WorldWideScience

Sample records for aquicludes

  1. Delineation of a shallow subsurface aquiclude relief with aero electromagnetic data

    Science.gov (United States)

    Römer, A.; Winkler, E.; Bieber, G.; Motschka, K.; Reitner, H.

    2009-04-01

    Within a governmental groundwater remediation project in Austria, a new (overworked) characterization of a large catchment area (600 km2) with aeroelectromagnetics (AEM) was carried out. This catchment area is a large and important zone of subsurface water resources for currently and future municipal and rural water supply. Conflicts in future land use between e.g. agricultura, excavigation of mass materials, city and regional planning, ect. are preassigned and have impacts concerning the quality and quantity of available groundwater. The geology of the investigation area is a typical post-glacial region, characterized by aggradational deposition areas. The thickness of the wide-spread terrace gravels ranges from 10m to 40m, being the preferred ground water aquifer. The subsurface of the investigation area is built up by a Neogen basement, the so called Molasse and is acting as an aquiclude relative to the overlying quaternary sediments. Aeroelectromagnetic data from a former aerogeophysical survey were reinterpreted with a new processing and interpretation approach for the determination of this geological 3 layer case. This aeroelectromagnetic inversion integrates results from borehole data, ground geoelectric surveys and from geological mapping as a priori input information. The inversion result for a measured AEM data value is determined by a combination of geostatistically weighted additional information and likelihood weighted theoretical models. The primary aim of the study was the delineation of the aquiclude relief. The ground water circulation within the different terrace gravels is substantially affected by this Neogen relief. Depressions and prequaternary (tertiary) riverbeds within the Molasse often show other trends of water flow than the surficial, recent vales. The knowledge of the hydrogeological framework is essential for identification and definition of water protection and catchment areas as a decision base for national land use regulations. The

  2. Experimental research of overburden movement and subsurface water seeping in shallow seam mining

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Shallow seam coal field has the largest coal reserve in China. Mining in shallow depth causes serious problems, and subsurface dewatering is a major issue. In this paper, the physical simulating models were prepared to study overburden movement and aquiclude stability in the shallow seam mining of Yushuwan Coalfield, China. According to the characteristic of clay aquiclude and bedrock in the overburden, the proper simulation materials for simulating the plastic clay aquiclude layers and brittle bedrock layers were determined by the stress-strain tests and hydrophilic tests. The physical simulating models of solid medium and two phases of solid-liquid medium were carried out to simulate the failure and caving process of the roof and overburden, as well as the subsurface water seeping. Based on the simulation, it was found that the movement of clay aquiclude follows the movement of the underlying bedrock layers. The stability of aquiclude is mainly affected by cracks in fracture zone. The tests also showed that the best way to control the stability of aquiclude is to reduce the subsiding gradient, and there is a possibility of ground water conservation under longwall mining in Yushuwan Mine. This research provides a foundation for further study on mining dewatering and water conservation.

  3. Partitions, Compartments and Portals: Cave Development in internally impounded karst masses.

    Directory of Open Access Journals (Sweden)

    Osborne R. Armstrong L.

    2005-07-01

    Full Text Available Dykes and other vertical bodies can act as aquicludes within bodies of karst rock. These partitions separate isolated bodies of solublerock called compartments. Speleogenetically each compartment will behave as a small impounded-karst until the partition becomesbreached. Breaches through partitions, portals, allow water, air and biota including humans to pass between sections of caves thatwere originally isolated.

  4. Martian Gullies and Groundwater: A Series of Unfortunate Exceptions

    Science.gov (United States)

    Treiman, A. H.

    2005-01-01

    Gullies are commonly inferred to represent debris flows, lubricated and carried by liquid water that flowed from underground. The inference of groundwater, based principally on the apparent initiation of gullies at specific bedrock layers, has not been considered for consistency with local geology. Here, I examine gully occurrences for: presence of impermeable layers (aquicludes) in the subsurface, that the layers not tilt away from the gully-bearing walls, and that liquid water could have been available at or above the gully elevations.

  5. Scaling thermal effects in radial flow

    Science.gov (United States)

    Hudspeth, R. T.; Guenther, R. B.; Roley, K. L.; McDougal, W. G.

    To adequately evaluate the environmental impact of siting nuclear waste repositories in basalt aquicludes, it is essential to know the effects on parameter identification algorithms of thermal gradients that exist in these basaltic aquicludes. Temperatures of approximately 60°C and pressures of approximately 150 atm can be expected at potential repository sites located at depths of approximately 1000 m. The phenomenon of over-recovery has been observed in some pumping tests conducted at the Hanford Nuclear Reservation located in the Pasco Basin adjacent to the Columbia River in the state of Washington, USA. This over-recovery phenomenon may possibly be due to variations in the fluid density caused by thermal gradients. To assess the potential effects of these thermal gradients on indirect parameter identification algorithms, a systematic scaling of the governing field equations is required in order to obtain dimensionless equations based on the principle of similarity. The constitutive relationships for the specific weight of the fluid and for the porosity of the aquiclude are shown to be exponentially dependent on the pressure gradient. The dynamic pressure is converted to the piezometric head and the flow equation for the piezometric head is then scaled in radial coordinates. Order-of-magnitude estimates are made for all variables in unsteady flow for a typical well test in a basaltic aquiclude. Retaining all nonlinear terms, the parametric dependency of the flow equation on the classical dimensionless thermal and hydraulic parameters is demonstrated. These classical parameters include the Batchelor, Fourier, Froude, Grashof, and Reynolds Numbers associated with thermal flows. The flow equation is linearized from order-of-magnitude estimates based on these classical parameters for application in parameter identification algorithms.

  6. Research on the water-inrush risk of coal floors based on Fisher-evaluation and AHP

    Science.gov (United States)

    Xu, D. J.; Wei, W. X.; Xiang, S. Y.

    2016-08-01

    There are many factors that influence floor water-inrush. Based on the widely collected data of floor water-inrush in China, the evaluation factors in this paper consist of water pressure, aquifer type, aquiclude thickness, floor failure depth and fault throw. These are used to build a single Fisher evaluation model and a Fisher evaluation with weighting model of an analytic hierarchy process (AHP). By comparision, through AHP weighting value, the interclass distribution of the data in the Fisher model is relatively more concentrated than the single Fisher evaluation method. It would produce higher reliability and more extensive application value.

  7. Sequestration of carbon in saline aquifers - mathematical and numerical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Nordbotten, Jan Martin

    2004-01-01

    The work in this thesis focuses equally on two main topics. The set of these subjects deals with development of criteria for monotonicity of control volume methods. These methods are important and frequently used for solving the pressure equation arising in porous media flow. First we consider homogeneous parallelogram grids, and subsequently general logical Cartesian grids in heterogeneous media. This subject is concluded by the development of a new class of Multi Point Flux Approximation methods, motivated by the monotonicity results obtained. The second topic of this thesis is the development of analytical and semi- analytical solutions to the problem of leakage through abandoned wells. More specially, we look at a set of aquifers, separated by impermeable layers (aquicludes), where injection of water or CO{sub 2} takes place in some or all the aquifers. The aquifers and aquicludes are frequently penetrated by abandoned wells from oil exploration, and our problem consists of finding solutions to flow and leakage through these wells. The goal is to obtain expressions for leakage rates that may be evaluated quickly enough such that Monte Carlo realizations over statistical distributions of properties for abandoned wells can be performed. (author)

  8. Nonlinear coupling analysis of coal seam floor during mining based on FLAC3D

    Institute of Scientific and Technical Information of China (English)

    YAO Duo-xi; XU Ji-ying; LU Hai-feng

    2011-01-01

    Based on the hydro-geological conditions of 1028 mining face in Suntuan Coal Mine, mining seepage strain mechanism of seam floor was simulated by a nonlinear coupling method, which applied fluid-solid coupling analysis module of FLAC3D. The results indicate that the permeability coefficient of adjoining rock changes a lot due to mining. The maximum value reaches 1 379.9 times to the original value, where it is at immediate roof of the mined-out area. According to the analysis on the seepage field, mining does not destroy water resistance of the floor aquiclude. The mining fissure does not conduct lime-stone aquifer, and it is less likely to form damage. The plastic zone does not exactly correspond to the seepage area, and the scope of the altered seepage area is much larger than the plastic zone.

  9. The general description of major ion concentrations in groundwater of Latvia

    Science.gov (United States)

    Kalvāns, A.; Delina, A.

    2012-04-01

    Latvia is situated at the North central part of the Baltic sedimentary basin where the crystalline basement is found in depth between 0.6 to 2 km. Three large aquifer complexes with distinct chemical composition of groundwater are identified: the stagnant water exchange zone where Na-Ca-Cl brine is found; the slow water exchange zone where Na-Ca-Cl-SO4 brackish water is found and active water exchange zone where the freshwater resides. These are separated by distinct regional aquicludes. The composition of the Cl- dominated brines at the base of sedimentary basin is characterised by shift from Na+ towards Ca++ as dominant cation, partially associated with depth of the aquifer and the strength of the brine. The concentration of SO4-- here is inversely linked to the concentration of Ca++ and, according to geochemical modelling, often is close to the solubility limit of the gypsum. The major ion concentrations in the E and W part of the territory are rather different. Therefore two different initial sources of the formation brine were suggested. Alternatively the observations can be explained by different thermal histories of different parts of the basin, affecting the rate of albitization - exchange of the Na for Ca in the solution due to water-rock interaction. The groundwater composition in the slow exchange zone can be nicely explained by the mixing of freshwater and brine residing deeper in the presence of gypsum during some but no all stages of mixing. In some shallow parts of the zone still bound by the Narva regional aquiclude freshwater is found. The question is posted - could this be a paleogroundwater originating from the extensive continental glaciations that override the territory several times during the Pleistocene? Initial isotope studies presented elsewhere seems to give negative answer to this question. The active water exchange zone is characterised by fresh Ca-Mg-HCO3 water with exceptions in cases where gypsum are abundant in sedimentary rocks and

  10. Developing a geological 3D model for the Tanour and Rasoun spring catchment area using ArcGIS and GOCAD

    Science.gov (United States)

    Hamdan, Ibraheem; Benhsinat, Mohamed; Wagner, Bianca; Sauter, Martin

    2016-04-01

    Key words: Karst, 3D model, GOCAD, ArcGIS, Jordan. Tanour and Rasoun karst springs (around 75 km northwest of the capital city of Amman in Jordan) are used as main local water supply for the surrounding villages. Carbonate rocks are the predominant rock type in the study area (Upper Cretaceous age). The karstification degree is moderate to high, with the availability of different karst features like dolines, caves, dry valleys, and highly fractured rocks. During the last years, the water supply from these springs had to be disconnected for several times due to microbial contamination and waste water pollution from local olive oil mills. For better understanding of the geological and the hydrogeological setting of the study area, in addition to the delineation of the groundwater catchment area for Tanour and Rasoun springs, a geological 3D model of the main geological formations within the study area was established using ArcGIS and GOCAD. The model is based on geological maps and well data; it was established for seven geological layers that act as prominent aquifers and aquicludes. ArcGIS software was used for data preparation, processing and interpolation of varying thickness, while GOCAD used for geometrical modeling steps. After the completion of the first modeling steps, major faults are included. Then the subsurface catchments will be delineated and compared with the superficial watersheds. The model still under development and open for further development.

  11. 超薄基岩下采煤防水煤岩柱合理高度的研究%Optimal coal pillar size for safe mining under efflorescent oxygenized strata

    Institute of Scientific and Technical Information of China (English)

    周增强; 张枫林

    2013-01-01

    通过对百善煤矿64采区强风氧化超薄基岩区域地质及水文地质条件进行系统分析,以实验室测试、现场实测为依据,重点研究分析了风化基岩、隔水层和含水层的物理特征及强风化岩石泥化对“两带”发育高度和渗透性的影响,并设计了合理的安全保护煤柱。实践表明:超薄基岩区域强风化岩石软弱、泥化、风化对工作面回采“两带”发育高度有降低作用,比较有利于工作面的安全回采。%This paper systematically analyzed the geological and hydrological conditions of 64 mining area in Baishan mine and tested the physical and mechanical property of weathering bedrock ,aquiclude and aquifer .Then ,The influence of rock argillization on roof fracture and its permeability were studied and the minimum protective rock pillar was obtained accordingly .Field practice shows that :the softening , argillization and weathering of rock could reduce the roof fracture height ,which be beneficial to coal miming under such area .

  12. High=porosity Cenozoic carbonate rocks of South Florida: progressive loss of porosity with depth

    Science.gov (United States)

    Halley, Robert B.; Schmoker, James W.

    1983-01-01

    Porosity measurements by borehole gravity meter in subsurface Cenozoic carbonates of South Florida reveal an extremely porous mass of limestone and dolomite which is transitional in total pore volume between typical porosity values for modern carbonate sediments and ancient carbonate rocks. A persistent decrease of porosity with depth, similar to that of chalks of the Gulf Coast, occurs in these rocks. Carbonate strata with less than 20% porosity are absent from the rocks studied here. Aquifers and aquicludes cannot be distinguished on the basis of porosity. Aquifers are not exceptionally porous when compared to other Tertiary carbonate rocks in South Florida. Permeability in these strata is governed more by the spacial distribution of pore space and matrix than by total volume of porosity present. Dolomite is as porous as, or slightly less porous than, limestones in these rocks. This observation places limits on any model proposed for dolomitization and suggests that dolomitization does not take place by a simple ion-for-ion replacement of magnesium for calcium. Dolomitization may be selective for less porous limestone, or it may involve the incorporation of significant amounts of carbonate as well as magnesium into the rock. The great volume of pore space in these rocks serves to highlight the inefficiency of early diagenesis in reducing carbonate porosity and to emphasize the importance of later porosity reduction which occurs during the burial or late near-surface history of limestones and dolomites.

  13. Karst morphology and groundwater vulnerability of high alpine karst plateaus

    Science.gov (United States)

    Plan, Lukas; Decker, Kurt; Faber, Robert; Wagreich, Michael; Grasemann, Bernhard

    2009-07-01

    High alpine karst plateaus are recharge areas for major drinking water resources in the Alps and many other regions. Well-established methods for the vulnerability mapping of groundwater to contamination have not been applied to such areas yet. The paper characterises this karst type and shows that two common vulnerability assessment methods (COP and PI) classify most of the areas with high vulnerability classes. In the test site on the Hochschwab plateau (Northern Calcareous Alps, Austria), overlying layers are mostly absent, not protective or even enhance point recharge, where they have aquiclude character. The COP method classifies 82% of the area as highly or extremely vulnerable. The resulting maps are reasonable, but do not differentiate vulnerabilities to the extent that the results can be used for protective measures. An extension for the upper end of the vulnerability scale is presented that allows identifying ultra vulnerable areas. The proposed enhancement of the conventional approach points out that infiltration conditions are of key importance for vulnerability. The method accounts for karst genetical and hydrologic processes using qualitative and quantitative properties of karst depressions and sinking streams including parameters calculated from digital elevations models. The method is tested on the Hochschwab plateau where 1.7% of the area is delineated as ultra vulnerable. This differentiation could not be reached by the COP and PI methods. The resulting vulnerability map highlights spots of maximum vulnerability and the combination with a hazard map enables protective measures for a manageable area and number of sites.

  14. Integrierter Einsatz von Scherwellenseismik und Direct-Push-Verfahren zur Erkundung eines urbanen Grundwasserleiters

    Science.gov (United States)

    Hoffmann, S.; Beilecke, T.; Polom, U.; Werban, U.; Leven, C.; Engeser, B.

    2008-06-01

    In a highly permeable urban aquifer with a lower cretaceous mudstone aquiclude in the district “Südstadt” of Hannover/Lower Saxony, a stationary plume of chlorinated hydrocarbons was investigated within a research framework on the use of monitored natural attenuation. In the vicinity of the isolated contaminant source a glacial channel was detected as a possible secondary source supplying the plume. Due to dense housing the channel morphology and possible pathways could not be mapped accurately by classical geological methods. Therefore, the structure of the aquifer was mapped with shear wave seismics on seven profiles covering a range of more than 3.5 km, utilizing a newly developed mobile land streamer unit. The seismic profiles were adjusted with 16 electric conductivity (EC) and penetration logs measured with direct push, delivering a high resolution image of the near surface bedrock. Due to its mobility and the characteristics of shear wave seismics this combination of methods is ideally suitable for work on sealed surfaces.

  15. 煤层底板承压水导升带影响因素正交模拟试验%Orthogonal test of the influential factors of confined water-conducting zone in coal floor

    Institute of Scientific and Technical Information of China (English)

    边凯; 杨志斌

    2016-01-01

    Confined water-conducting zone is an important factor for mining safety assessment in mining under water pressure, in order to study the role of the influential factors, based on the fluid-solid coupling theory, the hydrogeological conceptual model and numerical model of coal floor water inrush was established, then orthogonal simulation test of five factors and five levels was carried out by using numerical simulation software FLAC3D. The results show that confined water-conducting height is closely related to water pressure of aquifer and permeability coefficient of aquiclude, the greater the confined water pressure and permeability coefficient, the higher the initial water-conducting height. The influential order of the factors for the experimental results isE>C>D>B>A,E (permeability coefficient of aquiclude) andC (confined water pressure) significantly affect the result of the experiment. Different initial head pressure cause different head pressure attenuation rate during the process of confined water conduction. The greater the initial head pressure, the greater the head decay rate, this will increase with the conducting height. The fact that the change of the influencial factors leads to the changes of confined water pressure reveals the law of coal floor confined water conductivity in coal mining process, provides the theoretical basis for the safe mining of coal under pressure.%承压水导升带是煤层带压开采安全评价的重要因素。为了综合研究其影响因素的作用,基于流–固耦合理论,建立了煤层底板突水的水文地质物理概念模型和数值模型,采用FLAC3D数值模拟软件开展了工作面宽度(A)、隔水层厚度(B)、承压水压力(C)、煤层埋深(D)、隔水层渗透系数(E)5个因素5水平的有空列正交模拟试验。结果表明:煤层底板承压水导升高度与底板含水层水压和隔水层渗透性关系密切;各因素对试验结果的影响程度强弱顺序是 E

  16. Synthesis of the hydrogeological studies in the sedimentary basins Amazon and Solimões: the Aquifers Systems Içá-Solimões and Alter do Chão

    Directory of Open Access Journals (Sweden)

    José Geilson Alves Demétrio

    2013-03-01

    Full Text Available Geological maps and stratigraphic charts of the Amazon and Solimões sedimentary basins were reviewed, emphasizing the formations Alter do Chão, Içá and Solimões, the largest reserves of fresh groundwater in these basins. The lack of information on these formations was minimized by sample probe and stratigraphic profiles of construction, lithological and geophysical water and oil wells, obtained in the Base Operacional Geólogo Pedro de Moura, Urucu region, about 650 km southwest of Manaus (AM. In the Amazon Basin, the Aquifer System Alter do Chão is characterized by unconfined and confined aquifers, with transmissivity between 1.5 and 9.1 x 10-3 m2/s, indicated for public supply. In the Solimões Basin, this system is confined by Aquiclude Solimões, recovered by the I-Solimões Aquifers. The reserve is estimated as 33,000 km3. The Aquifer System Içá-Solimões, in Urucu, is unconfined-confined, with two aquifers hydraulically connected: the superficial, with top and bottom at depths near 20 and 70 m, respectively; and the deeper, between 50 and 120 m. With an outcrop area of 948,600 km2 in the Solimões Basin, the reservation of this system was estimated as 7,200 km3, less expressive than the Aquifer System Alter do Chão. The average hydrodynamic parameters were: T = 3 x 10-3 m2/s, S = 5 x 10-4 and K = 1 x 10-4 m/s, orders of magnitudes similar to those found in the aquifer Alter do Chão. Assessing the interrelationships and potential of these two regional aquifers sought to contribute to the hydrogeological knowledge in the Amazon Basin region, where researches on groundwater are still incipient.

  17. Hematite Bearing Ridge as Evidence for Anoxic Water Discharge in Gale Crater

    Science.gov (United States)

    Fraeman, A. A.; Arvidson, R. E.; Catalano, J. G.; Morris, R. V.; Murchie, S. L.; Seelos, F. P.; Seelos, K. D.; McGovern, A.; Viviano, C. E.

    2012-12-01

    Mars Reconnaissance Orbiter CRISM hyperspectral imaging data covering the northern flank of Mount Sharp and acquired with pixels spatially oversampled have been processed to retrieve high signal to noise single scattering albedo spectra from 0.45 to 2.6 μm with enhanced spatial resolution. Using these data and coordinated HiRISE images, a ~200 m wide and 6.5 km long ridge to the north of a large channel system emanating from Mount Sharp was identified and mapped. The ridge is composed of finely layered strata dipping to the north and exhibits a strong spectral signature of crystalline hematite. To the west, the ridge transitions to an escarpment overlain by younger strata; to the east, debris flows from Mount Sharp cover and obscure the ridge. The ridge is stratigraphically directly above the clay bearing strata. We interpret the ridge to be formed by erosion associated with outflow from the channel that preferentially stripped away flanking strata not as well cemented by hematite. We hypothesize that the hematite accumulated where anoxic groundwater discharged and came into contact with an oxidizing Martian atmosphere. Anoxic water may have originated as precipitation that percolated through the mound, leaching Fe2+ from the overlying sulfate layers until encountering the clay aquiclude. Alternatively, anoxic Fe2+-rich waters at Gale could have originated by groundwater discharge near the base of the mound. In this scenario, dissolved Fe2+ could be leached from an underlying basaltic aquifer or possibly the clay layer. Given that iron oxidation reactions on Earth may be mediated by chemolithotrophic microorganisms, the ridge provides a compelling site for a detailed measurement campaign by the Mars Science Laboratory Curiosity rover.

  18. Deposition and early diagenesis of playa glauberite in the Karinga Creek drainage system, Northern Territory, Australia

    Science.gov (United States)

    Arakel, A. V.; Cohen, A.

    1991-02-01

    Glauberite [Na 2Ca(SO 4) 2], in the form of discrete crystals, nodules and lenses, represents the second most common sulphate mineral type (after gypsum) in the chain of modern playa lakes located in the Karinga Creek drainage system, Northern Territory. These modern glauberite deposits exhibit textures and fabrics which reflect both syndeposition with gypsum within the playa phreatic zone, and early diagenetic replacement of host gypsite in the playa vadose zone. Because the distribution of hydrological zones in individual playa lakes vary significantly, the extent of glauberite facies development is highly irregular. Factors controlling glauberite deposition include the nature and extent of groundwater discharge from local and regional aquifers, playa surface evaporation rates, porewater geochemistry and the depth to basal aquicludes. Geochemical and petrographic evidence indicate that the paragenesis of sulphate minerals in the playa lakes of the study area is primarily dictated by the solubility of gypsum, which in turn reflects the extent of dilution and concentration of playa porewaters. On a regional scale, brine dilution and concentration can be related to seasonal and longer-term groundwater recharge-discharge patterns; but, on a local scale, the proximity to springs and ephemeral seepage creeks emanating from local calcrete aquifers is the dominating influence. Hence, a thorough knowledge of groundwater hydrodynamics, particularly the recharge-discharge pattern in playa-marginal areas, must be an essential part of any detailed assessment of the role of depositional and early diagenetic processes in the genesis of glauberite facies in similar arid drainage basins. The close relationship between glauberite facies development and the playa groundwater level has significant implications for interpretations of variation in the water table and other environmental conditions in the shallowing-upwards sequences of ancient lacustrine deposits. The presence of

  19. The Application of Stress-Strain Test in Floor Damage Depth Testing%应力应变法在底板破坏深度测试中的应用

    Institute of Scientific and Technical Information of China (English)

    周江东; 吕育强

    2015-01-01

    The floor aquiclude of Liu Jialiang coal mine in XuanGang area are faced with water inrush due to Ordovician high pressure water with mining. Controlling and preventing water inrush from coal floor had been the main task ,which need evaluate the floor damage depth under mining. Stress-strain test is used to detect the floor damage depth during mining as a new way, taking the ultimate strain of concrete when it is broken as the standard to evaluate the floor damage depth, good results was achieved that the floor damage depth was 13m Under full-mechanized caving mining.It provided reliable da-ta for rational evaluation of water inrush from floor under mining with pressure in working face 8416.%文中针对轩岗矿区刘家梁煤矿受底板下伏奥陶系灰岩岩溶裂隙水威胁的情况,指出当前底板突水防治成为矿井防治水的主要工作任务,需要探查回采工作对底板的破坏程度。通过采用应力应变法进行底板破坏深度测试,利用混凝土的破坏时产生的极限应变作为判断底板岩层破坏深度的依据,得到综放开采条件下采场底板破坏深度为13 m,为合理评价带压开采条件下8416工作面底板突水提供了可靠的数据支撑。

  20. Research about the Control of Geological Structure on Karst Groundwater system in Zhangfang, Beijing,China.

    Science.gov (United States)

    Qiao, X.

    2015-12-01

    Carbonate formations are intensively distributed throughout Zhangfang, fangshan, in West Mountain area in Beijing. Karst groundwater exits among the geological fracture network which is characterized by the different arrangements and levels in different types of fracture networks and structures. The influence of the tectonic environment on the dynamic change rule and the enrichment regulation of karst system is significant for the exploitation and protection of karst groundwater resources. From the control function of fault and fracture point of view, based on the developmental and distribution pattern of multi-episodic tectonism, this study analyzed fractures in the three-fold structural units characterized by NE-NW and NS trends and discussed the influence of multi-episodic tectonism on the groundwater flow system and rich water zones. The results showed that the geological fracture underwent two episodes of tectonism, thrusting nappe in the Jurassic and extension in the Cretaceous. The overprint of two episodes resulted in a number of faults with high hydraulic conductivity, which serve as conduits. The superiority joints groups are in the NE and NW directions, with conjugated characteristics. The high-angle or vertical dips directly benefit infiltration. The fractures in the intersection areas have formed groundwater runoff channels and strong space, controlling water-rich zones such as Baidai, Ganchi-Changgou and Gaozhuang-Shiwo. Magmatic rock and the aquiclude also contribute to the rich water zones and the location of springs, all of which have important significance for water supply. Keywords: system of Karst groundwater, geological structure, fracture network, hydrogeological flow field, Zhangfang karst area

  1. Dynamic processes in the Venice region outlined by environmental isotopes.

    Science.gov (United States)

    Zuppi, Gian Maria; Sacchi, Elisa

    2004-03-01

    Research carried out in the last 40 years has shown the scientific importance of groundwater circulation both in the Northern Adriatic sea bed and within the uppermost sedimentary layers of the Venice lagoon and of the Venice plain. Hydrodynamic processes are strictly controlled by a well-cemented sedimentary horizon lying under and around Venice ('caranto'), which plays the role of regional aquitard. This layer was attributed to the subaerial cementation of the Flandrian (8-10 ka Before Present) sedimentary surface. The caranto is generalised as a continuum horizon, being an easy explanation for several environmental, hydrogeological and geotechnical problems, e.g., a base layer for landfills, a confining layer for deep aquifers and the best substratum for locating the oak wooden pile-dwelling needed to support the largest buildings. The preservation of the isotope signal within the deep aquifers and aquiclude system records the changes in surface and groundwater characteristics and suggests the present and past recharge regimes. In this region, the heavily perturbed hydrodynamic conditions do not allow for the use of isotopic signals to derive a correct reconstruction of the present recharge. The perturbations induced by the intensive anthropogenic activity force to follow climate evolution by considering deep groundwater and pore waters. In addition, the presence of carbonatic rocks inside terrigeneous sediments affects the reconstruction of the past. Results indicate that carbonatic rocks are created by seepage, through the sediments, of gaseous carbon compounds from decaying organic layers. The gas interactions with the intra-sedimentary saline and fresh waters produce CO2, inducing the cementation of the sediments.

  2. A multidisciplinary approach for the management of the water resources hosted in the multi-layer coastal aquifers of Central-Southern Tuscany

    Science.gov (United States)

    Lelli, M.; Doveri, M.; Cerrina Feroni, A.; Da Prato, S.; Ellero, A.; Marini, L.; Masetti, G.; Nisi, B.; Raco, B.

    2012-12-01

    The correct management of subterranean water resources should be based on the studies aimed to acquire informations about geological, hydrogeological and geochemical characteristics of water and aquifer. Taking in mind this idea, the subterranean water resources hosted in the multi-layer aquifers below the coastal plains of the Cecina River, Cornia River, Follonica, Grosseto, and Albegna River were recently investigated through a multidisciplinary approach in the framework of the Significant Groundwater Bodies (SGB) Project, funded by the Tuscany Region (Italy). In the first step, the distinction of main aquifer, aquitard, and aquiclude levels has been done by means of the geometrical reconstruction of the geological sequences, using available stratigraphical data. For each hydrogeological complex, the total volumes and the percentages of the different grain sizes were also calculated. The second step was addressed to elaborate the piezometric surfaces during low-flow and high-flow conditions, aimed to individuate the main flow pattern and the most exploited zones of the multi-layer aquifers. Moreover, considering the saturated zone and applying an effective porosity (weighed in function of grain sizes percentages), the amounts of the total water volumes stored in the aquifer system were estimate. The third step comprised the hydrogeochemical characterization of the areas of interest, by means of both: a deterministic approach, including the elaboration and interpretation of classification diagrams, Eh-pH plots, calculation of water speciation and saturation state, activity diagrams, etc. a geo-statistical approach, aimed to the study of the spatial distribution of the most significant geochemical parameters, such as the concentrations of chloride, sulfate, nitrate and boron. If suitable database is available, this multidisciplinary approach can allow to identify the main recharge areas and flow path and the physical-chemical processes (naturals or antropics

  3. The impermeability of limestone aquifuge in bottom coal seam floor and its application in Xinji Second Coal Mine%新集二矿下组煤底板石灰岩层隔水性及应用研究

    Institute of Scientific and Technical Information of China (English)

    白海波; 戎虎仁; 杨城; 韦晓琪; 王延蒙; 陈耀杰

    2015-01-01

    Limestone layer is often regarded as the main cause of coal mine water damage and water inrush events, which actually happened more than once in old mining area in Huainan. A conception has been put forward that reconstruction or direct utility of relative impermeability of floor limestone layer can solve the problem of high water pressure and thin aquiclude and ensure safety during mining under pressure. Xinji Second coal mine has been selected as the research field which is located in the southern edge of the midwest coalfields and comprehensive methods have been used to research including the index test of rock composition, chemical action of compositions of groundwater, and rock mechanic, micro-pore structure, the laboratory experiment about permeability and the field test about hydrogeolog-ic drilling, geophysical prospecting. The research results show that:1) Xinji Second Coal Mine is cut by faults all around, with the top covered by quaternary system and metamorphic nappe. The in-situ stress changes from tensile in the shallow part to compressive at a depth under 500 m. The crack of deep rock layer is not easy to open up. 2) The hydrochemical type is Cl-Na. Salinity is greater than 1.5 g/L and rock voids is filled by the precipitation. 3) The permeability and water rich property of limestone floor is poor, so it can be regarded as aquiclude. It is confirmed that inrush boreholes mostly close to the large faults and water yield is small and disappear quickly through boreholes in the coal mine. Safe mining of the first coal mining face and safety tunneling of the second working face testify the result that the floor limestone layer is aquiclude and the water-resisting key strata after reconstruct is correct.%石灰岩层往往成为煤矿开采防水害的主要对象,且淮南老矿区也发生了多次底板灰岩层突水,为解决新区水压高、传统隔水层薄的问题,提出改造或直接利用底板石灰岩层相对隔水性实现带压安

  4. Uma classificação físico-hídrica dos solos A physico-hydrical soil classification

    Directory of Open Access Journals (Sweden)

    T. B. Ottoni Filho

    2003-04-01

    minus field capacity values and steady state infiltration rate. On this basis, 10 soil orders and 28 soil classes are defined. Input variables are: density of solids, bulk density, porosity, field capacity, wilting point, and steady state infiltration rate. The classification is based on strictly numerical criteria, and there are no components of subjective evaluation. The nine principal orders, containing three classes each, are: aerated-aquiferous soils (I; aerated-mesaquiferous soils (II; mesaerated-aquiferous soils (III; mesaerated-mesaquiferous soils (IV; aerated-aquicludeous soils (V; mesaerated-aquicludeous soils (VI; unaerated-aquiferous soils (VII; unaerated-mesaquiferous soils (VIII; unaerated-aquicludeous soils (IX. One last order is possible (order X: the flooded soil order, with only one class. The methodology is applied by selecting soils from literature with varying textural classes, from sands to very fine clayey soils. It is demonstrated that there is no direct relation between the textural class and the soil system class or order. It is suggested that the methodology could also be utilized as a tool for soil management or for the evaluation of agricultural capability of lands where other information (meteorological, phythological, topographic, and management level is included. Furthermore, the methodology contains useful information for irrigation system projects.

  5. The Pliocene Yafo Formation in Israel: Hydrogeologically inert or active?

    Science.gov (United States)

    Avisar, D.; Rosenthal, E.; Shulman, H.; Zilberbrand, M.; Flexer, A.; Kronfeld, J.; Ben Avraham, Z.; Fleischer, L.

    For several decades the ``Saqiye beds'' (later renamed Yafo Formation) underlying the Coastal Plain aquifer (Kurkar Group) aquifer of Israel, were regarded as an extremely thick, tectonically undisturbed, and absolutely impervious aquiclude. Following intensive groundwater exploitation from the overlying Kurkar Group aquifer, brackish and saline waters were locally encountered in the lower parts of this aquifer and always at the contact with the underlying Yafo Formation aquiclude. The present study revealed that this aquiclude is not a uniform and impervious rock unit, but rather an alternation of pervious and impervious strata within the Yafo Formation containing highly pressured fluids of different - mostly high - salinities. The permeable beds are at an angular unconformity and in direct contact with the overlying Kurkar Group aquifer. The Yafo Formation and the underlying and overlying rock units are dislocated by numerous fault systems, which facilitate accessibility of brines into the Kurkar Group aquifer. The mobilization of the saline fluids and their injection into the Kurkar Group aquifer could be due either to diffusion of saline fluids occurring in the permeable horizons of the Petah Tiqva Member through the clays of the Yafo Formation or to their upconing following intensive pumping in the Coastal Plain aquifer. It could have also been caused by up-dip movement of saline water as the result of overpressure generated by major accumulation of gas in the permeable horizons. Another possible mechanism could be hydraulic contact with pressurized brines up-flowing along fault zones from deep-seated Jurassic or Cretaceous reservoirs. The squeezing of saline interstitial water from the clays of the Yafo Formation into the overlying Kurkar Group aquifer, is of secondary importance for groundwater salinization (its input is comparable with salt input from rain). Depuis longtemps, les «couches de Saqiye», nommées maintenant formation de Yafo, constituant le

  6. A Study on Saltwater Intrusion Around Kolleru Lake, Andhra Pradesh, India

    Directory of Open Access Journals (Sweden)

    K.Harikrishna

    2012-07-01

    Full Text Available Kolleru Lake, the largest natural fresh water lake in Andhra Pradesh in India, located between Krishna and Godavari deltas is acting as a natural flood balancing reservoir and is fed directly by water from the seasonal rivers Budameru, Ramileru and Tammileru, and is also connected to the Krishna and Godavari drainage system consists of over 68 inflowing drains and channels. Over-exploitation of groundwater and land use conversions to aqua-culture are becoming the sources for salt-water intrusion to this lake and coastal aquifers, in specific, are highly vulnerable to seawater intrusion. Hydrogeomorphological study indicates that the potential aquifers around the Kolleru lake are paleo beach ridges and buried river courses. All other geomorphic features either aquiclude or aquitards are may not be considered as prospective zones for groundwater. Though there are number of open wells present in the villages used for potable water earlier, people switched over to imported water as their drinking water source may be due to significant contaminationof groundwater resources. Present land use activities like aqua-culture, agriculture, large-scale industries and allied industries in and around the Kolleru lake region has large contribution for the change of water quality. The paleo beach ridge areas, where the permeability of the sandy soil is very high, are also converted into aqua ponds. Integrated study using remote sensing, hydrogeology, hydrochemistry and geophysical investigations revealed the extent of salt-water intrusion up to the northern part of the lake which is about 40 km from the coast line. The electrical resistivity of aquifers is less than 1.0 (ohm-m having salinity of more than 1.2 ppt and the resistivity is around 20 (ohm-m where the salinity is less than 0.5 ppt, has also served as an excellent criteria for delineating the fresh-water and salt-water interface. Lenses of fresh water/ brackish water are noticed only in the beach

  7. An ecological mechanism to create regular patterns of surface dissolution in a low-relief carbonate landscape

    Science.gov (United States)

    Cohen, M. J.; Martin, J. B.; Mclaughlin, D. L.; Osborne, T.; Murray, A.; Watts, A. C.; Watts, D.; Heffernan, J. B.

    2012-12-01

    Development of karst landscapes is controlled by focused delivery of water undersaturated with respect to the soluble rock minerals. As that water comes to equilibrium with the rock, secondary porosity is incrementally reinforced creating a positive feedback that acts to augment the drainage network and subsequent water delivery. In most self-organizing systems, spatial positive feedbacks create features (in landscapes: patches; in karst aquifers: conduits) whose size-frequency relationship follows a power function, indicating a higher probability of large features than would occur with a random or Gaussian genesis process. Power functions describe several aspects of secondary porosity in the Upper Floridan Aquifer in north Florida. In contrast, a different pattern arises in the karst landscape in southwest Florida (Big Cypress National Preserve; BICY), where low-relief and a shallow aquiclude govern regional hydrology. There, the landscape pattern is highly regular (Fig. 1), with circular cypress-dominated wetlands occupying depressions that are hydrologically isolated and distributed evenly in a matrix of pine uplands. Regular landscape patterning results from spatially coupled feedbacks, one positive operating locally that expands patches coupled to another negative that operates at distance, eventually inhibiting patch expansion. The positive feedback in BICY is thought to derive from the presence of surface depressions, which sustain prolonged inundation in this low-relief setting, and facilitate wetland development that greatly augments dissolution potential of infiltrating water in response to ecosystem metabolic processes. In short, wetlands "drill" into the carbonate leading to both vertical and lateral basin expansion. Wetland expansion occurs at the expense of surrounding upland area, which is the local catchment that subsidizes water availability. A distal inhibitory feedback on basin expansion thus occurs as the water necessary to sustain prolonged

  8. Groundwater and urbanisation, risks and mitigation: The case for the city of Windhoek, Namibia

    Science.gov (United States)

    Mapani, B. S.

    The City of Windhoek is underlain by the Kuiseb Schist, locally known as the “Windhoek Schist” and amphibolites. In the low-lying parts of the Windhoek valley, gravels and sands are present. The Windhoek schist has several lithologies, dominated by garnet-muscovite-chlorite-biotite schist, with distinctive cleavage. This pervasive cleavage renders the underlying lithology permeable to fluids percolating from the surface into the aquifer. Other minor lithologies are trachytes, metarhyolites and quartzites found to the east of the city. The amphibolite is part of the Matchless belt, and traverses the city in a NE-SW fashion. When weathered, it forms a perfect aquiclude. North-south and northeast-southwest trending faults with a few splays cut across the Kuiseb Schist. The faults play a significant role in increasing the fracture density of the fissile schist. The faults are the major links that form channels between the surface and the aquifer below. The city of Windhoek uses the aquifer both as a source of fresh water and as a storage facility. The recharge areas of the aquifer lie to the east and south- to southeast of the city in the vicinity of the suburb of Kleine Kuppe. The soil horizon over the Windhoek schist is very shallow and most buildings are built directly on bedrock. The thin soil horizon makes the aquifer prone to pollution, caused either by accidents such as spills or by carelessness due to unsupervised dumping. The fissility and fracture density of the schist imply that leakage of surface waters, phenols, septic-tank spills, sewer-bursts, chemical and industrial contaminants and other such materials can reach the aquifer in unusually high rainfall years. The effects of fuels and oils are much more adverse, as they may remain in soils for long periods. The rapid urbanization and building of informal settlements without sewage reticulation has increased the risk of pollution to the Windhoek aquifer. The close monitoring of sewage pipes, filling

  9. Mining-induced fault reactivation associated with the main conveyor belt roadway and safety of the Barapukuria Coal Mine in Bangladesh: Constraints from BEM simulations

    Energy Technology Data Exchange (ETDEWEB)

    Islam, Md. Rafiqul; Shinjo, Ryuichi [Department of Physics and Earth Sciences, University of the Ryukyus, Okinawa, 903-0213 (Japan)

    2009-09-01

    Fault reactivation during underground mining is a critical problem in coal mines worldwide. This paper investigates the mining-induced reactivation of faults associated with the main conveyor belt roadway (CBR) of the Barapukuria Coal Mine in Bangladesh. The stress characteristics and deformation around the faults were investigated by boundary element method (BEM) numerical modeling. The model consists of a simple geometry with two faults (Fb and Fb1) near the CBR and the surrounding rock strata. A Mohr-Coulomb failure criterion with bulk rock properties is applied to analyze the stability and safety around the fault zones, as well as for the entire mining operation. The simulation results illustrate that the mining-induced redistribution of stresses causes significant deformation within and around the two faults. The horizontal and vertical stresses influence the faults, and higher stresses are concentrated near the ends of the two faults. Higher vertical tensional stress is prominent at the upper end of fault Fb. High deviatoric stress values that concentrated at the ends of faults Fb and Fb1 indicate the tendency towards block failure around the fault zones. The deviatoric stress patterns imply that the reinforcement strength to support the roof of the roadway should be greater than 55 MPa along the fault core zone, and should be more than 20 MPa adjacent to the damage zone of the fault. Failure trajectories that extend towards the roof and left side of fault Fb indicate that mining-induced reactivation of faults is not sufficient to generate water inflow into the mine. However, if movement of strata occurs along the fault planes due to regional earthquakes, and if the faults intersect the overlying Lower Dupi Tila aquiclude, then liquefaction could occur along the fault zones and enhance water inflow into the mine. The study also reveals that the hydraulic gradient and the general direction of groundwater flow are almost at right angles with the trends of

  10. Evidence of spring formation and subrosion-induced sinkhole development at Ghor Al-Haditha, Jordan, from repeated close-range photogrammetry

    Science.gov (United States)

    Al-Halbouni, Djamil; Eoghan, P. Holohan; Leila, Saberi; Hussam, Alrshdan; Thomas, Walter; Ali, Sawarieh; Torsten, Dahm

    2016-04-01

    The widespread development of sinkholes and land subsidence poses a major geological hazard to infrastructure, local population, agriculture and industry in the Dead Sea area. For assessment of the key physical factors in this development, repeated photogrammetric and field surveys at Ghor Al-Haditha in Jordan have been undertaken. Recent results provide evidence for subrosion based on strong periodic water flows, as the basic underlying physical process of such land subsidence phenomena. From combined Helikite- and Quatrocopter-based photogrammetric surveys, high resolution Digital Surface Models from October 2014 and October 2015 are compared. Change detection reveals: (1) active subsidence in a hundred metre-scale depression zone, (2) a highly-dynamic spring and canyon system connected with recent sinkhole collapses and (3) the rapid formation of new sinkholes both in alluvium and mud cover sediments. The formation of new sinkholes has been documented locally by means of aerial and field observations during a storm with strong rainfall. A new artesian spring formed in the former Dead Sea bed (mud-flat) at this event. The alluvial sediment load of the stream, a periodic location change of the spring and a connected uphill sinkhole cluster formation provide strong evidence for subrosion of weak material with subsequent underground void collapse. Additionally a documented lake and its' subsequent drainage forming a new canyon reveals the local penetration of the aquiclude behavior of the mud-flat in the major depression area, which can be explained by an under-saturated groundwater flow at a strong hydrostatic gradient. Furthermore an enlargement of the investigated area in the 2015 survey indicates a continuation of subsidence and sinkhole activity towards the North. It reveals several points of emanation of water streams in the mud-flat beneath the alluvial cover and vegetation as an indicator of relatively fresh groundwater inflow. This repeated photogrammetry

  11. Eight years of groundwater monitoring at the building site of the MOSE system for the safeguard of Venice

    Science.gov (United States)

    Casasso, Alessandro; Sethi, Rajandrea; Di Molfetta, Antonio

    2015-04-01

    The survival of Venice is threatened by the continuous increase of frequency and intensity of tidal floods. To prevent these events, a safeguarding system known as MOSE is under construction at the inlets of the Lagoon of Venice. Four arrays of mobile barriers will be lifted in the case of exceptionally high tides (>1.10 m) to insulate the Lagoon. The prefabrication of the mobile barriers required a large construction area close to the final installation sites. Given the lack of space in the inlets of Lido and Chioggia, two basins of the future navigation locks were used for this purpose, and a system of water pumps and wells was therefore installed in each site to ensure the accessibility and safety of the construction areas. The impact of dewatering on the aquifers on the mainland in Punta Sabbioni (inlet of Lido) was monitored by means of continuous hydraulic head measurements in a network 25 piezometers, 11 screened in the phreatic aquifer and 14 in the shallowest confined aquifer. These aquifers are separated by a 5 m thick clayey aquiclude, and a 30 m thick impervious layer isolates them from the underlying confined aquifers, which were therefore not monitored. Each monitoring well was equipped with an automatic water pressure transducer and the hourly recorded hydraulic heads were compensated with the barometric pressure. The time series were compared with the natural driving forces (tides, rainfall, evapotranspiration) and the anthropogenic impact sources (dewatering pumping, slurry walls, land reclamation channels). The dynamics of seawater intrusion were also studied through monthly measurements of the vertical profiles of the electrical conductivity (EC) of groundwater. The monitoring activity was successful in assessing the impacts of the construction works. A drawdown was observed in the confined aquifer due to the dewatering pumping, with a maximum displacement of some 5 m on the mainland and an extension of some 1000 m from the dewatered basin. By

  12. Lessons Learned from a Complex FUSRAP Site - Sylvania Corning FUSRAP Site - 12269

    Energy Technology Data Exchange (ETDEWEB)

    Ewy, Ann; Hays, David [United States Army Corps of Engineers, Kansas City, Missouri, 64106 (United States)

    2012-07-01

    Since its addition to the Formerly Utilized Sites Remedial Action Program (FUSRAP) in 2005, the Sylvania Corning FUSRAP Site (the Site) in Hicksville, New York, has provided challenges and opportunities from which to gain lessons learned for conducting investigation work at a complex multi-contaminant FUSRAP Site. The United States Army Corps of Engineers (USACE) and its contractors conducted a Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) Remedial Investigation (RI) and are currently in the Feasibility Study (FS) phase at the Site. This paper presents the planning, execution, and reporting lessons learned by USACE during the RI/FS. The Site, operated from 1952 to 1967 for the research, development, and fabrication of nuclear elements under the Atomic Energy Commission, and other government and commercial contracts. Previous investigations performed by the New York State Department of Environmental Conservation (NYSDEC) and the current property owner have identified uranium, thorium, nickel, and chlorinated solvents, as Site contaminants [1]. The property owner is currently under two separate voluntary agreements with NYSDEC to investigate and remediate the Site. USACE's work at the site has been independent of this voluntary agreement and has moved on a parallel path with any work the property owner has completed. The project at the Site is complex because of the radiological and chemical concerns in both soils and groundwater, high hydraulically conductive soils, lack of a shallow aquiclude/aquitard, and a principal water table aquifer underlying the site. Contaminants are migrating from the Site and may potentially impact local drinking water supplies (municipal wells). During the RI/FS process the project team has encountered many issues and has thus developed many resolutions. The issues are organized into three categories: Planning and Contracting, Execution, and Reporting. Planning and Contracting lessons learned include

  13. Characterization of alluvial aquifers by multiscale hydrostratigraphic interpretation of DC resistivity data

    Science.gov (United States)

    Mele, Mauro; Bersezio, Riccardo; Giudici, Mauro

    2010-05-01

    The characterization of aquifer heterogeneity plays a key role for the 3-D modelling of conductivity (K) distribution in the subsurface of alluvial plains. DC methods such as Vertical Electrical Soundings (VES) and Electrical Resistivity Ground Imaging (ERGI) yield respectively the 1-D and 2-D resistivity (ρ) distribution in the ground and are often applied in hydrogeology because ρ is controlled by the prevailing process of current conduction ('shale' vs. electrolytic conduction) determined by the occurrence of fine-grained sediments and saline groundwater. Assuming that the sedimentary heterogeneity can be described with hierarchical elements at different scales (from hydrofacies to hydrostratigraphic systems) and recalling that the resolution of DC surveys decreases with depth, we propose an interpretation of the subsurface ρ distribution as a function of the hierarchical properties of aquifers (i.e., the vertical trends of facies with prevailing 'shale' or electrolytic conduction) with hydrostratigraphic constrains. A correlation between ρ and pore-fluid saturation and chemistry permits the use of resistivity as a 'proxy' of facies stacking. Our case-study is the Quaternary valley of palaeo-Sillaro extinct meandering river (Po plain, Italy). The local stratigraphy up to 80 m below ground surface consists of LGM sand-gravel point bar and channel bodies overlying: i) clay to fine sand aquitard of an Upper Pleistocene flood plain, ii) alternating gravel-sand aquifer bodies and fine sand to silty-clay drapes formed by Middle-Upper Pleistocene braiding to meandering depositional systems that developed above iii) a basal aquiclude of silty-clays. To interpret 1-D resistivity models obtained by 89 VES collected with Schlumberger array (maximum half-spacing 300 m) over an area of 30 km2, a Coarse-to-Fine (C/F) litho-textural ratio (particle size cut-off=0.30 mm) was used to classify hydrofacies. The variability of C/F was compared with the K and ρ values of

  14. Kinematics of the 1991 Randa rockslides (Valais, Switzerland

    Directory of Open Access Journals (Sweden)

    M. Sartori

    2003-01-01

    mineralogical alteration of the fault gouge accumulated along the sliding surface, reducing its angle of internal friction, and sealing the surface against water circulation. Once this basal fracture began to act as an aquiclude, the seasonal increase of the hydraulic head in the fissures promoted hydraulic fracturing on the highly stressed edges of the key block. Acceleration of this mechanical degradation occurred during the 20-year period before the 1991 rockslides, giving rise to an increasing rockfall activity, that constituted a forewarning sign. The final triggering event corresponded to a snow-melt period with high water table, leading to fracturation around the key block. On 18 April 1991, the key block finally failed, allowing subsidiary orthogneiss blocks to slide. They fell in turn over a period of several hours. The 9 May 1991, rockslide was the first of a series of expected future retrogressive reequilibrium stages of the very fractured and decompressed paragneisses, which lie on the orthogneiss base cut by the 18 April event.

  15. Impacts of convection on high-temperature aquifer thermal energy storage

    Science.gov (United States)

    Beyer, Christof; Hintze, Meike; Bauer, Sebastian

    2016-04-01

    Seasonal subsurface heat storage is increasingly used in order to overcome the temporal disparities between heat production from renewable sources like solar thermal installations or from industrial surplus heat and the heat demand for building climatisation or hot water supply. In this context, high-temperature aquifer thermal energy storage (ATES) is a technology to efficiently store and retrieve large amounts of heat using groundwater wells in an aquifer to inject or withdraw hot or cold water. Depending on the local hydrogeology and temperature amplitudes during high-temperature ATES, density differences between the injected hot water and the ambient groundwater may induce significant convective flow components in the groundwater flow field. As a consequence, stored heat may accumulate at the top of the storage aquifer which reduces the heat recovery efficiency of the ATES system. Also, an accumulation of heat at the aquifer top will induce increased emissions of heat to overlying formations with potential impacts on groundwater quality outside of the storage. This work investigates the impacts of convective heat transport on the storage efficiency of a hypothetical high-temperature ATES system for seasonal heat storage as well as heat emissions to neighboring formations by numerical scenario simulations. The coupled groundwater flow and heat transport code OpenGeoSys is used to simulate a medium scale ATES system operating in a sandy aquifer of 20 m thickness with an average groundwater temperature of 10°C and confining aquicludes at top and bottom. Seasonal heat storage by a well doublet (i.e. one fully screened "hot" and "cold" well, respectively) is simulated over a period of 10 years with biannual injection / withdrawal cycles at pumping rates of 15 m³/h and for different scenarios of the temperature of the injected water (20, 35, 60 and 90 °C). Simulation results show, that for the simulated system significant convective heat transport sets in when

  16. Ground-water resources of Pavant Valley, Utah

    Science.gov (United States)

    Mower, R.W.

    1965-01-01

    from the recharge areas near the mountains, it becomes confined beneath clay beds; thus artesian conditions prevail in the lower parts of the valley. Although as many as 12 saturated beds of sand and gravel are penetrated in drilling wells to depths of 800 feet, they constitute, generally, one aquifer. The beds of coarser material are interconnected laterally, and the confining beds between them are not perfect aquicludes but merely impede the vertical movement of water. Artesian pressure increases with depth; thus, there is a continual upward flow of water from the lowest to the highest aquifer, and water not withdrawn through wells is discharged at the land surface or into basalt flows along the western edge of the valley. Most recharge to the sand and gravel aquifers enters the ground on the alluvial fans as percolation from streams, irrigation ditches, and irrigated fields. Some recharge results from underflow from the canyons and the face of the mountains and also from precipitation on the alluvial fans. Leakage from the Central Utah Canal is a major source of recharge to alluvial aquifers in the northern half of the valley. The Pavant Flow in the western part of the valley and the basalt underlying the area west of the Black Rock Volcano in the southern part are both major unconfined basalt aquifers. The Pavant Flow is recharged by upward leakage of water from the underlying artesian aquifer, by percolation of irrigation water, by water moving laterally in shallow sand and gravel deposits, and by precipitation on outcrops along the western side of the valley. The basalt underlying the area west of the Black Rock Volcano is recharged by precipitation in the mountains, leakage from the artesian aquifer, and percolation of irrigation water. The ,basalt ,aquifers are relatively thin, averaging 30-60 feet in thickness where -they supply water to irrigation wells. The valley is divided into six districts based on geologic and hydrologic diffe

  17. Calculation of infiltration coefficient of precipitation based on long-term observation data of spring water:a case study of ore deposit bearing karst water in Dazhuyuan bauxite mining area in Wuchuan%利用泉水长观资料计算降水入渗系数--以务川自治县大竹园铝土矿区岩溶充水矿床为例

    Institute of Scientific and Technical Information of China (English)

    黄作明

    2016-01-01

    Dazhuyuan bauxite mining area in Wuchuan Autonomous County is a positive landform of mountain platform syncline.The deposits are ore deposits filled with karst water with deep depth of water level.At-mospheric precipitation is the only recharge source of the ground water.In the north,east and west there are escarpments or steep slopes.Metallogenic series and aquiclude occur on the foot of escarpments.A surface watershed is distributed along the upper edge of escarpments with an opening to the west,and forms a com-plete hydrogeological unit.The ground water in the syncline runs from east to west and collects at Meigudong for discharge.The bauxite layer directly touches the thin and discontinuous roof of shale of Liangshan For-mation (P2 l ),and the strong aquifer above of limestone of Maokouqixia Formation (P2m +q )is in direct contact with ore bed,while the karst pipelines are well developed.Therefore,it is more appropriate to apply the water balance method in terms of calculating the water inflow in the mine.The observational data of spring water is used to calculate infiltration coefficient,so as to predict the water inflow in the mine and to evaluate the water yield property of the aquifer.%务川自治县大竹园铝土矿区为高山台地向斜正地形,岩溶充水矿床,水位埋藏较深,大气降水是地下水的唯一补给源,北、东、西为陡崖或陡坡,崖脚为矿系和隔水层,沿陡崖上部边缘分布一条开口向西的地表分水岭,形成完整的水文地质单元,地下水在向斜内由东向西汇集于梅古洞排泄。铝土矿层直接顶板梁山组(P2 l )页岩,厚度小,不连续,其上部茅口栖霞组(P2 m +q )灰岩强含水层与矿层直接接触,并且岩溶管道发育。因此,计算矿坑涌水量的方法用水均衡法较为恰当,即利用泉水观测资料计算入渗系数,从而达到预测矿坑涌水量、评价含水层富水性的目的。

  18. Organic compounds as indicators for transport in an urban characterized complex karst system

    Science.gov (United States)

    Reh, R.; Licha, T.; Nödler, K.; Geyer, T.; Sauter, M.

    2012-04-01

    In northern Hesse (Germany), sediments of the Upper Permian (Zechstein-Formations) are outcropping in a coastal facies along the western rim of the Rhenish Massif. The geologic section is characterized by a sequence of carbonate rocks (carbonates of the Werra-, Staßfurt- and Leine-Formations) and predominantly fine clastic sediments. The carbonate aquifers of the Werra-Formation and the Leine-Formation are used for drinking water abstraction of a provincial town and surrounding communities. Concurrently, the urban area is characterized by industrial and commercial uses. The groundwater flow system is composed of three potential karst aquifers, aquitards and aquicludes within a complex tectonically faulted area. The study area is divided into three spring catchment areas. However, the locations of the subsurface water divides are unknown. Traditional methods to determine the catchment areas (e.g. artificial tracer tests) are difficult to apply, due to a lack of adequate injection points. The presented work deals with the use of organic compounds as indicators for subsurface flow paths. Medical drugs, pesticides, corrosion inhibitors and such typical waste water compounds as caffeine (NÖDLER ET AL. 2010) are observed in approximately fifty groundwater observation points by regular sampling. The seasonal variability of the distribution pattern of organic compounds is low. The most common compounds are atrazine and its metabolites desethylatrazine and desisopropylatrazine, as well as the corrosion inhibitor 1H-benzotriazole. Since these substances are applied in different regions different input functions can be assumed. However, the highest concentrations are detected along a North-orientated axis, which also exhibits the greatest compound variety. This distribution pattern indicates preferential flow and transport pathways in the subsurface. The absence of organic compounds in other parts of the investigation area implies the existence of a water divide between

  19. Large sedimentary aquifer system and sustainable management: investigations of hydrogeological and geochemical variations in Eocene sand aquifer, south western France

    Science.gov (United States)

    Malcuit, E.; Negrel, P. J.; Petelet-Giraud, E.; Durst, P.

    2010-12-01

    In the sedimentary Aquitaine Basin, the Eocene Sand Aquifer system, mostly confined, represents strategic resources for drinking water, irrigation, gas storage and geothermal resources. Therefore, its quantity and quality issues are essential for the sustainable management in this large region that extends over 116,000 km2 (i.e. one-fifth of the French territory). The Eocene Sand Aquifer system comprises at least five aquifers: Paleocene, Eocene infra-molassic sands, early Eocene, middle Eocene, and late Eocene. The extension and thickness of Eocene aquifer layers and negative confined layers vary throughout the basin, from several tens of metres to a hundred metres. The deposit sequences characterizing the Eocene Aquifer System are progradational westward from detrital deposits to carbonates. Eocene sands and Eocene limestones are hydraulically connected and covered by an aquiclude of up to several hundred metres thick of molassic sediments. The groundwater recharge is assumed to occur through the Eocene outcrops located in the north and north-east, and in the south east in contact with the Montagne Noire as well as by vertical leakage from the upper and lower aquifers. Another recharge is suspected in the south near the Petites Pyrenees. According to isotopic data, both present-day recharge and old recharge (16-35 ky) can be evidenced. The north and south evolutions of the piezometric surface are different. In the north, because of years of pumping, a trough in the potentiometric surface has been formed. The piezometric decline is roughly one meter per year in the depression centre. In the south, the decline of the water table is roughly half a meter per year. Furthermore, in the south part, around two sites of gas storage, significant fluctuations of the potentiometric surface are superimposed to the variations resulting from water abstraction, due to the injection and abstraction of gas. However, a major difficulty for the sustainable management is the lack of

  20. A refined genetic model for the Laisvall and Vassbo Mississippi Valley-type sandstone-hosted deposits, Sweden: constraints from paragenetic studies, organic geochemistry, and S, C, N, and Sr isotope data

    Science.gov (United States)

    Saintilan, Nicolas J.; Spangenberg, Jorge E.; Samankassou, Elias; Kouzmanov, Kalin; Chiaradia, Massimo; Stephens, Michael B.; Fontboté, Lluís

    2016-06-01

    hydrocarbons in sandstone. Other minor H2S sources are identified. Upward migration and fluctuation of the hydrocarbon-water interface in sandstone below shale aquicludes and the formation of H2S along this interface explain the shape of the orebodies that splay out like smoke from a chimney and the conspicuous alternating layers of galena and sphalerite. Intimate intergrowth of bitumen with sphalerite suggests that subordinate amounts of H2S might have been produced by TSR during Pb-Zn mineralization. Gas chromatograms of the saturated hydrocarbon fraction from organic-rich shale and from both mineralized and barren sandstone samples indicate that hydrocarbons migrated from source rocks in the overlying Alum Shale Formation buried in the foredeep into sandstone, where they accumulated in favorable traps in the forebulge setting.

  1. Multi-isotope tracing of CO2 leakage and water-rock interaction in a natural CCS analogue.

    Science.gov (United States)

    Kloppmann, Wolfram; Gemeni, Vasiliki; Lions, Julie; Koukouzas, Nikolaos; Humez, Pauline; Vasilatos, Charalampos; Millot, Romain; Pauwels, Hélène

    2015-04-01

    Natural analogues of CO2 accumulation and, potentially, leakage, provide a highly valuable opportunity to study (1) geochemical processes within a CO2-reservoir and the overlying aquifers or aquicludes, i.e. gas-water-rock interactions, (2) geology and tightness of reservoirs over geological timescales, (3) potential or real leakage pathways, (3) impact of leakage on shallow groundwater resources quality, and (4) direct and indirect geochemical indicators of gas leakage (Lions et al., 2014, Humez et al., 2014). The Florina Basin in NW Macedonia, Greece, contains a deep CO2-rich aquifer within a graben structure. The graben filling consists of highly heterogeneous Neogene clastic sediments constituted by components from the adjacent massifs including carbonates, schists, gneiss as well as some ultramafic volcanic rocks. Clay layers are observed that isolate hydraulically the deep, partly artesian aquifer. Organic matter, in form of lignite accumulations, is abundant in the Neogene series. The underlying bedrocks are metamorphic carbonates and silicate rocks. The origin of the CO2 accumulation is controversial (deep, partially mantle-derived D'Allessandro et al., 2008 or resulting from thermal decomposition of carbonates, Hatziyannis and Arvanitis, 2011). Groundwaters have been sampled from springs and borewells over 3 years at different depths. First results on major, minor and trace elements give evidence of water-rock interaction, mainly with carbonates but also with ultramafic components but do not indicate that CO2-seepage is the principal driver of those processes (Gemeni et al., submitted). Here we present isotope data on a selection of groundwaters (δ2H , δ18O, δ13CTDIC, 87Sr/86Sr, δ11B, δ7Li). Stable isotopes of water indicate paleo-recharge for some of the groundwaters, limited exchange with gaseous CO2 and, in one case, possibly thermal exchange processes with silicates. Sr isotope ratios vary between marine ratios and radiogenic values indicating