animal health or ecosystem alterations. IMPORTANCE The microbiomes of wild animals are currently understudied but may provide information about animal health and/or animal-environment interactions. In the largest sampling of any marine mammal microbiome, this study demonstrates conservation in the skin microbiome of 89 seemingly healthy humpback whales sampled in the Western Antarctic Peninsula, with shifts in the bacterial community composition related to temporal and regional variability. This study is important because it suggests that the skin microbiome of humpback whales could provide insight into animal nutritional or seasonal/environment-related factors, which are becoming

  10. Groundwater modelling: Towards an estimation of the acceleration factors of iterative methods via an analysis of the transmissivity spatial variability

    Science.gov (United States)

    Benali, Abdelmajid

    2013-01-01

    When running a groundwater flow model, a recurrent and seemingly subsidiary question arises at the starting step of computations: what value of acceleration parameter do we need to optimize the numerical solver? A method is proposed to provide a practical estimate of the optimal acceleration parameter via a geostatistical analysis of the spatial variability of the logarithm of the transmissivity field Y. The background of the approach is illustrated on the successive over-relaxation method (SOR) used, either as a stand-alone solver, or as a symmetric preconditioner (SSOR) to the gradient conjugate method, or as a smoother in multigrid methods. It shows that this optimum acceleration factor is a function of the standard deviation and the correlation length of Y. This provides an easy-to-use heuristic procedure to estimate the acceleration factors, which could even be incorporated in the software package. A case study illustrates the steps needed to perform this estimation.

  11. The geovisualisation window of the temporal and spatial variability for Volunteered Geographic Information activities

    Science.gov (United States)

    Medynska-Gulij, Beata; Myszczuk, Miłosz

    2012-11-01

    This study presents an attempt to design geographical visualisation tools that allow to tackle the immensity of spatial data provided by Volunteered Geographic Information (VGI), both in terms of temporal and spatial aspects. In accordance with the assumptions made at the conceptual stage, the final action was the implementation of the window entitled ‘Geovisualisation of the Panoramio.com Activities in District of Poznan 2011’ into the web browser. The concept has been based on a division of the geovisualisation window into three panels, of which the most important - in order to capture spatial variability - have statistical maps at the general level (dot map and choropleth map), while at the detailed level - a dot map on a topographic reference map or tourist map. For two ranges, temporal variability is presented by graphs, while a review of attributes of individual activities of the social website in question is set forward in the table panel. The element that visually interlinks all of the panels is the emphasised individual activity. Problemem podjetym w tych badaniach stało sie wykorzystanie metod z nurtu geograficznej wizualizacji do wskazania cech fenomenu VGI w zakresie zmiennosci czasowo-przestrzennej. Zgodnie z załozeniami poczynionymi w etapie koncepcyjnym finalnym działaniem stało sie zaimplementowanie do przegladarki internetowej okna pod tytułem: ”Geowizualizacja aktywnosci społecznosci Panoramio.com w powiecie poznanskim w 2011 roku”. Koncepcja została oparta na podziale okna geowizualizacji na trzy panele, z których najwazniejsze znaczenie dla uchwycenia zmiennosci przestrzennej na poziomie ogólnym ma kartogram, natomiast na poziomie szczegółowym mapa kropkowa wyswietlana na podkładzie mapy topograficznej lub turystycznej. Zmiennosc czasowa w dwóch zakresach prezentuja wykresy, a przeglad atrybutów poszczególnych aktywnosci prezentowanego portalu społecznosciowego zapewnia tabela. Elementem spajajacym wizualnie wszystkie

  12. Effects of a structured midsole on spatio-temporal variables and running economy in overground running.

    Science.gov (United States)

    Wunsch, Tobias; Kröll, Josef; Stöggl, Thomas; Schwameder, Hermann

    2017-04-01

    Research to enhance running performance has led to the design of a leaf spring-structured midsole shoe (LEAF). In treadmill running, it has been shown that LEAF led to an increased running economy and increased stride length (SL) through a horizontal foot shift during stance compared to a standard foam shoe (FOAM). The purpose of this study was to analyse whether (a) these findings can also be observed in overground running and (b) relations exist between spatio-temporal variables and running economy. Ten male long-distance heel-strike runners ran at their individual 2 mmol/l blood lactate speed with LEAF and FOAM in randomized order. Kinematic data were recorded with an inertial measurement unit synchronized with 2D video. Oxygen consumption was measured using an automated metabolic gas analysis system. Blood lactate was collected after each run. The strike pattern was unaffected by LEAF. SL was increased by 0.9 ± 1.1 cm (95% CI 0.2 to 1.5; p = .040; d z  = 0.76), stride rate (SR) was reduced by -0.4 ± 0.3 strides/min (95% CI -0.6 to -0.1; p = .029; d z  = 0.82) and oxygen consumption tended to be reduced by 1% (-0.4 ± 0.6 ml/min/kg; 95% CI -0.8 to 0.0; p = .082; d z  = 0.62) when running with LEAF compared to FOAM. Changes in oxygen consumption in LEAF were correlated with SL (r = 0.71; p = .022) and SR (r = -0.68; p = .031). It can be concluded that LEAF has the potential to cause small changes in spatio-temporal variables during running. Runners increasing SL and decreasing SR in response to LEAF can achieve small improvements in running economy, which is beneficial in terms of performance.

  13. Spatial and temporal variability of rainfall and their effects on hydrological response in urban areas – a review

    Directory of Open Access Journals (Sweden)

    E. Cristiano

    2017-07-01

    Full Text Available In urban areas, hydrological processes are characterized by high variability in space and time, making them sensitive to small-scale temporal and spatial rainfall variability. In the last decades new instruments, techniques, and methods have been developed to capture rainfall and hydrological processes at high resolution. Weather radars have been introduced to estimate high spatial and temporal rainfall variability. At the same time, new models have been proposed to reproduce hydrological response, based on small-scale representation of urban catchment spatial variability. Despite these efforts, interactions between rainfall variability, catchment heterogeneity, and hydrological response remain poorly understood. This paper presents a review of our current understanding of hydrological processes in urban environments as reported in the literature, focusing on their spatial and temporal variability aspects. We review recent findings on the effects of rainfall variability on hydrological response and identify gaps where knowledge needs to be further developed to improve our understanding of and capability to predict urban hydrological response.

  14. Peritidal stromatolites at the convergence of groundwater seepage and marine incursion: Patterns of salinity, temperature and nutrient variability

    Science.gov (United States)

    Rishworth, Gavin M.; Perissinotto, Renzo; Bornman, Thomas G.; Lemley, Daniel A.

    2017-03-01

    Living peritidal stromatolites forming at the interface of coastal groundwater seepage and regular marine input are known from only a few locations globally, including South Africa, Western Australia and Northern Ireland. In contrast to modern stromatolites from exclusively fresh or marine waters, which persist due to high calcium carbonate saturation states or hypersaline and erosive conditions (which exclude organisms that might disrupt or out-compete the stromatolite-forming benthic microalgae), the factors supporting stromatolite formation at peritidal locations have not been well-documented. Therefore, the aim of this study was to investigate the fine-scale physico-chemical parameters in terms of pool temperature, salinity and nutrient dynamics at three representative sites along the coastline near Port Elizabeth, South Africa. These parameters were assessed with reference to potential physical, meteorological and ocean drivers using a linear or linear mixed-effects modelling approach. Results demonstrate that nutrient inputs into the pools supporting the majority of stromatolite accretion (barrage pools) are driven by groundwater seepage site-specific properties related to anthropogenic occupation (dissolved inorganic nitrogen; DIN) as well as marine water incursion (dissolved inorganic phosphorus; DIP). Pool temperature is a function of seasonal ambient variability while salinity reflects regular state shifts from fresh to marine conditions, which are related to tidal amplitude and swell height. The regular marine incursions likely promote benthic primary biomass in the phosphorus-limited stromatolite pools, as well as preclude organisms which might otherwise outcompete or disrupt the stromatolite microalgae due to intolerances to extreme ( 1.5 to ≥ 30) salinity variability.

  15. Investigating temporal trends in the explanatory variables related to the severity of drivers' injuries in single-vehicle collisions

    Directory of Open Access Journals (Sweden)

    Essam Dabbour

    2017-02-01

    Full Text Available This study identifies and quantifies the effects of different explanatory variables that increase the severity of drivers' injuries related to single-vehicle collisions involving light-duty vehicles. The research is based on utilizing logistic regression to analyze records of all traffic collisions that occurred in North Carolina for the years from 2007 to 2013. The study also investigates temporal stability of the identified explanatory variables throughout the analysis period. The identified explanatory variables include those related to the roadway, vehicle, driver, and environmental conditions. The explanatory variables related to the roadway include whether the roadway is divided or undivided, and whether it is in an urban or rural area. The explanatory variables related to the vehicle include vehicle's age, travel speed, and the type of the light-duty vehicle. The explanatory variables related to the driver include driver's age, gender, influence by alcohol or illicit drugs, and the use of seatbelt. The explanatory variables related to the environmental conditions include weather, lighting, and road surface conditions. Three of the investigated explanatory variables were found to be temporally unstable with significantly varying effects on the severity of drivers' injuries. Those temporally unstable variables include the travel speed, the type of the light-duty vehicle, and the age of the driver. All other investigated variables were found to be consistently significant throughout the analysis period. The findings of this research have the potential to help decision makers develop policies and countermeasures that reduce the severity of drivers' injuries by focusing on explanatory variables that consistently exhibit significant effects on the severity of drivers' injuries. The findings of this research also provide quantitative measures that may be used to determine the feasibility of implementing those countermeasures in reducing the

  16. Effects of climate and terrestrial storage on temporal variability of actual evapotranspiration

    Science.gov (United States)

    Wu, Chuanhao; Hu, Bill X.; Huang, Guoru; Zhang, Hang

    2017-06-01

    Knowledge of the temporal variability in actual evapotranspiration (E) is essential for a better understanding of the interaction and feedback between atmospheric and land surface hydrologic processes under various natural and anthropogenic conditions. Recently, Zeng and Cai (2015) proposed a decomposition framework of the E variance, based on water balance and the Budyko hypothesis. On the basis of a long-term (1960-2008) land surface dataset, this study applies the theoretical framework to assess the effects of climate and terrestrial storage factors on the interannual and intra-annual variance in E across China. An error decomposition framework is developed to quantify the key factors in the error of the predicted E variance. The results show that the prediction of the E variance is more accurate in arid climates than in humid climates, and the corresponding error is primarily controlled by the variability of precipitation (P) and runoff (R). Climate is the primary source for the E variance, and the dominant sources shift from potential evaporation (PET) in humid climates to P in arid climates. The interactions between P and PET tend to dampen the E interannual variance and enhance the E intra-annual variance, and this effect is especially significant in humid climates. Terrestrial storage change is more capable of accommodating climatic fluctuations at the intra-annual scale than at the interannual scale, and for some arid regions it is the dominant factor influencing the E variance. The response of terrestrial storage to P is more significant than its response to PET, especially for regions with strong human impact. Neglecting the effects of terrestrial storage would possibly underestimate or overestimate the E variance in both humid and arid climates, due to the interactions between climate and the change in the terrestrial storage.

  17. Associations of Dragonflies (Odonata) to Habitat Variables within the Maltese Islands: A Spatio-Temporal Approach

    Science.gov (United States)

    Balzan, Mario V.

    2012-01-01

    Relatively little information is available on environmental associations and the conservation of Odonata in the Maltese Islands. Aquatic habitats are normally spatio-temporally restricted, often located within predominantly rural landscapes, and are thereby susceptible to farmland water management practices, which may create additional pressure on water resources. This study investigates how odonate assemblage structure and diversity are associated with habitat variables of local breeding habitats and the surrounding agricultural landscapes. Standardized survey methodology for adult Odonata involved periodical counts over selected water-bodies (valley systems, semi-natural ponds, constructed agricultural reservoirs). Habitat variables relating to the type of water body, the floristic and physiognomic characteristics of vegetation, and the composition of the surrounding landscape, were studied and analyzed through a multivariate approach. Overall, odonate diversity was associated with a range of factors across multiple spatial scales, and was found to vary with time. Lentic water-bodies are probably of high conservation value, given that larval stages were mainly associated with this habitat category, and that all species were recorded in the adult stage in this habitat type. Comparatively, lentic and lotic seminatural waterbodies were more diverse than agricultural reservoirs and brackish habitats. Overall, different odonate groups were associated with different vegetation life-forms and height categories. The presence of the great reed, Arundo donax L., an invasive alien species that forms dense stands along several water-bodies within the Islands, seems to influence the abundance and/or occurrence of a number of species. At the landscape scale, roads and other ecologically disturbed ground, surface water-bodies, and landscape diversity were associated with particular components of the odonate assemblages. Findings from this study have several implications for the

  18. Spatio-Temporal Variability of Western Central African Convection from Infrared Observations

    Directory of Open Access Journals (Sweden)

    Derbetini A. Vondou

    2012-08-01

    Full Text Available The present study has used Meteosat infrared brightness temperature images to investigate the regional and interannual variability of Central African cloudiness. Spatial and temporal variability were investigated using half–hourly data from the Meteosat-7 during June–July–August (JJA of 1998–2002. The full domain of study (1.5E–17E, 1N–15N was divided into six regions and statistics in each region were derived. Analysis of the dependence of cloud fraction to the brightness temperature threshold is explored both over land and ocean. Three diurnal cycle regimes (continental, oceanic, and coastal are depicted according to the amplitude and peak time. Over regions of relatively flat terrain, results indicate enhancement of deep convection in the afternoon followed by a gradual decrease in the night. The diurnal cycle of convection is characterised by afternoon and early evening (around 15:00–18:00 LST maxima located mainly downwind of the major mountain chains, and a more rapid nighttime decay. In terms of the harmonic amplitude, the diurnal signal shows significant regional contrast with the strongest manifestation over the Adamaoua Plateau and the weakest near the South Cameroon Plateau. This remarkable spatial dependence is clear evidence of orographic and heterogeneous land-surface impacts on convective development. Oceanic region exhibits weak activity of convective cloudiness with a maximum at noon. It is suggested that daytime heating of the land surface and moist environment may play a role in determining the spatial distribution of cloud fraction. This study further demonstrates the importance of the Cameroon coastline concavity and coastal mountains in regulating regional frequencies of convection and their initialization. The strength of the diurnal cycle of convective activity depends on mountain height, mean flow, coastal geometry.

  19. Temporal variability of stemflow volume in a beech-yellow poplar forest in relation to tree species and size

    Science.gov (United States)

    Levia, D. F.; Van Stan, J. T., II; Mage, S. M.; Kelley-Hauske, P. W.

    2010-01-01

    SummaryStemflow has distinguishable effects on the hydrology and biogeochemistry of wooded ecosystems. Nonetheless, it is a relatively poorly understood hydrologic process. No known studies have investigated the temporal variability of stemflow volume at 5-min intervals in a beech-yellow poplar forest of eastern North America. The aim of this research is to compare the temporal variability of stemflow generation by Fagus grandifolia Ehrh. (American beech) and Liriodendron tulipifera L. (yellow poplar) in relation to tree species and size. Employing a dense network of tipping-bucket stemflow gages interfaced with a datalogger, a 5 min stemflow yield database was assembled and analyzed to better discern how stemflow production varies (temporally) with tree species and size. Results indicate that both tree species and size have detectable effects on the temporal variability of stemflow yield. Observational data, scientific analysis, and correspondence analysis reveals that stemflow yield: (1) is more similar within than between the two tree species with differences likely being attributable to differences in bark texture and water storage capacity; (2) tree size affects stemflow yield within species; (3) rain event characteristics affect stemflow yield; and (4) stemflow yield for particular trees and rain events is the result of a complex set of interactions among tree species, tree size, and meteorological conditions. These results suggest that the temporal variation in stemflow yield from co-occurring forest trees may play a significant role in subsurface drainage of wooded ecosystems during rain events.

  20. Composition, variability, and temporal stability of the intestinal microbiota of the elderly.

    LENUS (Irish Health Repository)

    Claesson, Marcus J

    2011-03-15

    Alterations in the human intestinal microbiota are linked to conditions including inflammatory bowel disease, irritable bowel syndrome, and obesity. The microbiota also undergoes substantial changes at the extremes of life, in infants and older people, the ramifications of which are still being explored. We applied pyrosequencing of over 40,000 16S rRNA gene V4 region amplicons per subject to characterize the fecal microbiota in 161 subjects aged 65 y and older and 9 younger control subjects. The microbiota of each individual subject constituted a unique profile that was separable from all others. In 68% of the individuals, the microbiota was dominated by phylum Bacteroides, with an average proportion of 57% across all 161 baseline samples. Phylum Firmicutes had an average proportion of 40%. The proportions of some phyla and genera associated with disease or health also varied dramatically, including Proteobacteria, Actinobacteria, and Faecalibacteria. The core microbiota of elderly subjects was distinct from that previously established for younger adults, with a greater proportion of Bacteroides spp. and distinct abundance patterns of Clostridium groups. Analyses of 26 fecal microbiota datasets from 3-month follow-up samples indicated that in 85% of the subjects, the microbiota composition was more like the corresponding time-0 sample than any other dataset. We conclude that the fecal microbiota of the elderly shows temporal stability over limited time in the majority of subjects but is characterized by unusual phylum proportions and extreme variability.

  1. THE SPATIO-TEMPORAL VARIABILITY OF MAXIMUM FLOW IN THE UZ HYDROGRAPHICAL BASIN

    Directory of Open Access Journals (Sweden)

    I.D. MIFTODE

    2016-03-01

    Full Text Available The analysis of the maximum flow, resulting from the influences of several miscellaneous control factors, leads to the empirical knowledge of the quantitative and qualitative hydrological characteristics of the rivers. The temporal and spatial variability of the maximum flow has been analyzed in this paper, based on the study of the monthly and annual maximum discharges recorded between 1985-2006, at the Valea Uzului, Cremenea, and Darmanesti hydrometric stations, in the Uz watershed. The data is provided by the Water Basin Administration Siret from Bacău which for this study was statistically processed. For the assessment of the maximum flows with different exceeding probabilities, the Pearson III empirical and theoretical curves have been utilized. The concluding results have been obtained using hydrologic regionalization relations; these take into account the specific maximum flows (qmaxp% with different insurances, the average altitude (Hm and the area (F of the drainage basin (Hm/√F. By selecting maximum flows with values exceeding the flooding stage (FS, the occurrence frequency has been established in the studied area. The highest floods in the Uz hydrographical basin have occurred in the months of June-July.

  2. Temporal variability in shell mound formation at Albatross Bay, northern Australia.

    Directory of Open Access Journals (Sweden)

    Simon J Holdaway

    Full Text Available We report the results of 212 radiocarbon determinations from the archaeological excavation of 70 shell mound deposits in the Wathayn region of Albatross Bay, Australia. This is an intensive study of a closely co-located group of mounds within a geographically restricted area in a wider region where many more shell mounds have been reported. Valves from the bivalve Tegillarca granosa (Linnaeus, 1758 were dated. The dates obtained are used to calculate rates of accumulation for the shell mound deposits. These demonstrate highly variable rates of accumulation both within and between mounds. We assess these results in relation to likely mechanisms of shell deposition and show that rates of deposition are affected by time-dependent processes both during the accumulation of shell deposits and during their subsequent deformation. This complicates the interpretation of the rates at which shell mound deposits appear to have accumulated. At Wathayn, there is little temporal or spatial consistency in the rates at which mounds accumulated. Comparisons between the Wathayn results and those obtained from shell deposits elsewhere, both in the wider Albatross Bay region and worldwide, suggest the need for caution when deriving behavioural inferences from shell mound deposition rates, and the need for more comprehensive sampling of individual mounds and groups of mounds.

  3. Evolution of learning strategies in temporally and spatially variable environments: A review of theory

    Science.gov (United States)

    Aoki, Kenichi; Feldman, Marcus W.

    2013-01-01

    The theoretical literature from 1985 to the present on the evolution of learning strategies in variable environments is reviewed, with the focus on deterministic dynamical models that are amenable to local stability analysis, and on deterministic models yielding evolutionarily stable strategies. Individual learning, unbiased and biased social learning, mixed learning, and learning schedules are considered. A rapidly changing environment or frequent migration in a spatially heterogeneous environment favors individual learning over unbiased social learning. However, results are not so straightforward in the context of learning schedules or when biases in social learning are introduced. The three major methods of modeling temporal environmental change – coevolutionary, two-timescale, and information decay – are compared and shown to sometimes yield contradictory results. The so-called Rogers’ paradox is inherent in the two-timescale method as originally applied to the evolution of pure strategies, but is often eliminated when the other methods are used. Moreover, Rogers’ paradox is not observed for the mixed learning strategies and learning schedules that we review. We believe that further theoretical work is necessary on learning schedules and biased social learning, based on models that are logically consistent and empirically pertinent. PMID:24211681

  4. Temporal variability in shell mound formation at Albatross Bay, northern Australia.

    Science.gov (United States)

    Holdaway, Simon J; Fanning, Patricia C; Petchey, Fiona; Allely, Kasey; Shiner, Justin I; Bailey, Geoffrey

    2017-01-01

    We report the results of 212 radiocarbon determinations from the archaeological excavation of 70 shell mound deposits in the Wathayn region of Albatross Bay, Australia. This is an intensive study of a closely co-located group of mounds within a geographically restricted area in a wider region where many more shell mounds have been reported. Valves from the bivalve Tegillarca granosa (Linnaeus, 1758) were dated. The dates obtained are used to calculate rates of accumulation for the shell mound deposits. These demonstrate highly variable rates of accumulation both within and between mounds. We assess these results in relation to likely mechanisms of shell deposition and show that rates of deposition are affected by time-dependent processes both during the accumulation of shell deposits and during their subsequent deformation. This complicates the interpretation of the rates at which shell mound deposits appear to have accumulated. At Wathayn, there is little temporal or spatial consistency in the rates at which mounds accumulated. Comparisons between the Wathayn results and those obtained from shell deposits elsewhere, both in the wider Albatross Bay region and worldwide, suggest the need for caution when deriving behavioural inferences from shell mound deposition rates, and the need for more comprehensive sampling of individual mounds and groups of mounds.

  5. Temporal variability in the suspended sediment load and streamflow of the Doce River

    Science.gov (United States)

    Oliveira, Kyssyanne Samihra Santos; Quaresma, Valéria da Silva

    2017-10-01

    Long-term records of streamflow and suspended sediment load provide a better understanding of the evolution of a river mouth, and its adjacent waters and a support for mitigation programs associated with extreme events and engineering projects. The aim of this study is to investigate the temporal variability in the suspended sediment load and streamflow of the Doce River to the Atlantic Ocean, between 1990 and 2013. Streamflow and suspended sediment load were analyzed at the daily, seasonal, and interannual scales. The results showed that at the daily scale, Doce River flood events are due to high intensity and short duration rainfalls, which means that there is a flashy response to rainfall. At the monthly and season scales, approximately 94% of the suspended sediment supply occurs during the wet season. Extreme hydrological events are important for the interannual scale for Doce River sediment supply to the Atlantic Ocean. The results suggest that a summation of anthropogenic interferences (deforestation, urbanization and soil degradation) led to an increase of extreme hydrological events. The findings of this study shows the importance of understanding the typical behavior of the Doce River, allowing the detection of extreme hydrological conditions, its causes and possible environmental and social consequences.

  6. Spatial and temporal variability of suspended-sediment concentrations in a shallow estuarine environment

    Directory of Open Access Journals (Sweden)

    Catherine A. Ruhl

    2004-05-01

    Full Text Available Shallow subembayments respond differently than deep channels to physical forces acting in estuaries. The U.S. Geological Survey measured suspended-sediment concentrations at five locations in Honker Bay, a shallow subembayment of San Francisco Bay, and the adjacent channel to investigate the spatial and temporal differences between deep and shallow estuarine environments. During the first freshwater pulse of the wet season, the channel tended to transport suspended sediments through the system, whereas the shallow area acted as off-channel storage where deposition would likely occur. Following the freshwater pulse, suspended-sediment concentrations were greater in Honker Bay than in the adjacent deep channel, due to the larger supply of erodible sediment on the bed. However, the tidal variability of suspended-sediment concentrations in both Honker Bay and in the adjacent channel was greater after the freshwater pulse than before. During wind events, suspended-sediment concentrations in the channel were not affected; however, wind played a crucial role in the resuspension of sediments in the shallows. Despite wind-wave sediment resuspension in Honker Bay, tidally averaged suspended-sediment flux was controlled by the flood-dominated currents.

  7. Spatio-temporal snowmelt variability across the headwaters of the Southern Rocky Mountains

    Science.gov (United States)

    Fassnacht, S. R.; López-Moreno, J. I.; Ma, C.; Weber, A. N.; Pfohl, A. K. D.; Kampf, S. K.; Kappas, M.

    2017-09-01

    Understanding the rate of snowmelt helps inform how water stored as snow will transform into streamflow. Data from 87 snow telemetry (SNOTEL) stations across the Southern Rocky Mountains were used to estimate spatio-temporal melt factors. Decreases in snow water equivalent were correlated to temperature at these monitoring stations for eight half-month periods from early March through late June. Time explained 70% of the variance in the computed snow melt factors. A residual linear correlation model was used to explain subsequent spatial variability. Longitude, slope, and land cover type explained further variance. For evergreen trees, canopy density was relevant to find enhanced melt rates; while for all other land cover types, denoted as non-evergreen, lower melt rates were found at high elevation, high latitude and north facing slopes, denoting that in cold environments melting is less effective than in milder sites. A change in the temperature sensor about mid-way through the time series (1990 to 2013) created a discontinuity in the temperature dataset. An adjustment to the time series yield larger computed melt factors.

  8. Evolution of learning strategies in temporally and spatially variable environments: a review of theory.

    Science.gov (United States)

    Aoki, Kenichi; Feldman, Marcus W

    2014-02-01

    The theoretical literature from 1985 to the present on the evolution of learning strategies in variable environments is reviewed, with the focus on deterministic dynamical models that are amenable to local stability analysis, and on deterministic models yielding evolutionarily stable strategies. Individual learning, unbiased and biased social learning, mixed learning, and learning schedules are considered. A rapidly changing environment or frequent migration in a spatially heterogeneous environment favors individual learning over unbiased social learning. However, results are not so straightforward in the context of learning schedules or when biases in social learning are introduced. The three major methods of modeling temporal environmental change--coevolutionary, two-timescale, and information decay--are compared and shown to sometimes yield contradictory results. The so-called Rogers' paradox is inherent in the two-timescale method as originally applied to the evolution of pure strategies, but is often eliminated when the other methods are used. Moreover, Rogers' paradox is not observed for the mixed learning strategies and learning schedules that we review. We believe that further theoretical work is necessary on learning schedules and biased social learning, based on models that are logically consistent and empirically pertinent. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Fives decades of strong temporal variability in the flow of the Brunt Ice Shelf, Antarctica

    Science.gov (United States)

    De Rydt, Jan; Gudmundsson, Hilmar; Nagler, Thomas

    2017-04-01

    The Brunt Ice Shelf, East Antarctica, is a complex conglomerate of meteoric and marine ice, weakly connected to the much larger and faster-flowing Stancomb Wills Glacier Tongue to the east, and pinned down to the seabed in a small area around the McDonalds Ice Rumples in the north. The ice shelf is home to the UK research station Halley, from which changes to the ice shelf have been monitored closely since the 1960s. A unique 50-year record of the flow speed and an intense surveying programme over the past 10 years, have revealed a strong temporal variability in the flow. In particular, the speed of the ice shelf has increased by 10% each year over the past few years. In order to understand these rapid changes, we use a state-of-the-art flow model in combination with a range of satellite, ground-based and airborne radar data, to accurately simulate the historical flow and recent changes. In particular, we model the effects of a recently formed rift that is propagating at a speed of up to 600m/day and threatens to dislodge the ice shelf from its pinning point at the McDonalds Ice Rumples. We also report on the recent reactivation of a large chasm which has prompted the relocation of the station during the 2016/17 austral summer.

  10. Coupled effect of flow variability and mass transfer on contaminant transport and attenuation in groundwater

    Science.gov (United States)

    Cvetkovic, Vladimir; Fiori, Aldo; Dagan, Gedeon

    2016-04-01

    The driving mechanism of contaminant transport in aquifers is groundwater flow, which is controlled by boundary conditions and heterogeneity of hydraulic properties. In this work we show how hydrodynamics and mass transfer can be combined in a general analytical manner to derive a physically-based (or process-based) residence time distribution for a given integral scale of the hydraulic conductivity; the result can be applied for a broad class of linear mass transfer processes. The derived tracer residence time distribution is a transfer function with parameters to be inferred from combined field and laboratory measurements. It is scalable relative to the correlation length and applicable for an arbitrary statistical distribution of the hydraulic conductivity. Based on the derived residence time distribution, the coefficient of variation and skewness of contaminant residence time are illustrated assuming a log-normal hydraulic conductivity distribution and first-order mass transfer. We show that for a low Damkohler number the coefficient of variation is more strongly influenced by mass transfer than by heterogeneity, whereas skewness is more strongly influenced by heterogeneity. The derived physically-based residence time distribution for solute transport in heterogeneous aquifers is particularly useful for studying natural attenuation of contaminants. We illustrate the relative impacts of high heterogeneity and a generalised (non-Fickian) multi-rate mass transfer on natural attenuation defined as contaminant mass loss from injection to a downstream compliance boundary.

  11. Temporal variability in urinary excretion of bisphenol A and seven other phenols in spot, morning, and 24-h urine samples

    DEFF Research Database (Denmark)

    Lassen, Tina Harmer; Frederiksen, Hanne; Jensen, Tina Kold

    2013-01-01

    of bisphenol A (BPA) and seven other phenols. All analytes were determined using TurboFlow-LC-MS/MS. Two spot, three first morning and three 24-h urine samples were collected from 33 young Danish men over a three months period. Temporal variability was estimated by means of intraclass correlation coefficients...

  12. Assessing spatio-temporal variability and trends in modelled and measured Greenland Ice Sheet albedo (2000-2013)

    NARCIS (Netherlands)

    Alexander, P. M.; Tedesco, M.; Fettweis, X.; Van De Wal, R. S W; Smeets, C. J P P; Van Den Broeke, M. R.

    2014-01-01

    Accurate measurements and simulations of Greenland Ice Sheet (GrIS) surface albedo are essential, given the role of surface albedo in modulating the amount of absorbed solar radiation and meltwater production. In this study, we assess the spatio-temporal variability of GrIS albedo during June, July,

  13. Analysis of the spatio-temporal variability of extreme hydro-meteorological events over Germany

    Science.gov (United States)

    Samaniego-Eguiguren, L. E.; Coskun, M.; Kumar, R.; Zink, M.; Attinger, S.

    2010-12-01

    Extreme hydro-meteorological events are the major cause of Great Natural Disasters according to the United Nations. In 2008 overall losses due to flood and drought related events amounted to US\\~570 bn (Munich RE). Discharge regimes of river basins are expected to be altered due to possible effects of climate change. For planning and water resources management, it is fundamental to estimate the probability of occurrence of extreme hydro-meteorological events as well as its intensity. Predictions of climatic variables such as temperature and precipitation are currently done with GCM and RCM for global and regional scales, respectively. A fundamental research question at the moment is: are current RCMs able to reproduce the spatio-temporal variability of extreme events that were observed during the past decades? If not, what kind of bias exist in those data sets and how can these simulations be made useful for hydrologic projections? In this study we analyze these questions using the most recent comprehensive RCM data sets available from the ENSEMBLES project over whole Germany for the period from 1961 to 2000. During this period all RCMs were driven by ERA-40 reanalysis at spatial resolutions of 25 km and 50 km. Among the analyzed variables were the time evolution and the areal extend of various extreme statistics such as precipitation and temperature above and below a threshold value, maxiμm and miniμm air temperatures, maxiμm daily precipitation in summer. Additionally the spatial correlation structure of daily precipitation and the spatial pattern of a wetness index for each synoptic circulation pattern were also considered. These indices were compared with their respective ones obtained from observations of more than five thousand meteorological stations over Germany. Preliminary results indicate that the various RCMs were able to reproduce in some cases and for some indices the observed spatial patterns. The magnitudes of extreme event indices (Fig. 1) were

  14. Butterfly Sprint Swimming Technique, Analysis of Somatic and Spatial-Temporal Coordination Variables.

    Science.gov (United States)

    Strzała, Marek; Stanula, Arkadiusz; Krężałek, Piotr; Ostrowski, Andrzej; Kaca, Marcin; Głąb, Grzegorz

    2017-12-01

    The aim of this study was to investigate somatic properties and force production of leg extensor muscles measured in the countermovement jump test (CMJ), as well as to analyse kinematic variables of sprint surface butterfly swimming. Thirty-four male competitive swimmers were recruited with an average age of 19.3 ± 1.83 years. Their average body height (BH) was 183.7 ± 5.93 cm, body fat content 10.8 ± 2.64% and body mass (BM) 78.3 ± 5.0 kg. Length measurements of particular body segments were taken and a counter movement jump (CMJ) as well as an all-out 50 m butterfly speed test were completed. The underwater movements of the swimmers' bodies were recorded with a digital camera providing side-shots. We registered a significant relationship between body mass (r = 0.46), lean body mass (r = 0.48) and sprint surface butterfly swimming (VSBF). The anaerobic power measured in the CMJ test, total body length (TBL) as well as upper and lower extremity length indices did not influence swimming speed significantly. The temporal entry-kick index (the time ratio between the first kick and arm entry) significantly influenced VSBF (r = -0.45). Similarly, medium power of the coefficient was indicated between a) stroke rate kinematics (SR), b) duration of the first leg kick (LP1), c) air phase duration of arm recovery (Fly-arm), and VSBF (r = 0.40; r = 0.40 and r = 0.41, respectively). The entry-kick temporal index showed that, in the butterfly cycle, an appropriately early executed initial kick when compared to arm entry was associated with a longer arm propulsion phase, which in turn was associated with minimizing resistive gliding phases and enabled relatively longer and less resistive air arm recovery (higher value of the fly-arm index). The higher value of SR kinematic was another important element of the best butterfly results in this study.

  15. Spatial and Temporal Variability of Rainfall over the South-West Coast of Bangladesh

    Directory of Open Access Journals (Sweden)

    Md. Sarwar Hossain

    2014-04-01

    Full Text Available This study examined the spatial and temporal rainfall variability from the 1940s to 2007 in the south west coastal region of Bangladesh. Time series statistical tests were applied to examine the spatial and temporal trends in three time segments (1948–1970, 1971–1990 and 1991–2007 and four seasons (Pre-monsoon; Monsoon; Post-Monsoon and Winter, during the period 1948–2007. Eight weather stations were divided into two zones: exposed (exposed to sea and interior (distant to sea. Overall, rainfall increased during the period 1948–2007, while the trends intensified during post-1990s. Post-monsoon and winter rainfall was observed to follow significant positive trends at most weather stations during the time period 1948–2007. The rate of change was found in exposed zone and interior zone are +12.51 and +4.86 mm/year, respectively, over post monsoon and +0.9 and +1.86 mm/year, respectively, over winter. These trends intensified both in the exposed zone (+45.81 mm/year and the interior zone (+27.09 mm/year 1990 onwards. Winter rainfall does not exhibit significant change (p > 0.1 over the exterior or interior zone, though individual stations like Jessore, Satkhira and Bhola show significant negative trends after 1990s. Although the trends were observed to weaken in the monsoon and pre-monsoon seasons, they are not significant. Moreover, an 11-year cyclicity was found within these two seasons, whilst no cyclicity was observed in the post-monsoon and winter seasons. Sequential Mann Kendal test reveals that the changes in two zones rainfall trends are started around mid-80s, where step change found only for fours season in Khulna stations and also for winter seasons in all weather stations. These changes may have a detrimental effect on rain-fed agriculture in Bangladesh. The application of palaeo-environmental techniques, threshold determination and rainfall analysis across the whole country could be useful to support adaptation planning of

  16. Butterfly Sprint Swimming Technique, Analysis of Somatic and Spatial-Temporal Coordination Variables

    Directory of Open Access Journals (Sweden)

    Strzała Marek

    2017-12-01

    Full Text Available The aim of this study was to investigate somatic properties and force production of leg extensor muscles measured in the countermovement jump test (CMJ, as well as to analyse kinematic variables of sprint surface butterfly swimming. Thirty-four male competitive swimmers were recruited with an average age of 19.3 ± 1.83 years. Their average body height (BH was 183.7 ± 5.93 cm, body fat content 10.8 ± 2.64% and body mass (BM 78.3 ± 5.0 kg. Length measurements of particular body segments were taken and a counter movement jump (CMJ as well as an all-out 50 m butterfly speed test were completed. The underwater movements of the swimmers’ bodies were recorded with a digital camera providing side-shots. We registered a significant relationship between body mass (r = 0.46, lean body mass (r = 0.48 and sprint surface butterfly swimming (VSBF. The anaerobic power measured in the CMJ test, total body length (TBL as well as upper and lower extremity length indices did not influence swimming speed significantly. The temporal entry-kick index (the time ratio between the first kick and arm entry significantly influenced VSBF (r = -0.45. Similarly, medium power of the coefficient was indicated between a stroke rate kinematics (SR, b duration of the first leg kick (LP1, c air phase duration of arm recovery (Fly-arm, and VSBF (r = 0.40; r = 0.40 and r = 0.41, respectively. The entry-kick temporal index showed that, in the butterfly cycle, an appropriately early executed initial kick when compared to arm entry was associated with a longer arm propulsion phase, which in turn was associated with minimizing resistive gliding phases and enabled relatively longer and less resistive air arm recovery (higher value of the fly-arm index. The higher value of SR kinematic was another important element of the best butterfly results in this study.

  17. Large temporal changes in contributions of groundwater-borne nutrients to coastal waters off a volcanic island

    Science.gov (United States)

    Cho, Hyung-Mi; Kim, Guebuem

    2017-09-01

    We examined the contribution of submarine groundwater discharge (SGD) to nutrient budgets in Hwasun Bay, Jeju Island, Korea in August 2009, October 2014, and May 2015. The concentrations of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) in fresh groundwater were in the range of 285-716 μM and 2.3-3.2 μM, respectively, which were each 1-2 orders of magnitude higher than those in the bay seawater. The outer-bay seawater flowing into the bay was oligotrophic (2.9 ± 1.9 μM for DIN and 0.2 ± 0.3 μM for DIP). Nutrient budget calculations were performed for each season by accounting for submarine fresh groundwater discharge (SFGD) and water residence times. In August 2009 (DIN = 1.8 μM and DIN:DIP ratio = 4.6 for the outerbay water), DIN inputs from SFGD accounted for approximately 40% of the DIN inventory in the bay seawater. In October 2014 (DIN = 1.1 μM and DIP nutrient budgets and stoichiometry in coastal waters off a volcanic island depending on open-ocean nutrient conditions.

  18. Spatial and temporal variability of grass cover in two olive grove catchments on contrasting soil types

    Science.gov (United States)

    Aguilera, Laura; Taguas, Encarnación V.; Gimeno, Enrique; Gómez, José A.

    2013-04-01

    Mediterranean climate conditions -characterized by the concentration of the precipitation in the seasons of autumn and spring, the low temperatures in winter and extremely warm and dry summers- determine that ground cover by adventitious (or cover crop) vegetation shows significant seasonal and annual variability. In addition, its spatial variability associates also, partially, to water availability among the landscape. This is especially relevant in olive orchards, an agricultural system under high erosion risk in the region where the establishment of herbaceous cover has proved to improve soil protection reducing erosion risk, as well as the improvement of soil properties (Gómez et al., 2009). All these benefits are based on small scale studies where full ground cover by the cover crop is relatively easy to obtain. However, few information is available about the actual ground cover achieved at farm scale, although preliminary observations suggests that this might be extremely variable (Gómez and Giráldez, 2009). This study presents the preliminary results evaluating the spatial and temporal evolution of ground cover by adventitious vegetation (the preferred option by farmers to achieve a cover crop) in two commercial olive farms during 2 hydrological years (2011-2012). The study was conducted in two farms located in the province of Cordoba, Southern Spain. Both were olive orchards grown under deficit irrigation systems and present a gauge station where rainfall, runoff and sediment loads have been measured from the year 2005. The soil management in "La Conchuela" farm was based in the use of herbicide in the line of olive trees to keep the bare soil all year round, and the application of selective herbicide in the lane between the olive trees to promote the grown of graminaceae grasses . In addition, the grass is mechanically killed in June. In the another farm, "Arroyo Blanco", the grass spontaneous cover is allowed until mid-spring in which is also

  19. Solar light induced removal of arsenic from contaminated groundwater: the interplay of solar energy and chemical variables

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, M.G.; D' Hiriart, J.; Giullitti, J.; Hidalgo, M. del V. [Universidad Nacional de Tucaman (Argentina). Centro de Investigaciones y Transferencia en Quimica Aplicada; Lin, H.; Custo, G.; Litter, M.I. [Comision Nacional de Energia Atomica, Buenos Aires (Argentina). Unidad de Actividad Quimica; Blesa, M.A. [Comision Nacional de Energia Atomica, Buenos Aires (Argentina). Unidad de Actividad Quimica; Universidad Nacional de General San Martin (Argentina)

    2004-11-01

    The removal of arsenic by solar oxidation in individual units (SORAS) is currently being explored as a possible economic and simple technology to treat groundwater in Bangladesh and India. Hydroarsenicism affects also large regions of America, especially Argentina, Chile, Mexico and Peru. In this paper, the efficiency of arsenic removal by solar oxidation coupled with precipitation of iron (hydr)oxide, was assessed under various experimental conditions, both on samples of synthetic water and of groundwater of the province of Tucuman (Argentina). The results demonstrate that the underlying chemistry is very complex, and the efficiency is affected often in unpredictable ways by changes in the chemical matrix, or by changes in the operative conditions. Oxides generated from ferrous salts are more efficient than solids formed by hydrolysis of Fe(III); alkalinity contents (bicarbonate) is also important to permit the adequate precipitation. Addition of small amounts of citric acid (lemon juice) is beneficial, but at larger concentrations the effect is negative, probably because of interference in the formation of the solid. The effect of solar irradiation is variable, depending on the other experimental conditions. Although it is possible to remove As partially without solar irradiation under certain special conditions, a procedure versatile enough to cope with waters of different compositions must be based in the use of solar energy. Light plays the role of accelerating the oxidation of As(III) to As(V), and also affects the nature of the solid and, hence, its sorptive properties. The rationale of the effect of light is therefore appreciably more complex than in the case of heterogeneous photocatalysis with TiO{sub 2}. (Author)

  20. Spatial and Temporal Variability of Fugitive Dust Flux from Colorado Plateau Landscapes

    Science.gov (United States)

    Flagg, C.; Neff, J.; Reynolds, R. L.; Belnap, J.

    2011-12-01

    tridentata shrubland, Coleogyne ramosissima shrubland, and Atriplex spp. shrubland averaged 1.5, 1.1, 2.2, 6.6, and 7.5 g m-2 d-1 respectively during the winter. The seasonal variation in dust flux was highest in shrublands and lowest in both perennial grasslands and Pinyon-Juniper woodlands. Surfaces dominated by perennial grass consistently had the lowest dust flux. Atriplex spp.-dominated-shrubland appeared to consistently exhibit higher dust flux than Artemisia spp.- and Coleogyne ramosissima-dominated shrublands. The year 2010 was a significantly dustier year than 2009 (59 vs. 9.1 g m-2 d-1) averaged over all plant communities, with surfaces of Coleogyne and Atriplex plant communities contributing the most to temporal variability. In contrast, temporal dust-flux patterns from Pinyon-Juniper woodland, perennial grassland, and Artemisia tridentata shrubland, three of the most prevalent plant communities, were nearly indistinguishable but still showed higher dust flux in 2010 versus 2009. C. Flagg, R.L. Reynolds: U.S. Geological Survey Denver CO 80225; J.C. Neff: University of Colorado - Boulder CO 80202; J. Belnap: U.S. Geological Survey Moab UT 84532

  1. Investigating temporal and spatial patterns of groundwater-surface water interaction on a river reach by applying transient thermal modelling

    Science.gov (United States)

    Anibas, Christian; Debele Tolche, Abebe; Ghysels, Gert; Schneidewind, Uwe; Nossent, Jiri; Touhidul Mustafa, Syed Md; Huysmans, Marijke; Batelaan, Okke

    2017-04-01

    The quantification of groundwater-surface water interaction is an important challenge for hydrologists and ecologists. Within the last decade, many new analytical and numerical estimation methods have been developed, including heat tracer techniques. In a number of publications, their sources of errors were investigated, and future directions for the research in groundwater-surface water exchange were discussed. To improve our respective knowledge of the Belgian lowland Aa River we reinvestigate temperature data which was gathered in the river bed and used for the quantification of the 1D vertical groundwater-surface water exchange. By assuming a thermal steady state of the river bed temperature distribution, Anibas et al. (2011) were unable to use the full potential of the entire large data set. The analysis tool STRIVE is modified to use the river water temperature time series as the upper model boundary. This transient thermal set up overcomes many of the limitations of the steady state assumption and allows for the analysis of vertical 1D exchange fluxes in space and time. Results of about 380 transient simulations covering a period of more than 1.5 years show high absolute changes in exchange fluxes in the upstream part of the river. However, in the downstream part, the relative changes in fluxes are larger. The 26 spatially distributed thermal profiles along the river reach are interpolated using kriging based on variograms calculated from the temperature dataset. Results indicate gaining conditions for most locations and most of the time. Few places in the downstream part show losing conditions in late winter and early spring. While in autumn and winter the mean exchange fluxes can be -90 mmd-1, in spring to early summer fluxes are only -42 mmd-1. The river bed near the banks shows elevated fluxes compared to the center of the river. Probably driven by regional groundwater flow, the river bed near the left and right bank shows fluxes respectively a factor 3

  2. Modeling variably saturated multispecies reactive groundwater solute transport with MODFLOW-UZF and RT3D

    Science.gov (United States)

    Bailey, Ryan T.; Morway, Eric D.; Niswonger, Richard G.; Gates, Timothy K.

    2013-01-01

    A numerical model was developed that is capable of simulating multispecies reactive solute transport in variably saturated porous media. This model consists of a modified version of the reactive transport model RT3D (Reactive Transport in 3 Dimensions) that is linked to the Unsaturated-Zone Flow (UZF1) package and MODFLOW. Referred to as UZF-RT3D, the model is tested against published analytical benchmarks as well as other published contaminant transport models, including HYDRUS-1D, VS2DT, and SUTRA, and the coupled flow and transport modeling system of CATHY and TRAN3D. Comparisons in one-dimensional, two-dimensional, and three-dimensional variably saturated systems are explored. While several test cases are included to verify the correct implementation of variably saturated transport in UZF-RT3D, other cases are included to demonstrate the usefulness of the code in terms of model run-time and handling the reaction kinetics of multiple interacting species in variably saturated subsurface systems. As UZF1 relies on a kinematic-wave approximation for unsaturated flow that neglects the diffusive terms in Richards equation, UZF-RT3D can be used for large-scale aquifer systems for which the UZF1 formulation is reasonable, that is, capillary-pressure gradients can be neglected and soil parameters can be treated as homogeneous. Decreased model run-time and the ability to include site-specific chemical species and chemical reactions make UZF-RT3D an attractive model for efficient simulation of multispecies reactive transport in variably saturated large-scale subsurface systems.

  3. Reproducibility of the spatio-temporal variables and the ground reaction forces walking with fire fighting boots

    Directory of Open Access Journals (Sweden)

    Jesús Cámara Tobalina

    2010-11-01

    Full Text Available AbstractThe aim of this study is to analyze the reproducibility of the spatio-temporal variables and the ground reaction forces (GRF when walking with fire fighting boots in comparison to walking with low calf shoes. Spatio-temporal parameters and the variables related to the three components of the GRF of 39 people were recorded under two different walking conditions. A T-test to contrast the difference between the coefficients of variation (CV in both conditions was used. The CV of the spatio-temporal variables (i.e velocity (V, condition I = 2.01%; condition II = 1.81%, of the vertical (i.e. contact force (FZA of the left foot, condition I = 2.54%; condition II = 2.73% and of the antero-posterior GRF (i.e. maximum force (FXMAX of the left foot, condition I = 4.47%; condition II = 4.59% was lower than 12.5%, suggesting that these variables could be used to analyze the influence of fire fighting boots on the gait. However, the low reproducibility showed by medium-lateral parameters does not allow to use them. Apart from the bipodal phase no differences were found between the two walking conditions. Key words: biomechanics, footwear, variability.

  4. The Spatial and Temporal Variability of the North Atlantic Oscillation Recorded in Ice Core Major Ion Time Series

    Science.gov (United States)

    Wawrzeniak, T. L.; Wake, C. P.; Fischer, H.; Fisher, D. A.; Schwikowski, M.

    2006-05-01

    The North Atlantic Oscillation represents a significant mode of atmospheric variability for the Arctic and sub- Artic climate system. Developing a longer-term record of the spatial and temporal variability of the NAO could improve our understanding of natural climate variability in the region. Previous work has shown a significant relationship between Greenland ice core records and the NAO. Here, we have compared sea-salt and dust records from nine ice cores around the Arctic region to sea level pressure and NAO indices to evaluate the extent to which these ice cores can be used to reconstruct the NAO.

  5. Spatial and temporal variability in sedimentation rates associated with cutoff channel infill deposits: Ain River, France

    Science.gov (United States)

    Piegay, H.; Hupp, C.R.; Citterio, A.; Dufour, S.; Moulin, B.; Walling, D.E.

    2008-01-01

    Floodplain development is associated with lateral accretion along stable channel geometry. Along shifting rivers, the floodplain sedimentation is more complex because of changes in channel position but also cutoff channel presence, which exhibit specific overflow patterns. In this contribution, the spatial and temporal variability of sedimentation rates in cutoff channel infill deposits is related to channel changes of a shifting gravel bed river (Ain River, France). The sedimentation rates estimated from dendrogeomorphic analysis are compared between and within 14 cutoff channel infills. Detailed analyses along a single channel infill are performed to assess changes in the sedimentation rates through time by analyzing activity profiles of the fallout radionuclides 137Cs and unsupported 210Pb. Sedimentation rates are also compared within the channel infills with rates in other plots located in the adjacent floodplain. Sedimentation rates range between 0.65 and 2.4 cm a -1 over a period of 10 to 40 years. The data provide additional information on the role of distance from the bank, overbank flow frequency, and channel geometry in controlling the sedimentation rate. Channel infills, lower than adjacent floodplains, exhibit higher sedimentation rates and convey overbank sediment farther away within the floodplain. Additionally, channel degradation, aggradation, and bank erosion, which reduce or increase the distance between the main channel and the cutoff channel aquatic zone, affect local overbank flow magnitude and frequency and therefore sedimentation rates, thereby creating a complex mosaic of sedimentation zones within the floodplain and along the cutoff channel infills. Last, the dendrogeomorphic and 137Cs approaches are cross validated for estimating the sedimentation rate within a channel infill. Copyright 2008 by the American Geophysical Union.

  6. Spatial and temporal variability and long-term trends in skew surges globally

    Directory of Open Access Journals (Sweden)

    Robert eMawdsley

    2016-03-01

    Full Text Available Storm surges and the resulting extreme high sea levels are among the most dangerous natural disasters and are responsible for widespread social, economic and environmental consequences. Using a set of 220 tide gauges, this paper investigates the temporal variations in storm surges around the world and the spatial coherence of its variability. We compare results derived from two parameters used to represent storm surge: skew surge and the more traditional, non-tidal residual. We determine the extent of tide-surge interaction, at each study site, and find statistically significant (95% confidence levels of tide-surge interaction at 59% of sites based on tidal level and 81% of sites based on tidal-phase. The tide-surge interaction was strongest in regions of shallow bathymetry such as the North Sea, north Australia and the Malay Peninsula. At most sites the trends in the skew surge time series were similar to those of non-tidal residuals, but where there were large differences in trends, the sites tended to have a large tidal range. Only 13% of sites had a statistically significant trend in skew surge, and of these approximately equal numbers were positive and negative. However, for trends in the non-tidal residual there are significantly more negative trends. We identified 8 regions where there were strong positive correlations in skew surge variability between sites, which meant that a regional index could be created to represent these groups of sites. Despite, strong correlations between some regional skew surge indices, none are significant at the 95% level, however, at the 80% level there was significant positive correlation between the north-west Atlantic - south and the North Sea. Correlations between the regional skew surge indices and climate indices only became significant at the 80% level, where Nińo 4 was positively correlated with the Gulf of Mexico skew surge index and negatively correlated with the east Australia skew surge index

  7. A hydrochemical modelling framework for combined assessment of spatial and temporal variability in stream chemistry: application to Plynlimon, Wales

    Directory of Open Access Journals (Sweden)

    H.J. Foster

    2001-01-01

    Full Text Available Recent concern about the risk to biota from acidification in upland areas, due to air pollution and land-use change (such as the planting of coniferous forests, has generated a need to model catchment hydro-chemistry to assess environmental risk and define protection strategies. Previous approaches have tended to concentrate on quantifying either spatial variability at a regional scale or temporal variability at a given location. However, to protect biota from ‘acid episodes’, an assessment of both temporal and spatial variability of stream chemistry is required at a catchment scale. In addition, quantification of temporal variability needs to represent both episodic event response and long term variability caused by deposition and/or land-use change. Both spatial and temporal variability in streamwater chemistry are considered in a new modelling methodology based on application to the Plynlimon catchments, central Wales. A two-component End-Member Mixing Analysis (EMMA is used whereby low and high flow chemistry are taken to represent ‘groundwater’ and ‘soil water’ end-members. The conventional EMMA method is extended to incorporate spatial variability in the two end-members across the catchments by quantifying the Acid Neutralisation Capacity (ANC of each in terms of a statistical distribution. These are then input as stochastic variables to a two-component mixing model, thereby accounting for variability of ANC both spatially and temporally. The model is coupled to a long-term acidification model (MAGIC to predict the evolution of the end members and, hence, the response to future scenarios. The results can be plotted as a function of time and space, which enables better assessment of the likely effects of pollution deposition or land-use changes in the future on the stream chemistry than current methods which use catchment average values. The model is also a useful basis for further research into linkage between hydrochemistry

  8. Spatial and temporal variability of throughfall and soil moisture in a deciduous forest in the low mountain ranges (Hesse, Germany)

    Science.gov (United States)

    Chifflard, Peter; Weishaupt, Philipp; Reiss, Martin

    2017-04-01

    Spatial and temporal patterns of throughfall can affect the heterogeneity of ecological, biogeochemical and hydrological processes at a forest floor and further the underlying soil. Previous research suggests different factors controlling the spatial and temporal patterns of throughfall, but most studies focus on coniferous forest, where the vegetation coverage is more or less constant over time. In deciduous forests the leaf area index varies due to the leaf fall in autumn which implicates a specific spatial and temporal variability of throughfall and furthermore of the soil moisture. Therefore, in the present study, the measurements of throughfall and soil moisture in a deciduous forest in the low mountain ranges focused especially on the period of leaf fall. The aims of this study were: 1) to detect the spatial and temporal variability of both the throughfall and the soil moisture, 2) to examine the temporal stability of the spatial patterns of the throughfall and soil moisture and 3) relate the soil moisture patterns to the throughfall patterns and further to the canopy characteristics. The study was carried out in a small catchment on middle Hesse (Germany) which is covered by beech forest. Annual mean air temperature is 9.4°C (48.9˚F) and annual mean precipitation is 650 mm. Base materials for soil genesis is greywacke and clay shale from Devonian deposits. The soil type at the study plot is a shallow cambisol. The study plot covers an area of about 150 m2 where 77 throughfall samplers where installed. The throughfall and the soil moisture (FDR-method, 20 cm depth) was measured immediately after every rainfall event at the 77 measurement points. During the period of October to December 2015 altogether 7 events were investigated. The geostatistical method kriging was used to interpolate between the measurements points to visualize the spatial patterns of each investigated parameter. Time-stability-plots were applied to examine temporal scatters of each

  9. Spatio-temporal dependencies between hospital beds, physicians and health expenditure using visual variables and data classification in statistical table

    Directory of Open Access Journals (Sweden)

    Medyńska-Gulij Beata

    2016-06-01

    Full Text Available This paper analyses the use of table visual variables of statistical data of hospital beds as an important tool for revealing spatio-temporal dependencies. It is argued that some of conclusions from the data about public health and public expenditure on health have a spatio-temporal reference. Different from previous studies, this article adopts combination of cartographic pragmatics and spatial visualization with previous conclusions made in public health literature. While the significant conclusions about health care and economic factors has been highlighted in research papers, this article is the first to apply visual analysis to statistical table together with maps which is called previsualisation.

  10. Temporal stability and variability of soil-water content in a gravel-mulched field in northwestern China

    Science.gov (United States)

    Zhao, Wenju; Cui, Zhen; Zhang, Jiyi; Jin, Jian

    2017-09-01

    Characterizing the spatiotemporal variability of soil-water content (SWC) is of paramount importance in many scientific fields and operational applications. We present a case study of the temporal stability and variability of SWC in a gravel-mulched field, a form of mulching that has been widely used by farmers on the loessial area of China for over 300 years, using Spearman correlation coefficients, frequency distributions and an index of temporal stability. SWC was measured weekly from May to August 2013 in the 0-10, 10-20, 20-30 and 30-50 cm layers. SWC was more variable in the surface soil, due to several environmental factors, and the variability gradually decreased with depth. A large sample size was needed for estimating the mean SWC of the field under dry conditions. High Spearman correlation coefficients between the SWCs measured on different sampling campaigns indicated a high temporal stability. The stability of the SWC spatial patterns over time and along the soil profile allowed us to identify a location representative of the field-mean SWC, with high coefficients of determination ranging between 0.8564 and 0.9325. The large-scale monitoring of SWC from few observations is thus feasible, which will aid the management of soil moisture in gravel-mulched fields in arid regions.

  11. Spatio-temporal variability in accretion and erosion of coastal foredunes in the Netherlands: regional climate and local topography.

    Science.gov (United States)

    Keijsers, Joep G S; Poortinga, Ate; Riksen, Michel J P M; Maroulis, Jerry

    2014-01-01

    Depending on the amount of aeolian sediment input and dune erosion, dune size and morphology change over time. Since coastal foredunes play an important role in the Dutch coastal defence, it is important to have good insight in the main factors that control these changes. In this paper the temporal variations in foredune erosion and accretion were studied in relation to proxies for aeolian transport potential and storminess using yearly elevation measurements from 1965 to 2012 for six sections of the Dutch coast. Longshore differences in the relative impacts of erosion and accretion were examined in relation to local beach width. The results show that temporal variability in foredune accretion and erosion is highest in narrow beach sections. Here, dune erosion alternates with accretion, with variability displaying strong correlations with yearly values of storminess (maximum sea levels). In wider beach sections, dune erosion is less frequent, with lower temporal variability and stronger correlations with time series of transport potential. In erosion dominated years, eroded volumes decrease from narrow to wider beaches. When accretion dominates, dune-volume changes are relatively constant alongshore. Dune erosion is therefore suggested to control spatial variability in dune-volume changes. On a scale of decades, the volume of foredunes tends to increase more on wider beaches. However, where widths exceed 200 to 300 m, this trend is no longer observed.

  12. Spatial variability of the shallow groundwater level and its chemistry characteristics in the low plain around the Bohai Sea, North China.

    Science.gov (United States)

    Zhou, Zaiming; Zhang, Guanghui; Yan, Mingjiang; Wang, Jinzhe

    2012-06-01

    To characterize the spatial distribution of groundwater level (GWL) and its chemistry characteristics in the low plain around the Bohai Sea, shallow groundwater depth of 130 wells were determined. Water soluble ions composition, total dissolved solid (TDS), electric conductivity (EC), total hardness (TH), total alkalinity (TA), and total salt content (TS) of 128 representative groundwater samples were also measured. Classical statistics, geostatistical method combined with GIS technique were then used to analyze the spatial variability and distribution of GWL and groundwater chemical properties. Results show that GWL, TDS, EC, TH, TA, and TS all presented a lognormal distribution and could be fitted by different semivariogram models (spherical, exponential, and Gaussian). Spatial structure of GWL, TDS, EC, TH, TA, and TS changed obviously. GWL decreased from west inland plain to the east coastal plain, however, TDS, EC, and TS increased from west to east, TH and TA were higher in the middle and coastal plain area. Groundwater chemical type in the coastal plain was SO (4) (2-) ·Cl(-)-Na(+) while chemical types in the inland plain were SO (4) (2-) ·Cl(-)-Ca(2+)·Mg(2+) and HCO (3) (-) -Ca(2+)·Mg(2+).

  13. Trajectory analysis of land use and land cover maps to improve spatial-temporal patterns, and impact assessment on groundwater recharge

    Science.gov (United States)

    Zomlot, Z.; Verbeiren, B.; Huysmans, M.; Batelaan, O.

    2017-11-01

    Land use/land cover (LULC) change is a consequence of human-induced global environmental change. It is also considered one of the major factors affecting groundwater recharge. Uncertainties and inconsistencies in LULC maps are one of the difficulties that LULC timeseries analysis face and which have a significant effect on hydrological impact analysis. Therefore, an accuracy assessment approach of LULC timeseries is needed for a more reliable hydrological analysis and prediction. The objective of this paper is to assess the impact of land use uncertainty and to improve the accuracy of a timeseries of CORINE (coordination of information on the environment) land cover maps by using a new approach of identifying spatial-temporal LULC change trajectories as a pre-processing tool. This ensures consistency of model input when dealing with land-use dynamics and as such improves the accuracy of land use maps and consequently groundwater recharge estimation. As a case study the impact of consistent land use changes from 1990 until 2013 on groundwater recharge for the Flanders-Brussels region is assessed. The change trajectory analysis successfully assigned a rational trajectory to 99% of all pixels. The methodology is shown to be powerful in correcting interpretation inconsistencies and overestimation errors in CORINE land cover maps. The overall kappa (cell-by-cell map comparison) improved from 0.6 to 0.8 and from 0.2 to 0.7 for forest and pasture land use classes respectively. The study shows that the inconsistencies in the land use maps introduce uncertainty in groundwater recharge estimation in a range of 10-30%. The analysis showed that during the period of 1990-2013 the LULC changes were mainly driven by urban expansion. The results show that the resolution at which the spatial analysis is performed is important; the recharge differences using original and corrected CORINE land cover maps increase considerably with increasing spatial resolution. This study indicates

  14. Uncertainty in the modelling of spatial and temporal patterns of shallow groundwater flow paths: The role of geological and hydrological site information

    Science.gov (United States)

    Woodward, Simon J. R.; Wöhling, Thomas; Stenger, Roland

    2016-03-01

    Understanding the hydrological and hydrogeochemical responses of hillslopes and other small scale groundwater systems requires mapping the velocity and direction of groundwater flow relative to the controlling subsurface material features. Since point observations of subsurface materials and groundwater head are often the basis for modelling these complex, dynamic, three-dimensional systems, considerable uncertainties are inevitable, but are rarely assessed. This study explored whether piezometric head data measured at high spatial and temporal resolution over six years at a hillslope research site provided sufficient information to determine the flow paths that transfer nitrate leached from the soil zone through the shallow saturated zone into a nearby wetland and stream. Transient groundwater flow paths were modelled using MODFLOW and MODPATH, with spatial patterns of hydraulic conductivity in the three material layers at the site being estimated by regularised pilot point calibration using PEST, constrained by slug test estimates of saturated hydraulic conductivity at several locations. Subsequent Null Space Monte Carlo uncertainty analysis showed that this data was not sufficient to definitively determine the spatial pattern of hydraulic conductivity at the site, although modelled water table dynamics matched the measured heads with acceptable accuracy in space and time. Particle tracking analysis predicted that the saturated flow direction was similar throughout the year as the water table rose and fell, but was not aligned with either the ground surface or subsurface material contours; indeed the subsurface material layers, having relatively similar hydraulic properties, appeared to have little effect on saturated water flow at the site. Flow path uncertainty analysis showed that, while accurate flow path direction or velocity could not be determined on the basis of the available head and slug test data alone, the origin of well water samples relative to the

  15. Calculation of the temporal gravity variation from spatially variable water storage change in soils and aquifers

    DEFF Research Database (Denmark)

    Leiriao, Silvia; He, Xin; Christiansen, Lars

    2009-01-01

    Total water storage change in the subsurface is a key component of the global, regional and local water balances. It is partly responsible for temporal variations of the earth's gravity field in the micro-Gal (1 mu Gal = 10(-8) m s(-2)) range. Measurements of temporal gravity variations can thus......-induced temporal variations in gravity from any hydrological model, provided earth curvature effects can be neglected. The method allows for the routine assimilation of ground-based gravity data into hydrological models....... be used to determine the water storage change in the hydrological system. A numerical method for the calculation of temporal gravity changes from the output of hydrological models is developed. Gravity changes due to incremental prismatic mass storage in the hydrological model cells are determined to give...

  16. Temporal variability of vertical export flux at the DYFAMED time-series station (Northwestern Mediterranean Sea)

    Science.gov (United States)

    Heimbürger, Lars-Eric; Lavigne, Héloïse; Migon, Christophe; D'Ortenzio, Fabrizio; Estournel, Claude; Coppola, Laurent; Miquel, Juan-Carlos

    2013-12-01

    The temporal evolution of the vertical export flux at the DYFAMED time-series station (Ligurian Sea) over the last 20 years reveals a strong interannual variability. Winter convection allows particulate (and dissolved) matter to be vertically exported (“flush-down” effect). The efficiency of this process determines also the concentration of nutrients brought to surface waters and, therefore, the intensity of the subsequent phytoplankton bloom. The sequence “convection-bloom” is the main driving force of vertical export flux in this region. The present work attempts to better identify the parameters that control vertical export flux dynamics by observing a 20 year time-series in relation with the temporal variability of mixed layer depth and surface primary production. The consequences of a more stratified water column in the future on biological productivity and vertical export flux are pointed out. In winter, the cooling of surface water, combined with evaporation, increases its density and determines the vertical convection. This allows for a rapid downward transfer of dissolved and particulate matter, yielding high vertical export flux. This “flush-down effect” results from a combination of convection and gravitational flux, since the diving of dense surface waters breaks the stratification of the water column and carries all material (particulate + dissolved) accumulated in the surface layer to depth. The rapid downward transfer of dissolved and particulate matter by this “flush-down effect” yields high vertical export fluxes. The magnitude of these fluxes may vary according to the amount of atmospheric material accumulated in surface waters during the preceding stratified period. In the present data set, highest vertical export fluxes were observed in 1999, 2003 and 2004. In those years, the MLD was greater (Fig. 2), suggesting a causal relationship between the efficiency of vertical mixing and the subsequent vertical export flux. In spring

  17. Variability in Regularity: Mining Temporal Mobility Patterns in London, Singapore and Beijing Using Smart-Card Data.

    Directory of Open Access Journals (Sweden)

    Chen Zhong

    Full Text Available To discover regularities in human mobility is of fundamental importance to our understanding of urban dynamics, and essential to city and transport planning, urban management and policymaking. Previous research has revealed universal regularities at mainly aggregated spatio-temporal scales but when we zoom into finer scales, considerable heterogeneity and diversity is observed instead. The fundamental question we address in this paper is at what scales are the regularities we detect stable, explicable, and sustainable. This paper thus proposes a basic measure of variability to assess the stability of such regularities focusing mainly on changes over a range of temporal scales. We demonstrate this by comparing regularities in the urban mobility patterns in three world cities, namely London, Singapore and Beijing using one-week of smart-card data. The results show that variations in regularity scale as non-linear functions of the temporal resolution, which we measure over a scale from 1 minute to 24 hours thus reflecting the diurnal cycle of human mobility. A particularly dramatic increase in variability occurs up to the temporal scale of about 15 minutes in all three cities and this implies that limits exist when we look forward or backward with respect to making short-term predictions. The degree of regularity varies in fact from city to city with Beijing and Singapore showing higher regularity in comparison to London across all temporal scales. A detailed discussion is provided, which relates the analysis to various characteristics of the three cities. In summary, this work contributes to a deeper understanding of regularities in patterns of transit use from variations in volumes of travellers entering subway stations, it establishes a generic analytical framework for comparative studies using urban mobility data, and it provides key points for the management of variability by policy-makers intent on for making the travel experience more

  18. Variability in Regularity: Mining Temporal Mobility Patterns in London, Singapore and Beijing Using Smart-Card Data

    Science.gov (United States)

    Zhong, Chen; Batty, Michael; Manley, Ed; Wang, Jiaqiu; Wang, Zijia; Chen, Feng; Schmitt, Gerhard

    2016-01-01

    To discover regularities in human mobility is of fundamental importance to our understanding of urban dynamics, and essential to city and transport planning, urban management and policymaking. Previous research has revealed universal regularities at mainly aggregated spatio-temporal scales but when we zoom into finer scales, considerable heterogeneity and diversity is observed instead. The fundamental question we address in this paper is at what scales are the regularities we detect stable, explicable, and sustainable. This paper thus proposes a basic measure of variability to assess the stability of such regularities focusing mainly on changes over a range of temporal scales. We demonstrate this by comparing regularities in the urban mobility patterns in three world cities, namely London, Singapore and Beijing using one-week of smart-card data. The results show that variations in regularity scale as non-linear functions of the temporal resolution, which we measure over a scale from 1 minute to 24 hours thus reflecting the diurnal cycle of human mobility. A particularly dramatic increase in variability occurs up to the temporal scale of about 15 minutes in all three cities and this implies that limits exist when we look forward or backward with respect to making short-term predictions. The degree of regularity varies in fact from city to city with Beijing and Singapore showing higher regularity in comparison to London across all temporal scales. A detailed discussion is provided, which relates the analysis to various characteristics of the three cities. In summary, this work contributes to a deeper understanding of regularities in patterns of transit use from variations in volumes of travellers entering subway stations, it establishes a generic analytical framework for comparative studies using urban mobility data, and it provides key points for the management of variability by policy-makers intent on for making the travel experience more amenable. PMID:26872333

  19. Spatial and temporal variability of particulate polycyclic aromatic hydrocarbons in Mexico City

    Science.gov (United States)

    Thornhill, D. A.; de Foy, B.; Herndon, S. C.; Onasch, T. B.; Wood, E. C.; Zavala, M.; Molina, L. T.; Gaffney, J. S.; Marley, N. A.; Marr, L. C.

    2008-06-01

    As part of the Megacities Initiative: Local and Global Research Observations (MILAGRO) study in the Mexico City Metropolitan Area in March 2006, we measured particulate polycyclic aromatic hydrocarbons (PAHs) and other gaseous species and particulate properties, including light absorbing carbon or effective black carbon (BC), at six locations throughout the city. The measurements were intended to support the following objectives: to describe spatial and temporal patterns in PAH concentrations, to gain insight into sources and transformations of PAHs and BC, and to quantify the relationships between PAHs and other pollutants. Total particulate PAHs at the Instituto Mexicano del Petróleo (T0 supersite) located near downtown averaged 50 ng m-3, and aerosol active surface area averaged 80 mm2 m-3. PAHs were also measured on board the Aerodyne Mobile Laboratory, which visited six sites encompassing a mixture of different land uses and a range of ages of air parcels transported from the city core. A combination of analyses of time series, back trajectories, concentration fields, pollutant ratios, and correlation coefficients supports the concept of T0 as an urban source site, T1 as a receptor site with strong local sources, Pedregal and PEMEX as intermediate sites, Pico Tres Padres as a vertical receptor site, and Santa Ana as a downwind receptor site. Weak intersite correlations suggest that local sources are important and variable and that exposure to PAHs and BC cannot be represented by a single regional-scale value. The relationships between PAHs and other pollutants suggest that a variety of sources and ages of particles are present. Among carbon monoxide, nitrogen oxides (NOx), and carbon dioxide, particulate PAHs are most strongly correlated with NOx. Mexico City's PAH/BC mass ratio of 0.01 is similar to that found on a freeway loop in the Los Angeles area and approximately 8 30 times higher than that found in other cities. Evidence also suggests that primary

  20. Linkage between the temporal and spatial variability of dissolved organic matter and whole-stream metabolism

    Directory of Open Access Journals (Sweden)

    S. Halbedel

    2013-08-01

    Full Text Available Dissolved organic matter (DOM is an important resource for microbes, thus affecting whole-stream metabolism. However, the factors influencing its chemical composition and thereby also its bio-availability are complex and not thoroughly understood. It was hypothesized that whole-stream metabolism is linked to DOM composition and that the coupling of both is influenced by seasonality and different land-use types. We tested this hypothesis in a comparative study on two pristine forestry streams and two non-forestry streams. The investigated streams were located in the Harz Mountains (central Europe, Germany. The metabolic rate was measured with a classical two-station oxygen change technique and the variability of DOM with fluorescence spectroscopy. All streams were clearly net heterotrophic, whereby non-forestry streams showed a higher primary production, which was correlated to irradiance and phosphorus concentration. We detected three CDOM components (C1, C2, C3 using parallel factor (PARAFAC analysis. We compared the excitation and emission maxima of these components with the literature and correlated the PARAFAC components with each other and with fluorescence indices. The correlations suggest that two PARAFAC components are derived from allochthonous sources (C1, C3 and one is derived autochthonously (C2. The chromophoric DOM matrix was dominated by signals of humic-like substances with a highly complex structure, followed by humic-like, fulfic acids, low-molecular-weight substances, and with minor amounts of amino acids and proteins. The ratios of these PARAFAC components (C1 : C2, C1 : C3, C3 : C2 differed with respect to stream types (forestry versus non-forestry. We demonstrated a significant correlation between gross primary production (GPP and signals of autochthonously derived, low-molecular-weight humic-like substances. A positive correlation between P / R (i.e. GPP/daily community respiration and the fluorescence index FI suggests

  1. Linkage between the temporal and spatial variability of dissolved organic matter and whole-stream metabolism

    Science.gov (United States)

    Halbedel, S.; Büttner, O.; Weitere, M.

    2013-08-01

    Dissolved organic matter (DOM) is an important resource for microbes, thus affecting whole-stream metabolism. However, the factors influencing its chemical composition and thereby also its bio-availability are complex and not thoroughly understood. It was hypothesized that whole-stream metabolism is linked to DOM composition and that the coupling of both is influenced by seasonality and different land-use types. We tested this hypothesis in a comparative study on two pristine forestry streams and two non-forestry streams. The investigated streams were located in the Harz Mountains (central Europe, Germany). The metabolic rate was measured with a classical two-station oxygen change technique and the variability of DOM with fluorescence spectroscopy. All streams were clearly net heterotrophic, whereby non-forestry streams showed a higher primary production, which was correlated to irradiance and phosphorus concentration. We detected three CDOM components (C1, C2, C3) using parallel factor (PARAFAC) analysis. We compared the excitation and emission maxima of these components with the literature and correlated the PARAFAC components with each other and with fluorescence indices. The correlations suggest that two PARAFAC components are derived from allochthonous sources (C1, C3) and one is derived autochthonously (C2). The chromophoric DOM matrix was dominated by signals of humic-like substances with a highly complex structure, followed by humic-like, fulfic acids, low-molecular-weight substances, and with minor amounts of amino acids and proteins. The ratios of these PARAFAC components (C1 : C2, C1 : C3, C3 : C2) differed with respect to stream types (forestry versus non-forestry). We demonstrated a significant correlation between gross primary production (GPP) and signals of autochthonously derived, low-molecular-weight humic-like substances. A positive correlation between P / R (i.e. GPP/daily community respiration) and the fluorescence index FI suggests that the

  2. Spatio-temporal variability of vertical gradients of major meteorological observations around the Tibetan Plateau

    Science.gov (United States)

    Guo, X.; Wang, L.; Tian, L.

    2015-12-01

    The near-surface air temperature lapse rate (TLR), wind speed gradient (WSG), and precipitation gradient (PG) provide crucial parameters used in models of mountain climate and hydrology. The complex mountain terrain and vast area of the Tibetan Plateau (TP) make such factors particularly important. With daily data from 161 meteorological stations over the past 43 years (1970-2012), we analyse the spatio-temporal variations of TLRs, WSGs, and PGs over and around TP, derived using linear regression methods and dividing the study area into zones based on spatial variations. Results of this study include: (1) The observed TLR varies from -0.46 to -0.73 ∘C (100 m) -1, with averaged TLRs of -0.60,-0.62, and -0.59 ∘C (100 m) -1 for Tmax, Tmin,and Tmean , respectively. The averaged TLR is slightly less than the global mean of -0.65 ∘C (100 m) -1 . The spatial variability of TLR relates to climate conditions, wherein the TLR increases in dry conditions and in cold months (October-April), while it lessens in humid regions and during warm months (May-September). (2) The estimated annual WSG ranges from 0.07 to 0.17m s -1 (100 m) -1. Monthly WSGs show a marked seasonal shift, in which higher WSGs can be explained by the high intensity of prevailing wind. (3) Positive summer PGs vary from 12.08 in the central TP to 26.14 mm (100 m) -1 in northeastern Qinghai and the southern TP, but a reverse gradient prevails in Yunnan and parts of Sichuan Province. (4) The regional warming over TP is more evident in winter, and Tmin demonstrated the most prominent warming compared with Tmax and Tmean. Environments at high elevations experience more rapid changes in temperatures (Tmax, Tmin,and Tmean) than those at low elevations, which is especially true in winter and for Tmin. Furthermore, inter-annual variation of TLRs is linked to elevation-dependent warming.

  3. Temporal and spatial variability of ammonia in urban and agricultural regions of northern Colorado, United States

    Science.gov (United States)

    Li, Yi; Thompson, Tammy M.; Van Damme, Martin; Chen, Xi; Benedict, Katherine B.; Shao, Yixing; Day, Derek; Boris, Alexandra; Sullivan, Amy P.; Ham, Jay; Whitburn, Simon; Clarisse, Lieven; Coheur, Pierre-François; Collett, Jeffrey L., Jr.

    2017-05-01

    Concentrated agricultural activities and animal feeding operations in the northeastern plains of Colorado represent an important source of atmospheric ammonia (NH3). The NH3 from these sources contributes to regional fine particle formation and to nitrogen deposition to sensitive ecosystems in Rocky Mountain National Park (RMNP), located ˜ 80 km to the west. In order to better understand temporal and spatial differences in NH3 concentrations in this source region, weekly concentrations of NH3 were measured at 14 locations during the summers of 2010 to 2015 using Radiello passive NH3 samplers. Weekly (biweekly in 2015) average NH3 concentrations ranged from 2.66 to 42.7 µg m-3, with the highest concentrations near large concentrated animal feeding operations (CAFOs). The annual summertime mean NH3 concentrations were stable in this region from 2010 to 2015, providing a baseline against which concentration changes associated with future changes in regional NH3 emissions can be assessed. Vertical profiles of NH3 were also measured on the 300 m Boulder Atmospheric Observatory (BAO) tower throughout 2012. The highest NH3 concentration along the vertical profile was always observed at the 10 m height (annual average concentration of 4.63 µg m-3), decreasing toward the surface (4.35 µg m-3) and toward higher altitudes (1.93 µg m-3). The NH3 spatial distributions measured using the passive samplers are compared with NH3 columns retrieved by the Infrared Atmospheric Sounding Interferometer (IASI) satellite and concentrations simulated by the Comprehensive Air Quality Model with Extensions (CAMx). The satellite comparison adds to a growing body of evidence that IASI column retrievals of NH3 provide very useful insight into regional variability in atmospheric NH3, in this case even in a region with strong local sources and sharp spatial gradients. The CAMx comparison indicates that the model does a reasonable job simulating NH3 concentrations near sources but tends to

  4. Spatial and temporal variability of surface water pollution in the Mekong Delta, Vietnam.

    Science.gov (United States)

    Wilbers, Gert-Jan; Becker, Mathias; Nga, La Thi; Sebesvari, Zita; Renaud, Fabrice G

    2014-07-01

    Surface water pollution in the Vietnamese Mekong Delta (MD) could threaten human, animal and ecosystem health given the fact that this water source is intensively used for drinking, irrigation and domestic services. We therefore determined the levels of pollution by organic pollutants, salts, metals and microbial indicators by (bi)monthly monitoring of canals between November 2011 and July 2012 at 32 sampling locations, representing fresh and saline/brackish environments. The results were compared with national water quality guidelines, between the studied regions and with water quality data from main waterways. Key factors explaining the observed levels of pollution in surface water were identified through principal component analysis (PCA). Temporal variations due to tidal regime and seasonality were also assessed. Based on regression models, the spatial variability of five water quality parameters was visualized using GIS based maps. Results indicate that pH (max. 8.6), turbidity (max. 461 FTU), maximum concentrations of ammonium (14.7 mg L(-1)), arsenic (44.1 μg L(-1)), barium (157.5 μg L(-1)), chromium (84.7 μg L(-1)), mercury (45.5 μg L(-1)), manganese (1659.7 μg L(-1)), aluminum (14.5 mg L(-1)), iron (17.0 mg L(-1)) and the number of Escherichia coli (87,000 CFU 100 mL(-1)) and total coliforms (2,500,000 CFU 100 mL(-1)) in canals exceed the thresholds set by Vietnamese quality guidelines for drinking and domestic purposes. The PCA showed that i) urbanization; ii) metal leaching from soils; iii) aquaculture; and iv) tidal regime explain 85% of the variance of surface water quality attributes. Significant differences in water quality were found due to daily tidal regime and as a result of seasonality. Surface water quality maps for dissolved oxygen, ammonium, ortho-phosphate, manganese and total coliforms were developed to highlight hot-spot areas of pollution. The results of this study can assist policy makers in developing water management strategies

  5. Investigation of temporal and spatial climate variability and aridity of Iran

    Science.gov (United States)

    Ashraf, B.; Yazdani, R.; Mousavi-Baygi, M.; Bannayan, M.

    2014-10-01

    The aim of this research is to study the spatial and temporal variability of aridity in Iran, through analysis of temperature and precipitation trends during the 48-year period of 1961-2008. In this study, four different aridity criteria have been used to investigate the aridity situation. These aridity indexes included Lang's index or rain factor, Budyko index or radiational index of dryness, UNEP aridity index, and Thornthwaite moisture index. The results of the analysis indicated that the highest and lowest mean temperatures occurred in July and January respectively in all locations. Among the study locations, Ahvaz with 37.1 °C and Kermanshah with 20.2 °C has the highest and lowest in July. For January, the highest was 12.4 °C for Ahvaz and the lowest was -4.5 °C for Hamedan and Kermanshah together. The range of monthly mean temperature of study locations indicated that the maximum and minimum difference between day and night temperatures, almost in all study locations, occurred in September and January, respectively, and the highest and lowest fluctuation of temperature was observed in Kerman and Tehran. The temperature anomalies showed that the most significant increasing temperature occurred at the beginning of twenty-first century (2000-2008) in all locations. The long-term mean of monthly rainfall showed that, in most study locations, the maximum and minimum of mean precipitation occurred in winter and summer, respectively. Rasht with 1,355 mm had the highest and Yazd with 55 mm had the lowest of total precipitation compared with other locations. According to precipitation anomalies, all locations experienced dry and wet periods, but generally dry periods occurred more often especially in the beginning of twenty-first century. According to applied different aridity indexes, all the study locations often experienced semi-arid to arid climate, severe water deficit to desert climate, arid to hyperarid climate, and semi-arid climate during the study period.

  6. Spatial and temporal variability of particulate polycyclic aromatic hydrocarbons in Mexico City

    Directory of Open Access Journals (Sweden)

    D. A. Thornhill

    2008-06-01

    Full Text Available As part of the Megacities Initiative: Local and Global Research Observations (MILAGRO study in the Mexico City Metropolitan Area in March 2006, we measured particulate polycyclic aromatic hydrocarbons (PAHs and other gaseous species and particulate properties, including light absorbing carbon or effective black carbon (BC, at six locations throughout the city. The measurements were intended to support the following objectives: to describe spatial and temporal patterns in PAH concentrations, to gain insight into sources and transformations of PAHs and BC, and to quantify the relationships between PAHs and other pollutants. Total particulate PAHs at the Instituto Mexicano del Petróleo (T0 supersite located near downtown averaged 50 ng m−3, and aerosol active surface area averaged 80 mm2 m−3. PAHs were also measured on board the Aerodyne Mobile Laboratory, which visited six sites encompassing a mixture of different land uses and a range of ages of air parcels transported from the city core. A combination of analyses of time series, back trajectories, concentration fields, pollutant ratios, and correlation coefficients supports the concept of T0 as an urban source site, T1 as a receptor site with strong local sources, Pedregal and PEMEX as intermediate sites, Pico Tres Padres as a vertical receptor site, and Santa Ana as a downwind receptor site. Weak intersite correlations suggest that local sources are important and variable and that exposure to PAHs and BC cannot be represented by a single regional-scale value. The relationships between PAHs and other pollutants suggest that a variety of sources and ages of particles are present. Among carbon monoxide, nitrogen oxides (NOx, and carbon dioxide, particulate PAHs are most strongly correlated with NOx. Mexico City's PAH/BC mass ratio of 0.01 is similar to that found on a freeway loop in the Los Angeles area and approximately 8–30

  7. Inverse modeling of variable-density groundwater flow in a semi-arid area in Iran using a genetic algorithm

    Science.gov (United States)

    Bastani, Mehrdad; Kholghi, Majid; Rakhshandehroo, Gholam Reza

    2010-08-01

    Flow and mass transport parameter estimation was done by creating an inverse model of a seawater intrusion system using a genetic algorithm (GA) method as the optimization procedure. Firstly, the SEAWAT code was used for the forward solution part and then a program was written in MATLAB for coupling the forward and inverse processes. The auto-calibration objective function was defined with the root mean square errors (RMSE) between the observed and the simulated values. A simple GA was used to minimize the RMSE criterion. The methodology was applied to a coastal aquifer with heterogeneous formations in a semi-arid area near salty Tashk Lake (electrical conductivity 61,420 µS/cm), Fars province, Iran. In the last two decades, the overexploitation of groundwater has caused a major water level drawdown and, consequently, salt-water intrusion. Firstly, flow and transport parameters (hydraulic conductivity, porosity, specific storage coefficient and longitudinal dispersivity) were estimated simultaneously in steady-state and, secondly, in the developed code, these results were used as initial values of the parameters in transient-state. Results show a good match for observed and simulated data. It can be concluded that GA is a helpful tool for automatic calibration of variable density fluid systems such as seawater intrusion cases.

  8. Spatial and Temporal Variability of Soil Respiration Fluxes from Alpine and Subalpine Soils in the East River Watershed, Colorado

    Science.gov (United States)

    McCormick, M. E.; Winnick, M.; Rainaldi, G. R.; Lawrence, C. R.; Druhan, J. L.; Hsu, H. T.; Maher, K.

    2016-12-01

    Soil respiration of carbon to the atmosphere represents one of the largest fluxes of the terrestrial carbon cycle and is sensitive to changes in temperature, soil moisture, and processes affecting carbon stability. Despite the importance of these sensitivities, few studies have examined the spatial and temporal heterogeneity of soil CO2 fluxes and their controls on intermediate- to large-scale integrated soil fluxes. In this study, we examine spatial variability at scales of 10-5 -101 km2 and temporal variability at scales of hours to months of soil CO2 fluxes through the 2016 growing season in the East River Watershed, CO. We present analyses of (1) temporal variability of CO2 fluxes from four locations with depth-resolved temperature, moisture content, soil gas pCO2, and soil carbon content measurements; (2) spatial variability of CO2 fluxes and surface soil water content across a gridded hillslope with 74 points over an area of 2.5 x 10-3 km2 measured at multiple times throughout the growing season; and (3) variability of CO2 fluxes and surface soil water content from >20 point locations across the 85 km2 catchment targeting a range of vegetation, slope, and aspect characteristics. Comparing soil CO2 fluxes with depth-resolved temperature, moisture, pCO2 and carbon content, we calculate depth-resolved CO2 production rates and their correlations with soil conditions. Gridded hillslope flux measurements reveal strong and consistent variability across separation distances of 1 - 30 m with a slight dependence on slope position, likely representing the controls of lateral flow on soil moisture content. Finally, we analyze correlations of soil CO2 fluxes from point measurements representing broad-scale landscape units with vegetation and geomorphological characteristics. Combining these observations, we examine the implications of our results for interpolating point flux measurements to the catchment scale and for calculating integrated fluxes through the growing

  9. Spatial and temporal variability of stable isotope composition of precipitation over the south american continent

    Directory of Open Access Journals (Sweden)

    1995-01-01

    centra en el estudio de la variabilidad espacial y temporal de la composición de isótopos estables de la precipitación a escala del continente. En este estudio se examina con cierto detalle la relación aparente entre la composición isotópica de la precipitación en la región y algunos parámetros climáticos tales como la cantidad de precipitación y la temperatura del aire. The International Atomic Energy Agency (IAEA, in collaboration with the World Meteorological Organization (WMO is conducting a world-wide survey of the isotope composition of precipitation. At present, around 60 stations are providing information on the stable isotope composition of precipitation over the South American continent. During the recent years, several national monitoring networks have been initiated (Argentina, Brazil, Chile, Ecuador, Peru. They provide a valuable contribution to the global IAEA/WMO database. The paper is focused on spatial and temporal variability of the stable isotope composition of precipitation, observed over the South American continent. The relationship between isotopic signature of precipitation and climatically relevant parameters, such as surface air temperature or amount of precipitation is discussed in some detail.

  10. DISCOVERY 2010: Spatial and temporal variability in a dynamic polar ecosystem

    Science.gov (United States)

    Tarling, G. A.; Ward, P.; Atkinson, A.; Collins, M. A.; Murphy, E. J.

    2012-01-01

    DIC deficits, the South Georgia bloom was found to contain the strongest seasonal carbon uptake in the ice-free zone of the Southern Ocean. The surveys also encountered low-production, iron-limited regions, a situation more typical of the wider Southern Ocean. The response of primary and secondary consumers to spatial and temporal heterogeneity in production was complex. Many of the life-cycles of small pelagic organisms showed a close coupling to the seasonal cycle of food availability. For instance, Antarctic krill showed a dependence on early, non-ice-associated blooms to facilitate early reproduction. Strategies to buffer against environmental variability were also examined, such as the prevalence of multiyear life-cycles and variability in energy storage levels. Such traits were seen to influence the way in which Scotia Sea communities were structured, with biomass levels in the larger size classes being higher than in other ocean regions. Seasonal development also altered trophic function, with the trophic level of higher predators increasing through the course of the year as additional predator-prey interactions emerged in the lower trophic levels. Finally, our studies re-emphasised the role that the simple phytoplankton-krill-higher predator food chain plays in this Southern Ocean region, particularly south of the SACCF. To the north, alternative food chains, such as those involving copepods, macrozooplankton and mesopelagic fish, were increasingly important. Continued ocean warming in this region is likely to increase the prevalence of such alternative such food chains with Antarctic krill predicted to move southwards.

  11. Temporal variability and spatial distribution of suspended matter and organic C pool in the Zambezi River

    Science.gov (United States)

    Teodoru, Cristian R.; Bouillon, Steven; Borges, Alberto V.; Darchambeau, François; Nyoni, Frank C.; Nyambe, Imasiku

    2014-05-01

    It is increasingly recognized that rivers are active components of global carbon (C) cycling, able of processing, emitting into atmosphere, and transporting to the oceans large quantities of both organic and inorganic carbon derived from the surrounding terrestrial landscape. Although tropical rivers contribute with more than half to the global freshwater discharge to the oceans, there is surprisingly little information on biogeochemistry and C cycling of those systems, especially for Africa. As part of a broader study on the biogeochemistry of large African river basins, we present here data on temporal and spatial variability of total suspended matter (TSM), particulate (POC) and dissolved organic C (DOC) in the Zambezi River (length = 2900 km, catchment area > 1.4 million km2, annual discharge ~ 4150 m3/s) in relation to physico-chemical proprieties (conductivity, oxygen, pH, total alkalinity), bacterial respiration, primary production and net aquatic metabolism. Data were collected along the entire river stretch during 2012 and 2013, and over 2 climatic (dry and wet) seasons to constrain the interannual variability, seasonality and spatial heterogeneity of the investigated parameters, and at two monitoring stations: one on the Zambezi mainstream, and one on the Kafue River (major tributary of the Zambezi; total length ~ 1900 km, catchment ~ 156, 000 km2, annual discharge = 350 m3/s), both located several km upstream their confluence. During the two sampled years, TSM concentrations varied from 1.6 mg/L to 110 mg/L (mean 17 in 2012 and 29 mg/L in 2013) and were systematically higher in the river mainstream (mean 21 mg/L and 36 mg/L in 2012 and 2013, respectively) compared to both reservoirs (the Kariba and the Cahora Bassa) where TSM concentrations average 2.5 mg/L. Despite the disturbance along the aquatic continuum caused by the presence of the two man-made reservoirs, a distinct longitudinal pattern was observed during both years, with TSM increasing

  12. Jarosite in Gale Crater, Mars: The Importance of Temporal and Spatial Variability and Implications for Habitiability

    Science.gov (United States)

    Leveille, R. J.; Oehler, D. Z.; Fairen, A. G.; Clark, B. C.; Niles, P. B.; Blank, J. G.

    2015-01-01

    The Curiosity rover has recently found evidence for small amounts of jarosite, a ferric sulfate, in the Pahrump Hills region at the base of Aeolis Mons (Mount Sharp), Gale crater. While jarosite has been described previously at other locations on Mars, including several sites at Meridiani Planum (explored by the Opportunity rover; and Mawrth Vallis (by remote MRO-CRISM observations; this is the first identification in Gale. Jarosite is interpreted to be a mineral indicator of acidic conditions (pH less than 4; on Earth, it is most commonly found in acid rock-drainage or acid sulfate soil environments. However, jarosite has also been described from a number of terrestrial environments where widespread acidic conditions are not prevalent. As a case study, we describe here an occurrence of sedimentary pyrite nodules that have been variably oxidized in situ to gypsum, schwertmannite, K-/Na-jarosite and iron oxides in a polar desert environment on Devon Island, Nunavut, Canada. Remarkably, these nodules occur in loosely consolidated carbonate sediments, which would have required a higher pH environment at their time of formation and deposition. Thus, acidic conditions may only exist at a small (sub-cm) scale or in a restricted temporal window in an otherwise well-buffered environment. On Devon Island, the jarosite occurs in the most oxidized nodules and is never associated directly with pyrite. Schwertmannite, a metastable iron oxyhydroxysulfate that can form at pH higher than that required for jarosite, occurs in association with partially oxidized pyrite. The paragenetic sequence observed here suggests initial formation of schwertmannite and late-stage precipitation of jarosite in restricted micro-environments, possibly forming via transformation of an amorphous schwertmannite-like phase. While the carbonate environment on Devon Island differs significantly from that of Gale crater, i.e., where we find predominantly basaltic sedimentary rocks, this terrestrial analog

  13. Temporal and spatial variability of frost-free seasons in the Great Lakes region of the United States

    Science.gov (United States)

    Lejiang Yu; Shiyuan Zhong; Xindi Bian; Warren E. Heilman; Jeffrey A. Andresen

    2014-01-01

    The frequency and timing of frost events and the length of the growing season are critical limiting factors in many human and natural ecosystems. This study investigates the temporal and spatial variability of the date of last spring frost (LSF), the date of first fall frost (FFF), and the length of the frost-free season (FFS) in the Great Lakes region of the United...

  14. Temporal dynamic of wood formation in Pinus cembra along the alpine treeline ecotone and the effect of climate variables

    OpenAIRE

    GRUBER, Andreas; Baumgartner, Daniel; Zimmermann, Jolanda; Oberhuber, Walter

    2009-01-01

    We determined the temporal dynamic of cambial activity and xylem development of stone pine (Pinus cembra L.) throughout the treeline ecotone. Repeated micro-sampling of the developing tree ring was carried out during the growing seasons 2006 and 2007 at the timberline (1950 m a.s.l.), treeline (2110 m a.s.l.) and within the krummholz belt (2180 m a.s.l.) and the influence of climate variables on intra-annual wood formation was determined.

  15. Spatial and temporal variability in nutrients and carbon uptake during 2004 and 2005 in the eastern equatorial Pacific Ocean

    DEFF Research Database (Denmark)

    Palacz, A. P.; Chai, F.

    2012-01-01

    to the tropical instability waves (TIWs). The aim of this study was to examine patterns of spatial and temporal variability in the biological uptake of NO3, Si(OH)(4) and carbon in this region, and to evaluate the role of biological and physical interactions controlling this variability over seasonal...... and intraseasonal time scales. Here, high resolution Pacific ROMS-CoSiNE (Regional Ocean Modeling System-Carbon, Silicon, Nitrogen Ecosystem) model results were evaluated with in situ and remote sensing data. The results of model-data comparison revealed a good agreement in domain-average hydrographic...

  16. Spatio-temporal variability of trace elements fingerprints in cockle (Cerastoderma edule) shells and its relevance for tracing geographic origin.

    Science.gov (United States)

    Ricardo, Fernando; Pimentel, Tânia; Génio, Luciana; Calado, Ricardo

    2017-06-14

    Understanding spatio-temporal variability of trace elements fingerprints (TEF) in bivalve shells is paramount to determine the discrimination power of this analytical approach and secure traceability along supply chains. Spatio-temporal variability of TEF was assessed in cockle (Cerastoderma edule) shells using inductively coupled plasma-mass spectrometry (ICP-MS). Four elemental ratios (Mg/Ca, Mn/Ca, Sr/Ca and Ba/Ca) were measured from the shells of specimens originating from eight different ecosystems along the Portuguese coast, as well as from four different areas, within one of them, over two consecutive years (2013 and 2014). TEF varied significantly in the shells of bivalves originating from the eight ecosystems surveyed in the present study. Linear discriminant function analyses assigned sampled cockles to each of the eight ecosystems with an average accuracy of 90%. Elemental ratios also displayed significant differences between the two consecutive years in the four areas monitored in the same ecosystem. Overall, while TEF displayed by cockle shells can be successfully used to trace their geographic origin, a periodical verification of TEF (>6 months and <1 year) is required to control for temporal variability whenever comparing specimens originating from the same area collected more than six months apart.

  17. Temporal Variability of Source-Specific Solvent-Extractable Organic Compounds in Coastal Aerosols over Xiamen, China

    Directory of Open Access Journals (Sweden)

    Shuqin Tao

    2017-02-01

    Full Text Available This study describes an analysis of ambient aerosols in a southeastern coastal city of China (Xiamen in order to assess the temporal variability in the concentrations and sources of organic aerosols (OA. Molecular-level measurements based on a series of solvent extractable lipid compounds reveal inherent heterogeneity in OA, in which the concentration and relative contribution of at least three distinct components (terrestrial plant wax derived, marine/microbial and fossil fuel derived organic matter (OM exhibited distinct and systematic temporal variability. Plant wax lipids and associated terrestrial OM are influenced by seasonal variability in plant growth; marine/microbial lipids and associated marine OM are modulated by sea spill and temperature change, whereas fossil fuel derived OM reflects the anthropogenic utilization of fossil fuels originated from petroleum-derived sources and its temporal variation is strongly controlled by meteorological conditions (e.g., the thermal inversion layer, which is analogous to other air organic pollutions. A comparative study among different coastal cities was applied to estimate the supply of different sources of OM to ambient aerosols in different regions, where it was found that biogenic OM in aerosols over Xiamen was much lower than that of other cities; however, petroleum-derived OM exhibited a high level of contribution with a higher concentration of unresolved complex matters (UCM and higher a ratio between UCM and resolved alkanes (UCM/R.

  18. Temporal variability of foliar nutrients: responses to nitrogen deposition and prescribed fire in a temperate steppe

    Science.gov (United States)

    Lü, Xiao-Tao; Reed, Sasha C.; Hou, Shuang-Li; Hu, Yan-Yu; Wei, Hai-Wei; Lü, Fu-Mei; Cui, Qiang; Han, Xing Guo

    2017-01-01

    Plant nutrient concentrations and stoichiometry drive fundamental ecosystem processes, with important implications for primary production, diversity, and ecosystem sustainability. While a range of evidence exists regarding how plant nutrients vary across spatial scales, our understanding of their temporal variation remains less well understood. Nevertheless, we know nutrients regulate plant function across time, and that important temporal controls could strongly interact with environmental change. Here, we report results from a 3-year assessment of inter-annual changes of foliar nitrogen (N) and phosphorus (P) concentrations and stoichiometry in three dominant grasses in response to N deposition and prescribed fire in a temperate steppe of northern China. Foliar N and P concentrations and their ratios varied greatly among years, with this temporal variation strongly related to inter-annual variation in precipitation. Nitrogen deposition significantly increased foliar N concentrations and N:P ratios in all species, while fire significantly altered foliar N and P concentrations but had no significant impacts on N:P ratios. Generally, N addition enhanced the temporal stability of foliar N and decreased that of foliar P and of N:P ratios. Our results indicate that plant nutrient status and response to environmental change are temporally dynamic and that there are differential effects on the interactions between environmental change drivers and timing for different nutrients. These responses have important implications for consideration of global change effects on plant community structure and function, management strategies, and the modeling of biogeochemical cycles under global change scenarios.

  19. Regional scale spatio-temporal variability of soil moisture and its relationship with meteorological factors over the Korean peninsula

    Science.gov (United States)

    Cho, Eunsang; Choi, Minha

    2014-08-01

    An understanding soil moisture spatio-temporal variability is essential for hydrological and meteorological research. This work aims at evaluating the spatio-temporal variability of near surface soil moisture and assessing dominant meteorological factors that influence spatial variability over the Korean peninsula from May 1 to September 29, 2011. The results of Kolmogorov-Smirnov tests for goodness of fit showed that all applied distributions (normal, log-normal and generalized extreme value: GEV) were appropriate for the datasets and the GEV distribution described best spatial soil moisture patterns. The relationship between the standard deviation and coefficient of variation (CV) of soil moisture with mean soil moisture contents showed an upper convex shape and an exponentially negative pattern, respectively. Skewness exhibited a decreasing pattern with increasing mean soil moisture contents and kurtosis exhibited the U-shaped relationship. In this regional scale (99,720 km2), we found that precipitation indicated temporally stable features through an ANOVA test considering the meteorological (i.e. precipitation, insolation, air temperature, ground temperature and wind speed) and physical (i.e. soil texture, elevation, topography, and land use) factors. Spatial variability of soil moisture affected by the meteorological forcing is shown as result of the relationship between the meteorological factors (precipitation, insolation, air temperature and ground temperature) and the standard deviation of relative difference of soil moisture contents (SDRDt) which implied the spatial variability of soil moisture. The SDRDt showed a positive relationship with the daily mean precipitation, while a negative relationship with insolation, air temperature and ground temperature. The variation of spatial soil moisture pattern is more sensitive to change in ground temperature rather than air temperature changes. Therefore, spatial variability of soil moisture is greatly affected

  20. Characterizing functional integrity: intraindividual brain signal variability predicts memory performance in patients with medial temporal lobe epilepsy.

    Science.gov (United States)

    Protzner, Andrea B; Kovacevic, Natasa; Cohn, Melanie; McAndrews, Mary Pat

    2013-06-05

    Computational modeling suggests that variability in brain signals provides important information regarding the system's capacity to adopt different network configurations that may promote optimal responding to stimuli. Although there is limited empirical work on this construct, a recent study indicates that age-related decreases in variability across the adult lifespan correlate with less efficient and less accurate performance. Here, we extend this construct to the assessment of cerebral integrity by comparing fMRI BOLD variability and fMRI BOLD amplitude in their ability to account for differences in functional capacity in patients with focal unilateral medial temporal dysfunction. We were specifically interested in whether either of these BOLD measures could identify a link between the affected medial temporal region and memory performance (as measured by a clinical test of verbal memory retention). Using partial least-squares analyses, we found that variability in a set of regions including the left hippocampus predicted verbal retention and, furthermore, this relationship was similar across a range of cognitive tasks measured during scanning (i.e., the same pattern was seen in fixation, autobiographical recall, and word generation). In contrast, signal amplitude in the hippocampus did not predict memory performance, even for a task that reliably activates the medial temporal lobes (i.e., autobiographical recall). These findings provide a powerful validation of the concept that variability in brain signals reflects functional integrity. Furthermore, this measure can be characterized as a robust biomarker in this clinical setting because it reveals the same pattern regardless of cognitive challenge or task engagement during scanning.

  1. Complex, Dynamic Combination of Physical, Chemical and Nutritional Variables Controls Spatio-Temporal Variation of Sandy Beach Community Structure

    Science.gov (United States)

    Ortega Cisneros, Kelly; Smit, Albertus J.; Laudien, Jürgen; Schoeman, David S.

    2011-01-01

    Sandy beach ecological theory states that physical features of the beach control macrobenthic community structure on all but the most dissipative beaches. However, few studies have simultaneously evaluated the relative importance of physical, chemical and biological factors as potential explanatory variables for meso-scale spatio-temporal patterns of intertidal community structure in these systems. Here, we investigate macroinfaunal community structure of a micro-tidal sandy beach that is located on an oligotrophic subtropical coast and is influenced by seasonal estuarine input. We repeatedly sampled biological and environmental variables at a series of beach transects arranged at increasing distances from the estuary mouth. Sampling took place over a period of five months, corresponding with the transition between the dry and wet season. This allowed assessment of biological-physical relationships across chemical and nutritional gradients associated with a range of estuarine inputs. Physical, chemical, and biological response variables, as well as measures of community structure, showed significant spatio-temporal patterns. In general, bivariate relationships between biological and environmental variables were rare and weak. However, multivariate correlation approaches identified a variety of environmental variables (i.e., sampling session, the C∶N ratio of particulate organic matter, dissolved inorganic nutrient concentrations, various size fractions of photopigment concentrations, salinity and, to a lesser extent, beach width and sediment kurtosis) that either alone or combined provided significant explanatory power for spatio-temporal patterns of macroinfaunal community structure. Overall, these results showed that the macrobenthic community on Mtunzini Beach was not structured primarily by physical factors, but instead by a complex and dynamic blend of nutritional, chemical and physical drivers. This emphasises the need to recognise ocean-exposed sandy

  2. Seasonal variability of oxygen and hydrogen isotopes in a wetland system of the Yunnan-Guizhou Plateau, southwest China: a quantitative assessment of groundwater inflow fluxes

    Science.gov (United States)

    Cao, Xingxing; Wu, Pan; Zhou, Shaoqi; Han, Zhiwei; Tu, Han; Zhang, Shui

    2018-02-01

    The Caohai Wetland serves as an important ecosystem on the Yunnan-Guizhou Plateau and as a nationally important nature reserve for migratory birds in China. In this study, surface water, groundwater and wetland water were collected for the measurement of environmental isotopes to reveal the seasonal variability of oxygen and hydrogen isotopes (δ18O, δD), sources of water, and groundwater inflow fluxes. Results showed that surface water and groundwater are of meteoric origin. The isotopes in samples of wetland water were well mixed vertically in seasons of both high-flow (September) and low-flow (April); however, marked seasonal and spatial variations were observed. During the high-flow season, the isotopic composition in surface wetland water varied from -97.13 to -41.73‰ for δD and from -13.17 to -4.70‰ for δ18O. The composition of stable isotopes in the eastern region of this wetland was lower than in the western region. These may have been influenced by uneven evaporation caused by the distribution of aquatic vegetation. During the low-flow season, δD and δ18O in the more open water with dead aquatic vegetation ranged from -37.11 to -11.77‰, and from -4.25 to -0.08‰, respectively. This may result from high evaporation rates in this season with the lowest atmospheric humidity. Groundwater fluxes were calculated by mass transfer and isotope mass balance approaches, suggesting that the water sources of the Caohai Wetland were mainly from groundwater in the high-flow season, while the groundwater has a smaller contribution to wetland water during the low-flow season.

  3. Temporal variability of bacterial communities in cryoconite on an alpine glacier.

    Science.gov (United States)

    Franzetti, Andrea; Navarra, Federico; Tagliaferri, Ilario; Gandolfi, Isabella; Bestetti, Giuseppina; Minora, Umberto; Azzoni, Roberto Sergio; Diolaiuti, Guglielmina; Smiraglia, Claudio; Ambrosini, Roberto

    2017-04-01

    Cryoconite holes, that is, small ponds that form on glacier surface, are considered the most biologically active environments on glaciers. Bacterial communities in these environments have been extensively studied, but often through snapshot studies based on the assumption of a general stability of community structure. In this study, the temporal variation of bacterial communities in cryoconite holes on the Forni Glacier (Italian Alps) was investigated by high throughput DNA sequencing. A temporal change of bacterial communities was observed with autotrophic Cyanobacteria populations dominating communities after snowmelt, and heterotrophic Sphingobacteriales populations increasing in abundance later in the season. Bacterial communities also varied according to hole depth and area, amount of organic matter in the cryoconite and oxygen concentration. However, variation in environmental features explained a lower fraction of the variation in bacterial communities than temporal variation. Temporal change along ablation season seems therefore more important than local environmental conditions in shaping bacterial communities of cryoconite of the Forni Glacier. These findings challenge the assumption that bacterial communities of cryoconite holes are stable. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  4. Estimating spatial and temporal variability of juvenile North Sea plaice from opportunistic data

    NARCIS (Netherlands)

    Poos, J.J.; Aarts, G.M; Vandemaele, S.; Willems, W.; Bolle, L.J.; van Helmond, A.T.M.

    2013-01-01

    Surveys are often insufficient to accurately capture the distribution of a species in both space and time. Complementary to the use of research vessel data, platforms of opportunity can be a powerful strategy to monitor species distributions at high temporal and spatial resolution.
    In this study

  5. Agricultural Groundwater Demands in the Conterminous United States

    Science.gov (United States)

    Ho, M. W.; Parthasarathy, V.; Etienne, E.; Russo, T. A.; Devineni, N.; Lall, U.

    2016-12-01

    In the conterminous United States (CONUS), over 40% of water consumed for irrigation, livestock and domestic water is sourced from groundwater. The late 20th century and 21st century saw an expansion in irrigated agriculture across the CONUS that was accompanied by increased pumping of groundwater. Groundwater is typically used to mitigate impacts of drought on surface water supplies enabling water demands to be met as well as to augment sparse surface water resources in arid regions or where surface water availability is highly variable temporally and/or spatially. A Demand Sensitive Drought Index (DSDI) is used to examine the impacts of agricultural water needs on groundwater in the CONUS. The DSDI accounts for agricultural water deficits driven by low precipitation, high agricultural water demand, or a combination of both. Changes in groundwater levels relative to agricultural water deficits are characterized relative to precipitation during the growing season and winter precipitation. In several key irrigated agricultural regions in the CONUS, long-term trends in groundwater levels appear to reflect prolonged periods of surface water deficits resulting from land use and associated unsustainable water demands. These areas are subsequent unable to recover from persistent states of agricultural drought. Conversely, reductions in agricultural water demands for crops do not necessarily lead to immediate recovery of groundwater levels due to the demand for groundwater in other sectors. Calls to establish or reform groundwater policies have recently been made in an effort to achieve holistic groundwater management strategies that consider the human demands on both surface water and groundwater. There is a need for relevant groundwater policies to ensure that water demands are adequately managed across sectors without unsustainably depleting groundwater resources and to ensure efficient economic activity.

  6. Integrated groundwater resource management in Indus Basin using satellite gravimetry and physical modeling tools.

    Science.gov (United States)

    Iqbal, Naveed; Hossain, Faisal; Lee, Hyongki; Akhter, Gulraiz

    2017-03-01

    Reliable and frequent information on groundwater behavior and dynamics is very important for effective groundwater resource management at appropriate spatial scales. This information is rarely available in developing countries and thus poses a challenge for groundwater managers. The in situ data and groundwater modeling tools are limited in their ability to cover large domains. Remote sensing technology can now be used to continuously collect information on hydrological cycle in a cost-effective way. This study evaluates the effectiveness of a remote sensing integrated physical modeling approach for groundwater management in Indus Basin. The Gravity Recovery and Climate Experiment Satellite (GRACE)-based gravity anomalies from 2003 to 2010 were processed to generate monthly groundwater storage changes using the Variable Infiltration Capacity (VIC) hydrologic model. The groundwater storage is the key parameter of interest for groundwater resource management. The spatial and temporal patterns in groundwater storage (GWS) are useful for devising the appropriate groundwater management strategies. GRACE-estimated GWS information with large-scale coverage is valuable for basin-scale monitoring and decision making. This frequently available information is found useful for the identification of groundwater recharge areas, groundwater storage depletion, and pinpointing of the areas where groundwater sustainability is at risk. The GWS anomalies were found to favorably agree with groundwater model simulations from Visual MODFLOW and in situ data. Mostly, a moderate to severe GWS depletion is observed causing a vulnerable situation to the sustainability of this groundwater resource. For the sustainable groundwater management, the region needs to implement groundwater policies and adopt water conservation techniques.

  7. Environmental Data Science: Discovering Hidden System of Spatiotemporal Groundwater

    Science.gov (United States)

    Lee, C. H.; Yu, H. L.

    2016-12-01

    Groundwater has been well known as one of the major water resources in the regions with water scarcity problems. As the results of the increasing water shortage concerns around the world recently, it is essential to realize the spatial and temporal variation of groundwater levels for water resources management. In general, hydrological models have been developed to describe groundwater flow system across space and time. Since hydrological models are simplified and conceptual representations, both parameter and model uncertainties play important roles while constructing. The performance of hydrological models depends on the subjective of hydrologists due to the uncertainties. However, environmental data like groundwater level observations is abundant and prevalent nowadays. It provides an opportunity to enhance previous subjective modeling in hydrological research. The present study will conduct feature extraction on groundwater levels to identify the spatiotemporal characteristics of groundwater. A three-dimensional groundwater model (MODFLOW) is used to create artificial cases that make sure the results will conform to the physical laws. By tuning parameters in model, the extracted features can show natural and anthropogenic disturbances under different scenarios. The data-driven analysis can effectively reveal insights of interactions between important variables of groundwater system. With a better view of spatiotemporal groundwater variations, it is useful for governmental agency to manage water resources.

  8. Spatio-Temporal Trends and Identification of Correlated Variables with Water Quality for Drinking-Water Reservoirs.

    Science.gov (United States)

    Gu, Qing; Wang, Ke; Li, Jiadan; Ma, Ligang; Deng, Jinsong; Zheng, Kefeng; Zhang, Xiaobin; Sheng, Li

    2015-10-20

    It is widely accepted that characterizing the spatio-temporal trends of water quality parameters and identifying correlated variables with water quality are indispensable for the management and protection of water resources. In this study, cluster analysis was used to classify 56 typical drinking water reservoirs in Zhejiang Province into three groups representing different water quality levels, using data of four water quality parameters for the period 2006-2010. Then, the spatio-temporal trends in water quality were analyzed, assisted by geographic information systems (GIS) technology and statistical analysis. The results indicated that the water quality showed a trend of degradation from southwest to northeast, and the overall water quality level was exacerbated during the study period. Correlation analysis was used to evaluate the relationships between water quality parameters and ten independent variables grouped into four categories (land use, socio-economic factors, geographical features, and reservoir attributes). According to the correlation coefficients, land use and socio-economic indicators were identified as the most significant factors related to reservoir water quality. The results offer insights into the spatio-temporal variations of water quality parameters and factors impacting the water quality of drinking water reservoirs in Zhejiang Province, and they could assist managers in making effective strategies to better protect water resources.

  9. Spatio-Temporal Trends and Identification of Correlated Variables with Water Quality for Drinking-Water Reservoirs

    Directory of Open Access Journals (Sweden)

    Qing Gu

    2015-10-01

    Full Text Available It is widely accepted that characterizing the spatio-temporal trends of water quality parameters and identifying correlated variables with water quality are indispensable for the management and protection of water resources. In this study, cluster analysis was used to classify 56 typical drinking water reservoirs in Zhejiang Province into three groups representing different water quality levels, using data of four water quality parameters for the period 2006–2010. Then, the spatio-temporal trends in water quality were analyzed, assisted by geographic information systems (GIS technology and statistical analysis. The results indicated that the water quality showed a trend of degradation from southwest to northeast, and the overall water quality level was exacerbated during the study period. Correlation analysis was used to evaluate the relationships between water quality parameters and ten independent variables grouped into four categories (land use, socio-economic factors, geographical features, and reservoir attributes. According to the correlation coefficients, land use and socio-economic indicators were identified as the most significant factors related to reservoir water quality. The results offer insights into the spatio-temporal variations of water quality parameters and factors impacting the water quality of drinking water reservoirs in Zhejiang Province, and they could assist managers in making effective strategies to better protect water resources.

  10. Spatio-Temporal Variability in Topoclimate Inferred from Land Surface Temperature Data and its Relevance for Mapping Climatic Refugia

    Science.gov (United States)

    Dobrowski, S.; Oyler, J.; Allred, B.

    2015-12-01

    Topoclimatic diversity is considered an important trait of climatic refugia as it should allow for short distance dispersal of organisms to ameliorate climatic shifts. Nevertheless, topoclimatic diversity can be a challenge to quantify in the absence of distributed sensors or extensive instrumentation. In practice, topographic complexity is used as a proxy for topoclimatic diversity with the assumption that complex terrain will necessarily lead to diverse climates. However, this ignores spatio-temporal variability in soil moisture, snow cover, land cover, and vegetation which mediates the influence terrain has on climate. To better quantify topoclimatic diversity, we examine ten year climatological means for each month for daytime and nighttime MODIS Aqua satellite land surface temperature (LST) observations over the pacific northwest of the U.S. LST is well suited for this application because it is sensitive to variability in regional climate, hydrology, and land cover all of which can dramatically alter the energy balance and temperature of a site. We decompose the spatio-temporal variability in LST into its drivers including geographic position (x,y,z), biophysical factors (e.g. snow cover, vegetation cover, land surface type), and topoclimatic factors (e.g. cold air drainage, aspect). We find that nighttime LST data can be readily used to identify topoclimatic diversity driven by cold air pooling and thermal stratification of minimum temperatures whereas daytime LST data primarily characterizes the influence of vegetation cover on maximum temperatures. For both daytime and nighttime LST, the relative influence of topoclimatic drivers varies seasonally and is also sensitive to maritime influences or continentality of the site. Our approach allows for the decomposition of thermal variability into spatial and temporal components and allows for directly mapping regions of high topoclimatic diversity, an initial step for identifying potential climate refugia.

  11. Geostatistical analysis of groundwater level using Euclidean and non-Euclidean distance metrics and variable variogram fitting criteria

    Science.gov (United States)

    Theodoridou, Panagiota G.; Karatzas, George P.; Varouchakis, Emmanouil A.; Corzo Perez, Gerald A.

    2015-04-01

    Groundwater level is an important information in hydrological modelling. Geostatistical methods are often employed to map the free surface of an aquifer. In geostatistical analysis using Kriging techniques the selection of the optimal variogram model is very important for the optimal method performance. This work compares three different criteria, the least squares sum method, the Akaike Information Criterion and the Cressie's Indicator, to assess the theoretical variogram that fits to the experimental one and investigates the impact on the prediction results. Moreover, five different distance functions (Euclidean, Minkowski, Manhattan, Canberra, and Bray-Curtis) are applied to calculate the distance between observations that affects both the variogram calculation and the Kriging estimator. Cross validation analysis in terms of Ordinary Kriging is applied by using sequentially a different distance metric and the above three variogram fitting criteria. The spatial dependence of the observations in the tested dataset is studied by fitting classical variogram models and the Matérn model. The proposed comparison analysis performed for a data set of two hundred fifty hydraulic head measurements distributed over an alluvial aquifer that covers an area of 210 km2. The study area is located in the Prefecture of Drama, which belongs to the Water District of East Macedonia (Greece). This area was selected in terms of hydro-geological data availability and geological homogeneity. The analysis showed that a combination of the Akaike information Criterion for the variogram fitting assessment and the Brays-Curtis distance metric provided the most accurate cross-validation results. The Power-law variogram model provided the best fit to the experimental data. The aforementioned approach for the specific dataset in terms of the Ordinary Kriging method improves the prediction efficiency in comparison to the classical Euclidean distance metric. Therefore, maps of the spatial

  12. Spatio-temporal variability of the polar middle atmosphere. Insights from over 30 years of research satellite observations

    Energy Technology Data Exchange (ETDEWEB)

    Lahoz, W.A.; Orsolini, Y.J.; Manney, G.L.; Minschwaner, K.; Allen, D.R.; Errera, Q.; Jackson, D.R.; Lambert, A.; Lee, J.; Pumphrey, H.; Schwartz, M.; Wu, D.

    2012-07-01

    We discuss the insights that research satellite observations from the last 30 years have provided on the spatio-temporal variability of the polar middle atmosphere. Starting from the time of the NASA LIMS (Limb Infrared Monitor of the Stratosphere) and TOMS (Total Ozone Mapping Spectrometer) instruments, both launched in 1978, we show how these observations have augmented our knowledge of the polar middle atmosphere, in particular how information on ozone and tracers has augmented our knowledge of: (i) the spatial and temporal characteristics of the wintertime polar stratosphere and the summertime circulation; and (ii) the roles of chemistry and transport in determining the stratospheric ozone distribution. We address the increasing joint use of observations and models, in particular in data assimilation, in contributing to this understanding. Finally, we outline requirements to allow continuation of the wealth of information on the polar middle atmosphere provided by research satellites over the last 30 years.(Author)

  13. A geomatic methodology for spatio-temporal analysis of climatologic variables and water related diseases

    Science.gov (United States)

    Quentin, E.; Gómez Albores, M. A.; Díaz Delgado, C.

    2009-04-01

    The main objective of this research is to propose, by the way of geomatic developments, an integrated tool to analyze and model the spatio-temporal pattern of human diseases related to environmental conditions, in particular the ones that are linked to water resources. The geomatic developments follows four generic steps : requirement analysis, conceptual modeling, geomatic modeling and implementation (in Idrisi GIS software). A first development consists of the preprocessing of water, population and health data in order to facilitate the conversion and validation of tabular data into the required structure for spatio-temporal analysis. Three parallel developments follow : water balance, demographic state and evolution, epidemiological measures (morbidity and mortality rates, diseases burden). The new geomatic modules in their actual state have been tested on various regions of Mexico Republic (Lerma watershed, Chiapas state) focusing on diarrhea and vector borne diseases (dengue and malaria) and considering records over the last decade : a yearly as well as seasonal spreading trend can be observed in correlation with precipitation and temperature data. In an ecohealth perspective, the geomatic approach results particularly appropriate since one of its purposes is the integration of the various spatial themes implied in the study problem, environmental as anthropogenic. By the use of powerful spatial analysis functions, it permits the detection of spatial trends which, combined to the temporal evolution, can be of particularly use for example in climate change context, if sufficiently valid historical data can be obtain.

  14. Spatial and Temporal Dust Source Variability in Northern China Identified Using Advanced Remote Sensing Analysis

    Science.gov (United States)

    Taramelli, A.; Pasqui, M.; Barbour, J.; Kirschbaum, D.; Bottai, L.; Busillo, C.; Calastrini, F.; Guarnieri, F.; Small, C.

    2013-01-01

    The aim of this research is to provide a detailed characterization of spatial patterns and temporal trends in the regional and local dust source areas within the desert of the Alashan Prefecture (Inner Mongolia, China). This problem was approached through multi-scale remote sensing analysis of vegetation changes. The primary requirements for this regional analysis are high spatial and spectral resolution data, accurate spectral calibration and good temporal resolution with a suitable temporal baseline. Landsat analysis and field validation along with the low spatial resolution classifications from MODIS and AVHRR are combined to provide a reliable characterization of the different potential dust-producing sources. The representation of intra-annual and inter-annual Normalized Difference Vegetation Index (NDVI) trend to assess land cover discrimination for mapping potential dust source using MODIS and AVHRR at larger scale is enhanced by Landsat Spectral Mixing Analysis (SMA). The combined methodology is to determine the extent to which Landsat can distinguish important soils types in order to better understand how soil reflectance behaves at seasonal and inter-annual timescales. As a final result mapping soil surface properties using SMA is representative of responses of different land and soil cover previously identified by NDVI trend. The results could be used in dust emission models even if they are not reflecting aggregate formation, soil stability or particle coatings showing to be critical for accurately represent dust source over different regional and local emitting areas.

  15. Temporal variability predicts the magnitude of between-group attentional blink differences in developmental dyslexia: a meta-analysis.

    Science.gov (United States)

    Badcock, Nicholas A; Kidd, Joanna C

    2015-01-01

    Background. Here we report on a meta-analysis of the between-group main effect (Group Difference) noted in the attentional blink (AB) research focused on specific reading impairment, commonly referred to as developmental dyslexia. The AB effect relates to a limitation in the allocation of attention over time and is examined in a dual-target rapid serial visual presentation (RSVP) paradigm. When the second target appears in close temporal proximity to the first target, the second target is reported less accurately. Method. A Web of Science search with terms "attentional blink" & dyslexia returned 13 AB experiments (11 papers) conducted with developmental dyslexia. After exclusions, 12 experiments were included in the meta-analysis. The main pattern of performance from those experiments was lower overall accuracy in groups of individuals with dyslexia relative to typically reading peers; that is, a between-group main effect. This meta-analysis examined the size of the Group Difference in relation to temporal and task-set related features, which differed between and within experiments. Results. Random effects modelling indicated a significant Group Difference of -0.74 standard deviation units, 95% CI [-.96, -.52], p < .001 (excluding one anomalous result): implicating significantly poorer overall dual-target performance in dyslexic readers. Meta-regression analyses indicated two variables related to the Group Difference; pre-RSVP time and temporal variability of the second target relative to the first target within the RSVP. Discussion. It is suggested that the endogenous engagement of the temporal features of task-set is slower or disrupted in developmental dyslexia.

  16. Evaluation of drought impact on groundwater recharge rate using SWAT and Hydrus models on an agricultural island in western Japan

    Directory of Open Access Journals (Sweden)

    G. Jin

    2015-06-01

    Full Text Available Clarifying the variations of groundwater recharge response to a changing non-stationary hydrological process is important for efficiently managing groundwater resources, particularly in regions with limited precipitation that face the risk of water shortage. However, the rate of aquifer recharge is difficult to evaluate in terms of large annual-variations and frequency of flood events. In our research, we attempt to simulate related groundwater recharge processes under variable climate conditions using the SWAT Model, and validate the groundwater recharge using the Hydrus Model. The results show that annual average groundwater recharge comprised approximately 33% of total precipitation, however, larger variation was found for groundwater recharge and surface runoff compared to evapotranspiration, which fluctuated with annual precipitation variations. The annual variation of groundwater resources is shown to be related to precipitation. In spatial variations, the upstream is the main surface water discharge area; the middle and downstream areas are the main groundwater recharge areas. Validation by the Hydrus Model shows that the estimated and simulated groundwater levels are consistent in our research area. The groundwater level shows a quick response to the groundwater recharge rate. The rainfall intensity had a great impact on the changes of the groundwater level. Consequently, it was estimated that large spatial and temporal variation of the groundwater recharge rate would be affected by precipitation uncertainty in future.

  17. Spatial and temporal variability of climate extremes in Romania and associated large‐scale mechanisms

    National Research Council Canada - National Science Library

    Busuioc, Aristita; Dobrinescu, Andreea; Birsan, Marius‐Victor; Dumitrescu, Alexandru; Orzan, Alina

    2015-01-01

    ...‐scale mechanisms responsible for this variability on the other are examined. Ten indices associated with temperature and precipitation extremes computed at high spatial resolution for the period 1961–2010 are analysed...

  18. Effects of shallow groundwater management on the spatial and temporal variability of boron and salinity in an irrigated field

    NARCIS (Netherlands)

    Shouse, P.J.; Goldberg, S.; Skaggs, T.H.; Soppe, R.W.O.; Ayars, J.E.

    2006-01-01

    In some irrigated regions, the disposal of agricultural drainage waters poses significant environmental challenges. Efforts are underway to develop irrigation water management practices that reduce the volume of drainage generated. One such management strategy involves restricting flow in subsurface

  19. Social Investment for Sustainability of Groundwater: A Revealed Preference Approach

    Directory of Open Access Journals (Sweden)

    Edna Tusak Loehman

    2014-08-01

    Full Text Available Groundwater is a form of natural capital that is valued for the goods it provides, including ecosystem health, water quality, and water consumption. Degradation of groundwater could be alleviated through social investment such as for water reuse and desalination to reduce the need for withdrawals from groundwater. This paper develops a participatory planning process—based on combining revealed preference with economic optimization—to choose a desired future for sustaining groundwater. Generation of potential groundwater futures is based on an optimal control model with investment and withdrawal from groundwater as control variables. In this model, groundwater stock and aquatic health are included as inter-temporal public goods. The social discount rate expressing time preference—an important parameter that drives optimization—is revealed through the participatory planning process. To implement the chosen future, a new method of inter-temporal pricing is presented to finance investment and supply costs. Furthermore, it is shown that the desired social outcome could be achieved by a form of privatization in which the pricing method, the appropriate discount rate, and the planning period are contractually specified.

  20. Spatial and temporal variability in nutrients and carbon uptake during 2004 and 2005 in the eastern equatorial Pacific Ocean

    DEFF Research Database (Denmark)

    Palacz, A. P.; Chai, F.

    2012-01-01

    to the Tropical Instability Waves. The aim of this study is to examine patterns of spatial and temporal variability in the biological uptake of NO3, Si(OH)4 and carbon in this region, and to evaluate the role of biological and physical interactions controlling these processes over seasonal...... and intra-seasonal time scales. Here, high resolution Pacific ROMS-CoSiNE model results are combined with in situ and remote sensing data. The results of model-data comparison reveal an excellent agreement in domain-average hydrographic and biological rate estimates, and patterns of spatio...

  1. Spatio-temporal variability of bee/wasp communities and their host-parasitoid interaction networks

    OpenAIRE

    Osorio Cañadas, Sergio

    2017-01-01

    Uno de los principales objetivos de la ecología es comprender cómo la biodiversidad está estructurada espacial y temporalmente, y cuáles son los mecanismos subyacentes a los gradientes de biodiversidad en diferentes escalas espaciales y temporales. En esta tesis, analizo la variabilidad espacio-temporal de comunidades de abejas/avispas (huéspedes) y de sus parasitoides, y de las redes de interacción huésped-parasitoide que se establecen entre ellas. Las especies de abejas y avispas muestran n...

  2. Spatio-temporal variability of the SPCZ fresh pool eastern front from coral-derived surface salinity data

    Science.gov (United States)

    Dassié, Emilie P.; Hasson, Audrey; Khodri, Myriam; Linsley, Braddock K.

    2017-04-01

    The South Pacific Convergence Zone (SPCZ) is a major atmospheric feature of the southern hemisphere. It is a low atmospheric convergence band associated with intense precipitations. Its position and intensity responds to global changes but also modulates regional weather patterns. Interannual to long-term SPCZ modifications result in extreme events such as severe droughts or flooding with profound socio-economic consequences. The SPCZ oceanic counterpart is a large body of fresh water (SSS<34.5 pss) extending southeast from the Maritime Continent to the dateline. This freshpool is separated from the high-salinity waters of the South Pacific gyre to the west by a steep salinity front. Various studies have shown a freshening of the freshpool and its south-eastward expansion since the 1970s, modulated by interannual to interdecadal variability (Cravatte et al., 2009). The scarcity of traditional SSS measurements limits our ability to describe accurately this variability. This study validates the use of coral d18O as a proxy for the reconstruction of SSS over the last 200 years. Derived SSS is validated against insitu data at 3 different locations along the SSS front (Fiji, Tonga and Rarotonga Islands). This new dataset enables us to investigate the spatio-temporal variations of the SSS front prior to the instrumental data. Two robust modes of variability are present in the reconstructed SSS datasets: interannual variability and a secular trend. The reconstructed SSS variability follows El Niño Southern Oscillation index. The three sites present secular trends toward fresher conditions, but do not present similar variability, neither in timing nor strength over their total length. Furthermore, the role of atmospheric freshwater fluxes on SSS variability is evaluated by comparing reconstructed SSS to available historical rain gauge data. Results highlight the role of both atmospheric freshwater fluxes and ocean dynamics on SSS variability.

  3. Future research needs involving pathogens in groundwater

    Science.gov (United States)

    Bradford, Scott A.; Harvey, Ronald W.

    2017-01-01

    Contamination of groundwater by enteric pathogens has commonly been associated with disease outbreaks. Proper management and treatment of pathogen sources are important prerequisites for preventing groundwater contamination. However, non-point sources of pathogen contamination are frequently difficult to identify, and existing approaches for pathogen detection are costly and only provide semi-quantitative information. Microbial indicators that are readily quantified often do not correlate with the presence of pathogens. Pathogens of emerging concern and increasing detections of antibiotic resistance among bacterial pathogens in groundwater are topics of growing concern. Adequate removal of pathogens during soil passage is therefore critical for safe groundwater extraction. Processes that enhance pathogen transport (e.g., high velocity zones and preferential flow) and diminish pathogen removal (e.g., reversible retention and enhanced survival) are of special concern because they increase the risk of groundwater contamination, but are still incompletely understood. Improved theory and modeling tools are needed to analyze experimental data, test hypotheses, understand coupled processes and controlling mechanisms, predict spatial and/or temporal variability in model parameters and uncertainty in pathogen concentrations, assess risk, and develop mitigation and best management approaches to protect groundwater.

  4. Future research needs involving pathogens in groundwater

    Science.gov (United States)

    Bradford, Scott A.; Harvey, Ronald W.

    2017-06-01

    Contamination of groundwater by enteric pathogens has commonly been associated with disease outbreaks. Proper management and treatment of pathogen sources are important prerequisites for preventing groundwater contamination. However, non-point sources of pathogen contamination are frequently difficult to identify, and existing approaches for pathogen detection are costly and only provide semi-quantitative information. Microbial indicators that are readily quantified often do not correlate with the presence of pathogens. Pathogens of emerging concern and increasing detections of antibiotic resistance among bacterial pathogens in groundwater are topics of growing concern. Adequate removal of pathogens during soil passage is therefore critical for safe groundwater extraction. Processes that enhance pathogen transport (e.g., high velocity zones and preferential flow) and diminish pathogen removal (e.g., reversible retention and enhanced survival) are of special concern because they increase the risk of groundwater contamination, but are still incompletely understood. Improved theory and modeling tools are needed to analyze experimental data, test hypotheses, understand coupled processes and controlling mechanisms, predict spatial and/or temporal variability in model parameters and uncertainty in pathogen concentrations, assess risk, and develop mitigation and best management approaches to protect groundwater.

  5. The influence of riparian woodland on the spatial and temporal variability of stream water temperatures in an upland salmon stream

    Directory of Open Access Journals (Sweden)

    I. A. Malcolm

    2004-01-01

    Full Text Available The spatio-temporal variability of stream water temperatures was investigated at six locations on the Girnock Burn (30km2 catchment, Cairngorms, Scotland over three hydrological years between 1998 and 2002. The key site-specific factors affecting the hydrology and climatology of the sampling points were investigated as a basis for physical process inference. Particular emphasis was placed on assessing the effects of riparian forest in the lower catchment versus the heather moorland riparian zones that are spatially dominant in the upper catchment. The findings were related to river heat budget studies that provided process detail. Gross changes in stream temperature were affected by the annual cycle of incoming solar radiation and seasonal changes in hydrological and climatological conditions. Inter-annual variation in these controlling variables resulted in inter-annual variability in thermal regime. However, more subtle inter-site differences reflected the impact of site-specific characteristics on various components of the river energy budget. Inter-site variability was most apparent at shorter time scales, during the summer months and for higher stream temperatures. Riparian woodland in the lower catchment had a substantial impact on thermal regime, reducing diel variability (over a period of 24 hours and temperature extremes. Observed inter-site differences are likely to have a substantial effect on freshwater ecology in general and salmonid fish in particular. Keywords: temperature, thermal regime, forest, salmon, hydrology, Girnock Burn, Cairngorm

  6. TEMPORAL AND SPATIAL VARIABILITY OF FECAL INDICATOR BACTERIA: IMPLICATIONS FOR THE APPLICATION OF MST METHODOLOGIES TO DIFFERENTIATE SOURCES OF FECAL CONTAMINATION

    Science.gov (United States)

    Temporal variability in the gastrointestinal flora of animals impacting water resources with fecal material can be one of the factors producing low source identification rates when applying microbial source tracking (MST) methods. Understanding how bacterial species and genotype...

  7. Gait variability is altered in older adults when listening to auditory stimuli with differing temporal structures.

    Science.gov (United States)

    Kaipust, Jeffrey P; McGrath, Denise; Mukherjee, Mukul; Stergiou, Nicholas

    2013-08-01

    Gait variability in the context of a deterministic dynamical system may be quantified using nonlinear time series analyses that characterize the complexity of the system. Pathological gait exhibits altered gait variability. It can be either too periodic and predictable, or too random and disordered, as is the case with aging. While gait therapies often focus on restoration of linear measures such as gait speed or stride length, we propose that the goal of gait therapy should be to restore optimal gait variability, which exhibits chaotic fluctuations and is the balance between predictability and complexity. In this context, our purpose was to investigate how listening to different auditory stimuli affects gait variability. Twenty-seven young and 27 elderly subjects walked on a treadmill for 5 min while listening to white noise, a chaotic rhythm, a metronome, and with no auditory stimulus. Stride length, step width, and stride intervals were calculated for all conditions. Detrended Fluctuation Analysis was then performed on these time series. A quadratic trend analysis determined that an idealized inverted-U shape described the relationship between gait variability and the structure of the auditory stimuli for the elderly group, but not for the young group. This proof-of-concept study shows that the gait of older adults may be manipulated using auditory stimuli. Future work will investigate which structures of auditory stimuli lead to improvements in functional status in older adults.

  8. Variability of spatial temporal gait parameters and center of pressure displacements during gait in elderly fallers and nonfallers: A 6-month prospective study

    OpenAIRE

    Svoboda, Zdeněk; Bizovská, Lucia; Janura, Miroslav; Kuboňová, Eliška; Janurová, Kateřina; Vuillerme, Nicolas

    2017-01-01

    Considering that most of the falls in elderly population arise during walking, tests derived from walking performance would be desirable for comprehensive fall risk assessment. The analysis of spatial temporal parameters and the center of pressure displacement, which represents the interaction between the human body and the ground, would be beneficial. The aim of this study was to compare spatial temporal gait parameters and their variability and the variability of the center of pressure disp...

  9. Simulation of Tritium Transport and Groundwater Age in a Variably Saturated 3D Model, Lake Rotorua Catchment, New Zealand

    Science.gov (United States)

    Daughney, C.; Toews, M. W.; Morgenstern, U.; Cornaton, F. J.; Jackson, B. M.

    2013-12-01

    Lake Rotorua is a focus of culture and tourism in New Zealand. The lake's water quality has declined since the 1970s, partly due to nutrient inputs that reach the lake via the groundwater system. Improved land use management within the catchment requires prediction of the spatial variations of groundwater transit time from land surface to the lake, and from this the prediction of current and future nutrient inflows to the lake. This study combines the two main methods currently available for determination of water age: numerical groundwater models and hydrological tracers. A steady-state 3D finite element model was constructed to simulate groundwater flow and transport of tritium and age at the catchment scale (555 km2). The model materials were defined using a 3D geologic model and included ignimbrites, rhyolites, alluvial and lake bottom sediments. The steady-state saturated groundwater flow model was calibrated using observed groundwater levels in boreholes (111 locations) and stream flow measurements from groundwater-fed streams and springs (61 locations). Hydraulic conductivities and Cauchy boundary conditions associated with the streams, springs and lake were parameterized. The transport parameters for the model were calibrated using 191 tritium samples from 105 locations (springs, streams and boreholes), with most locations having two sample dates. The transport model used steady-state flow, but simulated the transient transport and decay of tritium from rainfall recharge between 1945 and 2012. An additional 1D unsaturated sub-model was added to account for tritium decay from the ground surface to the water table. The sub-model is linked on top of the 3D model, and uses the water table depths and material properties from the 3D model. The adjustable calibration parameters for the transport model were porosity and van Genuchten parameters related to the unsaturated sub-models. Calibration of the flow model was achieved using a combination of automated least

  10. Resilience of estuarine phytoplankton and their temporal variability along salinity gradients during drought and hypersalinity

    Science.gov (United States)

    Nche-Fambo, F. A.; Scharler, U. M.; Tirok, K.

    2015-06-01

    In South African estuaries, there is no knowledge on the resilience and variability in phytoplankton communities under conditions of hypersalinity, extended droughts and reverse salinity gradients. Phytoplankton composition, abundance and biomass vary with changes in environmental variables and taxa richness declines specifically under hypersaline conditions. This research thus investigated the phytoplankton community composition, its resilience and variability under highly variable and extreme environmental conditions in an estuarine lake system (Lake St. Lucia, South Africa) over one year. The lake system was characterised by a reverse salinity gradient with hypersalinity furthest from the estuarine inlet during the study period. During this study, 78 taxa were recorded: 56 diatoms, eight green algae, one cryptophyte, seven cyanobacteria and six dinoflagellates. Taxon variability and resilience depended on their ability to tolerate high salinities. Consequently, the phytoplankton communities as well as total abundance and biomass differed along the salinity gradient and over time with salinity as the main determinant. Cyanobacteria were dominant in hypersaline conditions, dinoflagellates in marine-brackish salinities, green algae and cryptophytes in lower salinities (brackish) and diatoms were abundant in marine-brackish salinities but survived in hypersaline conditions. Total abundance and biomass ranged from 3.66 × 103 to 1.11 × 109 Cells/L and 1.21 × 106 to 1.46 × 1010 pgC/L respectively, with the highest values observed under hypersaline conditions. Therefore, even under highly variable, extreme environmental conditions and hypersalinity the phytoplankton community as a whole was resilient enough to maintain a relatively high biomass throughout the study period. The resilience of few dominant taxa, such as Cyanothece, Spirulina, Protoperidinium and Nitzschia and the dominance of other common genera such as Chlamydomonas, Chroomonas, Navicula, Gyrosigma

  11. Predictive modeling of groundwater nitrate pollution using Random Forest and multisource variables related to intrinsic and specific vulnerability: a case study in an agricultural setting (Southern Spain).

    Science.gov (United States)

    Rodriguez-Galiano, Victor; Mendes, Maria Paula; Garcia-Soldado, Maria Jose; Chica-Olmo, Mario; Ribeiro, Luis

    2014-04-01

    Watershed management decisions need robust methods, which allow an accurate predictive modeling of pollutant occurrences. Random Forest (RF) is a powerful machine learning data driven method that is rarely used in water resources studies, and thus has not been evaluated thoroughly in this field, when compared to more conventional pattern recognition techniques key advantages of RF include: its non-parametric nature; high predictive accuracy; and capability to determine variable importance. This last characteristic can be used to better understand the individual role and the combined effect of explanatory variables in both protecting and exposing groundwater from and to a pollutant. In this paper, the performance of the RF regression for predictive modeling of nitrate pollution is explored, based on intrinsic and specific vulnerability assessment of the Vega de Granada aquifer. The applicability of this new machine learning technique is demonstrated in an agriculture-dominated area where nitrate concentrations in groundwater can exceed the trigger value of 50 mg/L, at many locations. A comprehensive GIS database of twenty-four parameters related to intrinsic hydrogeologic proprieties, driving forces, remotely sensed variables and physical-chemical variables measured in "situ", were used as inputs to build different predictive models of nitrate pollution. RF measures of importance were also used to define the most significant predictors of nitrate pollution in groundwater, allowing the establishment of the pollution sources (pressures). The potential of RF for generating a vulnerability map to nitrate pollution is assessed considering multiple criteria related to variations in the algorithm parameters and the accuracy of the maps. The performance of the RF is also evaluated in comparison to the logistic regression (LR) method using different efficiency measures to ensure their generalization ability. Prediction results show the ability of RF to build accurate models

  12. Spatial and temporal variability of nitrous oxide emissions in a mixed farming landscape of Denmark

    DEFF Research Database (Denmark)

    Schelde, Kirsten; Cellier, P; Bertolini, T

    2012-01-01

    Nitrous oxide (N2O) emissions from agricultural land are variable at the landscape scale due to variability in land use, management, soil type, and topography. A field experiment was carried out in a typical mixed farming landscape in Denmark, to investigate the main drivers of variations in N2O...... emissions during spring 2009 were relatively low, with maximum values below 20 ng N m−2 s−1. This applied to all land use types including winter grain crops, grasslands, meadows, and wetlands. Slurry application to wheat fields resulted in short-lived two-fold increases in emissions. The moderate N2O fluxes...

  13. Pollutant fate and spatio-temporal variability in the choptank river estuary: Factors influencing water quality

    Science.gov (United States)

    Whitall, D.; Hively, W.D.; Leight, A.K.; Hapeman, C.J.; McConnell, L.L.; Fisher, T.; Rice, C.P.; Codling, E.; McCarty, G.W.; Sadeghi, A.M.; Gustafson, A.; Bialek, K.

    2010-01-01

    Restoration of the Chesapeake Bay, the largest estuary in the United States, is a national priority. Documentation of progress of this restoration effort is needed. A study was conducted to examine water quality in the Choptank River estuary, a tributary of the Chesapeake Bay that since 1998 has been classified as impaired waters under the Federal Clean Water Act. Multiple water quality parameters (salinity, temperature, dissolved oxygen, chlorophyll a) and analyte concentrations (nutrients, herbicide and herbicide degradation products, arsenic, and copper) were measured at seven sampling stations in the Choptank River estuary. Samples were collected under base flow conditions in the basin on thirteen dates between March 2005 and April 2008. As commonly observed, results indicate that agriculture is a primary source of nitrate in the estuary and that both agriculture and wastewater treatment plants are important sources of phosphorus. Concentrations of copper in the lower estuary consistently exceeded both chronic and acute water quality criteria, possibly due to use of copper in antifouling boat paint. Concentrations of copper in the upstream watersheds were low, indicating that agriculture is not a significant source of copper loading to the estuary. Concentrations of herbicides (atrazine, simazine, and metolachlor) peaked during early-summer, indicating a rapid surface-transport delivery pathway from agricultural areas, while their degradation products (CIAT, CEAT, MESA, and MOA) appeared to be delivered via groundwater transport. Some in-river processing of CEAT occurred, whereas MESA was conservative. Observed concentrations of herbicide residues did not approach established levels of concern for aquatic organisms. Results of this study highlight the importance of continued implementation of best management practices to improve water quality in the estuary. This work provides a baseline against which to compare future changes in water quality and may be used

  14. Active visual search in non-stationary scenes: coping with temporal variability and uncertainty

    Science.gov (United States)

    Ušćumlić, Marija; Blankertz, Benjamin

    2016-02-01

    Objective. State-of-the-art experiments for studying neural processes underlying visual cognition often constrain sensory inputs (e.g., static images) and our behavior (e.g., fixed eye-gaze, long eye fixations), isolating or simplifying the interaction of neural processes. Motivated by the non-stationarity of our natural visual environment, we investigated the electroencephalography (EEG) correlates of visual recognition while participants overtly performed visual search in non-stationary scenes. We hypothesized that visual effects (such as those typically used in human-computer interfaces) may increase temporal uncertainty (with reference to fixation onset) of cognition-related EEG activity in an active search task and therefore require novel techniques for single-trial detection. Approach. We addressed fixation-related EEG activity in an active search task with respect to stimulus-appearance styles and dynamics. Alongside popping-up stimuli, our experimental study embraces two composite appearance styles based on fading-in, enlarging, and motion effects. Additionally, we explored whether the knowledge obtained in the pop-up experimental setting can be exploited to boost the EEG-based intention-decoding performance when facing transitional changes of visual content. Main results. The results confirmed our initial hypothesis that the dynamic of visual content can increase temporal uncertainty of the cognition-related EEG activity in active search with respect to fixation onset. This temporal uncertainty challenges the pivotal aim to keep the decoding performance constant irrespective of visual effects. Importantly, the proposed approach for EEG decoding based on knowledge transfer between the different experimental settings gave a promising performance. Significance. Our study demonstrates that the non-stationarity of visual scenes is an important factor in the evolution of cognitive processes, as well as in the dynamic of ocular behavior (i.e., dwell time and

  15. A temporal and spatial analysis of ground-water levels for effective monitoring in Huron County, Michigan

    Science.gov (United States)

    Holtschlag, David J.; Sweat, M.J.

    1999-01-01

    Quarterly water-level measurements were analyzed to assess the effectiveness of a monitoring network of 26 wells in Huron County, Michigan. Trends were identified as constant levels and autoregressive components were computed at all wells on the basis of data collected from 1993 to 1997, using structural time series analysis. Fixed seasonal components were identified at 22 wells and outliers were identified at 23 wells. The 95- percent confidence intervals were forecast for water-levels during the first and second quarters of 1998. Intervals in the first quarter were consistent with 92.3 percent of the measured values. In the second quarter, measured values were within the forecast intervals only 65.4 percent of the time. Unusually low precipitation during the second quarter is thought to have contributed to the reduced reliability of the second-quarter forecasts. Spatial interrelations among wells were investigated on the basis of the autoregressive components, which were filtered to create a set of innovation sequences that were temporally uncorrelated. The empirical covariance among the innovation sequences indicated both positive and negative spatial interrelations. The negative covariance components are considered to be physically implausible and to have resulted from random sampling error. Graphical modeling, a form of multivariate analysis, was used to model the covariance structure. Results indicate that only 29 of the 325 possible partial correlations among the water-level innovations were statistically significant. The model covariance matrix, corresponding to the model partial correlation structure, contained only positive elements. This model covariance was sequentially partitioned to compute a set of partial covariance matrices that were used to rank the effectiveness of the 26 monitoring wells from greatest to least. Results, for example, indicate that about 50 percent of the uncertainty of the water-level innovations currently monitored by the 26

  16. Quantification of groundwater recharge in urban environments.

    Science.gov (United States)

    Tubau, Isabel; Vázquez-Suñé, Enric; Carrera, Jesús; Valhondo, Cristina; Criollo, Rotman

    2017-08-15

    Groundwater management in urban areas requires a detailed knowledge of the hydrogeological system as well as the adequate tools for predicting the amount of groundwater and water quality evolution. In that context, a key difference between urban and natural areas lies in recharge evaluation. A large number of studies have been published since the 1990s that evaluate recharge in urban areas, with no specific methodology. Most of these methods show that there are generally higher rates of recharge in urban settings than in natural settings. Methods such as mixing ratios or groundwater modeling can be used to better estimate the relative importance of different sources of recharge and may prove to be a good tool for total recharge evaluation. However, accurate evaluation of this input is difficult. The objective is to present a methodology to help overcome those difficulties, and which will allow us to quantify the variability in space and time of the recharge into aquifers in urban areas. Recharge calculations have been initially performed by defining and applying some analytical equations, and validation has been assessed based on groundwater flow and solute transport modeling. This methodology is applicable to complex systems by considering temporal variability of all water sources. This allows managers of urban groundwater to evaluate the relative contribution of different recharge sources at a city scale by considering quantity and quality factors. The methodology is applied to the assessment of recharge sources in the Barcelona city aquifers. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Colour constancy from temporal cues: better matches with less variability under fast illuminant changes.

    Science.gov (United States)

    Foster, D H; Amano, K; Nascimento, S M

    2001-02-01

    To test whether temporal transient cues could improve colour-constancy estimates, surface-colour matches were made across two Mondrian patterns illuminated by different daylights: the patterns were presented either in the same position in an alternating sequence or, as a control, simultaneously side-by-side. The degree of colour constancy was significantly higher with sequential stimulus presentation than with simultaneous presentation, in the best condition reaching 0.87 on a scale of 0 to 1 for matches averaged over 20 observers. The variance between observers was also markedly reduced with sequential stimulus presentation. The visual system appears to have mechanisms not requiring adaptation that can provide almost unbiased information about surface colour under changing illuminants.

  18. Spatial and Temporal Variability of Rainfall in Eastern Amazon during the Rainy Season

    Science.gov (United States)

    Batista da Silva Ferreira, Douglas; Barreiros de Souza, Everaldo; Cavalcanti de Moraes, Bergson; Meira Filho, Luiz Gylvan

    2015-01-01

    Empirical orthogonal functions (EOF) and composites analysis were employed on pentad data in order to investigate the tropical atmospheric-ocean patterns over the Atlantic Ocean and the spatial-temporal characteristics of the rainfall in eastern Amazon during the peak of the rainy season (February to April). The EOF results evidenced that the Intertropical Convergence Zone (ITCZ) is the main rainfall-producing system in eastern Amazon during the rainy season. Conditions associated with the southward SST gradient in the intertropical Atlantic formed the dynamic patterns that favored the position of the ITCZ to south of the equator, thus explaining the predominance of positive precipitation anomalies in eastern Amazon, especially in the state of Maranhão and northeastern Pará during the February and April months. PMID:25793218

  19. A Global Plume-Fed Europan Exosphere: Structure, Composition, Temporal Variability, and Surface Interactions

    Science.gov (United States)

    Teolis, B. D.; Waite, J. H., Jr.; Wyrick, D. Y.; Bouquet, A.; Magee, B.

    2014-12-01

    We present results from our Europa global exospheric modeling, which includes both sputtering / radiolytic and potential plume sources, and a sophisticated treatment of the exosphere-surface interaction, i.e., surface adsorption, regolith diffusion, polar cold trapping, and re-sputtering of adsorbed materials. We consider the effect of Europa's gravity in pulling plume vapor back to the surface and the subsequent spreading of adsorbed and exospheric material by thermal desorption and re-sputtering across the entire body. Our results show the global spatial distribution and temporal evolution of the surface exospheric density and composition for several scenarios, e.g., a solely sputtered / radiolytic exosphere, and the inclusion of transient and/or steady plume sources with an Enceladus-like composition. The model provides a useful tool for interpreting remote observations, and for extrapolating possible neutral and ion densities and compositional profiles along potential future spacecraft trajectories.

  20. Greenland ice core evidence for spatial and temporal variability of the Atlantic Multidecadal Oscillation

    NARCIS (Netherlands)

    Chylek, P.; Folland, C.K.; Frankcombe, L.M.; Dijkstra, H.A.; Lesins, G.; Dubey, M.

    2012-01-01

    [1] The Greenland δ18O ice core record is used as a proxy for Greenland surface air temperatures and to interpret Atlantic Multidecadal Oscillation (AMO) variability. An analysis of annual δ18O data from six Arctic ice cores (five from Greenland and one from Canada's Ellesmere Island) suggests a

  1. Exploiting temporal variability to understand tree recruitment response to climate change

    Science.gov (United States)

    Ines Ibanez; James S. Clark; Shannon LaDeau; Janneke Hill Ris Lambers

    2007-01-01

    Predicting vegetation shifts under climate change is a challenging endeavor, given the complex interactions between biotic and abiotic variables that influence demographic rates. To determine how current trends and variation in climate change affect seedling establishment, we analyzed demographic responses to spatiotemporal variation to temperature and soil moisture in...

  2. Environmental drivers of temporal variability in DMS (P) in the surfwater of a tropical intertidal beach

    Digital Repository Service at National Institute of Oceanography (India)

    Pandey, S.S.; LokaBharathi, P.A.

    from the intertidal beach of a tropical estuary, we monitored the DMS concentrations and estimated the flux from the surfwater of Dona Paula Bay for a period of one year The probable drivers of variability of this compound were also measured Our results...

  3. Ground-based measurements of spatial and temporal variability of snow accumulation in East Antarctica

    Science.gov (United States)

    Eisen, Olaf; Frezzotti, Massimo; Genthon, Christophe; Isaksson, Elisabeth; Magand, Olivier; van den Broeke, Michiel R.; Dixon, Daniel A.; Ekaykin, Alexey; Holmlund, Per; Kameda, Takao; KarlöF, Lars; Kaspari, Susan; Lipenkov, Vladimir Y.; Oerter, Hans; Takahashi, Shuhei; Vaughan, David G.

    2008-06-01

    The East Antarctic Ice Sheet is the largest, highest, coldest, driest, and windiest ice sheet on Earth. Understanding of the surface mass balance (SMB) of Antarctica is necessary to determine the present state of the ice sheet, to make predictions of its potential contribution to sea level rise, and to determine its past history for paleoclimatic reconstructions. However, SMB values are poorly known because of logistic constraints in extreme polar environments, and they represent one of the biggest challenges of Antarctic science. Snow accumulation is the most important parameter for the SMB of ice sheets. SMB varies on a number of scales, from small-scale features (sastrugi) to ice-sheet-scale SMB patterns determined mainly by temperature, elevation, distance from the coast, and wind-driven processes. In situ measurements of SMB are performed at single points by stakes, ultrasonic sounders, snow pits, and firn and ice cores and laterally by continuous measurements using ground-penetrating radar. SMB for large regions can only be achieved practically by using remote sensing and/or numerical climate modeling. However, these techniques rely on ground truthing to improve the resolution and accuracy. The separation of spatial and temporal variations of SMB in transient regimes is necessary for accurate interpretation of ice core records. In this review we provide an overview of the various measurement techniques, related difficulties, and limitations of data interpretation; describe spatial characteristics of East Antarctic SMB and issues related to the spatial and temporal representativity of measurements; and provide recommendations on how to perform in situ measurements.

  4. Temporal variability and social heterogeneity in disease transmission: the case of SARS in Hong Kong.

    Directory of Open Access Journals (Sweden)

    Anne Cori

    2009-08-01

    Full Text Available The extent to which self-adopted or intervention-related changes in behaviors affect the course of epidemics remains a key issue for outbreak control. This study attempted to quantify the effect of such changes on the risk of infection in different settings, i.e., the community and hospitals. The 2002-2003 severe acute respiratory syndrome (SARS outbreak in Hong Kong, where 27% of cases were healthcare workers, was used as an example. A stochastic compartmental SEIR (susceptible-exposed-infectious-removed model was used: the population was split into healthcare workers, hospitalized people and general population. Super spreading events (SSEs were taken into account in the model. The temporal evolutions of the daily effective contact rates in the community and hospitals were modeled with smooth functions. Data augmentation techniques and Markov chain Monte Carlo (MCMC methods were applied to estimate SARS epidemiological parameters. In particular, estimates of daily reproduction numbers were provided for each subpopulation. The average duration of the SARS infectious period was estimated to be 9.3 days (+/-0.3 days. The model was able to disentangle the impact of the two SSEs from background transmission rates. The effective contact rates, which were estimated on a daily basis, decreased with time, reaching zero inside hospitals. This observation suggests that public health measures and possible changes in individual behaviors effectively reduced transmission, especially in hospitals. The temporal patterns of reproduction numbers were similar for healthcare workers and the general population, indicating that on average, an infectious healthcare worker did not infect more people than any other infectious person. We provide a general method to estimate time dependence of parameters in structured epidemic models, which enables investigation of the impact of control measures and behavioral changes in different settings.

  5. Temporal and spatial variations in groundwater quality resulting from policy-induced reductions in nitrate leaching to the Rabis Creek aquifer, Denmark

    Science.gov (United States)

    Jessen, Søren; Engesgaard, Peter; Thorling, Lærke; Müller, Sascha; Leskelä, Jari; Postma, Dieke

    2016-04-01

    Twenty-five years of annual groundwater quality monitoring data from the sandy unconfined Rabis Creek aquifer were used to assess the effects of political actions aimed to reduce nitrate leaching to the aquifer. Data were collected from eight multilevel samplers along a ˜3 km transect, which follows the general direction of groundwater flow. Each multilevel sampler comprises 20 screens placed with a 1 m vertical distance from near the water table downwards. The transect covers areas of livestock, plantation & heath, and agriculture. The history of nitrate leaching to the aquifer was assessed using data from screens close to the water table of multilevel samplers placed within agricultural areas. According to these data, nitrate concentrations of infiltrating 'agricultural' water peaked at 2-3 mM (120-180 mg/L) in the year 1989, and then gradually decreased and stabilized at 0.25-1.0 mM (15-60 mg/L) from year 2000. Local farmers declare having used the maximum fertilization rate allowed during the period. The timing of the observed decrease therefore suggests a direct link to the political action plans implemented in the same period. Parallel to the development in nitrate leaching, although with a transport time lag, the average concentration of nitrate in the oxic zone of the aquifer was roughly halved between 2000 and 2013. As a response to political initiatives of the late 1980'ies, part of the area covering the aquifer was changed from agriculture to non-fertilized grass for livestock; the data shows that this effectively remediated the aquifer underneath in less than 20 years, to become nitrate-free and attain background sulfate levels. The oxidized and pyritic reduced zone of the aquifer is separated by a iron is precipitated. Nickel (Ni2+) is released at the redoxcline resulting in concentrations more than twice the 20 μg/L Danish drinking water limit. The data clearly indicate that this Ni2+ contamination can be ascribed to the agricultural nitrate loading

  6. Assessing gait variability in transtibial amputee fallers based on spatial-temporal gait parameters normalized for walking speed.

    Science.gov (United States)

    Hordacre, Brenton G; Barr, Christopher; Patritti, Benjamin L; Crotty, Maria

    2015-06-01

    To determine whether normalizing spatial-temporal gait data for walking speed obtained from multiple walking trials leads to differences in gait variability parameters associated with a history of falling in people with transtibial amputations. Cross-sectional study. Rehabilitation center. People with unilateral transtibial amputations (N=45; mean age ± SD, 60.5±13.7y; 35 men [78%]) were recruited. Not applicable. Participants completed 10 consecutive walking trials using an instrumented walkway system. Primary gait parameters were walking speed and step-length, step-width, step-time, and swing-time variability. A retrospective 12-month fall history was obtained from participants. Sixteen amputees (36%) were classified as fallers. Variation in gait speed across the 10 walking trials was 2.9% (range, 1.1%-12.1%). Variability parameters of normalized gait data were significantly different from variability parameters of nonnormalized data (all Pamputees with a fall history. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  7. Remote Sensing of Groundwater with GRACE and GRACE Follow On

    Science.gov (United States)

    Rodell, M.; Famiglietti, J. S.; Reager, J. T., II; Wiese, D. N.; Beaudoing, H. K.; Li, B.

    2016-12-01

    Aquifers provide an alternative, reliable source of fresh water when precipitation and surface waters are insufficient, and as a result people worldwide depend on groundwater for domestic water and crop irrigation. However, groundwater is difficult to monitor because it is hidden deep below the surface. Outside of a few industrialized nations groundwater is not monitored systematically, and where it is the data are rarely centralized and publicly available. Since 2002 the NASA/German Gravity Recovery and Climate Experiment (GRACE) satellite mission has delivered gravity field observations which have been used to infer variations in total terrestrial water storage, including groundwater, at regional to continental scales. Challenges to using GRACE for groundwater monitoring include its relatively coarse spatial and temporal resolutions, its inability to distinguish groundwater from other types of water on and under the land surface, and its typical 2-3 month data latency. Nevertheless, GRACE provides the only global, consistent measurements that are directly applicable for groundwater monitoring. This presentation will describe what we have learned to date from GRACE about regional to global scale groundwater variability and trends. While GRACE will stop delivering data near the end of 2017, the GRACE Follow On mission is scheduled to launch by February 2018, enabling this essential climate data record to continue.

  8. Groundwater Storage Changes: Present Status from GRACE Observations

    Science.gov (United States)

    Chen, Jianli; Famiglietti, James S.; Scanlon, Bridget R.; Rodell, Matthew

    2015-01-01

    Satellite gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) provide quantitative measurement of terrestrial water storage (TWS) changes with unprecedented accuracy. Combining GRACE-observed TWS changes and independent estimates of water change in soil and snow and surface reservoirs offers a means for estimating groundwater storage change. Since its launch in March 2002, GRACE time-variable gravity data have been successfully used to quantify long-term groundwater storage changes in different regions over the world, including northwest India, the High Plains Aquifer and the Central Valley in the USA, the North China Plain, Middle East, and southern Murray-Darling Basin in Australia, where groundwater storage has been significantly depleted in recent years (or decades). It is difficult to rely on in situ groundwater measurements for accurate quantification of large, regional-scale groundwater storage changes, especially at long timescales due to inadequate spatial and temporal coverage of in situ data and uncertainties in storage coefficients. The now nearly 13 years of GRACE gravity data provide a successful and unique complementary tool for monitoring and measuring groundwater changes on a global and regional basis. Despite the successful applications of GRACE in studying global groundwater storage change, there are still some major challenges limiting the application and interpretation of GRACE data. In this paper, we present an overview of GRACE applications in groundwater studies and discuss if and how the main challenges to using GRACE data can be addressed.

  9. Lack of temporal variability in the benthos of a coastal brackish water lagoon in Greece

    Directory of Open Access Journals (Sweden)

    A. NICOLAIDOU

    2007-12-01

    Benthic samples were collected at 10 stations at bimonthly intervals over a period of a year. Temperature, salinity, dissolved oxygen and sediment organic carbon were also measured at the same time. The environmental parameters showed the expected seasonal variability but the benthic community, the structure of which was only related to plant biomass, did not. This lack of seasonality is attributed to the continuous reproduction of some abundant species and to species interactions.

  10. Temporal variability of the Baltic Sea level based on satellite observations

    Science.gov (United States)

    Stramska, Malgorzata

    2013-11-01

    The main objective of this paper is to determine what are the most important time scales of variability of the sea level in the open Baltic Sea. The study is based on the 7-day resolution multimission global gridded sea level anomalies (SLA) for years 1992-2012 distributed by AVISO. For comparison satellite-derived SLA from the North Sea and North Atlantic, coastal data from the Stockholm tide gauge, the NCEP meteorological data, and river runoff data from the Balt-HYPE model have been also analyzed. We have applied time series analysis algorithms (Bendat and Piersol, 2011). Supporting earlier research, our results show that the variability of the sea level in the open Baltic Sea is highly coherent with the sea level in the North Sea. We have found out that the annual peak is not well pronounced in the open Baltic Sea SLA spectrum, but the semiannual peak is the most prevailing. In contrast, the annual peak is significant in the North Sea SLA power spectrum. The coherence between the open Baltic Sea and the Stockholm SLA is high and the SLA variability in these two locations is in phase. The results of the cross-spectral analysis between the SLA in the Baltic Sea and meteorological parameters (wind stress magnitude, zonal and meridional wind stress components, and barometric pressure at sea level) show that coherence is highest with the zonal wind stress component. Coherence between the river runoff and the SLA in Stockholm is not significant.

  11. Modelling spatial and temporal variability of hydrologic impacts under climate changes over the Nenjiang River Basin, China

    Science.gov (United States)

    Chen, Hao; Zhang, Wanchang

    2017-10-01

    The Variable Infiltration Capacity (VIC) hydrologic model was adopted for investigating spatial and temporal variability of hydrologic impacts of climate change over the Nenjiang River Basin (NRB) based on a set of gridded forcing dataset at 1/12th degree resolution from 1970 to 2013. Basin-scale changes in the input forcing data and the simulated hydrological variables of the NRB, as well as station-scale changes in discharges for three major hydrometric stations were examined, which suggested that the model was performed fairly satisfactory in reproducing the observed discharges, meanwhile, the snow cover and evapotranspiration in temporal and spatial patterns were simulated reasonably corresponded to the remotely sensed ones. Wetland maps produced by multi-sources satellite images covering the entire basin between 1978 and 2008 were also utilized for investigating the responses and feedbacks of hydrological regimes on wetland dynamics. Results revealed that significant decreasing trends appeared in annual, spring and autumn streamflow demonstrated strong affection of precipitation and temperature changes over the study watershed, and the effects of climate change on the runoff reduction varied in the sub-basin area over different time scales. The proportion of evapotranspiration to precipitation characterized several severe fluctuations in droughts and floods took place in the region, which implied the enhanced sensitiveness and vulnerability of hydrologic regimes to changing environment of the region. Furthermore, it was found that the different types of wetlands undergone quite unique variation features with the varied hydro-meteorological conditions over the region, such as precipitation, evapotranspiration and soil moisture. This study provided effective scientific basis for water resource managers to develop effective eco-environment management plans and strategies that address the consequences of climate changes.

  12. Temporal dynamic of wood formation in Pinus cembra along the alpine treeline ecotone and the effect of climate variables.

    Science.gov (United States)

    Gruber, Andreas; Baumgartner, Daniel; Zimmermann, Jolanda; Oberhuber, Walter

    2009-06-01

    We determined the temporal dynamic of cambial activity and xylem development of stone pine (Pinus cembra L.) throughout the treeline ecotone. Repeated micro-sampling of the developing tree ring was carried out during the growing seasons 2006 and 2007 at the timberline (1950 m a.s.l.), treeline (2110 m a.s.l.) and within the krummholz belt (2180 m a.s.l.) and the influence of climate variables on intra-annual wood formation was determined.At the beginning of both growing seasons, highest numbers of cambial and enlarging cells were observed at the treeline. Soil temperatures at time of initiation of cambial activity were c. 1.5 °C higher at treeline (open canopy) compared to timberline (closed canopy), suggesting that a threshold root-zone temperature is involved in triggering onset of above ground stem growth.The rate of xylem cell production determined in two weekly intervals during June through August 2006-2007 was significantly correlated with air temperature (temperature sums expressed as degree-days and mean daily maximum temperature) at the timberline only. Lack of significant relationships between tracheid production and temperature variables at the treeline and within the krummholz belt support past dendroclimatological studies that more extreme environmental conditions (e.g., wind exposure, frost desiccation, late frost) increasingly control tree growth above timberline.Results of this study revealed that spatial and temporal (i.e. year-to-year) variability in timing and dynamic of wood formation of Pinus cembra is strongly influenced by local site factors within the treeline ecotone and the dynamics of seasonal temperature variation, respectively.

  13. Pesticide occurrence and spatio-temporal variability in urban run-off across Australia.

    Science.gov (United States)

    Rippy, Megan A; Deletic, Ana; Black, Jeff; Aryal, Rupak; Lampard, Jane-Louise; Tang, Janet Yat-Man; McCarthy, David; Kolotelo, Peter; Sidhu, Jatinder; Gernjak, Wolfgang

    2017-05-15

    Stormwater is a major driving factor of aquatic ecosystem degradation as well as one of the largest untapped urban freshwater resources. We present results from a long-term, multi-catchment study of urban stormwater pesticides across Australia that addresses this dichotomous identity (threat and resource), as well as dominant spatial and temporal patterns in stormwater pesticide composition. Of the 27 pesticides monitored, only 19 were detected in Australian stormwater, five of which (diuron, MCPA, 2,4-D, simazine, and triclopyr) were found in >50% of samples. Overall, stormwater pesticide concentrations were lower than reported in other countries (including the United States, Canada and Europe), and exceedances of public health and aquatic ecosystem standards were rare (stormwater pesticide composition was relatively stable across seasons and years, it varied significantly by catchment. Common pesticide associations appear to reflect 1) user application of common registered formulations containing characteristic suites of active ingredients, and 2) pesticide fate properties (e.g., environmental mobility and persistence). Importantly, catchment-specific occurrence patterns provide opportunities for focusing treatment approaches or stormwater harvesting strategies. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

  14. Spatial Patterns and Temporal Variability of Drought in Beijing-Tianjin-Hebei Metropolitan Areas in China

    Directory of Open Access Journals (Sweden)

    Wanyuan Cai

    2015-01-01

    Full Text Available Drought identification and assessment are essential for regional water resources management. In this paper, the spatiotemporal characteristics of drought were evaluated based on monthly precipitation data from 33 synoptic stations during the period of 1960–2010. The percent of normal precipitation was applied to illustrate the driest years in Beijing-Tianjin-Hebei metropolitan areas (BTHMA (1965, 1997, and 2002. The modified Reconnaissance Drought Index (RDI was applied to capture the drought patterns and to estimate the drought severity at 33 meteorological stations. Agglomerative hierarchical cluster analysis (AHCA and principal component analysis (PCA were used to identify three different drought subregions R1, R2, and R3 based on the monthly precipitation values in BTHMA, which is located in southeast, north, and south of BTHMA, respectively. The year 1965 was the driest and 1964 was the wettest during the observed period. The characteristics of drought were analyzed in terms of the temporal evolution of the RDI-12 values and the frequency of drought for the three identified regions. The percentage of years characterized by drought was 13.73% for R1, 16.50% for R2, and 15.53% for R3. 66.91% of drought belongs to the near normal drought category. The obtained results can aid to improve water resources management in the area.

  15. Impacts of Climate Variability on the Spatio-temporal Characteristics of Water Stress in Korea

    Science.gov (United States)

    Kim, Soojun; Devineni, Naresh; Lall, Upmanu; Kim, Hung Soo

    2017-04-01

    This study intended to evaluate water stress quantitatively targeted at the Korean Peninsula and to analyze the spatial and temporal characteristics of its occurrence. First, the severity and multiyear influence of water stress were analyzed by realizing water balance based on water supply and demand and by calculating the normalized deficit index (NDI) and the normalized deficit cumulated (NDC) for 113 small basins in the Korean Peninsula. Next, a change in the periodic characteristics of water stress was analyzed using wavelet transform of the NDI by small basins and 3 bands of periods of 1 year, 2-4 years, and 4-8 years were separated. Through an analysis of the empirical orthogonal function (EOF) on each band, it was found that water stress occurring in the Korean Peninsula has the characteristics of spatial distribution that it is extended from the south coast to the northern area and inland as its period gets longer. An analysis of the band with a period of 2-8 years for water stress showed that it has a relationship with El Niño-Southern Oscillation (ENSO). Acknowledgment This research was supported by a grant (14AWMP-B082564-01) from Advanced Water Management Research Program funded by Ministry of Land, Infrastructure and Transport of Korean government.

  16. Interindividual variability in functional connectivity as long-term correlate of temporal discounting.

    Directory of Open Access Journals (Sweden)

    Cinzia Calluso

    Full Text Available During intertemporal choice (IT future outcomes are usually devaluated as a function of the delay, a phenomenon known as temporal discounting (TD. Based on task-evoked activity, previous neuroimaging studies have described several networks associated with TD. However, given its relevance for several disorders, a critical challenge is to define a specific neural marker able to predict TD independently of task execution. To this aim, we used resting-state functional connectivity MRI (fcMRI and measured TD during economic choices several months apart in 25 human subjects. We further explored the relationship between TD, impulsivity and decision uncertainty by collecting standard questionnaires on individual trait/state differences. Our findings indicate that fcMRI within and between critical nodes of task-evoked neural networks associated with TD correlates with discounting behavior measured a long time afterwards, independently of impulsivity. Importantly, the nodes form an intrinsic circuit that might support all the mechanisms underlying TD, from the representation of subjective value to choice selection through modulatory effects of cognitive control and episodic prospection.

  17. Study of the spatial and temporal variability of local ecosystems and glaciers of the Antisana Volcano

    Directory of Open Access Journals (Sweden)

    Mauricio Valladares Borja

    2014-12-01

    Full Text Available (Received: 2014/10/31 - Accepted: 2014/12/15The scientific interest in climate change allowed to uncover evidence demonstrating a general warming trend caused by human activities. Facts such as rising sea levels, extreme weather events and retreat of glaciers, are indicators of the presence of alterations of normal weather patterns. In Ecuador, the Antisana is a stratovolcano of strategic importance affecting the climate of the region, in the functioning of the surrounding ecosystems. It is also a reserve of water for the population of the Metropolitan District of Quito (DMQ. The glaciers of the tropical volcano are also suffering the effects of global warming. Its decline over time is of concern and should be analyzed. The present research work performed a spatial and temporal study based on historical series of aerial photographs taken between 1956 and 2011, through geo-processing capabilities of geographic information systems (GIS. The results show a significant decrease in the glaciers of the Antisana Volcano and significant changes in the surrounding local ecological formations.

  18. Spatial and temporal variability in growth of southern flounder (Paralichthys lethostigma)

    Science.gov (United States)

    Midway, Stephen R.; Wagner, Tyler; Arnott, Stephen A.; Biondo, Patrick; Martinez-Andrade, Fernando; Wadsworth, Thomas F.

    2015-01-01

    Delineation of stock structure is important for understanding the ecology and management of many fish populations, particularly those with wide-ranging distributions and high levels of harvest. Southern flounder (Paralichthys lethostigma) is a popular commercial and recreational species along the southeast Atlantic coast and Gulf of Mexico, USA. Recent studies have provided genetic and otolith morphology evidence that the Gulf of Mexico and Atlantic Ocean stocks differ. Using age and growth data from four states (Texas, Alabama, South Carolina, and North Carolina) we expanded upon the traditional von Bertalanffy model in order to compare growth rates of putative geographic stocks of southern flounder. We improved the model fitting process by adding a hierarchical Bayesian framework to allow each parameter to vary spatially or temporally as a random effect, as well as log transforming the three model parameters (L∞, K, andt0). Multiple comparisons of parameters showed that growth rates varied (even within states) for females, but less for males. Growth rates were also consistent through time, when long-term data were available. Since within-basin populations are thought to be genetically well-mixed, our results suggest that consistent small-scale environmental conditions (i.e., within estuaries) likely drive growth rates and should be considered when developing broader scale management plans.

  19. Small scale temporal variability in the phytoplankton of Independencia Bay, Pisco, Perú

    Directory of Open Access Journals (Sweden)

    Noemí Ochoa

    2013-06-01

    Full Text Available Temporal variations at small scale of the coastal marine phytoplankton assemblages were studied. Water samples were collected at a fixed station in Bahia Independencia (Pisco-Peru. The sampling took place in the morning (08:00 h. and afternoon (15:00 h over a period of 29 days (March 28 to April 25, 1988. Surface temperatures also were taken, fluctuating from 15,4 °C to 17,2 °C. Diatoms were the principal component of the phytoplankton community and were more related with the total of phytoplankton. Other groups as Dinoflagellates, Coccolitophorids, Silicoflagellates and small flagellates were present but were less important. Skeletonema costatum was the dominant specie during the first nine days of sampling, after that it was substituted by Thalassionema nitzschioides, which remained as dominant until the end of the study. Small variation in species composition but large fluctuations in density of phytoplankton were recorded over a period of few hours. Small increments in temperature influenced in the phytoplankton assemblages.

  20. Temporal Variability of Aerosol Properties during TCAP: Impact on Radiative Forcing

    Energy Technology Data Exchange (ETDEWEB)

    Kassianov, Evgueni I.; Barnard, James C.; Pekour, Mikhail S.; Berg, Larry K.; Fast, Jerome D.; Michalsky, Joseph J.; Lantz, K.; Hodges, G. B.

    2013-11-01

    Ground-based remote sensing and in situ observations of aerosol microphysical and optical properties have been collected during summertime (June-August, 2012) as part of the Two-Column Aerosol Project (TCAP; http://campaign.arm.gov/tcap/), which was supported by the U.S. Department of Energy’s (DOE’s) Atmospheric Radiation Measurement (ARM) Program (http://www.arm.gov/). The overall goal of the TCAP field campaign is to study the evolution of optical and microphysical properties of atmospheric aerosol transported from North America to the Atlantic and their impact on the radiation energy budget. During TCAP, the ground-based ARM Mobile Facility (AMF) was deployed on Cape Cod, an arm-shaped peninsula situated on the easternmost portion of Massachusetts (along the east coast of the United States) and that is generally downwind of large metropolitan areas. The AMF site was equipped with numerous instruments for sampling aerosol, cloud and radiative properties, including a Multi-Filter Rotating Shadowband Radiometer (MFRSR), a Scanning Mobility Particle Sizer (SMPS), an Aerodynamic Particle Sizer (APS), and a three-wavelength nephelometer. In this study we present an analysis of diurnal and day-to-day variability of the column and near-surface aerosol properties obtained from remote sensing (MFRSR data) and ground-based in situ measurements (SMPS, APS, and nephelometer data). In particular, we show that the observed diurnal variability of the MFRSR aerosol optical depth is strong and comparable with that obtained previously from the AERONET climatology in Mexico City, which has a larger aerosol loading. Moreover, we illustrate how the variability of aerosol properties impacts the direct aerosol radiative forcing at different time scales.

  1. Spontaneous temporal changes and variability of peripheral nerve conduction analyzed using a random effects model

    DEFF Research Database (Denmark)

    Krøigård, Thomas; Gaist, David; Otto, Marit

    2014-01-01

    . Peroneal nerve distal motor latency, motor conduction velocity, and compound motor action potential amplitude; sural nerve sensory action potential amplitude and sensory conduction velocity; and tibial nerve minimal F-wave latency were examined in 51 healthy subjects, aged 40 to 67 years. They were...... reexamined after 2 and 26 weeks. There was no change in the variables except for a minor decrease in sural nerve sensory action potential amplitude and a minor increase in tibial nerve minimal F-wave latency. Reproducibility was best for peroneal nerve distal motor latency and motor conduction velocity...

  2. Linking imaging spectroscopy and trait data to better understand spatial and temporal variability in functional traits

    Science.gov (United States)

    Townsend, Philip; Kruger, Eric; Wang, Zhihui; Singh, Aditya

    2017-04-01

    Imaging spectroscopy exhibits great potential for mapping foliar functional traits that are impractical or expensive to regularly measure on the ground, and are essentially impossible to characterize comprehensively across space. Specifically, the high information content in spectroscopic data enables us to identify narrow spectral feature that are associated with vegetation primary and secondary biochemistry (nutrients, pigments, defensive compounds), leaf structure (e.g., leaf mass per area), canopy structure, and physiological capacity. Ultimately, knowledge of the variability in such traits is critical to understanding vegetation productivity, as well as responses to climatic variability, disturbances, pests and pathogens. The great challenge to the use of imaging spectroscopy to supplement trait databases is the development of trait retrieval approaches that are broadly applicable within and between ecosystem types. Here, we outline how we are using the US National Ecological Observatory Network (NEON) to prototype the scaling and comparison of trait distributions derived from field measurements and imagery. We find that algorithms to map traits from imagery are robust across ecosystem types, when controlling for physiognomy and vegetation percent cover, and that among all vegetation types, the chemometric algorithms utilize similar features for mapping of traits.

  3. Spatio-temporal variability and the impact of Phailin on water quality of Chilika lagoon

    Science.gov (United States)

    Barik, Saroja K.; Muduli, Pradipta R.; Mohanty, Bita; Behera, Alaya T.; Mallick, Suprava; Das, Abhijit; Samal, R. N.; Rastogi, Gurdeep; Pattnaik, Ajit K.

    2017-03-01

    Chilika, Asia's largest brackish water lagoon was studied for 4 years (2011-2015) to understand the variability of water quality and the impact of a very severe cyclone storm ;Phailin; (Category-5). During the study period environmental variables exhibited a significant variation among sectors, seasons, and years (pinflux. Principal component analysis revealed that the biological factor and riverine flux mostly controlled the water quality. The overall 'water quality Index' indicated that the ecological health of the Chilika lagoon was ;Good;. The Phailin had a notable impact on water quality as substantiated by the trends of several parameters. The decrease in nitrate and phosphate after Phailin was attributed to dilution by low nutrient freshwater flux from major rivers whereas, the significant increase in reactive silicate was attributed to mixing of silicate enriched fresh water. Post Phailin increase in dissolved oxygen and chlorophyll-a was attributed to wind-induced mixing and resuspension of benthic chlorophyll respectively. A substantial change of nutrient stoichiometry and decrease in photic depth after Phailin resulted a pull down of primary productivity in the Chilika lagoon.

  4. Spatio-temporal variability in the GDH activity to ammonium excretion ratio in epipelagic marine zooplankton

    Science.gov (United States)

    Fernández-Urruzola, I.; Osma, N.; Packard, T. T.; Maldonado, F.; Gómez, M.

    2016-11-01

    Glutamate dehydrogenase (GDH) activities have been widely used in oceanographic research as an index of in situ NH4+ excretion rates (RNH4+) in zooplankton. Here we study the variability in the relationship between the enzymatic rates and the actual rates measured in epipelagic marine zooplankton between several marine ecosystems. Although both measures were significantly correlated across zooplankton assemblages, the regression models yielded different GDH/RNH4+ ratios across ecosystems. Accordingly, the error of a general equation increased up to ±42.5 % when regressing all our data together. Aside from possible interspecific differences, some of the variability was explained by the unequal allometric relation that each rate maintained with protein. Scaling exponents were 1.38 for GDH activities and 0.87 for RNH4+, which would induce uncertainties in the GDH/RNH4+ ratios when organisms with different sizes were considered. Nevertheless, the main factor causing divergence between GDH activities and RNH4+ was the potential prey availability. We compared the excretory metabolism of the zooplankton community at different productivity periods in waters off Gran Canaria, and observed an important decrease in the RNH4+ during stratification. A similar decrease was found in the internal pool of glutamate, which may be critical in the regulation of in vivo rates. Strengthening our knowledge of the relationship between GDH activities and the RNH4+ will lead to more meaningful predictions of phytoplankton regeneration and community nitrogen fluxes across large spatial scales.

  5. Spatial contexts for temporal variability in alpine vegetation under ongoing climate change

    Science.gov (United States)

    Fagre, Daniel B.; ,; George P. Malanson,

    2013-01-01

    A framework to monitor mountain summit vegetation (The Global Observation Research Initiative in Alpine Environments, GLORIA) was initiated in 1997. GLORIA results should be taken within a regional context of the spatial variability of alpine tundra. Changes observed at GLORIA sites in Glacier National Park, Montana, USA are quantified within the context of the range of variability observed in alpine tundra across much of western North America. Dissimilarity is calculated and used in nonmetric multidimensional scaling for repeated measures of vascular species cover at 14 GLORIA sites with 525 nearby sites and with 436 sites in western North America. The lengths of the trajectories of the GLORIA sites in ordination space are compared to the dimensions of the space created by the larger datasets. The absolute amount of change on the GLORIA summits over 5 years is high, but the degree of change is small relative to the geographical context. The GLORIA sites are on the margin of the ordination volumes with the large datasets. The GLORIA summit vegetation appears to be specialized, arguing for the intrinsic value of early observed change in limited niche space.

  6. Spatial and Temporal Variability of Winter Accumulation on Taku Glacier, Southeast Alaska, between 2012 and 2015

    Science.gov (United States)

    Smith, B.; Campbell, S. W.; Hollander, J.; Slavin, B. V.; Wolf, J.; Wilner, J.; Moore, T.

    2015-12-01

    Glacier mass balance is an integral part of understanding a glacier's health and dynamics. A key component of determining mass balance is winter accumulation which is traditionally estimated by digging and measuring snow densities from within snow pits. However, this method represents a labor-intensive point measurement which may not fully capture spatial variability of accumulation. To more efficiently estimate spatial variability of winter accumulation across Taku Glacier and its main tributaries in southeastern Alaska in 2015, we used a 400 MHz Ground Penetrating Radar (GPR) Common Offset (CO) surveys along centerline transects which were also collected during a 2012 study. We used common midpoint (CMP) surveys, migration, snow pits, and probing to improve depth estimates and provide ground truth of winter accumulation depth measurements from CO surveys. We determined that the winter accumulation was significantly lower in 2015 than in 2012. However, gradients in accumulation versus elevation were consistent from year to year along centerline transects. We suggest that this low accumulation may be influencing the recent two year stall of Taku Glacier which has exhibited an advancing terminus for nearly a century. We recommend that further studies be conducted to extend the reach of this dataset beyond 2 years. This data would be invaluable to future models and mass balance studies on the Icefield and may capture key components that suggest a tipping point from advance to retreat of Taku Glacier.

  7. Análisis de las variables sociosanitarias asociadas a la permanencia en incapacidad temporal

    Directory of Open Access Journals (Sweden)

    M.ª Luz Pérez Morote

    2015-06-01

    Full Text Available Introducción: La incapacidad temporal (IT constituye un proceso de origen multifactorial. Objetivo: Evaluar el proceso de IT en relación con la enfermedad, estado de salud, satisfacción laboral, perfil de locus de control y características sociodemográficas. Método: Estudio observacional de cohortes prospectivo sobre 404 pacientes en IT. Realizamos un análisis de supervivencia describiendo la evolución de los participantes en cuanto a su permanencia en IT. Resultados: La permanencia media en IT fue significativamente superior (p<0,05 en sujetos con nivel de instrucción bajo (9,4 meses, trabajadores manuales (8,5 meses, mayores de 60 años (10,0 meses, pacientes insatisfechos laboralmente (9,3 meses, con baja autopercepción de salud (10,2 meses, consumidores de medicación crónica (10,6 meses, fumadores (9,3 meses y consumidores de drogas no institucionalizadas (10,5 meses. Tras el análisis multivariante, se asocian a una menor duración de la IT: las enfermedades del aparato locomotor, sistema cardiorrespiratorio o problemas psicológicos, un nivel de instrucción alto, una buena autopercepción de salud y la abstención en el consumo de tóxicos. Conclusiones: Además de la enfermedad, otros factores relacionados con la percepción del estado de salud, características sociodemográficas y el estilo de vida, influyen de manera significativa en la reincorporación de un trabajador a su actividad laboral.

  8. Spatio-temporal variability of periphytic protozoa related to environment in the Niyang River, Tibet, China

    Science.gov (United States)

    Liu, Haiping; Ye, Shaowen; Yang, Xuefeng; Guo, Chuanbo; Zhang, Huijuan; Fan, Liqing; Zhang, Liangsong; Sovan, Lek; Li, Zhongjie

    2017-05-01

    The Niyang River, a main tributary of the Yarlung Zangbo River, is an important and typical plateau river ecosystem in Tibet, China. At present, few studies have focused on its aquatic living resources and river ecology. In this study, the composition, abundance, and diversity of periphytic protozoa were investigated across four seasons from 2008 to 2009 to better understand their spatio-temporal patterns and relationship to the environment. Our investigation shows that periphytic protozoa in the Niyang River contained 15 genera, belonged to Tubulinea, Alveolata, Discosea and Rhizaria, Alveolata possessed most genera, up to nine, with highest share in abundance, exceeding 50%, Difflugia and Glaucoma were dominant genera. Moreover, four diversity indices of periphytic protozoa, including species richness, total abundance, Shannon-Wiener diversity index and Pielou's evenness index, displayed a significant descending trend as the seasons continued, in the order of winter, spring, summer and autumn; with a significant difference existing between winter and summer (or autumn) for Shannon-Wiener diversity index and species richness ( P0.05). In addition, canonical correlation analysis (CCA) shows that the densities of Difflugia, Glaucomais, Enchelydium, Cyphoderia, and Enchelys correlate with water temperature, alkalinity, hardness, pH, and dissolved oxygen, respectively. Lastly, the relationship between periphytic protozoa diversity and the environmental factors of the Niyang River can be predicted using classification and regression trees (CART) annalysis, which suggests that the total abundance and Shannon-Wiener diversity index would be higher when the elevation is above 3 308 m. On the other hand, the Shannon-Wiener diversity index and Pielou's evenness index would be lower when pH and ammoniacal nitrogen have lower or higher values. Finally yet importantly, close attention should be paid to periphytic protozoa and its environment to ensure sustainable development

  9. Spatial and Temporal Variability of Potential Evaporation across North American Forests

    Directory of Open Access Journals (Sweden)

    Robbie A. Hember

    2017-01-01

    Full Text Available Given the widespread ecological implications that would accompany any significant change in evaporative demand of the atmosphere, this study investigated spatial and temporal variation in several accepted expressions of potential evaporation (PE. The study focussed on forest regions of North America, with 1 km-resolution spatial coverage and a monthly time step, from 1951–2014. We considered Penman’s model (EPen, the Priestley–Taylor model (EPT, ‘reference’ rates based on the Penman–Monteith model for grasslands (ERG, and reference rates for forests that are moderately coupled (ERFu and well coupled (ERFc to the atmosphere. To give context to the models, we also considered a statistical fit (EPanFit to measurements of pan evaporation (EPan. We documented how each model compared with EPan, differences in attribution of variance in PE to specific driving factors, mean spatial patterns, and time trends from 1951–2014. The models did not agree strongly on the sensitivity to underlying drivers, zonal variation of PE, or on the magnitude of trends from 1951–2014. Sensitivity to vapour pressure deficit (Da differed among models, being absent from EPT and strongest in ERFc. Time trends in reference rates derived from the Penman–Monteith equation were highly sensitive to how aerodynamic conductance was set. To the extent that EPanFit accurately reflects the sensitivity of PE to Da over land surfaces, future trends in PE based on the Priestley–Taylor model may underestimate increasing evaporative demand, while reference rates for forests, that assume strong canopy-atmosphere coupling in the Penman–Monteith model, may overestimate increasing evaporative demand. The resulting historical database, covering the spectrum of different models of PE applied in modern studies, can serve to further investigate biosphere-hydroclimate relationships across North America.

  10. The effects of temporally variable dispersal and landscape structure on invasive species spread.

    Science.gov (United States)

    Andrew, Margaret E; Ustin, Susan L

    2010-04-01

    Many invasive species are too widespread to realistically eradicate. For such species, a viable management strategy is to slow the rate of spread. However, to be effective, this will require detailed spread data and an understanding of the influence of environmental conditions and landscape structure on invasion rates. We used a time series of remotely sensed distribution maps and a spatial simulation model to study spread of the invasive Lepidium latifolium (perennial pepperweed) in California's Sacramento-San Joaquin River Delta. L. latifolium is a noxious weed and exhibited rapid, explosive spread. Annual infested area and empirical dispersal kernels were derived from the remotely sensed distributions in order to assess the influence of weather conditions on spread and to parameterize the simulation model. Spread rates and dispersal distances were highest for nascent infestations and in years with wet springs. Simulations revealed that spread rates were more strongly influenced by the length of long-distance dispersal than by temporal variation in its likelihood. It is thus important to capture long-distance dispersal and the conditions that facilitate spread when collecting data to parameterize spread models. Additionally, management actions performed in high-spread years, targeting long-distance recruits, can effectively contain infestations. Corridors were relatively unimportant to spread rates; their effectiveness at enhancing rate of spread was limited by the species' dispersal ability and the time needed to travel through the corridor. In contrast, habitat abundance and shape surrounding the introduction site strongly influenced invasion dynamics. Satellite patches invading large areas of invasible habitat present especially high risk.

  11. Spatial and temporal variability in desert dust and anthropogenic pollution in Iraq, 1997-2010.

    Science.gov (United States)

    Chudnovsky, A Alexandra; Koutrakis, Petros; Kostinski, Alex; Proctor, Susan P; Garshick, Eric

    2017-01-01

    Satellite imaging has emerged as a method for monitoring regional air pollution and detecting areas of high dust concentrations. Unlike ground observations, continuous data monitoring is available with global coverage of terrestrial and atmospheric components. In this study we test the utility of different sources of satellite data to assess air pollution concentrations in Iraq. SeaWiFS and MODIS Deep Blue (DB) aerosol optical depth (AOD) products were evaluated and used to characterize the spatial and temporal pollution levels from the late 1990s through 2010. The AOD and Ångström exponent (an indicator of particle size, since smaller Ångström exponent values reflect a source that includes larger particles) were correlated on 50 × 50 km spatial resolution. Generally, AOD and Ångström exponent were inversely correlated, suggesting a significant contribution of coarse particles from dust storms to AOD maxima. Although the majority of grid cells exhibited this trend, a weaker relationship in other locations suggested an additional contribution of fine particles from anthropogenic sources. Tropospheric NO2 densities from the OMI satellite were elevated over cities, also consistent with a contribution from anthropogenic sources. Our analysis demonstrates the use of satellite imaging data to estimate relative pollution levels and source contributions in areas of the world where direct measurements are not available. The authors demonstrated how satellite data can be used to characterize exposures to dust and to anthropogenic pollution for future health related studies. This approach is of a great potential to investigate the associations between subject-specific exposures to different pollution sources and their health effects in inaccessible regions and areas where ground monitoring is unavailable.

  12. Thaw depth spatial and temporal variability at the Limnopolar Lake CALM-S site, Byers Peninsula, Livingston Island, Antarctica.

    Science.gov (United States)

    de Pablo, M A; Ramos, M; Molina, A; Prieto, M

    2018-02-15

    A new Circumpolar Active Layer Monitoring (CALM) site was established in 2009 at the Limnopolar Lake watershed in Byers Peninsula, Livingston Island, Antarctica, to provide a node in the western Antarctic Peninsula, one of the regions that recorded the highest air temperature increase in the planet during the last decades. The first detailed analysis of the temporal and spatial evolution of the thaw depth at the Limnopolar Lake CALM-S site is presented here, after eight years of monitoring. The average values range between 48 and 29cm, decreasing at a ratio of 16cm/decade. The annual thaw depth observations in the 100×100 m CALM grid are variable (Variability Index of 34 to 51%), although both the Variance Coefficient and the Climate Matrix Analysis Residual point to the internal consistency of the data. Those differences could be explained then by the terrain complexity and node-specific variability due to the ground properties. The interannual variability was about 60% during 2009-2012, increasing to 124% due to the presence of snow in 2013, 2015 and 2016. The snow has been proposed here as one of the most important factors controlling the spatial variability of ground thaw depth, since its values correlate with the snow thickness but also with the ground surface temperature and unconfined compression resistance, as measured in 2010. The topography explains the thaw depth spatial distribution pattern, being related to snowmelt water and its accumulation in low-elevation areas (downslope-flow). Patterned grounds and other surface features correlate well with high thaw depth patterns as well. The edaphic factor (E=0.05842m2/°C·day; R2=0.63) is in agreement with other permafrost environments, since frozen index (F>0.67) and MAAT (CALM sites. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Decoupled temporal variability and signal synchronization of spontaneous brain activity in loss of consciousness: An fMRI study in anesthesia.

    Science.gov (United States)

    Huang, Zirui; Zhang, Jun; Wu, Jinsong; Qin, Pengmin; Wu, Xuehai; Wang, Zhiyao; Dai, Rui; Li, Yuan; Liang, Weimin; Mao, Ying; Yang, Zhong; Zhang, Jianfeng; Wolff, Annemarie; Northoff, Georg

    2016-01-01

    Two aspects of the low frequency fluctuations of spontaneous brain activity have been proposed which reflect the complex and dynamic features of resting-state activity, namely temporal variability and signal synchronization. The relationship between them, especially its role in consciousness, nevertheless remains unclear. Our study examined the temporal variability and signal synchronization of spontaneous brain activity, as well as their relationship during loss of consciousness. We applied an intra-subject design of resting-state functional magnetic resonance imaging (rs-fMRI) in two conditions: during wakefulness, and under anesthesia with clinical unconsciousness. In addition, an independent group of patients with disorders of consciousness (DOC) was included in order to test the reliability of our findings. We observed a global reduction in the temporal variability, local and distant brain signal synchronization for subjects during anesthesia. Importantly, we found a link between temporal variability and both local and distant signal synchronizations during wakefulness: the higher the degree of temporal variability, the higher its intra-regional homogeneity and inter-regional functional connectivity. In contrast, this link was broken down under anesthesia, implying a decoupling between temporal variability and signal synchronization; this decoupling was reproduced in patients with DOC. Our results suggest that there exist some as yet unclear physiological mechanisms of consciousness which "couple" the two mathematically independent measures, temporal variability and signal synchronization of spontaneous brain activity. Our findings not only extend our current knowledge of the neural correlates of anesthetic-induced unconsciousness, but have implications for both computational neural modeling and clinical practice, such as in the diagnosis of loss of consciousness in patients with DOC. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Temporal Learning and Rhythmic Responding: No Reduction in the Proportion Easy Effect with Variable Response-Stimulus Intervals

    Directory of Open Access Journals (Sweden)

    James R Schmidt

    2016-05-01

    Full Text Available The present report further investigates the proportion easy effect, a conflict-free version of the proportion congruent effect. In the proportion easy paradigm, it is observed that the difference in performance between easy (high contrast and hard (low contrast items is smaller in a task with mostly hard items relative to a task with mostly easy items. This effect has been interpreted as evidence for temporal learning: participants learn a faster pace (i.e., rhythm of responding in the mostly easy context, which boosts the contrast effect, and a slower pace in the mostly hard context. In the present experiment, intervals between trials were either fixed or randomly varied from trial to trial. Interestingly, the proportion easy effect was still present with variable intervals. These data suggest that participants do not learn the regularity in timing from one response to the next (which was highly inconsistent with variable intervals. As one alternative, participants might be learning the intervals between stimulus onset and responses, which were not manipulated. They could then use this learned timing information to prepare for responding at the anticipated time, resulting in rhythmic responding. The results further imply that variable response-stimulus intervals are insufficient for controlling for rhythmic biases.

  15. Temporal variation of Black Carbon concentration using Aethalometer observations and its relationships with meteorological variables in Karachi, Pakistan

    Science.gov (United States)

    Bibi, Samina; Alam, Khan; Chishtie, Farrukh; Bibi, Humera; Rahman, Said

    2017-05-01

    Black Carbon (BC) mass concentration was measured continuously for every five-minute interval with ground-based Aethalometer at an urban site in Karachi for the period from 2006 to 2008. In this study, the temporal (diurnal, monthly and seasonal) variations of BC and its relationship with meteorological variables were analyzed. Monthly averaged concentrations of BC ranged from 2.2 to 12.5 μg/m3, with maximum in the month of January 2007 and minimum in the month of June 2006. BC showed higher concentrations during the months of January, February and November while lower during the months of May, June, July and August throughout the years. It also displayed comparatively high concentrations during winter and postmonsoon, while moderate during premonsoon and low during summer. Diurnal analysis of BC concentration showed sharp peaks between 07:00 and 09:00 LST and again around 22:00 during all the months. Moreover, the relationship between BC concentration and meteorological variables such as Temperature (Temp), Relative Humidity (RH), Wind Speed (WS), Visibility (VIS) and RainFall (RF) was found and it was observed that BC concentration showed an inverse relationship with all these meteorological variables. Finally, the analysis of the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) cluster trajectories revealed that almost all the clusters were originating from southwest of the study site.

  16. Speciated mercury at marine, coastal, and inland sites in New England - Part 1: Temporal variability

    Science.gov (United States)

    Mao, H.; Talbot, R.

    2012-06-01

    A comprehensive analysis was conducted using long-term continuous measurements of gaseous elemental mercury (Hg0), reactive gaseous mercury (RGM), and particulate phase mercury (HgP) at coastal (Thompson Farm, denoted as TF), marine (Appledore Island, denoted as AI), and elevated inland (Pac Monadnock, denoted as PM) sites from the AIRMAP Observatories in southern New Hampshire, USA. Decreasing trends in background Hg0 were identified in the 7.5- and 5.5-yr records at TF and PM with decline rates of 3.3 parts per quadrillion by volume (ppqv) yr-1 and 6.3 ppqv yr-1, respectively. Common characteristics at these sites were the reproducible annual cycle of Hg0 with its maximum in winter-spring and minimum in fall, comprised of a positive trend in the warm season (spring - early fall) and a negative one in the cool season (late fall - winter). Year-to-year variability was observed in the warm season decline in Hg0 at TF varying from a minimum total (complete) seasonal loss of 43 ppqv in 2009 to a maximum of 92 ppqv in 2005, whereas variability remained small at AI and PM. The coastal site TF differed from the other two sites with its exceptionally low levels (as low as below 50 ppqv) in the nocturnal inversion layer possibly due to dissolution in dew water. Measurements of Hg0 at PM exhibited the smallest diurnal to annual variability among the three environments, where peak levels rarely exceeded 250 ppqv and the minimum was typically 100 ppqv. It should be noted that summertime diurnal patterns at TF and AI were opposite in phase indicating strong sink(s) for Hg0 during the day in the marine boundary layer, which was consistent with the hypothesis of Hg0 oxidation by halogen radicals there. Mixing ratios of RGM in the coastal and marine boundary layers reached annual maxima in spring and minima in fall, whereas at PM levels were generally below the limit of detection (LOD) except in spring. RGM levels at AI were higher than at TF and PM indicating a stronger source

  17. Spatial and Temporal Variability of Remotely Sensed Ocean Color Parameters in Coral Reef Regions

    Science.gov (United States)

    Otis, Daniel Brooks

    The variability of water-column absorption due to colored dissolved organic matter (CDOM) and phytoplankton in coral reef regions is the focus of this study. Hydrographic and CDOM absorption measurements made on the Bahamas Banks and in Exuma Sound during the spring of 1999 and 2000 showed that values of salinity and CDOM absorption at 440nm were higher on the banks (37.18 psu, 0.06 m. -1), compared to Exuma Sound (37.04 psu, 0.03 m. -1). Spatial patternsof CDOM absorption in Exuma Sound revealed that plumes of CDOM-rich water flow into Exuma Sound from the surrounding banks. To examine absorption variability in reef regions throughout the world, a thirteen-year time series of satellite-derived estimates of water-column absorption due to CDOM and phytoplankton were created from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer (MODIS) data. Time series data extracted adjacent to coral reef regions showed that variability in absorption depends on oceanographic conditions such as circulation patterns and winds as well as proximity to sources of light-absorbing materials that enter the water column, such as from terrestrial runoff. Waters near reef regions are generally clear, exhibiting a lower "baseline" level of CDOM absorption of approximately 0.01 m. -1 at 443nm. The main differences between regions lie in the periodsduring the year when increased levels of absorption are observed, which can be triggered by inputs of terrestrially-derived material, as in the Great Barrier Reef lagoon, or wind-driven upwelling as in the Andaman Sea and eastern Pacific Ocean near Panama. The lowest CDOM absorption levels found were approximately 0.003 m. -1 at 443nm near the islands of Palau and Yap, which are removed fromsources of colored materials. The highest absorption levels near reefs were associated with wind-driven upwelling during the northeast monsoon on the Andaman coast of Thailand where values of CDOM absorption at 443nm

  18. Spatio-temporal variability of phytoplankton dimensional classes in the Mediterranean Sea from satellite data

    Science.gov (United States)

    Sammartino, Michela; Di Cicco, Annalisa; Marullo, Salvatore; Santoleri, Rosalia

    2016-04-01

    Phytoplankton contributes to fix half of the carbon dioxide released on Earth, becoming a key component not only in the carbon cycle, but also in several biogeochemical cycles. It is involved in the control of greenhouse gases and, consequently, in the effect of climate change on marine system. Therefore, phytoplankton is often considered one of the most common bio-indicator for any environmental changes, which, in turn, can affect the algal community composition and structure. The alteration of the biological, physical and chemical conditions in the ocean can be reflected in the algal assemblage structure, in terms of variation of dominant size class and taxonomic composition. In this work, the seasonal and year-to-year variability of the phytoplankton size class (PSC) spatial distribution has been examined in the Mediterranean Sea using ten year of satellite observations. The estimation of PSCs from space is based on relationship between chlorophyll a (Chl a) and diagnostic pigments that should be verified at regional scales. Our analysis shows that the Mediterranean pigments ratios differs from the global ones; therefore, we regionalized the mathematical relation existing between the Chl a and the diagnostic pigments, used in the in situ PSC identification. This regionally tuned relation allowed to improve the estimation of PSCs from space by reducing the observed bias between modelled and measured PSCs. The analysis of PSC satellite time series allowed, for the first time, to have a quantitative description of the seasonal and inter-annual variability of the spatial distribution of the algal community in the Mediterranean Sea. The results demonstrated that the pico-phytoplankton contributes with high values to the total Chl a, especially in summer and in ultra-oligotrophic environments, such as the Levantine basin. Micro-phytoplankton contribution results high during spring bloom period in offshore areas, characterized by a strong water mixing; while, in

  19. Exploring the spatio-temporal relationship between two key aeroallergens and meteorological variables in the United Kingdom.

    Science.gov (United States)

    Khwarahm, Nabaz; Dash, Jadunandan; Atkinson, Peter M; Newnham, R M; Skjøth, C A; Adams-Groom, B; Caulton, Eric; Head, K

    2014-05-01

    Constructing accurate predictive models for grass and birch pollen in the air, the two most important aeroallergens, for areas with variable climate conditions such as the United Kingdom, require better understanding of the relationships between pollen count in the air and meteorological variables. Variations in daily birch and grass pollen counts and their relationship with daily meteorological variables were investigated for nine pollen monitoring sites for the period 2000-2010 in the United Kingdom. An active pollen count sampling method was employed at each of the monitoring stations to sample pollen from the atmosphere. The mechanism of this method is based on the volumetric spore traps of Hirst design (Hirst in Ann Appl Biol 39(2):257-265, 1952). The pollen season (start date, finish date) for grass and birch were determined using a first derivative method. Meteorological variables such as daily rainfall; maximum, minimum and average temperatures; cumulative sum of Sunshine duration; wind speed; and relative humidity were related to the grass and birch pollen counts for the pre-peak, post peak and the entire pollen season. The meteorological variables were correlated with the pollen count data for the following temporal supports: same-day, 1-day prior, 1-day mean prior, 3-day mean prior, 7-day mean prior. The direction of influence (positive/negative) of meteorological variables on pollen count varied for birch and grass, and also varied when the pollen season was treated as a whole season, or was segmented into the pre-peak and post-peak seasons. Maximum temperature, sunshine duration and rainfall were the most important variables influencing the count of grass pollen in the atmosphere. Both maximum temperature (pre-peak) and sunshine produced a strong positive correlation, and rain produced a strong negative correlation with grass pollen count in the air. Similarly, average temperature, wind speed and rainfall were the most important variables influencing

  20. Temporal and spatial variability of soil hydraulic properties with implications on soil moisture simulations and irrigation scheduling

    Science.gov (United States)

    Feki, Mouna; Ravazzani, Giovanni; Mancini, Marco

    2017-04-01

    The increase in consumption of water resources, combined with climate change impacts, calls for new sources of water supply and/or different managements of available resources in agriculture. One way to increase the quality and quantity of agricultural production is using modern technology to make farms more "intelligent", the so-called "precision agriculture" also known as 'smart farming'. To this aim hydrological models play crucial role for their ability to simulate water movement from soil surface to groundwater and to predict onset of stress condition. However, optimal use of mathematical models requires intensive, time consuming and expensive collection of soil related parameters. Typically, soils to be characterized, exhibit large variations in space and time as well during the cropping cycle, due to biological processes and agricultural management practices: tillage, irrigation, fertilization and harvest. Soil properties are subjected to diverse physical and chemical changes that lead to a non-stability in terms of water and chemical movements within the soil and to the groundwater as well. The aim of this study is to assess the variability of soil hydraulic properties over a cropping cycle. The study site is a surface irrigated Maize field located in Secugnago (45◦13'31.70" N, 9 ◦36'26.82 E), in Northern Italy-Lombardy region. The field belongs to the Consortium Muzza Bassa Lodigiana, within which meteorological data together with soil moisture were monitored during the cropping season of 2015. To investigate soil properties variations, both measurements in the field and laboratory tests on both undisturbed and disturbed collected samples were performed. Soil samples were taken from different locations within the study area and at different depths (surface, 20cm and 40cm) at the beginning and in the middle of the cropping cycle and after the harvest. During three measuring campaigns, for each soil samples several parameters were monitored (Organic

  1. Cluster analysis applied to the spatial and temporal variability of monthly rainfall in Mato Grosso do Sul State, Brazil

    Science.gov (United States)

    Teodoro, Paulo Eduardo; de Oliveira-Júnior, José Francisco; da Cunha, Elias Rodrigues; Correa, Caio Cezar Guedes; Torres, Francisco Eduardo; Bacani, Vitor Matheus; Gois, Givanildo; Ribeiro, Larissa Pereira

    2016-04-01

    The State of Mato Grosso do Sul (MS) located in Brazil Midwest is devoid of climatological studies, mainly in the characterization of rainfall regime and producers' meteorological systems and rain inhibitors. This state has different soil and climatic characteristics distributed among three biomes: Cerrado, Atlantic Forest and Pantanal. This study aimed to apply the cluster analysis using Ward's algorithm and identify those meteorological systems that affect the rainfall regime in the biomes. The rainfall data of 32 stations (sites) of the MS State were obtained from the Agência Nacional de Águas (ANA) database, collected from 1954 to 2013. In each of the 384 monthly rainfall temporal series was calculated the average and applied the Ward's algorithm to identify spatial and temporal variability of rainfall. Bartlett's test revealed only in January homogeneous variance at all sites. Run test showed that there was no increase or decrease in trend of monthly rainfall. Cluster analysis identified five rainfall homogeneous regions in the MS State, followed by three seasons (rainy, transitional and dry). The rainy season occurs during the months of November, December, January, February and March. The transitional season ranges between the months of April and May, September and October. The dry season occurs in June, July and August. The groups G1, G4 and G5 are influenced by South Atlantic Subtropical Anticyclone (SASA), Chaco's Low (CL), Bolivia's High (BH), Low Levels Jet (LLJ) and South Atlantic Convergence Zone (SACZ) and Maden-Julian Oscillation (MJO). Group G2 is influenced by Upper Tropospheric Cyclonic Vortex (UTCV) and Front Systems (FS). The group G3 is affected by UTCV, FS and SACZ. The meteorological systems' interaction that operates in each biome and the altitude causes the rainfall spatial and temporal diversity in MS State.

  2. Spatio-temporal variability of Δ13C in tree-rings of Aleppo pine

    Science.gov (United States)

    del Castillo, Jorge; Ferrio, Juan Pedro; Voltas, Jordi

    2014-05-01

    Aim: To study the spatiotemporal variability of Δ13C using a tree-ring network of Aleppo pine (Pinus halepensis Mill.) in the eastern part of the Iberian Peninsula. In this study, we tried to understand some of the environmental drivers behind changes in Δ13C as well as to decide the most optimal sites to infer paleoclimatic information using such variables. We also try to understand key physiological aspects of P. halepensis. Methods: In order to do that, we have collected biannual Δ13C time series (1950-1998) together with mean annual precipitation (MAP), tree-ring width (TRW) and remote sensing (NDVI) data, for 7 different locations along a precipitation gradient. We assessed how correlations between variables changed along that gradient. In addition to that, we have also looked at how that precipitation gradient changed along the years and thus its relationships with the Δ13C at the spatial level, giving us an idea whether changes in MAP at each site could affect the relationship between these two variables. Results: We found that a log model better explains the relationship between Δ13C and MAP and that it reaches a saturation point at values above 800 mm of MAP. Similarly, we found that, in the drier sites, correlations between Δ13C and precipitation were higher than in wetter ones. In addition, the coefficient of variation (CV) of Δ13C was a good indicator of the correlation between Δ13C and MAP. Similarly, the mean and the CV of TRW and summer NDVI were good indicators of the level of such correlation between Δ13C and MAP. On the other hand, the inter-site analysis of the data suggested that during dry years exists a stronger relationship between Δ13C and precipitation than in wet years. Discussion: Our results pointed out that the threshold for water limitation for Aleppo pine was around MAP=800 mm, an amount that might be sufficient for the tree to grow during most of the growing season without altering its water use efficiency (WUE) by closing

  3. Squeezing more information out of time variable gravity data with a temporal decomposition approach

    DEFF Research Database (Denmark)

    Barletta, Valentina Roberta; Bordoni, A.; Aoudia, A.

    2012-01-01

    A measure of the Earth's gravity contains contributions from solid Earth as well as climate-related phenomena, that cannot be easily distinguished both in time and space. After more than 7years, the GRACE gravity data available now support more elaborate analysis on the time series. We propose...... to design a screening algorithm to identify regions where anomalous gravity variations deserve further investigations. It also allows to raise the amount of information one can obtain exclusively from gravity data, prior and preliminary to any subsequent specifically targeted study. This approach has been...... used to assess the possibility of finding evidence of meaningful geophysical signals different from hydrology over Africa in GRACE data. In this case we conclude that hydrological phenomena are dominant and so time variable gravity data in Africa can be directly used to calibrate hydrological models....

  4. The effect of temporal variability in salinity on the invasive red alga Gracilaria vermiculophylla

    DEFF Research Database (Denmark)

    Nejrup, Lars Brammer; Pedersen, Morten Foldager

    2012-01-01

    become abundant in many shallow, soft-bottom estuaries. Salinity is important for the local and regional distribution of algae. The distribution of G. vermiculophylla in Europe suggests that it thrives well in hyposaline environments and that it may be more fit than some native algae under...... such conditions. Little, however, is known about the ecophysiology of G. vermiculophylla and it is therefore difficult to predict its spread and future distribution. Laboratory experiments with G. vermiculophylla showed that steady-state salinity above 15 psu was optimal for growth and that the growth rate...... was reduced at salinities below 15 psu. Variable salinity reduced the growth rate and larger oscillations were more stressful than small ones. Exposure to very low salinity (0–5 psu) was stressful for the alga and algae exposed to these low levels for 2–4 days were unable to recover fully. Gracilaria...

  5. Spatial and temporal variability of nitrous oxide emissions in a mixed farming landscape of Denmark

    Directory of Open Access Journals (Sweden)

    K. Schelde

    2012-08-01

    Full Text Available Nitrous oxide (N2O emissions from agricultural land are variable at the landscape scale due to variability in land use, management, soil type, and topography. A field experiment was carried out in a typical mixed farming landscape in Denmark, to investigate the main drivers of variations in N2O emissions, measured using static chambers. Measurements were made over a period of 20 months, and sampling was intensified during two weeks in spring 2009 when chambers were installed at ten locations or fields to cover different crops and topography and slurry was applied to three of the fields. N2O emissions during spring 2009 were relatively low, with maximum values below 20 ng N m−2 s−1. This applied to all land use types including winter grain crops, grasslands, meadows, and wetlands. Slurry application to wheat fields resulted in short-lived two-fold increases in emissions. The moderate N2O fluxes and their moderate response to slurry application were attributed to dry soil conditions due to the absence of rain during the four previous weeks. Cumulative annual emissions from two arable fields that were both fertilized with mineral fertilizer and manure were large (17 kg N2O-N ha−1 yr−1 and 5.5 kg N2O-N ha−1 yr−1 during the previous year when soil water conditions were favourable for N2O production during the first month following fertilizer application. Our findings confirm the importance of weather conditions as well as nitrogen management on N2O fluxes.

  6. WRF added value to capture the spatio-temporal drought variability

    Science.gov (United States)

    García-Valdecasas Ojeda, Matilde; Quishpe-Vásquez, César; Raquel Gámiz-Fortis, Sonia; Castro-Díez, Yolanda; Jesús Esteban-Parra, María

    2017-04-01

    Regional Climate Models (RCM) has been widely used as a tool to perform high resolution climate fields in areas with high climate variability such as Spain. However, the outputs provided by downscaling techniques have many sources of uncertainty associated at different aspects. In this study, the ability of the Weather Research and Forecasting (WRF) model to capture drought conditions has been analyzed. The WRF simulation was carried out for a period that spanned from 1980 to 2010 over a domain centered in the Iberian Peninsula with a spatial resolution of 0.088°, and nested in the coarser EURO-CORDEX domain (0.44° spatial resolution). To investigate the spatiotemporal drought variability, the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) has been computed at two different timescales: 3- and 12-months due to its suitability to study agricultural and hydrological droughts. The drought indices computed from WRF outputs were compared with those obtained from the observational (MOTEDAS and MOPREDAS) datasets. In order to assess the added value provided by downscaled fields, these indices were also computed from the ERA-Interim Re-Analysis database, which provides the lateral and boundary conditions of the WRF simulations. Results from this study indicate that WRF provides a noticeable benefit with respect to ERA-Interim for many regions in Spain in terms of drought indices, greater for SPI than for SPEI. The improvement offered by WRF depends on the region, index and timescale analyzed, being greater at longer timescales. These findings prove the reliability of the downscaled fields to detect drought events and, therefore, it is a remarkable source of knowledge for a suitable decision making related to water-resource management. Keywords: Drought, added value, Regional Climate Models, WRF, SPEI, SPI. Acknowledgements: This work has been financed by the projects P11-RNM-7941 (Junta de Andalucía-Spain) and

  7. Spatio-temporal variability of urban heat islands in local climate zones of Delhi-NCR

    Science.gov (United States)

    Budhiraja, Bakul; Pathak, Prasad; Agrawal, Girish

    2017-10-01

    Land use change is at the nexus of human territory expansion and urbanization. Human intrusion disturbs the natural heat energy balance of the area, although a new equilibrium of energy flux is attained but with greater diurnal range and adversely affecting the geo/physical variables. Modification in the trend of these variables causes a phenomenon known as Urban Heat Island (UHI) i.e. a dome of heat is formed around the city which has 7-10 °C high temperature than the nearby rural area at night. The study focuses on Surface UHI conventionally studied using thermal band of the remotely sensed satellite images. Land Surface Temperature (LST) is determined for the year 2015 using Landsat 8 for Delhi National Capital Region (NCR). This region was chosen because it is the biggest urban agglomeration in India, many satellite cities are coming in periphery and it has temperate climate. Quantification of UHI is predictably done using UHI intensity that is the difference between representative Urban and rural temperature. Recently the definition of urban and rural has been questioned because of various kinds of configurations of urban spaces across the globe. Delhi NCR urban configurations vary spatially- thus one UHI intensity does not give a deep understanding of the micro-climate. Advancement was made recently to standardize UHI intensity by dividing city into Local Climate Zones (LCZ), comes with 17 broad categories. LCZ map of Delhi NCR has been acquired from World Urban Database. The seasonality in LST across LCZ has been determined along with identifying warmest and coolest LCZ.

  8. Autonomous bed-sediment imaging-systems for revealing temporal variability of grain size

    Science.gov (United States)

    Buscombe, Daniel; Rubin, David M.; Lacy, Jessica R.; Storlazzi, Curt D.; Hatcher, Gerald; Chezar, Henry; Wyland, Robert; Sherwood, Christopher R.

    2014-01-01

    We describe a remotely operated video microscope system, designed to provide high-resolution images of seabed sediments. Two versions were developed, which differ in how they raise the camera from the seabed. The first used hydraulics and the second used the energy associated with wave orbital motion. Images were analyzed using automated frequency-domain methods, which following a rigorous partially supervised quality control procedure, yielded estimates to within 20% of the true size as determined by on-screen manual measurements of grains. Long-term grain-size variability at a sandy inner shelf site offshore of Santa Cruz, California, USA, was investigated using the hydraulic system. Eighteen months of high frequency (min to h), high-resolution (μm) images were collected, and grain size distributions compiled. The data constitutes the longest known high-frequency record of seabed-grain size at this sample frequency, at any location. Short-term grain-size variability of sand in an energetic surf zone at Praa Sands, Cornwall, UK was investigated using the ‘wave-powered’ system. The data are the first high-frequency record of grain size at a single location of a highly mobile and evolving bed in a natural surf zone. Using this technology, it is now possible to measure bed-sediment-grain size at a time-scale comparable with flow conditions. Results suggest models of sediment transport at sandy, wave-dominated, nearshore locations should allow for substantial changes in grain-size distribution over time-scales as short as a few hours.

  9. The spatial-temporal variability of air-sea momentum fluxes observed at a tidal inlet

    Science.gov (United States)

    Ortiz-Suslow, D. G.; Haus, B. K.; Williams, N. J.; Laxague, N. J. M.; Reniers, A. J. H. M.; Graber, H. C.

    2015-02-01

    Coastal waters are an aerodynamically unique environment that has been little explored from an air-sea interaction point of view. Consequently, most studies must assume that open ocean-derived parameterizations of the air-sea momentum flux are representative of the nearshore wind forcing. Observations made at the New River Inlet in North Carolina, during the Riverine and Estuarine Transport experiment (RIVET), were used to evaluate the suitability of wind speed-dependent, wind stress parameterizations in coastal waters. As part of the field campaign, a small, agile research vessel was deployed to make high-resolution wind velocity measurements in and around the tidal inlet. The eddy covariance method was employed to recover direct estimates of the 10 m neutral atmospheric drag coefficient from the three-dimensional winds. Observations of wind stress angle, near-surface currents, and heat flux were used to analyze the cross-shore variability of wind stress steering off the mean wind azimuth. In general, for onshore winds above 5 m/s, the drag coefficient was observed to be two and a half times the predicted open ocean value. Significant wind stress steering is observed within 2 km of the inlet mouth, which is observed to be correlated with the horizontal current shear. Other mechanisms such as the reduction in wave celerity or depth-limited breaking could also play a role. It was determined that outside the influence of these typical coastal processes, the open ocean parameterizations generally represent the wind stress field. The nearshore stress variability has significant implications for observations and simulations of coastal transport, circulation, mixing, and general surf-zone dynamics.

  10. Documentation and verification of VST2D; a model for simulating transient, Variably Saturated, coupled water-heat-solute Transport in heterogeneous, anisotropic 2-Dimensional, ground-water systems with variable fluid density

    Science.gov (United States)

    Friedel, Michael J.

    2001-01-01

    This report describes a model for simulating transient, Variably Saturated, coupled water-heatsolute Transport in heterogeneous, anisotropic, 2-Dimensional, ground-water systems with variable fluid density (VST2D). VST2D was developed to help understand the effects of natural and anthropogenic factors on quantity and quality of variably saturated ground-water systems. The model solves simultaneously for one or more dependent variables (pressure, temperature, and concentration) at nodes in a horizontal or vertical mesh using a quasi-linearized general minimum residual method. This approach enhances computational speed beyond the speed of a sequential approach. Heterogeneous and anisotropic conditions are implemented locally using individual element property descriptions. This implementation allows local principal directions to differ among elements and from the global solution domain coordinates. Boundary conditions can include time-varying pressure head (or moisture content), heat, and/or concentration; fluxes distributed along domain boundaries and/or at internal node points; and/or convective moisture, heat, and solute fluxes along the domain boundaries; and/or unit hydraulic gradient along domain boundaries. Other model features include temperature and concentration dependent density (liquid and vapor) and viscosity, sorption and/or decay of a solute, and capability to determine moisture content beyond residual to zero. These features are described in the documentation together with development of the governing equations, application of the finite-element formulation (using the Galerkin approach), solution procedure, mass and energy balance considerations, input requirements, and output options. The VST2D model was verified, and results included solutions for problems of water transport under isohaline and isothermal conditions, heat transport under isobaric and isohaline conditions, solute transport under isobaric and isothermal conditions, and coupled water

  11. Spatio-temporal variability of particulate matter in the key part of Gansu Province, Western China.

    Science.gov (United States)

    Guan, Qingyu; Cai, Ao; Wang, Feifei; Yang, Liqin; Xu, Chuanqi; Liu, Zeyu

    2017-11-01

    To investigate the spatial and temporal behaviors of particulate matter in Lanzhou, Jinchang and Jiayuguan during 2014, the hourly concentrations of PM2.5 and PM10 were collected from the Ministry of Environmental Protection (MEP) in this study. The analysis indicated that the mean annual PM10 (PM2.5) concentrations during 2014 were 115 ± 52 μg/m(3) (57 ± 28 μg/m(3)), 104 ± 75 μg/m(3) (38 ± 22 μg/m(3)) and 114 ± 72 μg/m(3) (32 ± 17 μg/m(3)) in Lanzhou, Jinchang and Jiayuguan, respectively, all of which exceeded the Chinese national ambient air quality II standards for PM. Higher values for both PM fractions were generally observed in spring and winter, and lower concentrations were found in summer and autumn. Besides, the trend of seasonal variation of particulate matter (PM) in each city monitoring site is consistent with the average of the corresponding cities. Anthropogenic activities along with the boundary layer height and wind scale contributed to diurnal variations in PM that varied bimodally (Lanzhou and Jinchang) or unimodally (Jiayuguan). With the arrival of dust events, the PM10 concentrations changed dramatically, and the PM10 concentrations during dust storm events were, respectively, 19, 43 and 17 times higher than the levels before dust events in Lanzhou, Jinchang and Jiayuguan. The ratios (PM2.5/PM10) were lowest, while the correlations were highest, indicating that dust events contributed more coarse than fine particles, and the sources of PM are similar during dust storms. The relationships between local meteorological parameters and PM concentrations suggest a clear association between the highest PM concentrations, with T ≤ 7 °C, and strong winds (3-4 scale). However, the effect of relative humidity is complicated, with more PM10 and PM2.5 exceedances being registered with a relative humidity of less than 40% and 40-60% in Lanzhou, while higher exceedances in Jinchang appeared at a relative humidity of 80

  12. Variations in spatial and temporal distribution of Archaea in the North Sea in relation to environmental variables.

    Science.gov (United States)

    Herfort, Lydie; Schouten, Stefan; Abbas, Ben; Veldhuis, Marcel J W; Coolen, Marco J L; Wuchter, Cornelia; Boon, Jan P; Herndl, Gerhard J; Sinninghe Damsté, Jaap S

    2007-12-01

    The spatial and temporal distribution of pelagic Archaea was studied in the southern North Sea by rRNA hybridization, sequencing and quantification of 16S rRNA gene and membrane lipid analyses and related to physical, chemical and biological parameters to determine the factors influencing archaeal biogeography. A clear temporal variability was observed, with marine Crenarchaeota (Group I.1a) being relatively more abundant in winter and Euryarchaeota dominating the archaeal assemblage in spring and summer. Spatial differences in the lateral distribution of Crenarchaeota were also evident. In fact, their abundance was positively correlated with the copy number of the gene encoding the alpha subunit of crenarchaeotal ammonia monooxygenase (amoA) and with concentrations of ammonia, nitrate, nitrite and phosphorus. This suggests that most Crenarchaeota in the North Sea are nitrifiers and that their distribution is determined by nutrient concentrations. However, Crenarchaeota were not abundant when larger phytoplankton (>3 microm) dominated the algal population. It is hypothesized that together with nutrient concentration, phytoplankton biomass and community structure can predict crenarchaeotal abundance in the southern North Sea. Euryarchaeotal abundance was positively correlated with chlorophyll a concentrations, but not with phytoplankton community structure. Whether this is related to the potential of Euryarchaeota to perform aerobic anoxygenic phototrophy remains to be shown, but the conspicuous seasonal distribution pattern of Crenarchaeota and Euryarchaeota suggests that they occupy a different ecological niche.

  13. A multi-tracer approach for determining the sources and spatial variability of groundwater-delivered nutrients to coastal waters: Maunalua Bay, Oahu, Hawai'i

    Science.gov (United States)

    Richardson, C. M.; Dulaiova, H.; Whittier, R. B.

    2015-12-01

    Nutrient pollution of coastal waters commonly arises from terrestrial non-point sources of N and P such as on-site disposal systems (OSDS) and fertilizer leachate. Elevated nutrient loading of submarine groundwater discharge (SGD) has been documented in the western edge of Maunalua Bay, Oahu, an area with high OSDS density. We examined coastal groundwater and nearshore marine water quality in two adjacent aquifers (Waialae West and Waialae East) within the study region with differing land-use and hydrogeological characteristics to better understand 1) the spatial variability of SGD nutrient and water fluxes and 2) the reasons for this spatial variability. Nutrient concentrations and NO3- stable isotope ratios were measured in coastal and terrestrial groundwater as well as nearshore marine water and integrated with SGD flux, land-use, and recharge data to examine potential nutrient sources in each aquifer. Regionally-elevated NO3- concentrations (169 µM) and δ15N-NO3- values (10.9 ‰) were apparent in SGD in the Waialae West Aquifer where OSDS density is highest. Coastal sites sampled in the neighboring Waialae East Aquifer exhibited significantly lower values for these parameters, with δ15N-NO3- values ranging from 5.7 - 5.9‰ and NO3- concentrations from 43 - 69 µM. The isotopic composition of NO3- in SGD originating from the Waialae West Aquifer was primarily influenced by mixing of a wastewater source, with wastewater effluent accounting for nearly 4.4% of total recharge and 79 - 97% of total N and P loads within the aquifer. These findings illustrate the utility of synthesizing nutrient concentrations and stable isotope parameters together with SGD flux determination, and aquifer-scale land-use and recharge data in determining the contribution of terrestrial sources to coastal nutrient loading via SGD.

  14. Temporal variability and drivers of net ecosystem production of a Turkey oak forest in Italy under coppice management

    Science.gov (United States)

    Belelli Marchesini, Luca; Rey, Ana; Papale, Dario; Valentini, Riccardo

    2010-05-01

    The progress in the understanding of the carbon exchange between forests and the atmosphere has been dramatic over the last few years, yet largely based on observations of middle-aged or mature stands in the temperate and boreal region while quite a few studies report on the temporal dynamics of carbon balance in forest stand chronosequences taking into account the effect of forest management (Law et al., 2003; Kowalski et al., 2003; Kolari et al, 2004; Zha et al., 2009). In order to quantify the temporal variability of CO2 fluxes at ecosystem level following coppicing, we analyze eddy covariance data of a deciduous oak (Quercus cerris L.) coppice forest in central Italy (Roccarespampani, VT) collected over two differently aged forest stands in the period 2000-2006 and covering most of the rotation period (0-6; 11-15 years). Data processing was performed evenly for whole data-set according to the CarboEurope database standard (Papale et al., 2006). The inter-annual variability and seasonal dynamics of net ecosystem exchange (NEE), partitioned into ecosystem respiration (Reco) and gross primary production (GPP), were analyzed looking at the relationships with the main structural (biomass) and environmental drivers (air and soil temperature, precipitation, soil water content, vapour pressure deficit, global radiation) to understand which factors control the carbon dynamics of these intensively managed forests After harvesting the forest acted as a carbon source of 69 gC m-2, while in the following years NEE ranged from -18.9 (stand age: 2 years) to -1077.9 g C m-2yr-1 (stand age: 15 years). Evidently the ecosystem promptly recovers its carbon sink capacity already in the years shortly after the harvest and increases its carbon sequestration capacity with stand age (R2= 0.75, P

  15. Temporal variability and cooperative breeding: testing the bet-hedging hypothesis in the acorn woodpecker.

    Science.gov (United States)

    Koenig, Walter D; Walters, Eric L

    2015-10-07

    Cooperative breeding is generally considered an adaptation to ecological constraints on dispersal and independent breeding, usually due to limited breeding opportunities. Although benefits of cooperative breeding are typically thought of in terms of increased mean reproductive success, it has recently been proposed that this phenomenon may be a bet-hedging strategy that reduces variance in reproductive success (fecundity variance) in populations living in highly variable environments. We tested this hypothesis using long-term data on the polygynandrous acorn woodpecker (Melanerpes formicivorus). In general, fecundity variance decreased with increasing sociality, at least when controlling for annual variation in ecological conditions. Nonetheless, decreased fecundity variance was insufficient to compensate for reduced per capita reproductive success of larger, more social groups, which typically suffered lower estimated mean fitness. We did, however, find evidence that sociality in the form of larger group size resulted in increased fitness in years following a small acorn crop due to reduced fecundity variance. Bet-hedging, although not the factor driving sociality in general, may play a role in driving acorn woodpecker group living when acorns are scarce and ecological conditions are poor. © 2015 The Author(s).

  16. Temporal Variability of Human Vaginal Bacteria and Relationship with Bacterial Vaginosis

    Science.gov (United States)

    Srinivasan, Sujatha; Liu, Congzhou; Mitchell, Caroline M.; Fiedler, Tina L.; Thomas, Katherine K.; Agnew, Kathy J.; Marrazzo, Jeanne M.; Fredricks, David N.

    2010-01-01

    Background Little is known about short-term bacterial fluctuations in the human vagina. This study used PCR to assess the variability in concentrations of key vaginal bacteria in healthy women and the immediate response to antibiotic treatment in women with bacterial vaginosis (BV). Methodology/Principal Findings Twenty-two women assessed for BV using Amsel's criteria were evaluated daily for 7 or 14 days, then at 2, 3 and 4 weeks, using a panel of 11 bacterium-specific quantitative PCR assays. Participants with BV were treated with 5 days of intravaginal metronidazole. Participants without BV had vaginal biotas dominated by lactobacilli, whose levels fluctuated with menses. With onset of menstruation, quantities of Lactobacillus jensenii and Lactobacillus crispatus decreased and were found to be inversely related to Gardnerella vaginalis concentrations (pvaginalis were observed during menses. Participants with BV have diverse communities of fastidious bacteria that are depleted by vaginal metronidazole therapy. Women with recurrent BV initially respond to antibiotic treatment with steep declines in bacterial concentrations, but these bacteria later reemerge, suggesting that antibiotic resistance in these bacteria is not an important factor mediating BV recurrence. PMID:20419168

  17. Spatial and temporal variability in the temperature and precipitation records of MEXICO state (1978-2000

    Directory of Open Access Journals (Sweden)

    X. Antonio-Némiga

    2017-07-01

    Full Text Available Comprender la naturaleza y magnitud de las variaciones climáticas regionales es fundamental para el desarrollo de políticas de adaptación y mitigación. Por ello, se evalúan los registros de temperatura máxima y mínima y precipitación en 92 estaciones meteorológicas del estado de México durante el periodo comprendido entre 1978 y 2000. Para hacerlo se calcularon los valores promedio y los coeficientes de variación de los registros. En ellos se buscan tendencias lineales de comportamiento y se calcula para cada estación el coeficiente de variación para encontrar aquellas estaciones que presentan mayor variabilidad. La misma variabilidad es expresada cartográfi- camente para para entender su distribución en el espacio y buscar relación con otras variables. Se encontró una tendencia estadísticamente significativa de creciente variabilidad en los registros de temperatura máxima de los meses de enero, abril y mayo y en los registros de temperatura mínima de mayo, junio y septiembre; así como una posible correlación entre la ubicación de las estaciones donde se registran mayores variaciones de temperatura máxima y los frentes de deforestación.

  18. Spatial and Temporal Variability of Rainfall in the Gandaki River Basin of Nepal Himalaya

    Directory of Open Access Journals (Sweden)

    Jeeban Panthi

    2015-03-01

    Full Text Available Landslides, floods, and droughts are recurring natural disasters in Nepal related to too much or too little water. The summer monsoon contributes more than 80% of annual rainfall, and rainfall spatial and inter-annual variation is very high. The Gandaki River, one of the three major rivers of Nepal and one of the major tributaries of the Ganges River, covers all agro-ecological zones in the central part of Nepal. Time series tests were applied for different agro-ecological zones of the Gandaki River Basin (GRB for rainfall trends of four seasons (pre-monsoon, monsoon, post-monsoon and winter from 1981 to 2012. The non-parametric Mann-Kendall and Sen’s methods were used to determine the trends. Decadal anomalies relative to the long-term average were analyzed using the APHRODITE precipitation product. Trends in number of rainy days and timing of the monsoon were also analyzed. We found that the post-monsoon, pre-monsoon and winter rainfalls are decreasing significantly in most of the zones but monsoon rainfall is increasing throughout the basin. In the hill region, the annual rainfall is increasing but the rainy days do not show any trend. There is a tendency toward later departure of monsoon from Nepal, indicating an increase in its duration. These seasonally and topographically variable trends may have significant impacts for the agriculture and livestock smallholders that form the majority of the population in the GRB.

  19. Spatial and temporal variability of bacterial communities in high alpine water spring sediments.

    Science.gov (United States)

    Esposito, Alfonso; Engel, Michael; Ciccazzo, Sonia; Daprà, Luca; Penna, Daniele; Comiti, Francesco; Zerbe, Stefan; Brusetti, Lorenzo

    2016-05-01

    Water springs are complex, fragile and taxa-rich environments, especially in highly dynamic ecosystems such as glacier forefields experiencing glacier retreat. Bacterial communities are important actors in alpine water body metabolism, and have shown both high seasonal and spatial variations. Seven springs from a high alpine valley (Matsch Valley, South Tyrol, Italy) were examined via a multidisciplinary approach using both hydrochemical and microbiological techniques. Amplified ribosomal intergenic spacer analysis (ARISA) and electric conductivity (EC) measurements, as well as elemental composition and water stable isotopic analyses, were performed. Our target was to elucidate whether and how bacterial community structure is influenced by water chemistry, and to determine the origin and extent of variation in space and time. There existed variations in both space and time for all variables measured. Diversity values more markedly differed at the beginning of summer and then at the end; the extent of variation in space was prevalent over the time scale. Bacterial community structural variation responded to hydrochemical parameter changes; moreover, the stability of the hydrochemical parameters played an important role in shaping distinctive bacterial communities. Copyright © 2016 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.