Scale-dependency of macroinvertebrate communities: responses to contaminated sediments within run-of-river dams.

Science.gov (United States)

Colas, Fanny; Archaimbault, Virginie; Devin, Simon

2011-03-01

Due to their nutrient recycling function and their importance in food-webs, macroinvertebrates are essential for the functioning of aquatic ecosystems. These organisms also constitute an important component of biodiversity. Sediment evaluation and monitoring is an essential aspect of ecosystem monitoring since sediments represent an important component of aquatic habitats and are also a potential source of contamination. In this study, we focused on macroinvertebrate communities within run-of-river dams, that are prime areas for sediment and pollutant accumulation. Little is known about littoral macroinvertebrate communities within run-of-river dam or their response to sediment levels and pollution. We therefore aimed to evaluate the following aspects: the functional and structural composition of macroinvertebrate communities in run-of-river dams; the impact of pollutant accumulation on such communities, and the most efficient scales and tools needed for the biomonitoring of contaminated sediments in such environments. Two run-of-river dams located in the French alpine area were selected and three spatial scales were examined: transversal (banks and channel), transversal x longitudinal (banks/channel x tail/middle/dam) and patch scale (erosion, sedimentation and vegetation habitats). At the patch scale, we noted that the heterogeneity of littoral habitats provided many available niches that allow for the development of diversified macroinvertebrate communities. This implies highly variable responses to contamination. Once combined on a global 'banks' spatial scale, littoral habitats can highlight the effects of toxic disturbances. Copyright © 2011 Elsevier B.V. All rights reserved.

Contaminated Sediment Management in Dam Removals and River Restoration Efforts: Critical Need for Research and Policy Development

Science.gov (United States)

Evans, J. E.

2015-12-01

Over 1,000 U.S. dams have been removed (1975-2015) for reasons including obsolescence, liability concerns, water quality upgrades, fisheries, or ecosystem enhancements. Contaminated sediment can significantly complicate the approval process, cost, and timeline of a dam removal, or stop it entirely. In a dam removal, reservoir sediment changes from a sink to a source of contaminants. Recently, the Sierra Club sued to stop the removal of a large dam in Ohio because of the potential impact of phosphate releases on toxic algal blooms in Lake Erie. Heavy metals, PCBs, PAHs, pesticides, and petroleum hydrocarbons can be present in reservoir sediments. In a non-dam removal scenario, reservoir management tools range from "no action" to dredging, dewatering and removal, or sediment capping. But it is not clear how these reservoir management techniques apply to dam removals. Case studies show typically >80% of the reservoir sediment is eventually eroded, precluding sediment capping as a containment option. However, the released contaminants are diluted by mixing with "clean" sediment and are transported to different physio-chemical environments which may immobilize or biodegrade the contaminants. Poorly understood options include phased drawdown/reseeding the former reservoir to contain sediments, diking contaminant "hot spots," and addressing contaminant stratigraphy (where historical use created "hot layers" in the reservoir sediment). Research and policy development needs include: (1) assessment methods based on synergistic effects of multiple contaminants being present; (2) ways to translate the pre-removal contaminant concentrations to post-removal health risks downstream; (3) evaluation of management practices for contaminant "hot spots" and "hot layers;" (4) tools to forecast the presence of contaminated sediment using easily accessible information; and (5) ways to limit liability risk for organizations participating in dam removals involving contaminated sediment.

Distribution and accumulation of heavy metals in the sediments of Akkaya Dam, Nigde, Turkey.

Science.gov (United States)

Keskin, Şeref

2012-01-01

Twenty-one surface sediment samples were collected from Akkaya Dam. Heavy metal concentrations (Mo, Cu, Pb, Zn, Ni, Co, Mn, Fe, Cr, As, V and Cd), grain size, organic carbon and carbonate contents were studied in order to assess the extent of environmental pollution and to discuss the origin of these contaminants in sediments of dam. The sediments in the study area are mostly very fine sands. However, mud was observed in the northeast of the dam. Sediment pollution assessment was carried out using enrichment factor. The calculation of enrichment factors showed that Mo is depleted by 1.0 whereas Cu, Pb, Zn, Ni, Co, Mn, As, V, Cr and Cd are enriched by 3, 5.4, 7, 2.7, 2.2, 3.4, 42.3, 2.1, 1.8 and 7.2, respectively. Relatively high concentrations heavy metals occurred in north (textile industry area) and east (Karasu River) due to enrichment controlled by anthropogenic wastes. The results of correlation analysis show low-medium positive and negative correlations among metals, grain size, carbonate contents and organic carbon and indicate that heavy metals in sediments of the Akkaya Dam have different anthropogenic sources.

Sediment and 137Cs transport and accumulation in the Ogaki Dam of eastern Fukushima

International Nuclear Information System (INIS)

Yamada, Susumu; Malins, Alex; Machida, Masahiko; Kitamura, Akihiro; Kurikami, Hiroshi; Yamaguchi, Masaaki

2015-01-01

The Ogaki Dam Reservoir is one of the principal irrigation dam reservoirs in the Fukushima Prefecture and its upstream river basin was heavily contaminated by radioactivity from the Fukushima Daiichi Nuclear Power Plant accident. For the purpose of environmental assessment, it is important to determine the present condition of the water in the reservoir and to understand the behavior of sediment-sorbed radioactive cesium under different modes of operation of the dam, as these factors affect further contamination of arable farmlands downstream of the reservoir through sediment migration. This paper addresses this issue with numerical simulations of fluvial processes in the reservoir using the two-dimensional Nays2D code. We distinguish three grades of sediment (clay, silt, and sand), as cesium adherence depends on sediment grain size and surface area. Boundary conditions for the simulations were informed by monitoring data of the upstream catchment and by the results from a separate watershed simulation for sediment transport into the reservoir. The performance of the simulation method was checked by comparing the results for a typhoon flood in September 2013 against field monitoring data. We present results for sediment deposition on the reservoir bed and the discharge via the dam under typical yearly flood conditions, for which the bulk of annual sediment migration from the reservoir occurs. The simulations show that almost all the sand and silt that enter into the reservoir deposit onto the reservoir bed. However, the locations where they tend to deposit differ, with sand tending to deposit close to the entrance of the reservoir, whereas silt deposits throughout the reservoir. Both sand and silt settle within a few hours of entering the reservoir. In contrast, clay remains suspended in the reservoir water for a period as long as several days, thus increasing the amount that is discharged downstream from the reservoir. Under the current operating mode of the dam

Large-scale dam removal on the Elwha River, Washington, USA: source-to-sink sediment budget and synthesis

Science.gov (United States)

Warrick, Jonathan A.; Bountry, Jennifer A.; East, Amy E.; Magirl, Christopher S.; Randle, Timothy J.; Gelfenbaum, Guy R.; Ritchie, Andrew C.; Pess, George R.; Leung, Vivian; Duda, Jeff J.

2015-01-01

Understanding landscape responses to sediment supply changes constitutes a fundamental part of many problems in geomorphology, but opportunities to study such processes at field scales are rare. The phased removal of two large dams on the Elwha River, Washington, exposed 21 ± 3 million m3, or ~ 30 million tonnes (t), of sediment that had been deposited in the two former reservoirs, allowing a comprehensive investigation of watershed and coastal responses to a substantial increase in sediment supply. Here we provide a source-to-sink sediment budget of this sediment release during the first two years of the project (September 2011–September 2013) and synthesize the geomorphic changes that occurred to downstream fluvial and coastal landforms. Owing to the phased removal of each dam, the release of sediment to the river was a function of the amount of dam structure removed, the progradation of reservoir delta sediments, exposure of more cohesive lakebed sediment, and the hydrologic conditions of the river. The greatest downstream geomorphic effects were observed after water bodies of both reservoirs were fully drained and fine (silt and clay) and coarse (sand and gravel) sediments were spilling past the former dam sites. After both dams were spilling fine and coarse sediments, river suspended-sediment concentrations were commonly several thousand mg/L with ~ 50% sand during moderate and high river flow. At the same time, a sand and gravel sediment wave dispersed down the river channel, filling channel pools and floodplain channels, aggrading much of the river channel by ~ 1 m, reducing river channel sediment grain sizes by ~ 16-fold, and depositing ~ 2.2 million m3 of sand and gravel on the seafloor offshore of the river mouth. The total sediment budget during the first two years revealed that the vast majority (~ 90%) of the sediment released from the former reservoirs to the river passed through the fluvial system and was discharged to the coastal

Modelling the impact of dam removal on geomorphic channel response and sediment delivery: an Austrian case study

Science.gov (United States)

Pöppl, Ronald; Coulthard, Tom; Keesstra, Saskia; Keiler, Margreth

2015-04-01

Dams are often considered to have the most significant impact on rivers as dam construction generally reduces downstream sediment fluxes which further involves geomorphic changes in the affected river reaches. Since many dams no longer fulfill their intended purpose (e.g. due to siltation), are dangerous (e.g. catastrophic dam failures) and/or are ecologically damaging (e.g. habitat destruction), within the last two decades several dams have been removed and many more are already proposed for removal. Unfortunately, there is still only little empirical knowledge about the geomorphic consequences of dam removals and the related sediment release which represents a big challenge for river management. Modelling is one way to approach this problem. In the presented study we modelled the impacts of dam removal on geomorphic channel processes, channel morphology and sediment delivery further considering the role of channel engineering measures and reservoir excavation within a river reach impacted by a series of dams using the landscape evolution model CAESAR-Lisflood. The model was run with data from a small catchment located in Lower Austria. Modelled geomorphic channel changes and sediment fluxes were spatio-temporally analyzed, related to real-world data and are discussed in the context of river management issues.

Soil erosion and sediment yield, a double barrel problem in South Africa's only large river network without a dam

Science.gov (United States)

Le Roux, Jay

2016-04-01

Soil erosion not only involves the loss of fertile topsoil but is also coupled with sedimentation of dams, a double barrel problem in semi-arid regions where water scarcity is frequent. Due to increasing water requirements in South Africa, the Department of Water and Sanitation is planning water resource development in the Mzimvubu River Catchment, which is the only large river network in the country without a dam. Two dams are planned including a large irrigation dam and a hydropower dam. However, previous soil erosion studies indicate that large parts of the catchment is severely eroded. Previous studies, nonetheless, used mapping and modelling techniques that represent only a selection of erosion processes and provide insufficient information about the sediment yield. This study maps and models the sediment yield comprehensively by means of two approaches over a five-year timeframe between 2007 and 2012. Sediment yield contribution from sheet-rill erosion was modelled with ArcSWAT (a graphical user interface for SWAT in a GIS), whereas gully erosion contributions were estimated using time-series mapping with SPOT 5 imagery followed by gully-derived sediment yield modelling in a GIS. Integration of the sheet-rill and gully results produced a total sediment yield map, with an average of 5 300 t km-2 y-1. Importantly, the annual average sediment yield of the areas where the irrigation dam and hydropower dam will be built is around 20 000 t km-2 y-1. Without catchment rehabilitation, the life expectancy of the irrigation dam and hydropower dam could be 50 and 40 years respectively.

A Study of the Impact of Dams on Streamflow and Sediment Retention in the Mekong River Basin

Science.gov (United States)

Munroe, T.; Anderson, E.; Markert, K. N.; Griffin, R.

2017-12-01

Dam construction in the Mekong Basin has many cascading effects on the ecology, economy, and hydrology of the surrounding region. Current studies that assess the hydrological impact of dams in the region focus on only one or a small subset (SWAT), a rainfall-runoff hydrologic model to determine change in streamflow and sedimentation in the Mekong Basin before and after the construction of dams. This study uses land cover land use and reservoir datasets created by the NASA SERVIR-Mekong Regional Land Cover Monitoring System and Dam Inundation Mapping Tool as inputs into the model. The study also builds on the capabilities of the SWAT model by using the sediment trapping efficiency (STE) equation from Brune (1953), rewritten by Kummu (2007), to calculate STE of dams and estimate change in sediment concentration downstream. The outputs from this study can be used to inform dam operation policies, study the correlation between dams and delta subsidence, and study the impact of dams on river fisheries, which are all pressing issues in the Mekong region.

Lost opportunities and future avenues to reconcile hydropower and sediment transport in the Mekong Basin through optimal sequencing of dam portfolios.

Science.gov (United States)

Castelletti, A.; Schmitt, R. J. P.; Bizzi, S.; Kondolf, G. M.

2017-12-01

Dams are essential to meet growing water and energy demands. While dams cumulatively impact downstream rivers on network-scales, dam development is mostly based on ad-hoc economic and environmental assessments of single dams. Here, we provide evidence that replacing this ad-hoc approach with early strategic planning of entire dam portfolios can greatly reduce conflicts between economic and environmental objectives of dams. In the Mekong Basin (800,000km2), 123 major dam sites (status-quo: 56 built and under construction) could generate 280,000 GWh/yr of hydropower. Cumulatively, dams risk interrupting the basin's sediment dynamics with severe impacts on livelihoods and eco-systems. To evaluate cumulative impacts and benefits of the ad-hoc planned status-quo portfolio, we combine the CASCADE sediment connectivity model with data on hydropower production and sediment trapping at each dam site. We couple CASCADE to a multi-objective genetic algorithm (BORG) identifying a) portfolios resulting in an optimal trade-off between cumulative sediment trapping and hydropower production and b) an optimal development sequence for each portfolio. We perform this analysis first for the pristine basin (i.e., without pre-existing dams) and then starting from the status-quo portfolio, deriving policy recommendations for which dams should be prioritized in the near future. The status-quo portfolio creates a sub-optimal trade-off between hydropower and sediment trapping, exploiting 50 % of the basin's hydro-electric potential and trapping 60 % of the sediment load. Alternative optimal portfolios could have produced equivalent hydropower for 30 % sediment trapping. Imminent development of mega-dams in the lower basin will increase hydropower production by 20 % but increase sediment trapping to >90 %. In contrast, following an optimal development sequence can still increase hydropower by 30 % with limited additional sediment trapping by prioritizing dams in upper parts of the basin. Our

THE ANALYSIS OF SABO DAM PERFORMANCE AS A SEDIMENT CONTROL STRUCTURE IN PUTIH RIVER, MT. MERAPI

Directory of Open Access Journals (Sweden)

Andre Wisoyo

2015-02-01

Full Text Available Mt. Merapi’s eruption which occurred on 26 October 2010 had disadvantageous impact for human life that live surrounds it. The primary disaster was pyroclastic cloud that destroyed villages surround it. In addition, the secondary disaster continuously became a threat for human life around the rivers that destroyed at Mount Merapi. One of the secondary disasters is Putih River’s volcanic material overflowing into Yogyakarta-Magelang Highway. The series of Sabo dam which had been built along the river could not handle that phenomenon. Sabo dam was built and expected to accommodate volcanic material or at least to resist the velocity of volcanic material (sediment controlling, so the damage caused by the flow became relatively small. However, this function could not work at that phenomenon. In order to know the function of sediment control of Sabo dam in Putih River, it is necessary to study the performance of Sabo dam. This research used Kanako software ver. 2.04 and reviewed Sabo dam PU-D1 Mranggen and PU-C8 Ngaglik. There were four simulated scenarios in this research: a scenario without Sabo dam; with Sabo dam PU-D1 Mranggen; with Sabo dam PU-C8 Ngaglik, and the last with two of Sabo dams. The simulation was based on 23 January 2011 event and simulated for 18.000 s. From this research, it can be concluded that Sabo dam PU-D1 Mranggen can reduce the total volume  passing through about 43,998.6 m3 or 1.53 % for 5 hours, and reduce the sediment volume that passing through about 28,482 m3 or 52.59 % for 5 hours. Sabo dam PU-C8 Ngaglik can reduce the total volume that passing through about 255.6 m3 or 0.01 % for 5 hours, and reduce the sediment volume that passing through about 124.8 m3 or 0.33 % for 5 hours, and Sabo dam PU-D1 Mranggen and PU-C8 Ngaglik in series can reduce the total volume that passing through about 2,340.6 m3 or 0.08 % for 5 hours, and reduce the sediment volume that passing through about 157.8 m3 or 0.41 % for 5 hours

Anticipated sediment delivery to the lower Elwha River during and following dam removal: Chapter 2 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

Science.gov (United States)

Czuba, Christiana R.; Randle, Timothy J.; Bountry, Jennifer A.; Magirl, Christopher S.; Czuba, Jonathan A.; Curran, Christopher A.; Konrad, Christopher P.; Duda, Jeffrey J.; Warrick, Jonathan A.; Magirl, Christopher S.

2011-01-01

During and after the planned incremental removal of two large, century-old concrete dams between 2011 and 2014, the sediment-transport regime in the lower Elwha River of western Washington will initially spike above background levels and then return to pre-dam conditions some years after complete dam removal. Measurements indicate the upper reaches of the steep-gradient Elwha River, draining the northeast section of the Olympic Mountains, carries between an estimated 120,000 and 290,000 cubic meters of sediment annually. This large load has deposited an estimated 19 million cubic meters of sediment within the two reservoirs formed by the Elwha and Glines Canyon Dams. It is anticipated that from 7 to 8 million cubic meters of this trapped sediment will mobilize and transport downstream during and after dam decommissioning, restoring the downstream sections of the sediment-starved river and nearshore marine environments. Downstream transport of sediment from the dam sites will have significant effects on channel morphology, water quality, and aquatic habitat during and after dam removal. Sediment concentrations are expected to be between 200 and 1,000 milligrams per liter during and just after dam removal and could rise to as much as 50,000 milligrams per liter during high flows. Downstream sedimentation in the river channel and flood plain will be potentially large, particularly in the lower Elwha River, an alluvial reach with a wide flood plain. Overall aggradation could be as much as one to several meters. Not all reservoir sediment, however, will be released to the river. Some material will remain on hill slopes and flood plains within the drained reservoirs in quantities that will depend on the hydrology, precipitation, and mechanics of the incising channel. Eventually, vegetation will stabilize this remaining reservoir sediment, and the overall sediment load in the restored river will return to pre-dam levels.

Estimating accumulation rates and physical properties of sediment behind a dam: Englebright Lake, Yuba River, northern California

Science.gov (United States)

Snyder, Noah P.; Rubin, David M.; Alpers, Charles N.; Childs, Jonathan R.; Curtis, Jennifer A.; Flint, Lorraine E.; Wright, Scott A.

2004-01-01

Studies of reservoir sedimentation are vital to understanding scientific and management issues related to watershed sediment budgets, depositional processes, reservoir operations, and dam decommissioning. Here we quantify the mass, organic content, and grain-size distribution of a reservoir deposit in northern California by two methods of extrapolating measurements of sediment physical properties from cores to the entire volume of impounded material. Englebright Dam, completed in 1940, is located on the Yuba River in the Sierra Nevada foothills. A research program is underway to assess the feasibility of introducing wild anadromous fish species to the river upstream of the dam. Possible management scenarios include removing or lowering the dam, which could cause downstream transport of stored sediment. In 2001 the volume of sediments deposited behind Englebright Dam occupied 25.5% of the original reservoir capacity. The physical properties of this deposit were calculated using data from a coring campaign that sampled the entire reservoir sediment thickness (6–32 m) at six locations in the downstream ∼3/4 of the reservoir. As a result, the sediment in the downstream part of the reservoir is well characterized, but in the coarse, upstream part of the reservoir, only surficial sediments were sampled, so calculations there are more uncertain. Extrapolation from one-dimensional vertical sections of sediment sampled in cores to entire three-dimensional volumes of the reservoir deposit is accomplished via two methods, using assumptions of variable and constant layer thickness. Overall, the two extrapolation methods yield nearly identical estimates of the mass of the reservoir deposit of ∼26 × 106 metric tons (t) of material, of which 64.7–68.5% is sand and gravel. Over the 61 year reservoir history this corresponds to a maximum basin-wide sediment yield of ∼340 t/km2/yr, assuming no contribution from upstream parts of the watershed impounded by other dams. The

Distribution of 137Cs and 226Ra in the sediments of Aswan High Dam lake

International Nuclear Information System (INIS)

Ismail, S.S.; Unfried, E.; Grass, F.

1994-01-01

Sediment samples of the High Dam lake were investigated for their 137 Cs, 226 Ra, 228 Th, and 40 K content, using low-level γ-spectroscopy. The results show that at the beginning of the lake (500 km from the High Dam), where sediments consist mostly of sand, the level of 137 Cs is very low (0.1 Bq*kg -1 ). The maximum value (22.3 Bq*kg -1 ) was found 40 km from the wall of the High Dam, where the composition of the sediments is nearly 50% clays. The distribution of the natural nuclides 226 Ra, 228 Th and 40 K shows a different trend. (author) 9 refs.; 9 figs.; 1 tab

Examination of dam induced sedimentation of small reservoir near Brennbergbánya

Science.gov (United States)

Csáfordi, P.; Kalicz, P.; Gribovszki, Z.; Kucsara, M.

2009-04-01

The dams' affects on the stream system also involve accelerated sedimentation of reservoirs, change of water and sediment regime. In consequence of sedimentation the lifetime and the recreational potential of reservoirs decrease and management practices have to be applied. The area of our study is a small forested catchment, where the erosion of forested land and the sedimentation of Brennberg Reservoir were investigated in relationship with each other. The Brennberg Reservoir has been built in 1981. It has been silting up forcefully since that time. It has to be dredged with hydraulic earth-moving to preserve its landscape-aesthetical function for the future. We have surveyed the surface to establish the rate of sedimentation. The results of this measurement were processed with a GIS software (named Digiterra Map). There were several uncertainties during our surveying in the field. Therefore three other methods were applied based on GIS and a simply mathematical calculation. The amount of deposited sediment was determined with these methods. Then we compared the results to each other. The annual specific soil loss was estimated according to results of our measurement. Keywords: dam impact, reservoir sedimentation, GIS

Reconstruction of the sediment flow regime in a semi-arid Mediterranean catchment using check dam sediment information.

Science.gov (United States)

Bussi, G.; Rodríguez, X.; Francés, F.; Benito, G.; Sánchez-Moya, Y.; Sopeña, A.

2012-04-01

When using hydrological and sedimentological models, lack of historical records is often one of the main problems to face, since observed data are essential for model validation. If gauged data are poor or absent, a source of additional proxy data may be the slack-water deposits accumulated in check dams. The aim of this work is to present the result of the reconstruction of the recent hydrological and sediment yield regime of a semi-arid Mediterranean catchment (Rambla del Poyo, Spain, 184 square km) by coupling palaeoflood techniques with a distributed hydrological and sediment cycle model, using as proxy data the sandy slack-water deposits accumulated upstream a small check dam (reservoir volume 2,500 square m) located in the headwater basin (drainage area 13 square km). The solid volume trapped into the reservoir has been estimated using differential GPS data and an interpolation technique. Afterwards, the total solid volume has been disaggregated into various layers (flood units), by means of a stratigraphical description of a depositional sequence in a 3.5 m trench made across the reservoir sediment deposit, taking care of identifying all flood units; the separation between flood units is indicated by a break in deposition. The sedimentary sequence shows evidence of 15 flood events that occurred after the dam construction (early '90). Not all events until the present are included; for the last ones, the stream velocity and energy conditions for generating slack-water deposits were not fulfilled due to the reservoir filling. The volume of each flood unit has been estimated making the hypothesis that layers have a simple pyramidal shape (or wedge); every volume represents an estimation of the sediments trapped into the reservoir corresponding to each flood event. The obtained results have been compared with the results of modeling a 20 year time series (1990 - 2009) with the distributed conceptual hydrological and sediment yield model TETIS-SED, in order to

Radiological assessment of dam water and sediments for natural ...

African Journals Online (AJOL)

Radiological assessment of dam water and sediments for natural radioactivity and its overall health detriments. ... No artificial gamma emitting radionuclide was detected in the samples. The projected ... However, the chances of radiological hazard to the health of human from radioactivity in the soil were generally low.

Large-scale dam removal on the Elwha River, Washington, USA: fluvial sediment load

Science.gov (United States)

Magirl, Christopher S.; Hilldale, Robert C.; Curran, Christopher A.; Duda, Jeffrey J.; Straub, Timothy D.; Domanski, Marian M.; Foreman, James R.

2015-01-01

The Elwha River restoration project, in Washington State, includes the largest dam-removal project in United States history to date. Starting September 2011, two nearly century-old dams that collectively contained 21 ± 3 million m3 of sediment were removed over the course of three years with a top-down deconstruction strategy designed to meter the release of a portion of the dam-trapped sediment. Gauging with sediment-surrogate technologies during the first two years downstream from the project measured 8,200,000 ± 3,400,000 tonnes of transported sediment, with 1,100,000 and 7,100,000 t moving in years 1 and 2, respectively, representing 3 and 20 times the Elwha River annual sediment load of 340,000 ± 80,000 t/y. During the study period, the discharge in the Elwha River was greater than normal (107% in year 1 and 108% in year 2); however, the magnitudes of the peak-flow events during the study period were relatively benign with the largest discharge of 292 m3/s (73% of the 2-year annual peak-flow event) early in the project when both extant reservoirs still retained sediment. Despite the muted peak flows, sediment transport was large, with measured suspended-sediment concentrations during the study period ranging from 44 to 16,300 mg/L and gauged bedload transport as large as 24,700 t/d. Five distinct sediment-release periods were identified when sediment loads were notably increased (when lateral erosion in the former reservoirs was active) or reduced (when reservoir retention or seasonal low flows and cessation of lateral erosion reduced sediment transport). Total suspended-sediment load was 930,000 t in year 1 and 5,400,000 t in year 2. Of the total 6,300,000 ± 3,200,000 t of suspended-sediment load, 3,400,000 t consisted of silt and clay and 2,900,000 t was sand. Gauged bedload on the lower Elwha River in year 2 of the project was 450,000 ± 360,000 t. Bedload was not quantified in year 1, but qualitative observations using bedload

GC51D-0831: A Study of the Impact of Dams on Sediment Retention in the Mekong River Basin

Science.gov (United States)

Munroe, Thailynn; Griffin, Robert; Anderson, Eric; Markert, Kel

2017-01-01

Dam construction in the Mekong Basin has many cascading effects on the ecology, economy, and hydrology of the surrounding region. The focus of this study is to utilize the Soil Water Assessment Tool (SWAT), developed at Texas A & M, a rainfall-runoff hydrologic model to determine change in sedimentation in the Mekong Basin after the construction of dams. This study uses land cover land use and reservoir datasets created by the NASA SERVIR-Mekong Regional Land Cover Monitoring System and Dam Inundation Mapping Tool as inputs into the model. The study also builds on the capabilities of the SWAT model by using the sediment trapping efficiency (STE) equation from Brune (1953), rewritten by Kummu & Varis (2007), to calculate STE of dams and estimate change in sediment concentration downstream. The outputs from this study can be used to inform dam operation policies, study the correlation between dams and delta subsidence, and study the impact of dams on river fisheries, which are all pressing issues in the Mekong region.

Detection of water leaks in the dam Joumine and study of sedimentation in the dam Ghezela by nuclear method

International Nuclear Information System (INIS)

Sari Souha

2013-01-01

The objective of this study is to determinate the paths of leaks observed in the dam Joumine and to identify the origin of salinity in the drain D2. In addition, the evaluation of the sedimentation measurement of suspended elements in the dam Ghezela is our second objective. The Joumine dam located in the North-east of Tunisia (governorate of Bizerte), was built in 1983 has an upstream watershed area of 418 km 2 . The reservoir capacity is 130 Mm 3 . This dam observed a water leakage from its implementation at the two drains D1 and D2 with a emerging flow rate reached a value close to 500 l/s, about 16 pour cent of its capacity. The injection of an insulating material in Karsts networks reduces the leakage rate to a value of 120 l / s in 1993 and 88 l / s in 2013, but this decrease was accompanied by an increase in salinity level in D2. The results from a multidisciplinary approach showed that the leakage path from the left bank of the reservoir where the leak was first detected, heading both D1 and D2 drains and the salinity in drain D2 due to the dissolution of the gypsum layer downstream of the dam and the contribution of brackish water from the left bank. The Ghezela dam located in the same area, was built in 1984 has an upstream watershed area of 48 km 2 . This dam has been an increase in sedimentation of 0.3 million m3 in 1994 to 1.7 million m 3 in 2010. In this study, the suspended elements were measured with a nuclear probe composed by a radioactive source of americium 241 and a NaI detector trained by a boat at different depth in the reservoir.

Sediment yield model implementation based on check dam infill stratigraphy in a semiarid Mediterranean catchment

Directory of Open Access Journals (Sweden)

G. Bussi

2013-08-01

Full Text Available Soil loss and sediment transport in Mediterranean areas are driven by complex non-linear processes which have been only partially understood. Distributed models can be very helpful tools for understanding the catchment-scale phenomena which lead to soil erosion and sediment transport. In this study, a modelling approach is proposed to reproduce and evaluate erosion and sediment yield processes in a Mediterranean catchment (Rambla del Poyo, Valencia, Spain. Due to the lack of sediment transport records for model calibration and validation, a detailed description of the alluvial stratigraphy infilling a check dam that drains a 12.9 km2 sub-catchment was used as indirect information of sediment yield data. These dam infill sediments showed evidences of at least 15 depositional events (floods over the time period 1990–2009. The TETIS model, a distributed conceptual hydrological and sediment model, was coupled to the Sediment Trap Efficiency for Small Ponds (STEP model for reproducing reservoir retention, and it was calibrated and validated using the sedimentation volume estimated for the depositional units associated with discrete runoff events. The results show relatively low net erosion rates compared to other Mediterranean catchments (0.136 Mg ha−1 yr−1, probably due to the extensive outcrops of limestone bedrock, thin soils and rather homogeneous vegetation cover. The simulated sediment production and transport rates offer model satisfactory results, further supported by in-site palaeohydrological evidences and spatial validation using additional check dams, showing the great potential of the presented data assimilation methodology for the quantitative analysis of sediment dynamics in ungauged Mediterranean basins.

Sediment trapping by dams creates methane emission hot spots

DEFF Research Database (Denmark)

Maeck, A.; Delsontro, T.; McGinnis, Daniel F.

2013-01-01

Inland waters transport and transform substantial amounts of carbon and account for similar to 18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams...... worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where...... sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (similar to 0.23 mmol CH4 m(-2) d(-1) vs similar to 19.7 mmol CH4 m(-2) d(-1), respectively) and that areal emission rates far exceed previous estimates for temperate...

Bed Degradation and Sediment Export from the Missouri River after Dam Construction and River Training: Significance to Lower Mississippi River Sediment Loads

Science.gov (United States)

Blum, M. D.; Viparelli, E.; Sulaiman, Z. A.; Pettit, B. S.

2016-12-01

More than 40,000 dams have been constructed in the Mississippi River drainage basin, which has had a dramatic impact on suspended sediment load for the Mississippi delta. The most significant dams were constructed in the 1950s on the Missouri River in South Dakota, after which total suspended loads for the lower Mississippi River, some 2500 km downstream, were cut in half: gauging station data from the Missouri-Mississippi system show significant load reductions immediately after dam closure, followed by a continued downward trend since that time. The delta region is experiencing tremendous land loss in response to acceleration of global sea-level rise, and load reductions of this magnitude may place severe limits on mitigation efforts. Here we examine sediment export from the Missouri system due to bed scour. The US Army Corps of Engineers has compiled changes in river stage at constant discharge for 8 stations between the lowermost dam at Yankton, South Dakota and the Missouri-Mississippi confluence at St. Louis (a distance of 1250 river km), for the period 1930-2010, which we have updated to 2015. These data show two general reaches of significant bed degradation. The first extends from the last major dam at Yankton, South Dakota downstream 300 km to Omaha, Nebraska, where degradation in response to the dam exceeds 3 m. The second reach, with >2.5 m of degradation, occurs in and around Kansas City, Missouri, and has been attributed to river training activities. The reach between Omaha and Kansas City, as well as the lower Missouri below Kansas City, show River due to bed scour following dam construction and river training. This number equates to 20-25 million tons per year, which is sufficient to account for 30% of the total Missouri River load, and 15% of the total post-dam annual sediment load for the lower Mississippi River. For perspective, the quantity of sediment exported from the Missouri River due to bed scour is greater than the total load for all

Recent coarsening of sediments on the southern Yangtze subaqueous delta front: A response to river damming

Science.gov (United States)

Yang, H. F.; Yang, S. L.; Meng, Y.; Xu, K. H.; Luo, X. X.; Wu, C. S.; Shi, B. W.

2018-03-01

After more than 50,000 dams were built in the Yangtze basin, especially the Three Gorges Dam (TGD) in 2003, the sediment discharge to the East China Sea decreased from 470 Mt/yr before dams to the current level of 140 Mt/yr. The delta sediment's response to this decline has interested many researchers. Based on a dataset of repeated samplings at 44 stations in this study, we compared the surficial sediment grain sizes in the southern Yangtze subaqueous delta front for two periods: pre-TGD (1982) and post-TGD (2012). External factors of the Yangtze River, including water discharge, sediment discharge and suspended sediment grain size, were analysed, as well as wind speed, tidal range and wave height of the coastal ocean. We found that the average median size of the sediments in the delta front coarsened from 8.0 μm in 1982 to 15.4 μm in 2012. This coarsening was accompanied by a decrease of clay components, better sorting and more positive skewness. Moreover, the delta morphology in the study area changed from an overall accretion of 1.0 cm/yr to an erosion of - 0.6 cm/yr. At the same time, the riverine sediment discharge decreased by 70%, and the riverine suspended sediment grain size increased from 8.4 μm to 10.5 μm. The annual wind speed and wave height slightly increased by 2% and 3%, respectively, and the tidal range showed no change trend. Considering the increased wind speed and wave height, there was no evidence that the capability of the China Coastal Current to transport sediment southward has declined in recent years. The sediment coarsening in the Yangtze delta front was thus mainly attributed to the delta's transition from accumulation to erosion which was originally generated by river damming. These findings have important implications for sediment change in many large deltaic systems due to worldwide human impacts.

The Impact of a Check Dam on Groundwater Recharge and Sedimentation in an Ephemeral Stream

Directory of Open Access Journals (Sweden)

Hakan Djuma

2017-10-01

Full Text Available Despite the widespread presence of groundwater recharge check dams, there are few studies that quantify their functionality. The objectives of this study are (i to assess groundwater recharge in an ephemeral river with and without a check dam and (ii to assess sediment build-up in the check-dam reservoir. Field campaigns were carried out to measure water flow, water depth, and check-dam topography to establish water volume, evaporation, outflow, and recharge relations, as well as sediment build-up. To quantify the groundwater recharge, a water-balance approach was applied at two locations: at the check dam reservoir area and at an 11 km long natural stretch of the river upstream. Prediction intervals were computed to assess the uncertainties of the results. During the four years of operation, the check dam (storage capacity of 25,000 m3 recharged the aquifer with an average of 3.1 million m3 of the 10.4 million m3 year−1 of streamflow (30%. The lower and upper uncertainty limits of the check dam recharge were 0.1 and 9.6 million m3 year−1, respectively. Recharge from the upstream stretch was 1.5 million m3 year−1. These results indicate that check dams are valuable structures for increasing groundwater resources in semi-arid regions.

Utilisation of Sepidrud dam basin sediments in fired clay bricks: laboratory scale experiment

OpenAIRE

Jamshidi-Chenari, R.; Rabanifar, H.; Veiseh, S.

2015-01-01

The prevailing disposal methods for dam basin sediments are not free from the environmental pollution and the ecological imbalance. At present, a new way to treat the dredged sediments to manufacture bricks is being investigated, prioritizing waste recovery over its deposition in landfills. However, construction materials such as clay bricks must comply with the international and local standards. Considering the perpetual availability of the sediments, particle sizing and their chemical compo...

Survey of Potential Hanford Site Contaminants in the Upper Sediment for the Reservoirs at McNary, John Day, The Dalles, and Bonneville Dams, 2003

Energy Technology Data Exchange (ETDEWEB)

Patton, Gregory W.; Priddy, M; Yokel, Jerel W.; Delistraty, Damon A.; Stoops, Thomas M.

2005-02-01

This report presents the results from a multi-agency cooperative environmental surveillance study. of the study looked at sediment from the pools upstream from dams on the Columbia River that are downstream from Hanford Site operations. The radiological and chemical conditions existing in the upper-level sediment found in the pools upstream from McNary Dam, John Day Dam, The Dalles Lock and Dam, and Bonneville Dam were evaluated. This study also evaluated beach sediment where available. Water samples were collected at McNary Dam to further evaluate potential Hanford contaminants in the lower Columbia River. Samples were analyzed for radionuclides, chemicals, and physical parameters. Results from this study were compared to background values from sediment and water samples collect from the pool upstream of Priest Rapids Dam (upstream of the Hanford Site) by the Hanford Site Surface Environmental Surveillance Project.

Check dam sediments: an important indicator of the effects of environmental changes on soil erosion in the Loess Plateau in China.

Science.gov (United States)

Wang, Yafeng; Chen, Liding; Fu, Bojie; Lü, Yihe

2014-07-01

Check dam sediments document the process of soil erosion for a watershed. The main objectives of this research are as follows: first, to determine whether the sediments trapped in check dams can provide useful information about local erosion and the environment, and second, to obtain the extent to which they can be stratigraphically interpreted and correlated to the land use history of an area controlled by check dams. Particle size and the concentration of (137)Cs in sediments are the indicators used to study the effects of environmental changes on soil erosion in the Loess Plateau, China. A total of 216 soil samples were collected from four sediment profile cores at the Yangjuangou watershed check dam constructed in 1955 and fully silted with sediments by 1965. The results indicated that (137)Cs dating and sediment particle size can characterize the sediment deposition process. Silt makes up more than 50 % of the sediment; both the clay and silt sediment fractions decrease gradually in the upstream direction. The sediment profiles are characterized by three depositional layers. These layers suggest changes in the land use. The top layer showed tillage disturbance, with moderate sediments and new soil mixed from 0 to 20 cm. A transition stage from wetlands (characterized by vegetation such as bulrush) to cropland is inferred from sediments at depths of 20-85 cm. Below 85 cm, sedimentary layering is obvious and there is no tillage disturbance. At the downstream site, A0, the average rate of sediment deposition from 1958 to 1963 was approximately 6,125.4 t year(-1) km(-2). Because of their high time resolution, check dam sediments indicate the effects of environmental changes on soil erosion, and they can provide a multiyear record of the soil erosion evolution at the local scale in the middle reaches of the Yellow River.

Natural and artificial radioactivity assessment of dam lakes sediments in Coruh River, Turkey

International Nuclear Information System (INIS)

Yasar Kobya; Sabit Korcak; Cafer Mert Yesilkanat

2015-01-01

In the sediment samples collected from 3 different dam reservoirs and 10 different stations on Coruh River, U-238, Th-232, K-40 and Cs-137 activity concentration levels were measured using high-resolution gamma-ray spectrometry. The mean concentrations of U-238, Th-232, K-40 and Cs-137 were found to be 15.8, 13.9, 551.5 and 18.1 Bq/kg in Deriner Dam Lake, 3.7, 12.5, 473.8 and 6.8 Bq/kg in Borcka Dam Lake, 14.4, 30.0, 491.7 and 18.2 Bq/kg in Muratli Dam Lake, respectively. Estimation calculations were made for the non-sampling zones by using Kriging method. Furthermore, results were compared with the similar studies done in different countries. (author)

Trace elements in sediment samples of the Aswan High Dam Lake

International Nuclear Information System (INIS)

Sherief, M.K.; Awadallah, R.M.; Grass, F.

1981-01-01

Main and trace elements in Nile sediments of the Aswan High Dam Lake were investigated by means of Instrumental Activation Analysis. It was shown that the composition of the Nile sediments changes in accordance with the large gradients in flow rate and with elution and absorption processes. Particles containing Ca, Ba, Hf, Ti, V, and Na are sedimented preferentially near the headwater of Lake Nubia, whereas some elements are rather uniformly distributed, e.g. Fe, Co, Sm, and Eu, and some, such as Al, Sc, Cs, Th, La, and Ce, show a distinct increase downstream. Some elements do not fit into any of these three groups. (author)

Coarse and fine sediment transportation patterns and causes downstream of the Three Gorges Dam

Science.gov (United States)

Li, Songzhe; Yang, Yunping; Zhang, Mingjin; Sun, Zhaohua; Zhu, Lingling; You, Xingying; Li, Kanyu

2017-11-01

Reservoir construction within a basin affects the process of water and sediment transport downstream of the dam. The Three Gorges Reservoir (TGR) affects the sediment transport downstream of the dam. The impoundment of the TGR reduced total downstream sediment. The sediment group d≤0.125 mm (fine particle) increased along the path, but the average was still below what existed before the reservoir impoundment. The sediments group d>0.125 mm (coarse particle) was recharged in the Yichang to Jianli reach, but showed a deposition trend downstream of Jianli. The coarse sediment in the Yichang to Jianli section in 2003 to 2007 was above the value before the TGR impoundment. However, the increase of both coarse and fine sediments in 2008 to 2014 was less than that in 2003 to 2007. The sediment retained in the dam is the major reason for the sediment reduction downstream. However, the retention in different river reaches is affected by riverbed coarsening, discharge, flow process, and conditions of lake functioning and recharging from the tributaries. The main conclusions derived from our study are as follows: 1) The riverbed in the Yichang to Shashi section was relatively coarse, thereby limiting the supply of fine and coarse sediments. The fine sediment supply was mainly controlled by TGR discharge, whereas the coarse sediment supply was controlled by the duration of high flow and its magnitude. 2) The supply of both coarse and fine sediments in the Shashi to Jianli section was controlled by the amount of total discharge. The sediment supply from the riverbed was higher in flood years than that in the dry years. The coarse sediment tended to deposit, and the deposition in the dry years was larger than that in the flood years. 3) The feeding of the fine sediment in the Luoshan to Hankou section was mainly from the riverbed. The supply in 2008 to 2014 was more than that in 2003 to 2007. Around 2010, the coarse sediments transited from depositing to scouring that was

Preliminary Experimental Results on the Technique of Artificial River Replenishment to Mitigate Sediment Loss Downstream Dams

Science.gov (United States)

Franca, M. J.; Battisacco, E.; Schleiss, A. J.

2014-12-01

The transport of sediments by water throughout the river basins, from the steep slopes of the upstream regions to the sea level, is recognizable important to keep the natural conditions of rivers with a role on their ecology processes. Over the last decades, a reduction on the supply of sand and gravel has been observed downstream dams existing in several alpine rivers. Many studies highlight that the presence of a dam strongly modifies the river behavior in the downstream reach, in terms of morphology and hydrodynamics, with consequences on local ecology. Sediment deficit, bed armoring, river incision and bank instability are the main effects which affect negatively the aquatic habitats and the water quality. One of the proposed techniques to solve the problem of sediment deficit downstream dams, already adopted in few Japanese and German rivers although on an unsatisfactory fashion, is the artificial replenishment of these. Generally, it was verified that the erosion of the replenishments was not satisfactory and the transport rate was not enough to move the sediments to sufficient downstream distances. In order to improve and to provide an engineering answer to make this technique more applicable, a series of laboratory tests are ran as preparatory study to understand the hydrodynamics of the river flow when the replenishment technique is applied. Erodible volumes, with different lengths and submergence conditions, reproducing sediment replenishments volumes, are positioned along a channel bank. Different geometrical combinations of erodible sediment volumes are tested as well on the experimental flume. The first results of the experimental research, concerning erosion time evolution, the influence of discharge and the distance travelled by the eroded sediments, will be presented and discussed.

A Falls Dam, Otago, sedimentation rate measured by the caesium-137 profile

International Nuclear Information System (INIS)

McCabe, W.J.; Mason, W.J.

1982-09-01

Two cores from the dam were examined. The lead-210 was measured from Core D, but because of the high sedimentation rate the ''unsupported'' lead-210 was not detectable above the ''supported'' lead background. Caesium-137 was determined from Core A and the profile obtained related to the pattern of the ''fallout'' caesium in rainwater. From this a sedimentation rate of 11 kg per sq. metre per year was calculated. In terms of the length of the core sample, this is equivalent to 1.3 cm per year

Comparative analysis of several sediment transport formulations applied to dam-break flows over erodible beds

Science.gov (United States)

Cea, Luis; Bladé, Ernest; Corestein, Georgina; Fraga, Ignacio; Espinal, Marc; Puertas, Jerónimo

2014-05-01

Transitory flows generated by dam failures have a great sediment transport capacity, which induces important morphological changes on the river topography. Several studies have been published regarding the coupling between the sediment transport and hydrodynamic equations in dam-break applications, in order to correctly model their mutual interaction. Most of these models solve the depth-averaged shallow water equations to compute the water depth and velocity. On the other hand, a wide variety of sediment transport formulations have been arbitrarily used to compute the topography evolution. These are based on semi-empirical equations which have been calibrated under stationary and uniform conditions very different from those achieved in dam-break flows. Soares-Frazao et al. (2012) proposed a Benchmark test consisting of a dam-break over a mobile bed, in which several teams of modellers participated using different numerical models, and concluded that the key issue which still needs to be investigated in morphological modelling of dam-break flows is the link between the solid transport and the hydrodynamic variables. This paper presents a comparative analysis of different sediment transport formulations applied to dam-break flows over mobile beds. All the formulations analysed are commonly used in morphological studies in rivers, and include the formulas of Meyer-Peter & Müller (1948), Wong-Parker (2003), Einstein-Brown (1950), van Rijn (1984), Engelund-Hansen (1967), Ackers-White (1973), Yang (1973), and a Meyer-Peter & Müller type formula but with ad-hoc coefficients. The relevance of corrections on the sediment flux direction and magnitude due to the bed slope and the non-equilibrium hypothesis is also analysed. All the formulations have been implemented in the numerical model Iber (Bladé et al. (2014)), which solves the depth-averaged shallow water equations coupled to the Exner equation to evaluate the bed evolution. Two different test cases have been

Pleniglacial sedimentation process reconstruction on laminated lacustrine sediments from lava-dammed Paleolake Alf, West Eifel Volcanic Field (Germany)

Science.gov (United States)

Eichhorn, Luise; Pirrung, Michael; Zolitschka, Bernd; Büchel, Georg

2017-09-01

Differentiating between regularly seasonal, irregular and event-based clastic sedimentation is difficult if sedimentation structures resemble and dating methods are imprecise. In this study - clastic light and dark laminae from lava-dammed Paleolake Alf in the Late Pleistocene in the Quaternary West Eifel Volcanic Field are analyzed to clarify how they formed and if they are of annual origin and comparable to assumed periglacial varves from neighboring Lake Holzmaar. Therefore, a multiproxy approach is applied combining sediment thin section analysis which focuses on composition and structure with 14C dates. The results are compared to recently-formed annually-laminated clastic sediments of, e.g., the High Canadian Arctic. Observed sedimentation structures reveal sediment delivery by over- and interflows and deposition from suspension forming two characteristic microfacies: Type I graded laminae and Type II laminae with graded sublayers. Additionally, erosional bases and event deposits indicate episodic underflows. Thus, lamination is potentially seasonal but is significantly veiled by extreme runoff causing erosion and resuspension processes or a mixed water body preventing sediment delivery into the lake basin. However, sedimentation processes between watershed and lake could be reconstructed by comparing recent and paleosediment structures.

Utilisation of Sepidrud dam basin sediments in fired clay bricks: laboratory scale experiment

Directory of Open Access Journals (Sweden)

Jamshidi-Chenari, R.

2015-12-01

Full Text Available The prevailing disposal methods for dam basin sediments are not free from the environmental pollution and the ecological imbalance. At present, a new way to treat the dredged sediments to manufacture bricks is being investigated, prioritizing waste recovery over its deposition in landfills. However, construction materials such as clay bricks must comply with the international and local standards. Considering the perpetual availability of the sediments, particle sizing and their chemical composition and the results of physical and qualification tests on Sepidrud Dam basin sediments it can be concluded that the utilization of basin sediments as a full or partial replacement in clay brick production will lead to the production of quality bricks that meet all the regulatory limits in the standards. This research is novel in view of both increasing the reservoir effective volume capacity and preventing the use of alternative land quarries which are mainly covered by green land.Los métodos actuales de eliminación de los sedimentos de las cuencas de las presas no están exentos de problemas de contaminación ambiental y ecológicos. En la actualidad, se está investigando la posibilidad de utilizar los sedimentos dragados para la fabricación de ladrillos, dando prioridad a su valoración como residuos frente a su depósito en vertederos. Sin embargo, los ladrillos, como otros materiales de construcción, deben de cumplir con las correspondientes normas nacionales e internacionales. Teniendo en cuenta la disponibilidad permanente de los sedimentos, el tamaño de sus partículas y su composición química y los resultados físicos de las pruebas de calificación de los sedimentos de la cuenca Sepidrud Dam, en este estudio se ha concluido su viabilidad como materiales de reemplazo total o parcial de las materias primas convencionales, para la producción de ladrillos. Estos ladrillos cumplen además con las normas vigentes. Este es un estudio novedoso

Top down arsenic uncertainty measurement in water and sediments from Guarapiranga dam (Brazil)

Science.gov (United States)

Faustino, M. G.; Lange, C. N.; Monteiro, L. R.; Furusawa, H. A.; Marques, J. R.; Stellato, T. B.; Soares, S. M. V.; da Silva, T. B. S. C.; da Silva, D. B.; Cotrim, M. E. B.; Pires, M. A. F.

2018-03-01

Total arsenic measurements assessment regarding legal threshold demands more than average and standard deviation approach. In this way, analytical measurement uncertainty evaluation was conducted in order to comply with legal requirements and to allow the balance of arsenic in both water and sediment compartments. A top-down approach for measurement uncertainties was applied to evaluate arsenic concentrations in water and sediments from Guarapiranga dam (São Paulo, Brazil). Laboratory quality control and arsenic interlaboratory tests data were used in this approach to estimate the uncertainties associated with the methodology.

Dam construction impacts on multiscale characterization of sediment discharge in two typical karst watersheds of southwest China

Science.gov (United States)

Li, Zhenwei; Xu, Xianli; Xu, Chaohao; Liu, Meixian; Wang, Kelin

2018-03-01

Southwest China, as one of the largest continuous karst areas in the world, is a severely eroded region due to its special geological condition. Thus, soil and water conservation measures such as dam construction have been extensively implemented in this region to control sediment delivery. However, it remains unclear how dam construction affects multiscale variability of sediment discharge (SD) and its potentially influential factors in southwest China. To assess this, annual SD, water discharge (WD), precipitation (PT), potential evapotranspiration (PET), and normalized differential vegetation index (NDVI) data from 1955 to 2015 were obtained from two karst watersheds of Liujiang (no large dams) and Hongshui (dam-controlled). These sites shared the similar climatic conditions. The Mann-Kendal test, Wilcoxon rank-sum test, and continuous wavelet transform analysis was used to detect the trends and periodicity in SD, and wavelet coherence analysis were employed to detect the temporal covariance between SD and WD, PT, PET, and NDVI. Results indicated that the multiscale variability of SD was strongly influenced by dam construction. The annual SD showed significant 4-year periodic oscillation in the Liujiang watershed, while no significant cycles were found in the Hongshui watershed. Dam construction exerted substantial influence on the multiscale correlations between SD and its associated factors. The time scales that the NDVI resonated with SD were concentrated on the periodicity of 2- and 3-year in the Liujiang watershed. In contrast, no significant periodicities were observed in the Hongshu watershed. This study yields a greater understanding of SD dynamics, and is helpful for better watershed management in karst areas of southwest China.

A Non-Equilibrium Sediment Transport Model for Dam Break Flow over Moveable Bed Based on Non-Uniform Rectangular Mesh

Directory of Open Access Journals (Sweden)

Gangfeng Wu

2018-05-01

Full Text Available The use of multiple-level non-uniform rectangular mesh in coupled flow and sediment transport modeling is preferred to achieve high accuracy in important region without increasing computational cost greatly. Here, a robust coupled hydrodynamic and non-equilibrium sediment transport model is developed on non-uniform rectangular mesh to simulate dam break flow over movable beds. The enhanced shallow water and sediment transport equations are adopted to consider the mass and momentum exchange between the flow phase and sediment phase. The flux at the interface is calculated by the positivity preserving central upwind scheme, which belongs to Godunov-type Riemann-problem-solver-free central schemes and is less expensive than other popular Riemann solvers while still capable of tracking wet/dry fronts accurately. The nonnegative water depth reconstruction method is used to achieve second-order accuracy in space. The model was first verified against two laboratory experiments of dam break flow over irregular fixed bed. Then the quantitative performance of the model was further investigated by comparing the computational results with measurement data of dam break flow over movable bed. The good agreements between the measurements and the numerical simulations are found for the flow depth, velocity and bed changes.

Surface water leakage, sedimentation and evaporation in arid regions: A case study of the Gargar dam, Algeria

Directory of Open Access Journals (Sweden)

Hassen Benfetta

2017-12-01

Full Text Available This study was carried out in order to assess the total capacity loss in Gargar dam, third-largest in Algeria, due to the mudding of the reservoir, intense evaporation and water leaks. We analysed the variation in leakage as a function of the reservoir level, and quantify losses due to leaks, sedimentation and evaporation. We relied on site visits and data obtained from the Algerian Agency for Dams and Transfers to assess the leakage volume; reservoir level; sedimentation and evaporation levels for the period 1988–2015. We present an updated report of this problem through the dam. We estimated total average losses of 23 million m3·year−1 for the period 1988–2015, made up of leakage (0.3 million m3·year−1, evaporation (18 million m3·year−1 and dead storage for 4.6 million m3·year−1. However, total losses for 2004 were estimated at 113.9 million m3, which increased to the alarming value of 166.8 million m3 in 2015. We suggest improving the waterproofness by a concrete screen, and reducing mudding and evaporation by reforestation, to increase the storage capacity of the dam.

Identifying and Evaluating Options for Improving Sediment Management and Fish Passage at Hydropower Dams in the Lower Mekong River Basin

Science.gov (United States)

Wild, T. B.; Reed, P. M.; Loucks, D. P.

2015-12-01

The Mekong River basin in Southeast Asia is undergoing intensive and pervasive hydropower development to satisfy demand for increased energy and income to support its growing population of 60 million people. Just 20 years ago this river flowed freely. Today some 30 large dams exist in the basin, and over 100 more are being planned for construction. These dams will alter the river's natural water, sediment and nutrient flows, thereby impacting river morphology and ecosystems, and will fragment fish migration pathways. In doing so, they will degrade one of the world's most valuable and productive freshwater fish habitats. For those dams that have not yet been constructed, there still exist opportunities to modify their siting, design and operation (SDO) to potentially achieve a more balanced set of tradeoffs among hydropower production, sediment/nutrient passage and fish passage. We introduce examples of such alternative SDO opportunities for Sambor Dam in Cambodia, planned to be constructed on the main stem of the Mekong River. To evaluate the performance of such alternatives, we developed a Python-based simulation tool called PySedSim. PySedSim is a daily time step mass balance model that identifies the relative tradeoffs among hydropower production, and flow and sediment regime alteration, associated with reservoir sediment management techniques such as flushing, sluicing, bypassing, density current venting and dredging. To date, there has been a very limited acknowledgement or evaluation of the significant uncertainties that impact the evaluation of SDO alternatives. This research is formalizing a model diagnostic assessment of the key assumptions and parametric uncertainties that strongly influence PySedSim SDO evaluations. Using stochastic hydrology and sediment load data, our diagnostic assessment evaluates and compares several Sambor Dam alternatives using several performance measures related to energy production, sediment trapping and regime alteration, and

Dam removal: Listening in

Science.gov (United States)

Foley, M. M.; Bellmore, J. R.; O'Connor, J. E.; Duda, J. J.; East, A. E.; Grant, G. E.; Anderson, C. W.; Bountry, J. A.; Collins, M. J.; Connolly, P. J.; Craig, L. S.; Evans, J. E.; Greene, S. L.; Magilligan, F. J.; Magirl, C. S.; Major, J. J.; Pess, G. R.; Randle, T. J.; Shafroth, P. B.; Torgersen, C. E.; Tullos, D.; Wilcox, A. C.

2017-07-01

Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam-removal studies over the last few decades motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far, some general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam-removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal tends to quickly reestablish connectivity, restoring the movement of material and organisms between upstream and downstream river reaches; (4) geographic context, river history, and land use significantly influence river restoration trajectories and recovery potential because they control broader physical and ecological processes and conditions; and (5) quantitative modeling capability is improving, particularly for physical and broad-scale ecological effects, and gives managers information needed to understand and predict long-term effects of dam removal on riverine ecosystems. Although these studies collectively enhance our understanding of how riverine ecosystems respond to dam removal, knowledge gaps remain because most studies have been short (< 5 years) and do not adequately represent the diversity of dam types, watershed conditions, and dam-removal methods in the U.S.

Improvement of the mechanical performance of Fergoug dam sediments treated for reuse in road engineering

Directory of Open Access Journals (Sweden)

Abdelkader LAROUCI

2018-01-01

Full Text Available The phenomenon of siltation is one of the main problems facing many dams throughout the world, and particularly in Algeria. The mud, before and even after extraction, is always harmful. Indeed, mud is a harmful material, first for dams, because it reduces their capacity of water storage, and second, for the environment following the desilting operations that generate large quantities of materials that occupy and sometimes pollute large areas. However, these materials can be exploited differently and used in other fields. The envisaged research work relates to real cases of silted dams, such as the dam of Fergoug (western Algeria whose siltation rate is very high; it is estimated at 97% of its initial capacity which, according to the National Agency for Dams (Agence Nationale des Barrages - ANB, is equal to 18 million m3. The large quantities of silt extracted present an environmental problem, and its use as a local raw material for the manufacture of civil engineering materials can contribute to solve this problem. The vulnerable lands of the sub-catchment of Wadi Fergoug (Fergoug River extend over an area of 122 km2, from a total surface of 8340 km2 for the dam catchment area. There is a great diversity of superficial formations with predominantly clay soils from marly formations. The rate of specific erosion has increased to 160 T/ km2/ year due to irregular annual rainfall resulting from a succession of dry and wet years. Sedimentary materials, which are found in considerable quantities, were collected at the foot of the dam, on its right bank. This study attempts to find a recycling pathway for these sediments. The objective of the present work is to investigate the behavior of silt from the dam of Fergoug (Algeria for the purpose of using it in road construction (foundation and base layers. The method adopted is to reconstitute, in the laboratory, samples of mixtures containing road aggregates with different proportions of silt. These

Reductions in fish-community contamination following lowhead dam removal linked more to shifts in food-web structure than sediment pollution.

Science.gov (United States)

Davis, Robert P; Sullivan, S Mažeika P; Stefanik, Kay C

2017-12-01

Recent increases in dam removals have prompted research on ecological and geomorphic river responses, yet contaminant dynamics following dam removals are poorly understood. We investigated changes in sediment concentrations and fish-community body burdens of mercury (Hg), selenium (Se), polychlorinated biphenyls (PCB), and chlorinated pesticides before and after two lowhead dam removals in the Scioto and Olentangy Rivers (Columbus, Ohio). These changes were then related to documented shifts in fish food-web structure. Seven study reaches were surveyed from 2011 to 2015, including controls, upstream and downstream of the previous dams, and upstream restored vs. unrestored. For most contaminants, fish-community body burdens declined following dam removal and converged across study reaches by the last year of the study in both rivers. Aldrin and dieldrin body burdens in the Olentangy River declined more rapidly in the upstream-restored vs. the upstream-unrestored reach, but were indistinguishable by year three post dam removal. No upstream-downstream differences were observed in body burdens in the Olentangy River, but aldrin and dieldrin body burdens were 138 and 148% higher, respectively, in downstream reaches than in upstream reaches of the Scioto River following dam removal. The strongest relationships between trophic position and body burdens were observed with PCBs and Se in the Scioto River, and with dieldrin in the Olentangy River. Food-chain length - a key measure of trophic structure - was only weakly related to aldrin body burdens, and unrelated to other contaminants. Overall, we demonstrate that lowhead dam removal may effectively reduce ecosystem contamination, largely via shifts in fish food-web dynamics versus sediment contaminant concentrations. This study presents some of the first findings documenting ecosystem contamination following dam removal and will be useful in informing future dam removals. Copyright © 2017 Elsevier Ltd. All rights reserved.

Physical modelling of sediment transport in mountain torrents upstream of open check dams

Science.gov (United States)

Schwindt, Sebastian; Franca, Mario J.; Schleiss, Anton J.

2015-04-01

Dynamic morphological processes in mountain torrents do not only attract the attention of many contemporary researchers, but are also a relevant issue for the design of flood protection measures in the downstream sections where dwellers may be threatened by the important potential of flows with high concentration of sediments. Events which have a morphodynamic effect are simulated at the Laboratory of Hydraulic Constructions (LCH) in order to optimize the design of a flood protection measure, notably open check dams. Different scenarios with a fix bed consisting of boulders as well as mobile beds are studied and the influence of flow constrictions, i.e. distinct geometric configurations of open check dams are analysed. Three varying water pumped discharges in the order of 5 to 20 l/s are tested with progressively increasing solid discharges of 1, 3 and 6 % of the liquid discharge according to the transport capacity. The moistened sediments are introduced via a system of conveyor belts and are then mixed with the liquid discharge in an about 3 m long rough trapezoidal channel with a base width of 24 cm. The mean diameter Dm of the injected sediments is 0.86 cm and the dimensionless grain size distribution is in line with a normalized shape derived from over 60 streams in the Alps. A wide range of frequent floods in morphologically diverging types of mountain torrents is covered, in particular regarding the sediment availability in the catchment area and along the river. A basic assumption here is considering that the frequent floods are floods with return periods between 1 to 5 years and are the most important process in terms of amounts of sediment transport. This may be arguable for some mountain torrents and landscape effective processes which are driven by floods with return periods of more than several decades. In order to identify benchmarks for hydraulic parameters which lead to the obstruction of flow restrictions at mountain torrents, the water depth is

Model analysis of check dam impacts on long-term sediment and water budgets in southeast Arizona, USA

Science.gov (United States)

Norman, Laura M.; Niraula, Rewati

2016-01-01

The objective of this study was to evaluate the effect of check dam infrastructure on soil and water conservation at the catchment scale using the Soil and Water Assessment Tool (SWAT). This paired watershed study includes a watershed treated with over 2000 check dams and a Control watershed which has none, in the West Turkey Creek watershed, Southeast Arizona, USA. SWAT was calibrated for streamflow using discharge documented during the summer of 2013 at the Control site. Model results depict the necessity to eliminate lateral flow from SWAT models of aridland environments, the urgency to standardize geospatial soils data, and the care for which modelers must document altering parameters when presenting findings. Performance was assessed using the percent bias (PBIAS), with values of ±2.34%. The calibrated model was then used to examine the impacts of check dams at the Treated watershed. Approximately 630 tons of sediment is estimated to be stored behind check dams in the Treated watershed over the 3-year simulation, increasing water quality for fish habitat. A minimum precipitation event of 15 mm was necessary to instigate the detachment of soil, sediments, or rock from the study area, which occurred 2% of the time. The resulting watershed model is useful as a predictive framework and decision-support tool to consider long-term impacts of restoration and potential for future restoration.

Stock of immobilized metals in 'Jose Antonio Alzate' dam mud sediment samples in the State of Mexico, Mexico

International Nuclear Information System (INIS)

Rodriguez, S.A.; Avila-Perez, P.

1997-01-01

'Jose Antonio Alzate' dam mud sediment samples were collected from six sampling sites. The samples were analyzed by combining multielemental studies with structural details, including heating to very high temperatures. Characterization of mud sediment samples have been shown to have low concentrations of metals (Cr, Mn, Ni, Cu, Zn, Pb). No systematic trend was observed as a function of the sampling points. (author)

Activity concentrations of primordial radionuclides in sediments of surface - water dams in southwest Nigeria - a baseline survey

International Nuclear Information System (INIS)

Isinkaye, M.O.; Farai, I.P.

2008-01-01

The radionuclide contents of sediment samples collected from 20 surface-water dams in southwestern Nigeria have been determined by low-level gamma-spectroscopy. The average concentration of 40 K in each of the dams varied between 110.9±11.9 Bq kg-1 and 1025.9±36.8 Bq kg -1 with an overall mean (±SD) of 549.3 ± 247.6 Bq kg -1 while that of 238 U varied from 17.1±3.6 to 51.9±8.7 Bq kg -1 with an overall mean (±SD) of 27.6±8.5 Bq kg -1 and that of 232 Th varied from 26.2 ±3.6 Bq kg -1 to 130.1±23.7 Bq kg -1 with overall mean (±SD) of 62.0±26.1 Bq kg -1 . The variability of the values shows the wide disparity in the measured activity concentrations. The mean radium equivalent of 158.9 Bq kg -1 was calculated for the sediments in the dams. No artificial gamma emitting radionuclide was detected in the samples. (authors)

Prediction of downstream geomorphological changes after dam construction: A stream power approach

DEFF Research Database (Denmark)

Brandt, Anders

2000-01-01

physical geography, hydrology, reservoirs, sediment transport, erosion, sedimentation, fluvial geomorphology, dams, river channel geometry......physical geography, hydrology, reservoirs, sediment transport, erosion, sedimentation, fluvial geomorphology, dams, river channel geometry...

Assessment of check-dam groundwater recharge with water-balance calculations

Science.gov (United States)

Djuma, Hakan; Bruggeman, Adriana; Camera, Corrado; Eliades, Marinos

2017-04-01

Studies on the enhancement of groundwater recharge by check-dams in arid and semi-arid environments mainly focus on deriving water infiltration rates from the check-dam ponding areas. This is usually achieved by applying simple water balance models, more advanced models (e.g., two dimensional groundwater models) and field tests (e.g., infiltrometer test or soil pit tests). Recharge behind the check-dam can be affected by the built-up of sediment as a result of erosion in the upstream watershed area. This natural process can increase the uncertainty in the estimates of the recharged water volume, especially for water balance calculations. Few water balance field studies of individual check-dams have been presented in the literature and none of them presented associated uncertainties of their estimates. The objectives of this study are i) to assess the effect of a check-dam on groundwater recharge from an ephemeral river; and ii) to assess annual sedimentation at the check-dam during a 4-year period. The study was conducted on a check-dam in the semi-arid island of Cyprus. Field campaigns were carried out to measure water flow, water depth and check-dam topography in order to establish check-dam water height, volume, evaporation, outflow and recharge relations. Topographic surveys were repeated at the end of consecutive hydrological years to estimate the sediment built up in the reservoir area of the check dam. Also, sediment samples were collected from the check-dam reservoir area for bulk-density analyses. To quantify the groundwater recharge, a water balance model was applied at two locations: at the check-dam and corresponding reservoir area, and at a 4-km stretch of the river bed without check-dam. Results showed that a check-dam with a storage capacity of 25,000 m3 was able to recharge to the aquifer, in four years, a total of 12 million m3 out of the 42 million m3 of measured (or modelled) streamflow. Recharge from the analyzed 4-km long river section without

An assessment study in the determination of chemical elements in sediments and fish in the Zarka River and King Talal Dam, Jordan

International Nuclear Information System (INIS)

Alsabbagh, A.; Khalayleh, L.; Dbissi, M.; Landsberger, S.

2017-01-01

Concentrations of several trace elements were detected in the sediments at King Talal Dam and at different locations along the Zarka River, Jordan. Chemical elements were also detected in the edible part of common fish types existing at the dam. Elemental concentrations were determined using neutron activation analysis (NAA). The results showed that the concentration of chemical elements in the sediments decreases as one moves away from the Khirbet Al Samra waste water treatment plant. The results also revealed that most of the elements had higher concentrations in Tilapia fish compared to the Catfish. (author)

Removal of the dam sediments as a way of control of eutrophication. Eliminacion de los sedimentos en los embalses como medida de control de la eutrofizacion

Energy Technology Data Exchange (ETDEWEB)

Lacalle Pareja, B.; Gonzalez Garcia, P.; Pino Izquierdo, M.I.; Gomez Artola, C.

1994-01-01

It is raised the advantage of thinking over the utility of removing the dam sediments as a way of control of eutrophication, attending to the distribution and concentration in different points of bottom on three dams of the Community of Madrid destined to the human consume. Attending to the sediments dynamic and the geomorphological and climatic characteristics. (Author) 6 refs.

[Heavy metals distribution characteristics and ecological risk evaluation in surface sediments of dammed Jinshan lake].

Science.gov (United States)

Zhou, Xiao-Hong; Liu, Long-Mei; Chen, Xi; Chen, Zhi-Gang; Zhang, Jin-Ping; Li, Yi-Min; Liu, Biao

2014-11-01

In order to reveal the pollution loading of heavy metals in Dammed Jinshan lake, six heavy metals (As, Cu, Pb, Cd, Zn, Cr) from 18 sediment samples were analyzed using ICP, and the distribution characteristics of heavy metals in the sediment were comprehensively evaluated through concentration coefficient, geo-acumulation indexes, potential ecological risk evaluation and traceability analysis. The results showed that (1) the average contents of As, Pb, Cu, Zn, Cr, Cd were 23.22, 26.20, 24.42, 143.12, 245.30 and 0.67 mg x kg(-1), respectively, in the surface sediments of dammed Jinshan Lake. The average contents of Pb and Cu were lower than the primary standard and secondary standards of soil environmental quality standards. The average contents of Zn and Cr were lower than the primary standard and higher than the secondary standards of soil environmental quality standards. The average contents of As and Cd were higher than the primary and secondary standards of soil environmental quality standards. From the spatial distribution, the contents of Pb and Zn were the highest at sampling site No. 1, which was located at the Beigushan Square. The contents of As,Cu, Cr, Cd were the highest at sampling sites Nos. 12, 3, 14, and 7, respectively; (2) The order of concentration coefficient was As > Cr > Cd > Pb > Zn > Cu, which indicated that the enrichment amount of As was the highest and that of Cu was the lowest; (3) Based on the geo-acumulation indexes, the Cu is clean and Pb, Zn, Cd is the light pollution and As, Cr moderate pollution; (4) The order of Potential ecological risk coefficient was Cd > As > Cr > Pb > Cu > Zn, Cr, Pb, Cu, Zn were of light ecological risk and As, Cd were of medium ecological risk. From the spatial distribution, the sampling sites Nos. 1, 6, 7 and 12 had medium potential ecological risk, and the rest sample points had slight potential ecological risk; (5) The principal component analysis (PCA) revealed that the main reason for the differences

Comparison of depth-averaged concentration and bed load flux sediment transport models of dam-break flow

Directory of Open Access Journals (Sweden)

Jia-heng Zhao

2017-10-01

Full Text Available This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms (a depth-averaged concentration flux model, and shallow water equations with a fully coupled Exner equation (a bed load flux model. Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored (HLLC. A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a one-dimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model, Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography.

Sedimentation in the Three Gorges Dam and the future trend of Changjiang (Yangtze River sediment flux to the sea

Directory of Open Access Journals (Sweden)

Guogang Li

2009-11-01

Full Text Available The Three Gorges Dam (TGD on the upper Changjiang (Yangtze River, China, disrupts the continuity of Changjiang sediment delivery to downstream and coastal areas. In this study, which was based on 54 years of annual water and sediment data from the mainstream and major tributaries of Changjiang, sediment deposition induced by the TGD in 2003–2008 was quantified. Furthermore, we determined the theoretical trapping efficiency of the cascade reservoir upstream of the TGD. Its impact on Changjiang sediment flux in the coming decades is discussed. Results show that about 172 million tons (Mt of sediment was trapped annually by the TGD in 2003–2008, with an averaged trapping efficiency of 75%. Most of the total sediment deposition, as induced by the TGD (88%, accumulated within the region between the TGD site and Cuntan. However, significant siltation (12% of the total sediment deposition also occurred upstream of Cuntan as a consequence of the upstream extended backwater region of the TGD. Additionally, the Changjiang sediment flux entered a third downward step in 2001, prior to operation of the TGD. This mainly resulted from sediment reduction in the Jinshajiang tributary since the late 1990s. As the cascade reservoir is put into full operation, it could potentially trap 91% of the Jinshajiang sediment discharge and, therefore, the Jinshajiang sediment discharge would most likely further decrease to 14 Mt/yr in the coming decades. Consequently, the Changjiang sediment flux to the sea is expected to continuously decrease to below 90 Mt/yr in the near future, or only 18% of the amount observed in the 1950s. In the presence of low sediment discharge, profound impacts on the morphology of estuary, delta and coastal waters are expected.

How have the river discharges and sediment loads changed in the Changjiang River basin downstream of the Three Gorges Dam?

Science.gov (United States)

Guo, Leicheng; Su, Ni; Zhu, Chunyan; He, Qing

2018-05-01

Streamflow and sediment loads undergo remarkable changes in worldwide rivers in response to climatic changes and human interferences. Understanding their variability and the causes is of vital importance regarding river management. With respect to the Changjiang River (CJR), one of the largest river systems on earth, we provide a comprehensive overview of its hydrological regime changes by analyzing long time series of river discharges and sediment loads data at multiple gauge stations in the basin downstream of Three Gorges Dam (TGD). We find profound river discharge reduction during flood peaks and in the wet-to-dry transition period, and slightly increased discharges in the dry season. Sediment loads have reduced progressively since 1980s owing to sediment yield reduction and dams in the upper basin, with notably accelerated reduction since the start of TGD operation in 2003. Channel degradation occurs in downstream river, leading to considerable river stage drop. Lowered river stages have caused a 'draining effect' on lakes by fostering lake outflows following TGD impoundments. The altered river-lake interplay hastens low water occurrence inside the lakes which can worsen the drought given shrinking lake sizes in long-term. Moreover, lake sedimentation has decreased since 2002 with less sediment trapped in and more sediment flushed out of the lakes. These hydrological changes have broad impacts on river flood and drought occurrences, water security, fluvial ecosystem, and delta safety.

DESIGN OF SLIT DAMS FOR CONTROLLING STONY DEBRIS FLOWS

Institute of Scientific and Technical Information of China (English)

Hui-Pang LIEN

2003-01-01

A new method to a slit dam for controlling the stony debris flow has been derived based on the mass conservation law of the stony debris flow passing through a slit dam and the laboratory experiment results.This new method is then combined with three primary efficiency expressions: the dimensionless sediment outflow ratio,the sediment concentration ratio,and the sediment storage rate to develop a simple module,with which the height and the spacing of the posts,as well as the total spacing of slit dam are determined.Furthermore,these expressions can also be applied to check those slit dams that have already been constructed with their effectiveness against various magnitudes of the debris flow. The comparison between these expressions and laboratory data is in reasonable agreement.

The potential for dams to impact lowland meandering river floodplain geomorphology.

Science.gov (United States)

Marren, Philip M; Grove, James R; Webb, J Angus; Stewardson, Michael J

2014-01-01

The majority of the world's floodplains are dammed. Although some implications of dams for riverine ecology and for river channel morphology are well understood, there is less research on the impacts of dams on floodplain geomorphology. We review studies from dammed and undammed rivers and include influences on vertical and lateral accretion, meander migration and cutoff formation, avulsion, and interactions with floodplain vegetation. The results are synthesized into a conceptual model of the effects of dams on the major geomorphic influences on floodplain development. This model is used to assess the likely consequences of eight dam and flow regulation scenarios for floodplain geomorphology. Sediment starvation downstream of dams has perhaps the greatest potential to impact on floodplain development. Such effects will persist further downstream where tributary sediment inputs are relatively low and there is minimal buffering by alluvial sediment stores. We can identify several ways in which floodplains might potentially be affected by dams, with varying degrees of confidence, including a distinction between passive impacts (floodplain disconnection) and active impacts (changes in geomorphological processes and functioning). These active processes are likely to have more serious implications for floodplain function and emphasize both the need for future research and the need for an "environmental sediment regime" to operate alongside environmental flows.

The Potential for Dams to Impact Lowland Meandering River Floodplain Geomorphology

Directory of Open Access Journals (Sweden)

Philip M. Marren

2014-01-01

Full Text Available The majority of the world's floodplains are dammed. Although some implications of dams for riverine ecology and for river channel morphology are well understood, there is less research on the impacts of dams on floodplain geomorphology. We review studies from dammed and undammed rivers and include influences on vertical and lateral accretion, meander migration and cutoff formation, avulsion, and interactions with floodplain vegetation. The results are synthesized into a conceptual model of the effects of dams on the major geomorphic influences on floodplain development. This model is used to assess the likely consequences of eight dam and flow regulation scenarios for floodplain geomorphology. Sediment starvation downstream of dams has perhaps the greatest potential to impact on floodplain development. Such effects will persist further downstream where tributary sediment inputs are relatively low and there is minimal buffering by alluvial sediment stores. We can identify several ways in which floodplains might potentially be affected by dams, with varying degrees of confidence, including a distinction between passive impacts (floodplain disconnection and active impacts (changes in geomorphological processes and functioning. These active processes are likely to have more serious implications for floodplain function and emphasize both the need for future research and the need for an “environmental sediment regime” to operate alongside environmental flows.

Geomorphic responses to dam removal in the United States – a two-decade perspective

Science.gov (United States)

Major, Jon J.; East, Amy; O'Connor, Jim E.; Grant, Gordon E.; Wilcox, Andrew C.; Magirl, Christopher S.; Collins, Matthias J.; Tullos, Desiree D.; Tsutsumi, Daizo; Laronne, Jonathan B.

2017-01-01

Recent decades have seen a marked increase in the number of dams removed in the United States. Investigations following a number of removals are beginning to inform how, and how fast, rivers and their ecosystems respond to released sediment. Though only a few tens of studies detail physical responses to removals, common findings have begun to emerge. They include: (1) Rivers are resilient and respond quickly to dam removals, especially when removals are sudden rather than prolonged. Rivers can swiftly evacuate large fractions of reservoir sediment (≥50% within one year), especially when sediment is coarse grained (sand and gravel). The channel downstream typically takes months to years—not decades—to achieve a degree of stability within its range of natural variability. (2) Modest streamflows (<2-year return interval flows) can erode and transport large amounts of reservoir sediment. Greater streamflows commonly are needed to access remnant reservoir sediment and transport it downstream. (3) Dam height, sediment volume, and sediment caliber strongly influence downstream response to dam removal. Removals of large dams (≥10 m tall) have had longer-lasting and more widespread downstream effects than more common removals of small dams. (4) Downstream valley morphology and position of a dam within a watershed influence the distribution of released sediment. Valley confinement, downstream channel gradient, locations and depths of channel pools, locations and geometries of extant channel bars, and locations of other reservoirs all influence the downstream fate of released sediment.

Deformation Monitoring and Bathymetry Analyses in Rock-Fill Dams, a Case Study at Ataturk Dam

Science.gov (United States)

Kalkan, Y.; Bilgi, S.

2014-12-01

Turkey has 595 dams constructed between 1936 and 2013 for the purposes of irrigation, flood control, hydroelectric energy and drinking water. A major portion of the dam basins in Turkey are deprived of vegetation and have slope topography on near surrounding area. However, landscaping covered with forest around the dam basin is desirable for erosion control. In fact; the dams, have basins deprived of vegetation, fill up quickly due to sediment transport. Erosion control and forestation are important factors, reducing the sediment, to protect the water basins of the dams and increase the functioning life of the dams. The functioning life of dams is as important as the investment and construction. Nevertheless, in order to provide safety of human life living around, well planned monitoring is essential for dams. Dams are very large and critical structures and they demand the use or application of precise measuring systems. Some basic physical data are very important for assessing the safety and performance of dams. These are movement, water pressure, seepage, reservoir and tail-water elevations, local seismic activities, total pressure, stress and strain, internal concrete temperature, ambient temperature and precipitation. Monitoring is an essential component of the dam after construction and during operation and must en­able the timely detection of any behavior that could deteriorate the dam, potentially result in its shutdown or failure. Considering the time and labor consumed by long-term measurements, processing and analysis of measured data, importance of the small structural motions at regular intervals could be comprehended. This study provides some information, safety and the techniques about the deformation monitoring of the dams, dam safety and related analysis. The case study is the deformation measurements of Atatürk Dam in Turkey which is the 6th largest dam of world considering the filling volume of embankment. Brief information is given about the

Toward improved design of check dam systems: A case study in the Loess Plateau, China

Science.gov (United States)

Pal, Debasish; Galelli, Stefano; Tang, Honglei; Ran, Qihua

2018-04-01

Check dams are one of the most common strategies for controlling sediment transport in erosion prone areas, along with soil and water conservation measures. However, existing mathematical models that simulate sediment production and delivery are often unable to simulate how the storage capacity of check dams varies with time. To explicitly account for this process-and to support the design of check dam systems-we developed a modelling framework consisting of two components, namely (1) the spatially distributed Soil Erosion and Sediment Delivery Model (WaTEM/SEDEM), and (2) a network-based model of check dam storage dynamics. The two models are run sequentially, with the second model receiving the initial sediment input to check dams from WaTEM/SEDEM. The framework is first applied to Shejiagou catchment, a 4.26 km2 area located in the Loess Plateau, China, where we study the effect of the existing check dam system on sediment dynamics. Results show that the deployment of check dams altered significantly the sediment delivery ratio of the catchment. Furthermore, the network-based model reveals a large variability in the life expectancy of check dams and abrupt changes in their filling rates. The application of the framework to six alternative check dam deployment scenarios is then used to illustrate its usefulness for planning purposes, and to derive some insights on the effect of key decision variables, such as the number, size, and site location of check dams. Simulation results suggest that better performance-in terms of life expectancy and sediment delivery ratio-could have been achieved with an alternative deployment strategy.

Records of pan (floodplain wetland) sedimentation as an approach for post-hoc investigation of the hydrological impacts of dam impoundment: The Pongolo river, KwaZulu-Natal.

Science.gov (United States)

Heath, S K; Plater, A J

2010-07-01

River impoundment by dams has far-reaching consequences for downstream floodplains in terms of hydrology, water quality, geomorphology, ecology and ecosystem services. With the imperative of economic development, there is the danger that potential environmental impacts are not assessed adequately or monitored appropriately. Here, an investigation of sediment composition of two pans (floodplain wetlands) in the Pongolo River floodplain, KwaZulu-Natal, downstream of the Pongolapoort dam constructed in 1974, is considered as a method for post-hoc assessment of the impacts on river hydrology, sediment supply and water quality. Bumbe and Sokhunti pans have contrasting hydrological regimes in terms of their connection to the main Pongolo channel - Bumbe is a shallow ephemeral pan and Sokhunti is a deep, perennial water body. The results of X-ray fluorescence (XRF) geochemical analysis of their sediment records over a depth of >1 m show that whilst the two pans exhibit similar sediment composition and variability in their lower part, Bumbe pan exhibits a shift toward increased fine-grained mineral supply and associated nutrient influx at a depth of c. 45 cm whilst Sokhunti pan is characterised by increased biogenic productivity at a depth of c. 26 cm due to enhanced nutrient status. The underlying cause is interpreted as a shift in hydrology to a 'post-dam' flow regime of reduced flood frequencies with more regular baseline flows which reduce the average flow velocity. In addition, Sokhunti shows a greater sensitivity to soil influx during flood events due to the nature of its 'background' of autochthonous biogenic sedimentation. The timing of the overall shift in sediment composition and the dates of the mineral inwash events are not well defined, but the potential for these wetlands as sensitive recorders of dam-induced changes in floodplain hydrology, especially those with a similar setting to Sokhunti pan, is clearly demonstrated. Copyright 2010 Elsevier Ltd. All

Preliminary Three-Dimensional Simulation of Sediment and Cesium Transport in the Ogi Dam Reservoir using FLESCOT – Task 6, Subtask 2

Energy Technology Data Exchange (ETDEWEB)

Onishi, Yasuo; Kurikami, Hiroshi; Yokuda, Satoru T.

2014-03-28

After the accident at the Fukushima Daiichi Nuclear Power Plant in March 2011, the Japan Atomic Energy Agency and the Pacific Northwest National Laboratory initiated a collaborative project on environmental restoration. In October 2013, the collaborative team started a task of three-dimensional modeling of sediment and cesium transport in the Fukushima environment using the FLESCOT (Flow, Energy, Salinity, Sediment Contaminant Transport) code. As the first trial, we applied it to the Ogi Dam Reservoir that is one of the reservoirs in the Japan Atomic Energy Agency’s (JAEA’s) investigation project. Three simulation cases under the following different temperature conditions were studied: • incoming rivers and the Ogi Dam Reservoir have the same water temperature • incoming rivers have lower water temperature than that of the reservoir • incoming rivers have higher water temperature than that of the reservoir. The preliminary simulations suggest that seasonal temperature changes influence the sediment and cesium transport. The preliminary results showed the following: • Suspended sand, and cesium adsorbed by sand, coming into the reservoirs from upstream rivers is deposited near the reservoir entrance. • Suspended silt, and cesium adsorbed by silt, is deposited farther in the reservoir. • Suspended clay, and cesium adsorbed by clay, travels the farthest into the reservoir. With sufficient time, the dissolved cesium reaches the downstream end of the reservoir. This preliminary modeling also suggests the possibility of a suitable dam operation to control the cesium migration farther downstream from the dam. JAEA has been sampling in the Ogi Dam Reservoir, but these data were not yet available for the current model calibration and validation for this reservoir. Nonetheless these preliminary FLESCOT modeling results were qualitatively valid and confirmed the applicability of the FLESCOT code to the Ogi Dam Reservoir, and in general to other reservoirs in

The geomorphic legacy of small dams — An Austrian study

NARCIS (Netherlands)

Poeppl, R.E.; Keesstra, S.D.; Hein, T.

2015-01-01

Dams represent one of the most dominant forms of human impact upon fluvial systems during the Anthropocene, as they disrupt the downstream transfer of water and sediments. Removing dams restores river continuity and channel morphology. Both dam construction and dam removal induce geomorphic channel

Longitudinal variability of phosphorus fractions in sediments of a canyon reservoir due to cascade dam construction: a case study in Lancang River, China.

Directory of Open Access Journals (Sweden)

Qi Liu

Full Text Available Dam construction causes the accumulation of phosphorus in the sediments of reservoirs and increases the release rate of internal phosphorus (P loading. This study investigated the longitudinal variability of phosphorus fractions in sediments and the relationship between the contents of phosphorus fractions and its influencing factors of the Manwan Reservoir, Lancang River, Yunnan Province, China. Five sedimentary phosphorus fractions were quantified separately: loosely bound P (ex-P; reductant soluble P (BD-P; metal oxide-bound P (NaOH-P; calcium-bound P (HCl-P, and residual-P. The results showed that the total phosphorus contents ranged from 623 to 899 µg/g and were correlated positively with iron content in the sediments of the reservoir. The rank order of P fractions in sediments of the mainstream was HCl-P>NaOH-P>residual-P>BD-P>ex-P, while it was residual-P>HCl-P>NaOH-P>BD-P>ex-P in those of the tributaries. The contents of bio-available phosphorus in the tributaries, including ex-P, BD-P and NaOH-P, were significantly lower than those in the mainstream. The contents of ex-P, BD-P, NaOH-P showed a similar increasing trend from the tail to the head of the Manwan Reservoir, which contributed to the relatively higher content of bio-available phosphorus, and represents a high bio-available phosphorus releasing risk within a distance of 10 km from Manwan Dam. Correlation and redundancy analyses showed that distance to Manwan Dam and the silt/clay fraction of sediments were related closely to the spatial variation of bio-available phosphorus.

Multiyear Downstream Response to Dam Removal on the White Salmon River, WA

Science.gov (United States)

Wilcox, A. C.; O'Connor, J. E.; Major, J. J.

2017-12-01

The 2011 removal of the 38 m tall Condit Dam on the White Salmon River, Washington was one of the largest dam removals to date, in terms of both dam height and sediment release. We examined the multiyear geomorphic response to this event, through 2015, including in a bedrock-confined canyon and in a less-confined, backwater-influenced pool reach near the river's mouth, to the large, rapid influx of fine reservoir sediment produced by the breach and to subsequent sediment transfer in the free-flowing White Salmon River. In the canyon reach, aggraded sediments were rapidly eroded from riffles, returning them toward pre-breach bed elevations within weeks, but pool aggradation persisted for longer. The downstream, less-confined reach transformed from a deep pool to a narrower pool-riffle channel with alternate bars; multiyear observations showed persistence of bars and of this new and distinct morphology. This downstream reach marks a rare case in post-dam removal channel response; in most dam removals, channels have rapidly reverted toward pre-removal morphology, as in the canyon reach here. Comparison of the multiyear geomorphic evolution of the White Salmon River to other recent large dam removals in the U.S. allows evaluation of the relative influences of antecedent channel morphology, post-breach hydrology, and dam removal style, as well as providing a basis for predicting responses to future dam removals.

Removing Dams: Project-Level Policy and Scientific Research Needs (Invited)

Science.gov (United States)

Graber, B.

2010-12-01

More than 800 dams have been removed around the country, mostly “small” dams, under 25 feet in height. The total number of removals, however, is small relative to the number of deteriorating dams and the ecological impacts those structures continue to have on native riverine species and natural river function. The number of dam removal projects is increasing as aging dams continue to deteriorate and riverine species continue to decline. Practitioners and regulators need to find cost-effective project approaches that minimize short-term environmental impacts and maximize long-term benefits while keeping project costs manageable. Dam removals can be a regulatory challenge because they inherently have short-term impacts in order to achieve larger, self-sustaining, long-term benefits. These short-term impacts include sediment movement, construction access roads, and habitat conversion from lacustrine to riverine. Environmental regulations are designed to prevent degradation and have presented challenges for projects designed to benefit the environment. For example, a short-term release of sediment may exceed water quality standards for some period of time, but lead to a long-term beneficial project. Other regulatory challenges include permitting the loss of wetland area for increased native river function, or allowing the release of some level of contaminated sediment when the downstream sediment is similarly contaminated. Dam removal projects raise a range of engineering and scientific questions on effective implementation techniques such as appropriate sediment management approaches, construction equipment access approaches, invasive species management, channel/floodplain reconstruction, and active versus passive habitat rehabilitation. While practitioners have learned and refined implementation approaches over the last decade, more input is needed from researchers to help assess the effectiveness of those techniques, and to provide more effective techniques

Will river erosion below the Three Gorges Dam stop in the middle Yangtze?

Science.gov (United States)

Lai, X.; Yin, D.; Finlayson, B. L.; Wei, T.; Li, M.; Yuan, W.; Yang, S.; Dai, Z.; Gao, S.; Chen, Z.

2017-11-01

The environmental impact of the Three Gorges Dam has been a subject of vigorous academic, political and social debate since its inception. This includes the key issue of post-dam river channel erosion, which was predicted by the feasibility study to extend to the river mouth. In this paper we examine the geomorphic response of the channel of the middle Yangtze for 660 km downstream of the dam. Using data on channel characteristics, bed material and sediment transport, we show that in the decade following the dam closure, pre-dam seasonal erosion has been replaced by year-round erosion, a pattern most marked at the upstream end of the study area. The sediment carrying capacity of the river channel has been largely reduced below the dam. The locus of bed scour has moved progressively downstream, ceasing as the bed material became too coarse to be transported (e.g. D50: 0.29 mm pre-dam coarsened to 20 mm below the dam by 2008). About 400 km below the dam there is a reduction in channel slope that changes the sediment carrying capacity from 0.25 kg m-3 to only about 0.05 kg m-3, which is insufficient to move bed sediment. The new long-term hydro-morphological equilibrium that will be established in this section of the middle Yangtze will prevent the further incision downstream initiated by the Three Gorges Dam. The results suggest that the full extent of adverse environmental impact predicted by the pre-dam studies will not eventuate.

Application of the alpha spectrometry for the study of core sediment extracted in the San Marcos dam in Chihuahua

Energy Technology Data Exchange (ETDEWEB)

Mendez G, C.; Renteria V, M.; Montero C, M. E. [Centro de Investigacion en Materiales Avanzados, S. C., Miguel de Cervantes No. 120, Complejo Industrial Chihuahua, 31109 Chihuahua (Mexico); Garcia T, R., E-mail: elena.montero@cimav.edu.mx [Universidad de Sevilla, Escuela Tecnica Superior de Arquitectura, Grupo de Fisica Nuclear Aplicada, Av. Reina Mercedes s/n, 41012 Sevilla (Spain)

2012-06-15

The determination of the specific activities of {sup 210}Po and isotopic uranium by alpha spectrometry was performed in a sediment core from San Marcos Dam. The objective of this work was to analyze the vertical distribution of isotopic uranium and {sup 210}Po and the behavior of these radionuclides along sediment core collected from the San Marcos Dam. Sample was divided into 11 sections, in which {sup 210}Po and isotopic uranium were determined using liquid-liquid extraction with tributyl phosphate. Furthermore, it was made a comparison between the tributyl phosphate technique and the technique of extraction chromatography using UTEVA resins for uranium. The results of specific activities for {sup 210}Po show a trend to decrease along the core, whereas the uranium isotopic does not show a pointed trend. The results of isotopic ratios between the {sup 234}U and {sup 238}U show that they are close to secular equilibrium in each of the core sections. The comparison between the two uranium extraction techniques indicates that the chemical yield is better using the UTEVA technique than tributyl phosphate extraction. (Author)

Application of the alpha spectrometry for the study of core sediment extracted in the San Marcos dam in Chihuahua

International Nuclear Information System (INIS)

Mendez G, C.; Renteria V, M.; Montero C, M. E.; Garcia T, R.

2012-01-01

The determination of the specific activities of 210 Po and isotopic uranium by alpha spectrometry was performed in a sediment core from San Marcos Dam. The objective of this work was to analyze the vertical distribution of isotopic uranium and 210 Po and the behavior of these radionuclides along sediment core collected from the San Marcos Dam. Sample was divided into 11 sections, in which 210 Po and isotopic uranium were determined using liquid-liquid extraction with tributyl phosphate. Furthermore, it was made a comparison between the tributyl phosphate technique and the technique of extraction chromatography using UTEVA resins for uranium. The results of specific activities for 210 Po show a trend to decrease along the core, whereas the uranium isotopic does not show a pointed trend. The results of isotopic ratios between the 234 U and 238 U show that they are close to secular equilibrium in each of the core sections. The comparison between the two uranium extraction techniques indicates that the chemical yield is better using the UTEVA technique than tributyl phosphate extraction. (Author)

Environmental effects of the Big Rapids dam remnant removal, Big Rapids, Michigan, 2000-02

Science.gov (United States)

Healy, Denis F.; Rheaume, Stephen J.; Simpson, J. Alan

2003-01-01

The U.S. Geological Survey (USGS), in cooperation with the city of Big Rapids, investigated the environmental effects of removal of a dam-foundation remnant and downstream cofferdam from the Muskegon River in Big Rapids, Mich. The USGS applied a multidiscipline approach, which determined the water quality, sediment character, and stream habitat before and after dam removal. Continuous water-quality data and discrete water-quality samples were collected, the movement of suspended and bed sediment were measured, changes in stream habitat were assessed, and streambed elevations were surveyed. Analyses of water upstream and downstream from the dam showed that the dam-foundation remnant did not affect water quality. Dissolved-oxygen concentrations downstream from the dam remnant were depressed for a short period (days) during the beginning of the dam removal, in part because of that removal effort. Sediment transport from July 2000 through March 2002 was 13,800 cubic yards more at the downstream site than the upstream site. This increase in sediment represents the remobilized sediment upstream from the dam, bank erosion when the impoundment was lowered, and contributions from small tributaries between the sites. Five habitat reaches were monitored before and after dam-remnant removal. The reaches consisted of a reference reach (A), upstream from the effects of the impoundment; the impoundment (B); and three sites below the impoundment where habitat changes were expected (C, D, and E, in downstream order). Stream-habitat assessment reaches varied in their responses to the dam-remnant removal. Reference reach A was not affected. In impoundment reach B, Great Lakes and Environmental Assessment Section (GLEAS) Procedure 51 ratings went from fair to excellent. For the three downstream reaches, reach C underwent slight habitat degradation, but ratings remained good; reach D underwent slight habitat degradation with ratings changing from excellent to good; and, in an area

Watershed restoration: planning and implementing small dam removals to maximize ecosystem services

Science.gov (United States)

Tonitto, C.; Riha, S. J.

2016-12-01

River restoration and enhancing watershed connectivity is of growing concern in industrialized nations. The past two decades have seen a number of small dam removals, though many removals remain unstudied and poorly documented. We summarize socio-economic and biophysical lessons learned during the past two decades of accelerated activity regarding small dam removals throughout the United States. We present frameworks for planning and implementing removals developed by interdisciplinary engagement. Toward the goal of achieving thorough dam removal planning, we present outcomes from well-documented small dam removals covering ecological, chemical, and physical change in rivers post-dam removal, including field observation and modeling methodologies. Guiding principles of a dam removal process should include: 1) stakeholder engagement to navigate the complexity of watershed landuse, 2) an impacts assessment to inform the planning process, 3) pre- and post-dam removal observations of ecological, chemical and physical properties, 4) the expectation that there are short- and long-term ecological dynamics with population recovery depending on whether dam impacts were largely related to dispersion or to habitat destruction, 5) an expectation that changes in watershed chemistry are dependent on sediment type, sediment transport and watershed landuse, and 6) rigorous assessment of physical changes resulting from dam removal, understanding that alteration in hydrologic flows, sediment transport, and channel evolution will shape ecological and chemical dynamics, and shape how stakeholders engage with the watershed.

Simulation of Sediment and Cesium Transport in the Ukedo River and the Ogi Dam Reservoir during a Rainfall Event using the TODAM Code

Energy Technology Data Exchange (ETDEWEB)

Onishi, Yasuo; Yokuda, Satoru T.; Kurikami, Hiroshi

2014-03-28

The accident at the Fukushima Daiichi Nuclear Power Plant in March 2011 caused widespread environmental contamination. Although decontamination activities have been performed in residential areas of the Fukushima area, decontamination of forests, rivers, and reservoirs is still controversial because of the economical, ecological, and technical difficulties. Thus, an evaluation of contaminant transport in such an environment is important for safety assessment and for implementation of possible countermeasures to reduce radiation exposure to the public. The investigation revealed that heavy rainfall events play a significant role in transporting radioactive cesium deposited on the land surface, via soil erosion and sediment transport in rivers. Therefore, we simulated the sediment and cesium transport in the Ukedo River and its tributaries in Fukushima Prefecture, including the Ogaki Dam Reservoir, and the Ogi Dam Reservoir of the Oginosawa River in Fukushima Prefecture during and after a heavy rainfall event by using the TODAM (Time-dependent, One-dimensional Degradation And Migration) code. The main outcomes are the following: • Suspended sand is mostly deposited on the river bottom. Suspended silt and clay, on the other hand, are hardly deposited in the Ukedo River and its tributaries except in the Ogaki Dam Reservoir in the Ukedo River even in low river discharge conditions. • Cesium migrates mainly during high river discharge periods during heavy rainfall events. Silt and clay play more important roles in cesium transport to the sea than sand does. • The simulation results explain variations in the field data on cesium distributions in the river. Additional field data currently being collected and further modeling with these data may shed more light on the cesium distribution variations. • Effects of 40-hour heavy rainfall events on clay and cesium transport continue for more than a month. This is because these reservoirs slow down the storm-induced high

Laboratory tests of bentonite stabilization of bottom sediments from a dam reservoir in relation to their usage in municipal solid waste landfill liners

Directory of Open Access Journals (Sweden)

Karolina Koś

2016-09-01

Full Text Available Geotechnical parameters of bottom sediments from a dam reservoir (Rzeszowski Reservoir, Poland with bentonite addition are presented in the paper. Tests were carried out in the aspect of the possible usage of sediments as a material for soil liners in Municipal Solid Waste Landfill. Mentioned sediments did not fulfilled the permeability and plasticity criteria defined for soils that can be used in liners. The bentonite addition caused, among other things, a decrease in permeability coefficient and increase in plasticity index. Based on the carried out tests it was stated that sediments with 6% addition of bentonite fulfil all requirements and can be used for liners in MSWL.

Investigating leaks in dams and reservoirs

International Nuclear Information System (INIS)

2003-01-01

Millions of people throughout the world depend on dams and reservoirs for electricity, water and flood protection. Dams require significant investment to build and maintain, and yet their usefulness and integrity are constantly threatened by leakage and sedimentation. Isotope hydrology techniques, combined with conventional analytical methods, are a cost-effective tool to reduce such threats. The International Atomic Energy Agency is promoting their use to protect these investments and improve management, particularly by supporting specialized teams of scientists and engineers to investigate dam leakage in African countries on request. (IAEA)

Characterization of channel substrate, and changes in suspended-sediment transport and channel geometry in white sturgeon spawning habitat in the Kootenai River near Bonners Ferry, Idaho, following the closure of Libby Dam

Science.gov (United States)

Barton, Gary J.

2004-01-01

Many local, State, and Federal agencies have concerns over the declining population of white sturgeon (Acipenser transmontanus) in the Kootenai River and the possible effects of the closure and subsequent operation of Libby Dam in 1972. In 1994, the Kootenai River white sturgeon was listed as an Endangered Species. A year-long field study was conducted in cooperation with the Kootenai Tribe of Idaho along a 21.7-kilometer reach of the Kootenai River including the white sturgeon spawning reach near Bonners Ferry, Idaho, approximately 111 to 129 kilometers below Libby Dam. During the field study, data were collected in order to map the channel substrate in the white sturgeon spawning reach. These data include seismic subbottom profiles at 18 cross sections of the river and sediment cores taken at or near the seismic cross sections. The effect that Libby Dam has on the Kootenai River white sturgeon spawning substrate was analyzed in terms of changes in suspended-sediment transport, aggradation and degradation of channel bed, and changes in the particle size of bed material with depth below the riverbed. The annual suspended-sediment load leaving the Kootenai River white sturgeon spawning reach decreased dramatically after the closure of Libby Dam in 1972: mean annual pre-Libby Dam load during 1966–71 was 1,743,900 metric tons, and the dam-era load during 1973–83 was 287,500 metric tons. The amount of sand-size particles in three suspended-sediment samples collected at Copeland, Idaho, 159 kilometers below Libby Dam, during spring and early summer high flows after the closure of Libby Dam is less than in four samples collected during the pre-Libby Dam era. The supply of sand to the spawning reach is currently less due to the reduction of high flows and a loss of 70 percent of the basin after the closure of Libby Dam. The river's reduced capacity to transport sand out of the spawning reach is compensated to an unknown extent by a reduced load of sand entering the

Potential Impact of Planned Andean Dams on the Amazon Fluvial Ecosystem

Science.gov (United States)

Forsberg, B.; Melack, J. M.; Dunne, T.; Barthem, R. B.; Paiva, R. C. D.; Sorribas, M.; Silva, U. L., Jr.

2016-12-01

Increased energy demand has led to plans for building 151 new dams in the western Amazon, mostly in the Andes Region. Historical data and simulation scenarios were used to explore potential impacts above and below six of the largest storage dams planned for the region. These impacts included: 1) reduction in the downstream sediment supply 2) reduction in the downstream nutrient supply, 3) attenuation of the downstream flood pulse and 4) increased greenhouse gas emissions. Together, the six dams are expected to reduce the total downstream supply of sediments, total phosphorus (TP) and total nitrogen (TN) from the Andes by 66, 65 and 49%, respectively. These large reductions in sediment and nutrient supplies will have major impacts on channel geomorphology, floodplain fertility and aquatic productivity. These impacts are expected to be greatest close to the dams but could also extend to the central Amazon floodplain and delta regions. The attenuation of the downstream flood pulse following impoundment is expected to alter the survival, phenology and growth patterns of floodplain vegetation and result in lower fish yields in the downstream regions closest to the dams. Greenhouse gas emissions above and below the dams are expected to increase, contributing to significantly higher regional and global emissions for dams. Gas fired power plants are suggested as a cleaner, less impactful alternative to meeting regional energy demands.

Matahina Dam : lessons learned from an earthquake-related internal erosion incident at the Matahina Dam, New Zealand

Energy Technology Data Exchange (ETDEWEB)

Gillon, M. [Damwatch Services Ltd., Wellington (New Zealand)

2009-07-01

This case history discussed internal erosion damage and crest subsidence caused by an earthquake at the Matahina Dam in New Zealand. The study showed that cracking and internal erosion was initiated during the 1967 reservoir filling operation. Located in an area of active volcanism and faulting, the dam is located on a river with extensive erosion through an ignimbrite flow. The dam's core is founded on compact Tertiary age sediments overlain by sand and gravel deposits beneath the shoulders of the dam. The earthquake caused a rupture along an unidentified fault trace 12 km from the dam. The horizontal base acceleration recorded at the dam was 3.25 m/s. Transverse cracking was observed at each abutment, and deformations were observed in the rockfill. An investigation program was conducted to determine the dam's integrity. Piezometer measurements showed widespread fluctuations. It was concluded that the lack of an effective filter was a significant design omission. 12 refs., 12 figs.

Geomorphic and habitat response to a large-dam removal in a Mediterranean river

Science.gov (United States)

Harrison, L.; East, A. E.; Smith, D. P.; Bond, R.; Logan, J. B.; Nicol, C.; Williams, T.; Boughton, D. A.; Chow, K.

2017-12-01

The presence of large dams has fundamentally altered physical and biological processes in riverine ecosystems, and dam removal is becoming more common as a river restoration strategy. We used a before-after-control-impact study design to investigate the geomorphic and habitat response to removal of 32-m-high San Clemente Dam on the Carmel River, CA. The project represents the first major dam removal in a Mediterranean river and is also unique among large dam removals in that most reservoir sediment was sequestered in place. We found that in the first year post-removal, a sediment pulse migrated 3.5 km downstream, filling pools and the interstitial pore spaces of gravels with sand. These sedimentary and topographic changes initially reduced the overall quality of steelhead (O. mykiss) spawning and rearing habitat in impacted reaches. Over the second winter after dam removal, a sequence of high flows flushed large volumes of sand from pools and mobilized the river bed throughout much of the active channel. The floods substantially altered fluvial evolution in the upper part of the reservoir, promoting new avulsion and the subsequent delivery of gravel and large wood to below dam reaches. These geomorphic processes increased the availability of spawning-sized gravel and enhanced channel complexity in reaches within several km of the former dam, which should improve habitat for multiple life stages of steelhead. Results indicate that when most reservoir sediment remains impounded, high flows become more important drivers of geomorphic and habitat change than dam removal alone. In such cases, the rates at which biophysical processes are reestablished will depend largely on post-dam removal flow sequencing and the upstream supply of sediment and large wood.

Profiling of Sediment Microbial Community in Dongting Lake before and after Impoundment of the Three Gorges Dam

Directory of Open Access Journals (Sweden)

Wei Huang

2016-06-01

Full Text Available The sediment microbial community in downstream-linked lakes can be affected by the operation of large-scale water conservancy projects. The present study determined Illumina reads (16S rRNA gene amplicons to analyze and compare the bacterial communities from sediments in Dongting Lake (China before and after impoundment of the Three Gorges Dam (TGD, the largest hydroelectric project in the world. Bacterial communities in sediment samples in Dongting Lake before impoundment of the TGD (the high water period had a higher diversity than after impoundment of the TGD (the low water period. The most abundant phylum in the sediment samples was Proteobacteria (36.4%–51.5%, and this result was due to the significant abundance of Betaproteobacteria and Deltaproteobacteria in the sediment samples before impoundment of the TGD and the abundance of Gammaproteobacteria in the sediment samples after impoundment of the TGD. In addition, bacterial sequences of the sediment samples are also affiliated with Acidobacteria (11.0% on average, Chloroflexi (10.9% on average, Bacteroidetes (6.7% on average, and Nitrospirae (5.1% on average. Variations in the composition of the bacterial community within some sediment samples from the river estuary into Dongting Lake were related to the pH values. The bacterial community in the samples from the three lake districts of Dongting Lake before and after impoundment of the TGD was linked to the nutrient concentration.

Longitudinal distribution of Chironomidae (Diptera) downstream from a dam in a neotropical river.

Science.gov (United States)

Pinha, G D; Aviz, D; Lopes Filho, D R; Petsch, D K; Marchese, M R; Takeda, A M

2013-08-01

The damming of a river causes dangerous consequences on structure of the environment downstream of the dam, modifying the sediment composition, which impose major adjustments in longitudinal distribution of benthic community. The construction of Engenheiro Sérgio Motta Dam in the Upper Paraná River has caused impacts on the aquatic communities, which are not yet fully known. This work aimed to provide more information about the effects of this impoundment on the structure of Chironomidae larvae assemblage. The analysis of data of physical and chemical variables in relation to biological data of 8 longitudinal sections in the Upper Paraná River showed that composition of Chironomidae larvae of stations near Engenheiro Sérgio Motta Dam differed of the other stations (farther of the Dam). The predominance of coarse sediments at stations upstream and finer sediments further downstream affected the choice of habitat by different morphotypes of Chironomidae and it caused a change in the structure of this assemblage in the longitudinal stretch.

EMergy analysis perspectives of Thailand and Mekong River dam proposals

International Nuclear Information System (INIS)

Brown, M.T.; McClanahan, T.R.

1996-01-01

Methods of EMergy analysis (a scientifically based measure of wealth with units of solar emjoules (sej)) are explained and illustrated, using the economy of Thailand and two proposed dams on the Mekong River. Thailand's EMergy/$ ratio is near the world average (3.46 ·10 12 sej/$), its EMergy per capita ratio (2.98·10 15 sej/capita) is low compared to developed economies (that of the United States is 29.3·10 15 sej/capita), and its EMergy balance of payments is negative (the EMergy in exports is almost twice the EMergy in imports). The calculated net yield ratios of the proposed dams were sensitive to the treatment of sediments. The analysis yielded high net yield ratios (12.3/1 and 20.3/1) if sediments were not included, but yielded ratios of only 1.4/1 and 1.3/1 if sediments were included. If the two dams were constructed as a cascade, the combined net yield ratio was 2.5/1 (sediments included). If compared to conventional fossil fuels as a primary source of energy to the economy, the net yield ratio of the electricity generated from the two-dam cascade expressed as fossil fuels was 7.4/1

Owyhee River intracanyon lava flows: does the river give a dam?

Science.gov (United States)

Ely, Lisa L.; Brossy, Cooper C.; House, P. Kyle; Safran, Elizabeth B.; O'Connor, Jim E.; Champion, Duane E.; Fenton, Cassandra R.; Bondre, Ninad R.; Orem, Caitlin A.; Grant, Gordon E.; Henry, Christopher D.; Turrin, Brent D.

2013-01-01

Rivers carved into uplifted plateaus are commonly disrupted by discrete events from the surrounding landscape, such as lava flows or large mass movements. These disruptions are independent of slope, basin area, or channel discharge, and can dominate aspects of valley morphology and channel behavior for many kilometers. We document and assess the effects of one type of disruptive event, lava dams, on river valley morphology and incision rates at a variety of time scales, using examples from the Owyhee River in southeastern Oregon. Six sets of basaltic lava flows entered and dammed the river canyon during two periods in the late Cenozoic ca. 2 Ma–780 ka and 250–70 ka. The dams are strongly asymmetric, with steep, blunt escarpments facing up valley and long, low slopes down valley. None of the dams shows evidence of catastrophic failure; all blocked the river and diverted water over or around the dam crest. The net effect of the dams was therefore to inhibit rather than promote incision. Once incision resumed, most of the intracanyon flows were incised relatively rapidly and therefore did not exert a lasting impact on the river valley profile over time scales >106 yr. The net long-term incision rate from the time of the oldest documented lava dam, the Bogus Rim lava dam (≤1.7 Ma), to present was 0.18 mm/yr, but incision rates through or around individual lava dams were up to an order of magnitude greater. At least three lava dams (Bogus Rim, Saddle Butte, and West Crater) show evidence that incision initiated only after the impounded lakes filled completely with sediment and there was gravel transport across the dams. The most recent lava dam, formed by the West Crater lava flow around 70 ka, persisted for at least 25 k.y. before incision began, and the dam was largely removed within another 35 k.y. The time scale over which the lava dams inhibit incision is therefore directly affected by both the volume of lava forming the dam and the time required for sediment

Influence of dams on sediment continuity: A study case of a natural metallic contamination.

Science.gov (United States)

Frémion, Franck; Bordas, François; Mourier, Brice; Lenain, Jean-François; Kestens, Tim; Courtin-Nomade, Alexandra

2016-03-15

Sediments play an important role on the quality of aquatic ecosystems, notably in the reservoir areas where they can either be a sink or a source of contaminants, depending on the management and hydrological conditions. The physicochemical properties of 25 surface sediments samples of a reservoir catchment (Vaussaire, Cantal, France) were studied. Results show a strong influence of dam presence, notably on the grain size and organic matter (OM) contents. The concentrations of trace metals and metalloids (As, Cd, Cr, Cu, Ni, Pb and Zn) were also measured and compared with worldwide reservoir concentrations and international sediment quality guideline levels in order to assess the intensity of the metallic contamination. Cr and Ni are the trace elements presenting the significantly highest values at the catchment scale. Enrichment Factors (EF), calculated using both local and national backgrounds, show that metals have mainly a natural origin, explaining especially the Cr and Ni values, linked with the composition of parental rocks. Unexpectedly, all the observed metal concentrations are lower in the reservoir than upstream and downstream, which might be related to the high fresh OM inputs in the reservoir, diluting the global metallic contamination. Multivariate statistical analyses, carried out in order to identify the relationship between the studied metals and sediment characteristics, tend to support this hypothesis, confirming the unusually low influence of such poorly-degraded OM on trace element accumulation in the reservoir. Copyright © 2016 Elsevier B.V. All rights reserved.

Incorporation of Fine-Grained Sediment Erodibility Measurements into Sediment Transport Modeling, Capitol Lake, Washington

Science.gov (United States)

Stevens, Andrew W.; Gelfenbaum, Guy; Elias, Edwin; Jones, Craig

2008-01-01

Capitol Lake was created in 1951 with the construction of a concrete dam and control gate that prevented salt-water intrusion into the newly formed lake and regulated flow of the Deschutes River into southern Puget Sound. Physical processes associated with the former tidally dominated estuary were altered, and the dam structure itself likely caused an increase in retention of sediment flowing into the lake from the Deschutes River. Several efforts to manage sediment accumulation in the lake, including dredging and the construction of sediment traps upriver, failed to stop the lake from filling with sediment. The Deschutes Estuary Feasibility Study (DEFS) was carried out to evaluate the possibility of removing the dam and restoring estuarine processes as an alternative ongoing lake management. An important component of DEFS was the creation of a hydrodynamic and sediment transport model of the restored Deschutes Estuary. Results from model simulations indicated that estuarine processes would be restored under each of four restoration alternatives, and that over time, the restored estuary would have morphological features similar to the predam estuary. The model also predicted that after dam-removal, a large portion of the sediment eroded from the lake bottom would be deposited near the Port of Olympia and a marina located in lower Budd Inlet seaward of the present dam. The volume of sediment transported downstream was a critical piece of information that managers needed to estimate the total cost of the proposed restoration project. However, the ability of the model to predict the magnitude of sediment transport in general and, in particular, the volume of sediment deposition in the port and marina was limited by a lack of information on the erodibility of fine-grained sediments in Capitol Lake. Cores at several sites throughout Capitol Lake were collected between October 31 and November 1, 2007. The erodibility of sediments in the cores was later determined in the

Documentation of particle-size analyzer time series, and discrete suspended-sediment and bed-sediment sample data collection, Niobrara River near Spencer, Nebraska, October 2014

Science.gov (United States)

Schaepe, Nathaniel J.; Coleman, Anthony M.; Zelt, Ronald B.

2018-04-06

The U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, monitored a sediment release by Nebraska Public Power District from Spencer Dam located on the Niobrara River near Spencer, Nebraska, during the fall of 2014. The accumulated sediment behind Spencer Dam ordinarily is released semiannually; however, the spring 2014 release was postponed until the fall. Because of the postponement, the scheduled fall sediment release would consist of a larger volume of sediment. The larger than normal sediment release expected in fall 2014 provided an opportunity for the USGS and U.S. Army Corps of Engineers to improve the understanding of sediment transport during reservoir sediment releases. A primary objective was to collect continuous suspended-sediment data during the first days of the sediment release to document rapid changes in sediment concentrations. For this purpose, the USGS installed a laser-diffraction particle-size analyzer at a site near the outflow of the dam to collect continuous suspended-sediment data. The laser-diffraction particle-size analyzer measured volumetric particle concentration and particle-size distribution from October 1 to 2 (pre-sediment release) and October 5 to 9 (during sediment release). Additionally, the USGS manually collected discrete suspended-sediment and bed-sediment samples before, during, and after the sediment release. Samples were collected at two sites upstream from Spencer Dam and at three bridges downstream from Spencer Dam. The resulting datasets and basic metadata associated with the datasets were published as a data release; this report provides additional documentation about the data collection methods and the quality of the data.

Geomorphic response of the Sandy River, Oregon, to removal of Marmot Dam

Science.gov (United States)

Major, Jon J.; O'Connor, Jim E.; Podolak, Charles J.; Keith, Mackenzie K.; Grant, Gordon E.; Spicer, Kurt R.; Pittman, Smokey; Bragg, Heather M.; Wallick, J. Rose; Tanner, Dwight Q.; Rhode, Abagail; Wilcock, Peter R.

2012-01-01

The October 2007 breaching of a temporary cofferdam constructed during removal of the 15-meter (m)-tall Marmot Dam on the Sandy River, Oregon, triggered a rapid sequence of fluvial responses as ~730,000 cubic meters (m3) of sand and gravel filling the former reservoir became available to a high-gradient river. Using direct measurements of sediment transport, photogrammetry, airborne light detection and ranging (lidar) surveys, and, between transport events, repeat ground surveys of the reservoir reach and channel downstream, we monitored the erosion, transport, and deposition of this sediment in the hours, days, and months following breaching of the cofferdam. Rapid erosion of reservoir sediment led to exceptional suspended-sediment and bedload-sediment transport rates near the dam site, as well as to elevated transport rates at downstream measurement sites in the weeks and months after breaching. Measurements of sediment transport 0.4 kilometers (km) downstream of the dam site during and following breaching show a spike in the transport of fine suspended sediment within minutes after breaching, followed by high rates of suspended-load and bedload transport of sand. Significant transport of gravel bedload past the measurement site did not begin until 18 to 20 hours after breaching. For at least 7 months after breaching, bedload transport rates just below the dam site during high flows remained as much as 10 times above rates measured upstream of the dam site and farther downstream. The elevated sediment load was derived from eroded reservoir sediment, which began eroding when a meters-tall knickpoint migrated about 200 m upstream in the first hour after breaching. Rapid knickpoint migration triggered vertical incision and bank collapse in unconsolidated sand and gravel, leading to rapid channel widening. Over the following days and months, the knickpoint migrated upstream more slowly, simultaneously decreasing in height and becoming less distinct. Within 7 months

Natural radioactivity investigation in Dam sediments of northeast Algeria using gamma spectroscopy

Directory of Open Access Journals (Sweden)

Benrachi Fatima

2017-01-01

Full Text Available Current research paper intends to estimate the natural radioactivity levels in sediments samples collected from Beni Haroun Dam in the northeast Algeria, using high resolution HPGe detector. The mean activity concentrations values measured for the radionuclides 232Th, 226Ra and 40K are 18.9 ± 1.9, 37.3 ± 2.7 and 149.9 ± 5.5 Bq/kg, respectively. The 137Cs anthropogenic radionuclide has been observed with maximum activity concentration value of 0.8 ± 0.4 Bq/kg, which is considered an insignificant amount. In order to assess the radiological threat of gamma radiations emitted by these radionuclides on the health of the population, absorbed dose rate, annual effective dose equivalent and radiation hazard indices were had been calculated. The obtained values are compared with the world wide average ones.

Valorization of mud from Fergoug dam in manufacturing mortars

Directory of Open Access Journals (Sweden)

L. Laoufi

2016-12-01

Full Text Available The production of calcined mud, with pozzolanic properties, from the large quantities of sediments dredged from Algerian dams, could be a good opportunity for the formulation of high performance mortars and pozzolanic concretes, with lower costs and less greenhouse gas (CO2 emissions. The optimal temperatures selected for calcination were 750, 850 and 950 °C. The burning operation was continuous over a period of 3 h. Therefore, a series of physical, chemical, mechanical and microstructural analyses were conducted on sediment samples, collected from the waters of Fergoug dam. The results obtained from the analyses of the calcined mud, from the dam, allowed saying that mortars with different percentages of that mud represent a potential source of high reactivity pozzolanic materials.

How Physical Processes are Informing River Management Actions at Marble Bluff Dam, Truckee River, Nevada

Science.gov (United States)

Bountry, J.; Godaire, J.; Bradley, D. N.

2017-12-01

At the terminus of the Truckee River into Pyramid Lake (Nevada, USA), upstream river management actions have dramatically reshaped the river landscape, posing significant challenges for the management of endangered aquatic species and maintenance of existing infrastructure. Within the last 100 years, upstream water withdrawal for human uses has resulted in a rapid lowering of Pyramid Lake which initiated up to 90 ft of channel incision. In 1976 Marble Bluff Dam was constructed to halt the upstream progression of channel incision and protect upstream agricultural lands, tribal resources, and infrastructure. Since construction an additional 40 ft of lake lowering and subsequent channel lowering now poses a potential risk to the structural integrity of the dam. The dynamic downstream river combined with ongoing reservoir sedimentation pose challenges to fish passage facilities that enable migration of numerous endangered cui-ui and threatened Lahontan Cutthroat Trout (LCT) to upstream spawning areas each year. These facilities include a fish lock at the dam, a fish bypass channel which allows fish to avoid the shallow delta area during low lake levels, and a meandering channel constructed by the Nature Conservancy to connect the bypass channel to the receding Pyramid Lake. The reservoir formed by Marble Bluff Dam has completely filled with sediment which impacts fish passage facilities. The original operating manual for the dam recommends year-round flushing of sediment through radial gates, but this can no longer be accomplished. During critical fish migration periods in the spring operators must ensure fish entrance channels downstream of the dam are not buried with released sediment and fish are not trapped in a portion of the reservoir full of sediment that would risk sending them back over the dam. To help inform future reservoir sediment and infrastructure management strategies, we bracket a range of potential river responses to lake level lowering and floods

Structural practices for controlling sediment transport from erosion

Science.gov (United States)

Gabriels, Donald; Verbist, Koen; Van de Linden, Bruno

2013-04-01

Erosion on agricultural fields in the hilly regions of Flanders, Belgium has been recognized as an important economical and ecological problem that requires effective control measures. This has led to the implementation of on-site and off-site measures such as reduced tillage and the installation of grass buffers trips, and dams made of vegetative materials. Dams made out of coir (coconut) and wood chips were evaluated on three different levels of complexity. Under laboratory conditions, one meter long dams were submitted to two different discharges and three sediment concentrations under two different slopes, to assess the sediment delivery ratios under variable conditions. At the field scale, discharge and sediment concentrations were monitored under natural rainfall conditions on six 3 m wide plots, of which three were equipped with coir dams, while the other three served as control plots. The same plots were also used for rainfall simulations, which allowed controlling sediment delivery boundary conditions more precisely. Results show a clear advantage of these dams to reduce discharge by minimum 49% under both field and laboratory conditions. Sediment delivery ratios (SDR) were very small under laboratory and field rainfall simulations (4-9% and 2% respectively), while larger SDRs were observed under natural conditions (43%), probably due to the small sediment concentrations (1-5 g l-1) observed and as such a larger influence of boundary effects. Also a clear enrichment of larger sand particles (+167%) could be observed behind the dams, showing a significant selective filtering effect.

Riparian soil development linked to forest succession above and below dams along the Elwha River, Washington, USA

Science.gov (United States)

Perry, Laura G; Shafroth, Patrick B.; Perakis, Steven

2017-01-01

Riparian forest soils can be highly dynamic, due to frequent fluvial disturbance, erosion, and sediment deposition, but effects of dams on riparian soils are poorly understood. We examined soils along toposequences within three river segments located upstream, between, and downstream of two dams on the Elwha River to evaluate relationships between riparian soil development and forest age, succession, and channel proximity, explore dam effects on riparian soils, and provide a baseline for the largest dam removal in history. We found that older, later-successional forests and geomorphic surfaces contained soils with finer texture and greater depth to cobble, supporting greater forest floor mass, mineral soil nutrient levels, and cation exchange. Forest stand age was a better predictor than channel proximity for many soil characteristics, though elevation and distance from the channel were often also important, highlighting how complex interactions between fluvial disturbance, sediment deposition, and biotic retention regulate soil development in this ecosystem. Soils between the dams, and to a lesser extent below the lower dam, had finer textures and higher mineral soil carbon, nitrogen, and cation exchange than above the dams. These results suggested that decreased fluvial disturbance below the dams, due to reduced sediment supply and channel stabilization, accelerated soil development. In addition, reduced sediment supply below the dams may have decreased soil phosphorus. Soil δ15N suggested that salmon exclusion by the dams had no discernable effect on nitrogen inputs to upstream soils. Recent dam removal may alter riparian soils further, with ongoing implications for riparian ecosystems.

Bank Erosion, Mass Wasting, Water Clarity, Bathymetry and a Sediment Budget Along the Dam-Regulated Lower Roanoke River, North Carolina

Science.gov (United States)

Schenk, Edward R.; Hupp, Cliff R.; Richter, Jean M.; Kroes, Daniel E.

2010-01-01

Dam construction and its impact on downstream fluvial processes may substantially alter ambient bank stability, floodplain inundation patterns, and channel morphology. Most of the world's largest rivers have been dammed, which has prompted management efforts to mitigate dam effects. Three high dams (completed between 1953 and 1963) occur along the Piedmont portion of the Roanoke River, North Carolina; just downstream, the lower part of the river flows across largely unconsolidated Coastal Plain deposits. To document bank erosion rates along the lower Roanoke River, more than 700 bank erosion pins were installed along 124 bank transects. Additionally, discrete measurements of channel bathymetry, water clarity, and presence or absence of mass wasting were documented along the entire 153-kilometer-long study reach. Amounts of bank erosion in combination with prior estimates of floodplain deposition were used to develop a bank erosion and floodplain deposition sediment budget for the lower river. Present bank erosion rates are relatively high [mean 42 milimeters per year (mm/yr)] and are greatest along the middle reaches (mean 60 mm/yr) and on lower parts of the bank on all reaches. Erosion rates were likely higher along upstream reaches than present erosion rates such that erosion rate maxima have migrated downstream. Mass wasting and water clarity also peak along the middle reaches.

Evaluating the Role of Small Impoundments in Legacy Sediment Storage

Science.gov (United States)

Bain, D. J.; Salant, N.; Green, M. B.; Wreschnig, A. J.; Urbanova, T.

2009-12-01

Recent research highlighting the prevalence of dams built for water power in the mid-1800s has led to suggestions that strategies for managing legacy sediment in the Eastern United States should be re-evaluated. However, the link between reach-scale observations of historic dam sites to processes at the catchment scale have not been examined, nor have the role of other, similar historic changes been evaluated. This presentation will compare dam dynamics, including mill density data and synthetic estimates of beaver populations with sedimentation rates recorded in sediment cores. If low-head dams were a dominant mechanism in sediment storage, we expect to see changes in sedimentation rates with the expatriation of the beaver and the rise and decline of water power. Further, we expect to see spatial variation in these changes as beaver and mill densities and potential sediment yield are spatially heterogeneous. Ultimately, dramatic changes in sediment yield due to land use and hydrological alterations likely drove sedimentation rates; the mechanistic importance of storage likely depends on temporal coincidence.

Heavy metal contamination of water and fish in peri-urban dams ...

African Journals Online (AJOL)

Heavy metals were measured in water, sediment and fish in dams located downstream of effluent discharge zones in Bulawayo and were compared to those in a pristine upstream dam. Water conductivity indicated pollution of downstream dams. Levels of lead (0.13 – 0.28 ppm) and cadmium (0.02 – 0.06 ppm) in water from ...

Radiological assessment and geochemical characterization of the sediments of Awba Dam, University of Ibadan, Nigeria

International Nuclear Information System (INIS)

Jibiri, Nnamdi Norbert; Akomolafe, Idowu Richard

2016-01-01

The distribution of natural radionuclides and geochemical parameters in the sediments of Awba Dam, University of Ibadan, Nigeria has been determined. The mean absorbed dose rates obtained were 72.3 nGy/h (upstream), 53.9 nGy/h (middle stream) and 50.29 nGy/h (downstream) with the corresponding mean annual effective dose rates of 0.09, 0.07 and 0.06 mSv/year, respectively. The geochemical analysis showed that Si, Al, Fe, Mn, Mg, Ca, Na, K, and Ti were the major elements and Zn, Cu, Cr, Rb, Ni, Ba, Ga, Ce, and Sr as heavy metals in the sediments. The moderate enrichment elements were Zn, Rb, Ba and Ga, whereas elements deficient in enrichment were Cr, Sr, Ce, Cu, and Ni. The geo-accumulation index was from unpolluted to moderately polluted environment. The enrichment factors (EF) observed in the elements indicate that these metals are entirely from crustal material or natural origin while EF >1.5 observed in Zn, Rb, Ba, and Ga suggests that the sources are more likely to be anthropogenic. The values of the radiological hazard parameter indices were below the recommended safe limits; an indication that the sediments can be used safely. (author)

Anthropocene streams and base-level controls from historic dams in the unglaciated mid-Atlantic region, USA

Science.gov (United States)

Merritts, Dorothy; Walter, Robert; Rahnis, Michael; Hartranft, Jeff; Cox, Scott; Gellis, Allen; Potter, Noel; Hilgartner, William; Langland, Michael; Manion, Lauren; Lippincott, Caitlin; Siddiqui, Sauleh; Rehman, Zain; Scheid, Chris; Kratz, Laura; Shilling, Andrea; Jenschke, Matthew; Datin, Katherine; Cranmer, Elizabeth; Reed, Austin; Matuszewski, Derek; Voli, Mark; Ohlson, Erik; Neugebauer, Ali; Ahamed, Aakash; Neal, Conor; Winter, Allison; Becker, Steven

2011-01-01

Recently, widespread valley-bottom damming for water power was identified as a primary control on valley sedimentation in the mid-Atlantic US during the late seventeenth to early twentieth century. The timing of damming coincided with that of accelerated upland erosion during post-European settlement land-use change. In this paper, we examine the impact of local drops in base level on incision into historic reservoir sediment as thousands of ageing dams breach. Analysis of lidar and field data indicates that historic milldam building led to local base-level rises of 2-5 m (typical milldam height) and reduced valley slopes by half. Subsequent base-level fall with dam breaching led to an approximate doubling in slope, a significant base-level forcing. Case studies in forested, rural as well as agricultural and urban areas demonstrate that a breached dam can lead to stream incision, bank erosion and increased loads of suspended sediment, even with no change in land use. After dam breaching, key predictors of stream bank erosion include number of years since dam breach, proximity to a dam and dam height. One implication of this work is that conceptual models linking channel condition and sediment yield exclusively with modern upland land use are incomplete for valleys impacted by milldams. With no equivalent in the Holocene or late Pleistocene sedimentary record, modern incised stream-channel forms in the mid-Atlantic region represent a transient response to both base-level forcing and major changes in land use beginning centuries ago. Similar channel forms might also exist in other locales where historic milling was prevalent.

The Effect of Paved Roads on Organic Carbon Content of Soil in Taham Dam Basin

Directory of Open Access Journals (Sweden)

Mazyar Peyda

2016-09-01

Full Text Available Background: Contamination of water and soil through non-point sources such as road runoff causes environmental concern. The aim of this study is to determine the effect of Zanjan – Chavarzagh road on the total organic carbon (TOC content of sediments in tributaries and the river that lead to Taham Lake. Methods: In tributaries and the river 69 soil and sediment samples were taken and the Total organic carbon (TOC was measured according to Walkely-Black method. Also, Taham Dam Basin area and its hydrologic properties were calculated by Global Information System (GIS software. Results: Results showed that, TOC concentration has a significant negative relationship with the distance from the lake. TOC in soil samples taken from hillside of the road had significantly lower mean and median concentration ( median= 3262 , mean = 4083 ± 3461 mg/kg than the valley side ( median = 5324 , mean = 6178 ± 3980 mg/kg. The check dams across the tributaries and the river have not been effective in the reduction of TOC in sediments. Conclusion: Roads in the Taham Dam Basin, increases TOC content of soil and sediments in Taham dam basin. TOC moves toward Taham dam lake.

Effects of dams and geomorphic context on riparian forests of the Elwha River, Washington

Science.gov (United States)

Shafroth, Patrick B.; Perry, Laura G; Rose, Chanoane A; Braatne, Jeffrey H

2016-01-01

Understanding how dams affect the shifting habitat mosaic of river bottomlands is key for protecting the many ecological functions and related goods and services that riparian forests provide and for informing approaches to riparian ecosystem restoration. We examined the downstream effects of two large dams on patterns of forest composition, structure, and dynamics within different geomorphic contexts and compared them to upstream reference conditions along the Elwha River, Washington, USA. Patterns of riparian vegetation in river segments downstream of the dams were driven largely by channel and bottomland geomorphic responses to a dramatically reduced sediment supply. The river segment upstream of both dams was the most geomorphically dynamic, whereas the segment between the dams was the least dynamic due to substantial channel armoring, and the segment downstream of both dams was intermediate due to some local sediment supply. These geomorphic differences were linked to altered characteristics of the shifting habitat mosaic, including older forest age structure and fewer young Populus balsamifera subsp. trichocarpa stands in the relatively static segment between the dams compared to more extensive early-successional forests (dominated by Alnus rubra and Salix spp.) and pioneer seedling recruitment upstream of the dams. Species composition of later-successional forest communities varied among river segments as well, with greater Pseudotsuga menziesii and Tsuga heterophylla abundance upstream of both dams, Acer spp. abundance between the dams, and P. balsamifera subsp. trichocarpa and Thuja plicata abundance below both dams. Riparian forest responses to the recent removal of the two dams on the Elwha River will depend largely on channel and geomorphic adjustments to the release, transport, and deposition of the large volume of sediment formerly stored in the reservoirs, together with changes in large wood dynamics.

Using high-resolution suspended-sediment measurements to infer changes in the topographic distribution and grain size of bed sediment in the Colorado River downstream from Glen Canyon Dam

Science.gov (United States)

Topping, D. J.; Rubin, D. M.; Melis, T. S.; Wright, S. A.

2004-12-01

Eddy sandbars and other sandy deposits in and along the Colorado River in Grand Canyon National Park (GCNP) were an integral part of the pre-dam riverscape, and are still important for habitat, protection of archeological sites, and recreation. Recent work has shown that eddy bars are dynamic landforms and represent the bulk of the ecosystem's sand reserves. These deposits began eroding following the 1963 closure of Glen Canyon Dam that reduced the supply of sand at the upstream boundary of GCNP by about 94% and are still eroding today. Sand transport in the post-dam river is limited by episodic resupply from tributaries, and is equally regulated by the discharge of water and short-term changes in the grain size of sand available for transport (Rubin and Topping, WRR, 2001). During tributary floods, sand on the bed of the Colorado River fines; this causes the suspended sand to fine and the suspended-sand concentration to increase even when the discharge of water remains constant. Subsequently, the bed is winnowed of finer sand, the suspended sand coarsens, and the suspended-sand concentration decreases independently of discharge. This prohibits the computation of sand-transport rates in the Colorado River using stable relations between water discharge and sand transport (i.e., sediment rating curves) and requires a more continuous method for measuring sand transport. To monitor suspended sediment at higher (i.e., 15-minute) resolutions, we began testing a laser-acoustic system at four locations along the Colorado River in Grand Canyon in August 2002. Because they are much easier to acquire, the high-resolution suspended-sediment datasets collected using the laser-acoustic systems greatly outnumber (by >5 orders of magnitude) direct grain-size measurements of the upstream bed sediment. Furthermore, suspension processes effectively provide an average "sample" of the bed sediment on the perimeter of the upstream channel and the underwater portions of the banks and

Coastal habitat and biological community response to dam removal on the Elwha River

Science.gov (United States)

Foley, Melissa M.; Warrick, Jonathan A.; Ritchie, Andrew C.; Stevens, Andrew; Shafroth, Patrick B.; Duda, Jeff; Beirne, Matthew M.; Paradis, Rebecca; Gelfenbaum, Guy R.; McCoy, Randall; Cubley, Erin S.

2017-01-01

Habitat diversity and heterogeneity play a fundamental role in structuring ecological communities. Dam emplacement and removal can fundamentally alter habitat characteristics, which in turn can affect associated biological communities. Beginning in the early 1900s, the Elwha and Glines Canyon dams in Washington, USA, withheld an estimated 30 million tonnes of sediment from river, coastal, and nearshore habitats. During the staged removal of these dams—the largest dam removal project in history—over 14 million tonnes of sediment were released from the former reservoirs. Our interdisciplinary study in coastal habitats—the first of its kind—shows how the physical changes to the river delta and estuary habitats during dam removal were linked to responses in biological communities. Sediment released during dam removal resulted in over a meter of sedimentation in the estuary and over 400 m of expansion of the river mouth delta landform. These changes increased the amount of supratidal and intertidal habitat, but also reduced the influx of seawater into the pre-removal estuary complex. The effects of these geomorphic and hydrologic changes cascaded to biological systems, reducing the abundance of macroinvertebrates and fish in the estuary and shifting community composition from brackish to freshwater-dominated species. Vegetation did not significantly change on the delta, but pioneer vegetation increased during dam removal, coinciding with the addition of newly available habitat. Understanding how coastal habitats respond to large-scale human stressors—and in some cases the removal of those stressors—is increasingly important as human uses and restoration activities increase in these habitats.

Large-scale dam removal on the Elwha River, Washington, USA: coastal geomorphic change

Science.gov (United States)

Gelfenbaum, Guy R.; Stevens, Andrew W.; Miller, Ian M.; Warrick, Jonathan A.; Ogston, Andrea S.; Eidam, Emily

2015-01-01

Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of mud, sand, and gravel since 1927, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams, initiated in September 2011, induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the geomorphic response of a coastal delta to these increases. Detailed measurements of beach topography and nearshore bathymetry show that ~ 2.5 million m3 of sediment was deposited during the first two years of dam removal, which is ~ 100 times greater than deposition rates measured prior to dam removal. The majority of the deposit was located in the intertidal and shallow subtidal region immediately offshore of the river mouth and was composed of sand and gravel. Additional areas of deposition include a secondary sandy deposit to the east of the river mouth and a muddy deposit west of the mouth. A comparison with fluvial sediment fluxes suggests that ~ 70% of the sand and gravel and ~ 6% of the mud supplied by the river was found in the survey area (within about 2 km of the mouth). A hydrodynamic and sediment transport model, validated with in-situ measurements, shows that tidal currents interacting with the larger relict submarine delta help disperse fine sediment large distances east and west of the river mouth. The model also suggests that waves and currents erode the primary deposit located near the river mouth and transport sandy sediment eastward to form the secondary deposit. Though most of the substrate of the larger relict submarine delta was unchanged during the first two years of dam removal, portions of the seafloor close to the river mouth became finer, modifying habitats for biological communities. These results show that river restoration, like natural changes in river sediment supply, can result in rapid and substantial coastal geomorphological

Heavy Metal Assessment in Water and Sediments at Jaikwadi Dam (Godavari River Maharashtra, India

Directory of Open Access Journals (Sweden)

Satish S Patil

2016-05-01

Full Text Available The indiscriminate release of industrial effluents, domestic sewage, agricultural runoff have resulted in extensive contamination of water and soil with heavy metals thereby causing hazard to flora and fauna and the aquatic ecosystem. Therefore, there is a need for biological monitoring studies to evaluate the toxic concentrations of various chemical compounds so that certain preventive measure can be taken to ensure the safety of the environment. Therefore, this study was focused at investigating few of the important heavy metals like zinc, chromium, cadmium, mercury and lead, in water along with sediments of the Jaikwadi dam. It has been found that the content of mercury was the highest in both water (15.24 - 18.21 μg/L and sediments, it is followed by lead (14.31 - 18.38 μg/L, cadmium (1.95 - 2.29 μg/L, chromium (0.68 - 4.00 μg/L and finally zinc (0.88 - 1.77 μg/L. High concentrations particularly of mercury and lead warrant studies for their remediation so that the concentration remains safe for the populace dependent on the water.INTERNATIONAL JOURNAL OF ENVIRONMENTVolume-5, Issue-2, March-May 2016, Page: 75-88

New evidence of Yangtze delta recession after closing of the Three Gorges Dam

Science.gov (United States)

Luo, X. X.; Yang, S. L.; Wang, R. S.; Zhang, C. Y.; Li, P.

2017-01-01

Many deltas are likely undergoing net erosion because of rapid decreases in riverine sediment supply and rising global sea levels. However, detecting erosion in subaqueous deltas is usually difficult because of the lack of bathymetric data. In this study, by comparing bathymetric data between 1981 and 2012 and surficial sediment grain sizes from the Yangtze subaqueous delta front over the last three decades, we found severe erosion and significant sediment coarsening in recent years since the construction of Three Gorges Dam (TGD), the largest dam in the world. We attributed these morphological and sedimentary variations mainly to the human-induced drastic decline of river sediment discharge. Combined with previous studies based on bathymetric data from different areas of the same delta, we theorize that the Yangtze subaqueous delta is experiencing overall (net) erosion, although local accumulation was also noted. We expect that the Yangtze sediment discharge will further decrease in the near future because of construction of new dams and delta recession will continue to occur. PMID:28145520

Sedimentation problems and solutions

International Nuclear Information System (INIS)

Williams, D.T.

1991-01-01

Roseires Dam and reservoir are located in Sudan, Africa on the Blue Nile River. The hydropower from the reservoir provides approximately 80% of the power used in Sudan, thus having a tremendous economic impact on the country. The reservoir was first impounded in 1966 and has been filled annually since then. The Blue Nile has historically been known to carry heavy sediment loads which is associated with erosion from overgrazing in Ethiopia, the Blue Nile's headwaters. During the flood season, the dam's turbine intakes become blocked with debris and sediment. After a severe blockage in 1981, which prevented hydropower generation for several days, consultants from USAID were asked to make recommendations on reducing the sediment and debris impacts on reservoir operations. This led to debris clearing and dredging equipment acquisitions in 1982. In 1988, blockage occurred again during the flood season. This writer was asked by the World Bank to travel to Sudan, investigate the sediment and debris problems, examine the USAID recommendations, comment on potential sediment and debris problems associated with a proposed plan to raise the dam, make additional recommendations, and return to Sudan several times to determine the effectiveness of there recommendations. This paper discussed the results of the aforementioned activities and describes the new recommendations made by this writer

Three Years Measuring Sediment Erosion and Deposition from the Largest Dam Removal Ever at Weekly-­to-­Monthly Scales Using SfM: Elwha River, Washington, USA.

Science.gov (United States)

Ritchie, A.; Randle, T. J.; Bountry, J.; Warrick, J. A.

2015-12-01

The stepwise removal of two dams on the Elwha River beginning in September 2011 exposed ~21 million cubic meters of sediment to fluvial erosion and created an unprecedented opportunity to monitor reservoir sediment erosion and river evolution during base level adjustment and a pulsed sediment release. We have conducted more than 60 aerial surveys with a Cessna 172 using a simple custom wing-mount for consumer grade cameras and SfM photogrammetry to produce orthoimagery and digital elevation models in near-real-time at weekly to monthly time intervals. Multiple lidar flights and ground survey campaigns have provided estimates of both systematic and random error for this uniquely dense dataset. Co-registration of multiple surveys during processing reduces systematic error and allows boot-strapping of subsequently established ground control to earlier flights. Measurements chronicle the erosion of 12 million cubic meters of reservoir sediment and record corresponding changes in channel braiding, wood loading and bank erosion. These data capture reservoir and river channel responses to dam removal at resolutions comparable to hydrologic forcing events, allowing us to quantify reservoir sediment budgets on a per-storm basis. This allows for the analysis of sediment transported relative to rates of reservoir drawdown and river stream power for dozens of intervals of time. Temporal decoupling of peak sediment flux and bank erosion rates is noted from these analyses. This dataset illustrates some of the challenges and opportunities emerging with the advent of big data in remote sensing of earth surface processes.

Physical and chemical investigation of water and sediment of the Keban Dam Lake, Turkey. Part 2. Distribution of radioactivity, heavy metals and major elements

International Nuclear Information System (INIS)

Kulahci, F.; Dogru, M.

2006-01-01

Thirtynine surface water and 20 deep sediment samples were taken in different locations in Keban Dam Lake (Elazig, Turkey) to identify major sources and assess major elements, heavy metals, 137 Cs, 90 Sr, total alpha- and, total beta-distribution in 2003 and 2004 in four seasons each year. As a preliminary study heavy metal (Zn, Fe, Mn, Ni, Cu, Cr, and Co), major element (Mg, Ca, Na, K) and radioactivity concentrations of 137 Cs, 90 Sr, total-α and total-β in the surface water and deep sediments were determined. (author)

Large-scale dam removal on the Elwha River, Washington, USA: river channel and floodplain geomorphic change

Science.gov (United States)

East, Amy E.; Pess, George R.; Bountry, Jennifer A.; Magirl, Christopher S.; Ritchie, Andrew C.; Logan, Joshua; Randle, Timothy J.; Mastin, Mark C.; Minear, Justin T.; Duda, Jeffrey J.; Liermann, Martin C.; McHenry, Michael L.; Beechie, Timothy J.; Shafroth, Patrick B.

2015-01-01

A substantial increase in fluvial sediment supply relative to transport capacity causes complex, large-magnitude changes in river and floodplain morphology downstream. Although sedimentary and geomorphic responses to sediment pulses are a fundamental part of landscape evolution, few opportunities exist to quantify those processes over field scales. We investigated the downstream effects of sediment released during the largest dam removal in history, on the Elwha River, Washington, USA, by measuring changes in riverbed elevation and topography, bed sediment grain size, and channel planform as two dams were removed in stages over two years.

Hydraulics of embankment-dam breaching

Science.gov (United States)

Walder, J. S.; Iverson, R. M.; Logan, M.; Godt, J. W.; Solovitz, S.

2012-12-01

the hydrograph in another way: the broader the initial dam crest, the longer the time before critical flow control is established. Flood duration is thus increased but peak discharge is decreased. Visual inspection and overhead videography reveal little turbidity in water pouring over the weir, implying that sediment there moves dominantly as bedload. Furthermore, underwater videography gives the overall impression that along the upstream dam face, erosion occurs without redeposition. Thus it would be a mistake to use empiricisms for equilibrium bedload transport to model erosion of the embankment. In mathematical terms, erosion rate cannot be backed out by calculating the divergence of transport rate; rather, transport rate should be regarded as the spatial integral of erosion rate. We use photogrammetry and motion of the colored markers to determine the erosion rate of the weir, and then infer shear stress at the weir by applying the van Rijn sediment-pickup function. Shear stress determined in this fashion is much less than what one calculates from the gradient of the energy head (an approach appropriate to steady flow). Shear stress inferred from the pickup-function calculation can serve as a constraint on computational fluid-dynamics models. Another constraint on such models, revealed by the underwater videography, is the upstream limit of sand movement, where bed shear stress equals the critical value for sand entrainment.

Tracing sediment sources in Royal Drainage basin, Iran

International Nuclear Information System (INIS)

Feiznia, S.; Kouhpelma, A.; Ahmadi, H.; Hashemi, S. A.

2009-01-01

For successful soil conservation measures, obtaining information about the relative importance of sediment source and their shares in sediment production is required. Tracing or source studies are emphasized in recent years due to their privileges. In this research, sediment sources were identified using tracing method. A small earth dam is constructed at the outlet of Royan Drainage Basin in 1993. In this study, sediments were sampled from dam reservoir, different sources were also sampled. The results of this research can be used in soil conservation projects for execution of suitable management strategies. (Author) 6 refs.

Tracing sediment sources in Royal Drainage basin, Iran

Energy Technology Data Exchange (ETDEWEB)

Feiznia, S.; Kouhpelma, A.; Ahmadi, H.; Hashemi, S. A.

2009-07-01

For successful soil conservation measures, obtaining information about the relative importance of sediment source and their shares in sediment production is required. Tracing or source studies are emphasized in recent years due to their privileges. In this research, sediment sources were identified using tracing method. A small earth dam is constructed at the outlet of Royan Drainage Basin in 1993. In this study, sediments were sampled from dam reservoir, different sources were also sampled. The results of this research can be used in soil conservation projects for execution of suitable management strategies. (Author) 6 refs.

Activity concentrations of primordial radionuclides in sediments of surface - water dams in southwest Nigeria - a baseline survey; Concentrations des activites des radionucleides primordiaux dans les sediments des retenues des eaux de ruissellement dans le sud-ouest du Nigeria. Etude de reference

Energy Technology Data Exchange (ETDEWEB)

Isinkaye, M.O. [University of Ado-Ekiti, Dept. of Physics (Nigeria); Farai, I.P. [Ibadan Univ., Dept. of Physics (Nigeria)

2008-10-15

The radionuclide contents of sediment samples collected from 20 surface-water dams in southwestern Nigeria have been determined by low-level gamma-spectroscopy. The average concentration of {sup 40}K in each of the dams varied between 110.9{+-}11.9 Bq kg-1 and 1025.9{+-}36.8 Bq kg{sup -1} with an overall mean ({+-}SD) of 549.3 {+-} 247.6 Bq kg{sup -1} while that of {sup 238}U varied from 17.1{+-}3.6 to 51.9{+-}8.7 Bq kg{sup -1} with an overall mean ({+-}SD) of 27.6{+-}8.5 Bq kg{sup -1} and that of {sup 232}Th varied from 26.2 {+-}3.6 Bq kg{sup -1} to 130.1{+-}23.7 Bq kg{sup -1} with overall mean ({+-}SD) of 62.0{+-}26.1 Bq kg{sup -1}. The variability of the values shows the wide disparity in the measured activity concentrations. The mean radium equivalent of 158.9 Bq kg{sup -1} was calculated for the sediments in the dams. No artificial gamma emitting radionuclide was detected in the samples. (authors)

Effects of Flaming Gorge Dam hydropower operations on sediment transport in the Browns Park reach of the Green River, Utah and Colorado

International Nuclear Information System (INIS)

Williams, G.P.; Tomasko, D.; Cho, H.E.; Yin, S.C.L.

1995-05-01

Three methods for comparing sediment transport were applied to four proposed hydropower operational scenarios under study for Flaming Gorge Dam on the Green River in Utah. These methods were effective discharge, equilibrium potential, and cumulative sediment load with flow exceedance plots. Sediment loads transported by the Green River in the Browns Park reach were calculated with the Engelund-Hansen equation for three historical water years and four hydropower operational scenarios. A model based on the Engelund-Hansen equation was developed using site-specific information and validated by comparing predictions for a moderate water year with measured historical values. The three methods were used to assess the impacts of hydropower operational scenarios on sediment resources. The cumulative sediment load method provided the most useful information for impact evaluation. Effective discharge was not a useful tool because of the limited number of discrete flows associated with synthetic hydrographs for the hydropower operational scenarios. The equilibrium potential method was relatively insensitive to the variations in operating conditions, rendering it comparatively ineffective for impact evaluation

Endocrine-disruptor molecular responses, occurrence of intersex and gonado-histopathological changes in tilapia species from a tropical freshwater dam (Awba Dam) in Ibadan, Nigeria

International Nuclear Information System (INIS)

Adeogun, Aina O.; Onibonoje, Kolawole; Ibor, Oju R.; Omiwole, Roseline A.; Chukwuka, Azubuike V.; Ugwumba, Alex O.; Ugwumba, Adiaha A.A.; Arukwe, Augustine

2016-01-01

Highlights: • Occurrence and severity of intersex in Nigerian aquatic environment. • Estrogenic and reproductive developmental effects of effluents from a University community. • Biomarker of endocrine disruption in fish from a developing country. • Relationship between estrogenic responses and sediment contaminants burden in a dam used for University domestic water supply and for fisheries. • Possible health consequences of environmental contamination - Abstract: In the present study, the occurrence of endocrine disruptive responses in Tilapia species from Awba Dam has been investigated, and compared to a reference site (Modete Dam). The Awba Dam is a recipient of effluents from University of Ibadan (Nigeria) and several other anthropogenic sources. A total of 132 Tilapia species (Sarotherodon malenotheron (n = 57 and 32, males and females, respectively) and Tilapia guineensis (n = 23 and 20, males and females, respectively)) were collected from June to September 2014. At the reference site, samples of adult male and female S. melanotheron (48 males and 47 females) and T. guineensis (84 males and 27 females) were collected. Gonads were morphologically and histologically examined and gonadosomatic index (GSI) was calculated. Hepatic mRNA transcriptions of vitellogenin (Vtg) and zona radiata protein (Zrp) genes were analyzed using validated RT-qPCR. Significant increase in Vtg and Zrp transcripts were observed in male tilapias from Awba Dam, compared to males from the reference site. In addition, male tilapias from Awba Dam produced significantly higher Vtg and Zrp mRNA, compared to females in June and July. However, at the natural peak spawning period in August and September, females produced, significantly higher Vtg and Zrp mRNA, compared to males. Fish gonads revealed varying incidence of intersex with a striking presence of two (2) pairs of testes and a pair of ovary in S. melanotheron from Awba Dam. The entire fish population examined at Awba Dam

Endocrine-disruptor molecular responses, occurrence of intersex and gonado-histopathological changes in tilapia species from a tropical freshwater dam (Awba Dam) in Ibadan, Nigeria

Energy Technology Data Exchange (ETDEWEB)

Adeogun, Aina O.; Onibonoje, Kolawole; Ibor, Oju R.; Omiwole, Roseline A.; Chukwuka, Azubuike V.; Ugwumba, Alex O.; Ugwumba, Adiaha A.A. [Department of Zoology, University of Ibadan, Ibadan (Nigeria); Arukwe, Augustine, E-mail: arukwe@bio.ntnu.no [Department of Biology, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway)

2016-05-15

Highlights: • Occurrence and severity of intersex in Nigerian aquatic environment. • Estrogenic and reproductive developmental effects of effluents from a University community. • Biomarker of endocrine disruption in fish from a developing country. • Relationship between estrogenic responses and sediment contaminants burden in a dam used for University domestic water supply and for fisheries. • Possible health consequences of environmental contamination - Abstract: In the present study, the occurrence of endocrine disruptive responses in Tilapia species from Awba Dam has been investigated, and compared to a reference site (Modete Dam). The Awba Dam is a recipient of effluents from University of Ibadan (Nigeria) and several other anthropogenic sources. A total of 132 Tilapia species (Sarotherodon malenotheron (n = 57 and 32, males and females, respectively) and Tilapia guineensis (n = 23 and 20, males and females, respectively)) were collected from June to September 2014. At the reference site, samples of adult male and female S. melanotheron (48 males and 47 females) and T. guineensis (84 males and 27 females) were collected. Gonads were morphologically and histologically examined and gonadosomatic index (GSI) was calculated. Hepatic mRNA transcriptions of vitellogenin (Vtg) and zona radiata protein (Zrp) genes were analyzed using validated RT-qPCR. Significant increase in Vtg and Zrp transcripts were observed in male tilapias from Awba Dam, compared to males from the reference site. In addition, male tilapias from Awba Dam produced significantly higher Vtg and Zrp mRNA, compared to females in June and July. However, at the natural peak spawning period in August and September, females produced, significantly higher Vtg and Zrp mRNA, compared to males. Fish gonads revealed varying incidence of intersex with a striking presence of two (2) pairs of testes and a pair of ovary in S. melanotheron from Awba Dam. The entire fish population examined at Awba Dam

Perencanaan Check Dam Sungai Dawe Kudus

OpenAIRE

Mustaanah, Adibatul; Pinandoyo, Nur; Sugiyanto, Sugiyanto; Wahyuni, Sri Eko

2013-01-01

Juana river's located in two administrative regions Kudus and Pati had superficial. This is because the slope of the river is quite gentle and the level of environmental degradation in the watershed (DAS) Juana river's have increased. Based on these conditions, it is necessary to plan the construction of sediment control (check dams) to reduce sedimentation along the river and optimize the function of the Juana river's. Planning is performed on Dawe river's ,the branch of Juana river's. From ...

The Impact of the Dachaoshan Dam on Seasonal Hydrological Dynamics in the Main Stream of the Mekong River

Science.gov (United States)

Kameyama, S.; Shimazaki, H.; Nohara, S.; Fukushima, M.; Kudo, K.; Sato, T.

2008-12-01

In the Mekong River watershed, traditional social and industrial systems have long existed in harmony with water and biological resources. Since the 1950s, many dam-construction projects have been started to develop power and water resources to meet increasing demand for energy and food production. Since the 1970s, there have been temporary interruptions to these projects because of civil war or regional volatility of international relations. Many of these projects have been restarted in the last 15 years. This raises international interest, as there are transboundary issues cross-border issues related to both development assistance and environmental conservation. By 2008, two Chinese dams had already been completed (the Manwan dam in 1996 and the Dachaoshan dam in 2003) on the Mekong River in Yunnan province. Dam construction has some positive impacts, such as electricity production, management of water resources, and flood control. However, upstream control of water discharge can have negative impacts on traditional agricultural systems and fisheries downstream from the dams, such as drastic changes in flow volume and sediment load. We used hydrological simulation of the watershed to quantify the impact of the construction of the Dachaoshan dam by comparing annual water discharge and sediment transport before and after the dam was completed. Our main objectives were to use watershed hydrologic modeling to simulate changes to annual hydrological parameters and sediment transport, and to map spatio-temporal changes of these data before and after dam construction. Our study area covered the part of the Mekong River main channel that extends about 100 km downstream from the junction of the borders of Myanmar, Thailand, and the Lao People's Democratic Republic. We used five data validation points at 25-km intervals along this section of the river and calculated model parameters every 1 km. The years we modeled were 1990 (began dam construction) and 2006 (after dam

Isotope technique in JPS dam surveillance: its potential

International Nuclear Information System (INIS)

Sabri Hassan

2006-01-01

Controlling seepage is one of the most important requirements for safe dams. Any leakage at an earth embankment may be potentially dangerous since rapid internal erosion may quickly enlarge an initially minor defect. Thus dam owners need to have thorough surveillance programs that can forewarn of impending problems from seepage or other factors influencing the safety of dams. In carrying out dam surveillance works, all possible efforts should be considered and foreseeing the potential of isotope technique, JPS (Department of Irrigation and Drainage, Malaysia) and MINT (Malaysian Institute for Nuclear Technology Research) participated actively in the UNDP/RCA/IAEA program under RAS/8/093 project sponsored by the International Atomic Energy Agency (IAEA). Through these activities, it was noted that the technique demonstrated very promising potentials such as in assisting dam site selections, site investigations, watershed studies, dam and reservoir design, leakage investigations and sediments related issues, the two latter ones being relatively critical during the operational life of the dam. Establishment of baseline isotopic characteristics (or fingerprint), hydrochemistry, electrical conductivity and temperature profiles is underway for all JPS dams to be later utilized in diagnosing seepage related issues it is suggested that application of this technique be extended to other dam owners nationwide. (Author)

Analysis of the sediments of the Julian Adame Alatorre dam by the INAA

International Nuclear Information System (INIS)

Oliva, J.E.; Lugo, J.F.; Mireles, F.; Quirino, L.L.; Davila, J.I.; Pinedo, J.L.; Rios, C.; Miller, W.H.

2003-01-01

Its were taken eight samples of sediment of the Julian Adame Alatorre dam located in the Villanueva municipality, in the State of Zacatecas, Mexico; with the end of determining the presence of elements of anthropogenic origin, as well as the concentration of the same ones. It was used the Instrumental neutron activation analysis (AANI) with a flow of thermal neutrons of 8 x 10 13 and 5 x 10 13 n cm -2 s -1 . With the purpose of determining the concentration of these elements at level of traces; finding presence of 32 elements among which its were find elements in greater concentrations and others at level of traces. Of these 32 elements, five of anthropogenic origin were identified which its were: Cr, Co, Zn, As and Mn; but that whose concentration is very low, in comparison with the one reported in other places of the world. In this work there are presented the obtained results of the elementary analysis of this samples. (Author)

Sedimentary Records of Hyperpycnal Flows and the Influence of River Damming on Sediment Dynamics of Estuaries: Examples from the Nelson, Churchill, Moisie and Sainte-Marguerite Rivers (Canada)

Science.gov (United States)

St-Onge, G.; Duboc, Q.; Boyer-Villemaire, U.; Lajeunesse, P.; Bernatchez, P.

2015-12-01

Sediment cores were sampled in the estuary of the Nelson and Churchill Rivers in western Hudson Bay, as well as in the estuary of the Moisie and Sainte-Marguerite Rivers in Gulf of St. Lawrence in order to evaluate the impact of hydroelectric dams on the sedimentary regime of these estuaries. The gravity cores at the mouth of the Nelson River recorded several cm-thick rapidly deposited layers with a reverse to normal grading sequence, indicating the occurrence of hyperpycnal flows generated by major floods during the last few centuries. These hyperpycnal flows were probably caused by ice-jam formation, which can increase both the flow and the sediment concentration following the breaching of such natural dams. Following the construction of hydroelectric dams since the 1960s, the regulation of river discharge prevented the formation of hyperpycnal flows, and hence the deposition of hyperpycnites in the upper part of the cores. In the core sampled in the estuary of the Churchill River, only one hyperpycnite was recorded. This lower frequency may be due to the enclosed estuary of the Churchill River, its weaker discharge and the more distal location of the coring site.In the Gulf of St. Lawrence, grain size measurements allowed the identification of a major flood around AD 1844±4 years in box cores from both the Sainte-Marguerite and Moisie Rivers, whereas a drastic decrease in variations in the median grain size occurred around AD ~1900 in the estuary of the Sainte-Marguerite River, highlighting the offshore impact of the SM1 dam construction in the early 1900s. Furthermore, sedimentological variations in the box cores from both estuaries have been investigated by wavelet analysis and the sharp disappearance of high frequencies around AD 1900 in the estuary of the dammed river (Sainte-Marguerite River), but not in the estuary of the natural river (Moisie River), also provides evidence of the influence of dams on the sedimentary regime of estuaries.

A Well-Balanced and Fully Coupled Noncapacity Model for Dam-Break Flooding

Directory of Open Access Journals (Sweden)

Zhiyuan Yue

2015-01-01

Full Text Available The last two decades have seen great progress in mathematical modeling of fluvial processes and flooding in terms of either approximation of the physical processes or dealing with the numerical difficulties. Yet attention to simultaneously taking advancements of both aspects is rarely paid. Here a well-balanced and fully coupled noncapacity model is presented of dam-break flooding over erodible beds. The governing equations are based on the complete mass and momentum conservation laws, implying fully coupled interactions between the dam-break flow and sediment transport. A well-balanced Godunov-type finite volume method is used to solve the governing equations, facilitating satisfactory representation of the complex flow phenomena. The well-balanced property is attained by using the divergence form of matrix related to the static force for the bottom slope source term. Existing classical tests, including idealized dam-break flooding over irregular topography and experimental dam-break flooding with/without sediment transport, are numerically simulated, showing a satisfactory quantitative performance of this model.

Effective mitigation of debris flows at Lemon Dam, La Plata County, Colorado

Science.gov (United States)

deWolfe, V.G.; Santi, P.M.; Ey, J.; Gartner, J.E.

2008-01-01

To reduce the hazards from debris flows in drainage basins burned by wildfire, erosion control measures such as construction of check dams, installation of log erosion barriers (LEBs), and spreading of straw mulch and seed are common practice. After the 2002 Missionary Ridge Fire in southwest Colorado, these measures were implemented at Knight Canyon above Lemon Dam to protect the intake structures of the dam from being filled with sediment. Hillslope erosion protection measures included LEBs at concentrations of 220-620/ha (200-600% of typical densities), straw mulch was hand spread at concentrations up to 5.6??metric tons/hectare (125% of typical densities), and seeds were hand spread at 67-84??kg/ha (150% of typical values). The mulch was carefully crimped into the soil to keep it in place. In addition, 13 check dams and 3 debris racks were installed in the main drainage channel of the basin. The technical literature shows that each mitigation method working alone, or improperly constructed or applied, was inconsistent in its ability to reduce erosion and sedimentation. At Lemon Dam, however, these methods were effective in virtually eliminating sedimentation into the reservoir, which can be attributed to a number of factors: the density of application of each mitigation method, the enhancement of methods working in concert, the quality of installation, and rehabilitation of mitigation features to extend their useful life. The check dams effectively trapped the sediment mobilized during rainstorms, and only a few cubic meters of debris traveled downchannel, where it was intercepted by debris racks. Using a debris volume-prediction model developed for use in burned basins in the Western U.S., recorded rainfall events following the Missionary Ridge Fire should have produced a debris flow of approximately 10,000??m3 at Knight Canyon. The mitigation measures, therefore, reduced the debris volume by several orders of magnitude. For comparison, rainstorm

Bedload transport over run-of-river dams, Delaware, U.S.A.

Science.gov (United States)

Pearson, Adam J.; Pizzuto, Jim

2015-11-01

We document the detailed morphology and bed sediment size distribution of a stream channel upstream and downstream of a 200-year-old run-of-river dam on the Red Clay Creek, a fifth order stream in the Piedmont of northern Delaware, and combine these data with HEC-RAS modeling and bedload transport computations. We hypothesize that coarse bed material can be carried through run-of-river impoundments before they completely fill with sediment, and we explore mechanisms to facilitate this transport. Only 25% of the accommodation space in our study site is filled with sediment, and maximum water depths are approximately equal to the dam height. All grain-size fractions present upstream of the impoundment are also present throughout the impoundment. A characteristic coarse-grained sloping ramp leads from the floor of the impoundment to the crest of the dam. A 2.3-m-deep plunge pool has been excavated below the dam, followed immediately downstream by a mid-channel bar composed of coarse bed material similar in size distribution to the bed material of the impoundment. The mid-channel bar stores 1472 m3 of sediment, exceeding the volume excavated from the plunge pool by a factor of 2.8. These field observations are typical of five other sites nearby and suggest that all bed material grain-size fractions supplied from upstream can be transported through the impoundment, up the sloping ramp, and over the top of the dam. Sediment transport computations suggest that all grain sizes are in transport upstream and within the impoundment at all discharges with return periods from 1 to 50 years. Our computations suggest that transport of coarse bed material through the impoundment is facilitated by its smooth, sandy bed. Model results suggest that the impoundment is currently aggrading at 0.26 m/year, but bed elevations may be recovering after recent scour from a series of large floods during water year 2011-2012. We propose that impoundments upstream of these run-of-river dams

Sediment transport in two mediterranean regulated rivers.

Science.gov (United States)

Lobera, G; Batalla, R J; Vericat, D; López-Tarazón, J A; Tena, A

2016-01-01

Mediterranean climate is characterized by highly irregular rainfall patterns with marked differences between wet and dry seasons which lead to highly variable hydrological fluvial regimes. As a result, and in order to ensure water availability and reduce its temporal variability, a high number of large dams were built during the 20th century (more than 3500 located in Mediterranean rivers). Dams modify the flow regime but also interrupt the continuity of sediment transfer along the river network, thereby changing its functioning as an ecosystem. Within this context, the present paper aims to assess the suspended sediment loads and dynamics of two climatically contrasting Mediterranean regulated rivers (i.e. the Ésera and Siurana) during a 2-yr period. Key findings indicate that floods were responsible for 92% of the total suspended sediment load in the River Siurana, while this percentage falls to 70% for the Ésera, indicating the importance of baseflows on sediment transport in this river. This fact is related to the high sediment availability, with the Ésera acting as a non-supply-limited catchment due to the high productivity of the sources (i.e. badlands). In contrast, the Siurana can be considered a supply-limited system due to its low geomorphic activity and reduced sediment availability, with suspended sediment concentration remaining low even for high magnitude flood events. Reservoirs in both rivers reduce sediment load up to 90%, although total runoff is only reduced in the case of the River Ésera. A remarkable fact is the change of the hydrological character of the River Ésera downstream for the dam, shifting from a humid mountainous river regime to a quasi-invariable pattern, whereas the Siurana experiences the opposite effect, changing from a flashy Mediterranean river to a more constant flow regime below the dam. Copyright © 2015 Elsevier B.V. All rights reserved.

STABILITAS CHECK DAM DI ARBORETUM DESA SUMBER BRANTAS

Directory of Open Access Journals (Sweden)

Endang Purwati

2012-09-01

Full Text Available Abstract: The stability of check-dam in arboretum of Sumber Brantas village. Sumber Brantas water sources area is arboretum territory which has to be maintained as conservation either for technical or vegetation (plants cover by sustainable development. Arboretum territory is made as asylum in irrigation system district of Brantas River. This research discusses technical conservation activity to build the check dam in conserving the area. Check dam is built dimensionally by using HEC-RAS Program to get safe and stable dimension for rolling, shifting and piping of Sf > 1.5, and based on hydrologic analysis to get maximum flood discharge of 48.01 m3second-1. Hydraulic analysis is used to get water level profile and pressure for the dam body. Stability of the structure will be controlled by construction load (weight of check dam and its fully sediment storage condition. The result of this research shows that the safe and stable dimension for check dam are as follows: 28 meter of width; 3 meter of main height; 1.5 meter of sub-height; 10 meter of stilling basin length (Main Dam–Sub Dam.

Impact of beaver ponds on river discharge and sediment deposition along the Chevral River, Ardennes, Belgium

Science.gov (United States)

Nyssen, Jan; Frankl, Amaury; Pontzeele, Jolien; De Visscher, Maarten; Billi, Paolo

2013-04-01

With the recovery of the European beaver (Castor fiber) and their capacity to engineer fluvial landscapes, questions arise as to how they influence river discharge and sediment transport. The Chevral river (Ardennes, Belgium) contains two beaver dam sequences which appeared in 2004 and count now about 30 dams. Flow discharges and sediment fluxes were measured at the in- and outflow of each dam sequence. Volumes of sediment deposited behind the dams were measured. Between 2004 and 2011, peak flows were topped off, and the magnitude of extreme events decreased. 1710 m³ of sediment were deposited behind the beaver dams, with an average sediment thickness of 25 cm. The thickness of the sediment layer is related to the area of the beaver ponds. Along the stream, beaver pond sediment thickness displayed a sinusoidal deposition pattern, in which ponds with thick sediment layers were preceded by a series of ponds with thinner sediment layers. A downstream textural coarsening in the dam sequences was also observed, probably due to dam failures subsequent to surges. Differences in sediment flux between the in- and outflow at the beaver pond sequence were related to the river hydrograph, with deposition taking place during the rising limbs and slight erosion during the falling limbs. The seven-year-old sequences have filtered 190 tons of sediment out of the Chevral river, which is of the same order of magnitude as the 374 tons measured in pond deposits, with the difference between the values corresponding to beaver excavations (60 tons), inflow from small tributaries, and runoff from the valley flanks. Hydrogeomorphic effects of C. fiber and C. canadensis activity are similar in magnitude. The detailed analysis of changes to hydrology in beaver pond sequences confirms the potential of beavers to contribute to river and wetland restoration and catchment management.

Efficiency testing of Red Lake protection dam on Rosu stream by 210Pb method

International Nuclear Information System (INIS)

Robert-Csaba Begy; Hedvig Simon; Edina Reizer

2015-01-01

The Red lake, a small lake from Romania is threatened by massive sedimentation, therefore two protection dams were constructed on Oii and Rosu brooks. The aim of this study is to get information about the variation of the retention capability of the dams using the 210 Pb method. 210 Pb, 226 Ra and 137 Cs were measured by gamma- and 210 Po by alpha spectrometry. The values for mass sedimentation are between 0.17 ± 0.03-2.3 ± 0.4 g/cm 2 y for the Red Lake and 0.21 ± 0.03-0.9 ± 0.1 g/cm 2 y for the dam lake. Due to these high values, the dam lake will fill up in 20 ± 8y and 80 % of the Red Lake in 81 ± 30y. (author)

Mitigating Dam Impacts Using Environmental Flow Releases

Science.gov (United States)

Richter, B. D.

2017-12-01

One of the most ecologically disruptive impacts of dams is their alteration of natural river flow variability. Opportunities exist for modifying the operations of existing dams to recover many of the environmental and social benefits of healthy ecosystems that have been compromised by present modes of dam operation. The potential benefits of dam "re-operation" include recovery of fish, shellfish, and other wildlife populations valued both commercially and recreationally, including estuarine species; reactivation of the flood storage and water purification benefits that occur when floods are allowed to flow into floodplain forests and wetlands; regaining some semblance of the naturally dynamic balance between river erosion and sedimentation that shapes physical habitat complexity, and arresting problems associated with geomorphic imbalances; cultural and spiritual uses of rivers; and many other socially valued products and services. Assessing the potential benefits of dam re-operation begins by characterizing the dam's effects on the river flow regime, and formulating hypotheses about the ecological and social benefits that might be restored by releasing water from the dam in a manner that more closely resembles natural flow patterns. These hypotheses can be tested by implementing a re-operation plan, tracking the response of the ecosystem, and continually refining dam operations through adaptive management. This presentation will highlight a number of land and water management strategies useful in implementing a dam re-operation plan, with reference to a variety of management contexts ranging from individual dams to cascades of dams along a river to regional energy grids. Because many of the suggested strategies for dam re-operation are predicated on changes in the end-use of the water, such as reductions in urban or agricultural water use during droughts, a systemic perspective of entire water management systems will be required to attain the fullest possible

Applying a two-dimensional morphodynamic model to assess impacts to Chinook salmon spawning habitat from dam removal

Science.gov (United States)

Lee, A. A.; Crosato, A.; Omer, A. Y. A.; Bregoli, F.

2017-12-01

The need for accurate and robust predictive methods of assessing fluvial ecosystems is highlighted by the accelerating practice of dam removal. Dam removal can be a restorative measure, but the sudden release of impounded sediment and change in flow regime may negatively impact aquatic biota and their habitat. This study assesses the performance of a quasi-three-dimensional morphodynamic numerical model, coupled with habitat suitability indices, to predict short-term impacts to Chinook salmon (Oncorhynchus tshawytscha) spawning habitat from dam removal. The 2007 removal of Marmot Dam on the Sandy River (Oregon, U.S.A.) is used as a case study. Delft3D-FLOW is employed to simulate changes in river channel topography, sediment composition and hydrodynamic conditions for a 20-kilometer reach of the Sandy River. The transport of non-uniform sediment and three-dimensional flow effects are included in the model. Output parameters such as flow depth, velocity and substrate are processed to evaluate habitat quality in the year following the Marmot Dam removal. Impacts are evaluated across four life-stages of Chinook salmon. As a hindcast analysis, the morphodynamic model sufficiently reproduces the evolution of river morphology at the reach-scale while requiring only a low level of calibration. The model performs well in predicting impacts to fish passage, but carries more uncertainty for developing life stages. By coupling flow-sediment-biota interactions, this method shows strong potential for habitat assessment in unsteady and non-uniform environments. Computation time is a primary constraint, as it limits grid-cell resolution, modelling of suspended sediment and capacity to characterize the sediment grain size distribution. Research on the effects of suspended sediment on habitat quality is ongoing, and further research is recommended for modelling reservoir erosion processes numerically.

Elwha Master Datafile - Elwha dam removal neashore monitoring

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Removal of two dams on the Elwha River, Washington will help restore natural sediment processes to the coastal environment near the river mouth. We are interested in...

Dam! Dam! Dam!

International Nuclear Information System (INIS)

McCully, P.

1997-01-01

The author of ''Silenced Rivers'' a book questioning the desirability of dam building and hydroelectric power generation argues the main themes of his book in this paper. Despite being hailed by politicians as good solutions to power generation problems, and enthusiastically pursued in China, the U.S.A., the former Soviet Union, India and Japan, dams have far-reaching ecological and human consequences. The ecosystems lost to flooding, and the agricultural land use lost, the human cost in terms of homes and employment lost to reservoirs, disease from water-borne infections such as malaria, and the hazards of dams overflowing or breaking are all factors which are against the case for dam construction. The author argues the hydroelectric power may be renewable, but the social, agricultural and ecological costs are too high to justify it as a method of first choice. (UK)

Radiometric survey of radioactive minerals in the Matias Romero dam, in Oaxaca

International Nuclear Information System (INIS)

Flores, J.H.; Pena, P.; Balcazar, M.; Lopez, A.M.; Juarez, S.F.; Cabrera, M.O.; Huizar, R.

2006-01-01

Migration of radioactive Uranium and Thorium minerals from the old mine El Muerto, to the dam Matias Romero in Oaxaca was detected in dam sediments. The identified elements were Th and U, from the decay series of the last one; 234 Th, 234 Pa and 214 Bi from the radioactive series of 238 U. The mineral was in the past extracted from high fractured zones. Total activity measurements in sediments from the dam increases as the particle size decrease, which indicates that main reason of the movement is produced by erosion of small particles from high altitude deposits to lower parts where the dam is located. Geo statistical analysis gives a general picture of mineral distribution. ICP-MS, Ge(hp) detector, and X-ray diffraction techniques were used for associated minerals and radioactive content evaluation. Oaxaca State presents a complex geology. Pre cambric metamorphic rocks (600 ma) are present at the southern part, covering 25% of the state surface; intrusive metamorphic and igneous rocks form the Paleozoic (375 m.a.) cover 6 % of the surface. (Author)

Restoring Environmental Flows by Modifying Dam Operations

Directory of Open Access Journals (Sweden)

Brian D. Richter

2007-06-01

Full Text Available The construction of new dams has become one of the most controversial issues in global efforts to alleviate poverty, improve human health, and strengthen regional economies. Unfortunately, this controversy has overshadowed the tremendous opportunity that exists for modifying the operations of existing dams to recover many of the environmental and social benefits of healthy ecosystems that have been compromised by present modes of dam operation. The potential benefits of dam "re-operation" include recovery of fish, shellfish, and other wildlife populations valued both commercially and recreationally, including estuarine species; reactivation of the flood storage and water purification benefits that occur when floods are allowed to flow into floodplain forests and wetlands; regaining some semblance of the naturally dynamic balance between river erosion and sedimentation that shapes physical habitat complexity, and arresting problems associated with geomorphic imbalances; cultural and spiritual uses of rivers; and many other socially valued products and services. This paper describes an assessment framework that can be used to evaluate the benefits that might be restored through dam re-operation. Assessing the potential benefits of dam re-operation begins by characterizing the dam's effects on the river flow regime, and formulating hypotheses about the ecological and social benefits that might be restored by releasing water from the dam in a manner that more closely resembles natural flow patterns. These hypotheses can be tested by implementing a re-operation plan, tracking the response of the ecosystem, and continually refining dam operations through adaptive management. The paper highlights a number of land and water management strategies useful in implementing a dam re-operation plan, with reference to a variety of management contexts ranging from individual dams to cascades of dams along a river to regional energy grids. Because many of the

Effect of Sediment Availability in Bedload-Dominated Rivers on Fluvial Geomorphic Equilibrium

Science.gov (United States)

Marti, M.

2016-12-01

Channels are known to compensate for changes in sediment supply via covariate changes in channel properties, yet the timescale for adjustment remains poorly constrained. We propose that reductions in sediment flux inhibit equilibrium re-establishment and thus impact the timescale of system adjustment. Using run-of-river dams as natural experiments, this study quantifies the geomorphic response of channels to sediment supply reduction. Channel traits that facilitate increased sediment trapping behind the dam, such as large reservoir storage capacity relative to annual inflow and low slope, were expected to inhibit a channel's ability to re-establish equilibrium following impoundment, lengthening the equilibrium establishment timescale to tens or hundreds of years. Reaches associated with increased trapping were therefore anticipated to exhibit non-equilibrium forms. Channel equilibrium was evaluated downstream of 8 ROR dams in New England with varying degrees of sediment trapping. Sites cover a range of watershed sizes (3-155 km2), channel slopes (.05-5%), 2-year discharges (1.5-60 m3/s) and storage capacity volumes. Because equilibrium channel form is just sufficient to mobilize grains under bankfull conditions in bedload-dominated rivers, the Shields parameter was used to assess equilibrium form. Unregulated, upstream Shields values and regulated, downstream values were calculated at 14 total cross-sections extending 300-450 m upstream and downstream of each dam. Sediment trapping was estimated using Brune's curve (1953). On the Charles Brown Brook (VT), a marginally significant (p=0.08) increase in Shields values from a mean of 0.14 upstream to 0.41 downstream of a 100+ year old dam was observed. In contrast, reaches downstream of the 100+ year old Pelham dam (MA) exhibit significantly lower Shields values. This suggests that trapping behind the dam inhibits the downstream channel from reaching an equilibrium state, but not always in the same way. Better

Fragmentation of Andes-to-Amazon connectivity by hydropower dams.

Science.gov (United States)

Anderson, Elizabeth P; Jenkins, Clinton N; Heilpern, Sebastian; Maldonado-Ocampo, Javier A; Carvajal-Vallejos, Fernando M; Encalada, Andrea C; Rivadeneira, Juan Francisco; Hidalgo, Max; Cañas, Carlos M; Ortega, Hernan; Salcedo, Norma; Maldonado, Mabel; Tedesco, Pablo A

2018-01-01

Andes-to-Amazon river connectivity controls numerous natural and human systems in the greater Amazon. However, it is being rapidly altered by a wave of new hydropower development, the impacts of which have been previously underestimated. We document 142 dams existing or under construction and 160 proposed dams for rivers draining the Andean headwaters of the Amazon. Existing dams have fragmented the tributary networks of six of eight major Andean Amazon river basins. Proposed dams could result in significant losses in river connectivity in river mainstems of five of eight major systems-the Napo, Marañón, Ucayali, Beni, and Mamoré. With a newly reported 671 freshwater fish species inhabiting the Andean headwaters of the Amazon (>500 m), dams threaten previously unrecognized biodiversity, particularly among endemic and migratory species. Because Andean rivers contribute most of the sediment in the mainstem Amazon, losses in river connectivity translate to drastic alteration of river channel and floodplain geomorphology and associated ecosystem services.

Massive accumulation of highly polluted sedimentary deposits by river damming

Energy Technology Data Exchange (ETDEWEB)

Palanques, Albert, E-mail: albertp@icm.csic.es [Institute of Marine Sciences (CSIC), Passeig Maritim de la Barceloneta, 37-49, Barcelona 08003 (Spain); Grimalt, Joan [Institute of Environmental Assessment and Water Research (CSIC), Jordi Girona, 18, Barcelona 08034 (Spain); Belzunces, Marc; Estrada, Ferran; Puig, Pere; Guillén, Jorge [Institute of Marine Sciences (CSIC), Passeig Maritim de la Barceloneta, 37-49, Barcelona 08003 (Spain)

2014-11-01

Uncontrolled dumping of anthropogenic waste in rivers regulated by dams has created contaminated deposits in reservoirs that have remained unidentified for decades. The Flix Reservoir is located in the Ebro River, the second largest river flowing into the NW Mediterranean, has been affected by residue dumping from a chlor-alkali electrochemical plant for decades. High-resolution seismic profiles, bathymetric data, surficial sediment samples and sediment cores were obtained in the Flix Reservoir to study the characteristics of the deposit accumulated by this dumping. These data were used to reconstruct the waste deposit history. Since the construction of the Flix Dam in 1948, more than 3.6 × 10{sup 5} t of industrial waste has accumulated in the reservoir generating a delta-like deposit formed by three sediment lobes of fine-grained material highly contaminated by Hg, Cd, Zn and Cr (max: 640, 26, 420 and 750 mg kg{sup −1}, respectively). This contamination was associated with the Hg that was used for the cathode in the electrochemical plant from 1949 and with the production of phosphorite derivatives from 1973. After the construction of two large dams only a few kilometres upstream during the 1960s, the solids discharged from the industrial complex became the main sediment source to the Flix Reservoir. The deposit has remained in the reservoir forming a delta that obstructs about 50% of the river water section. Its stability only depended on the flow retention by the Flix Dam. At present, this contaminated waste deposit is being removed from the water reservoir as it is a cause of concern for the environment and for human health downriver. - Highlights: • A delta-like anthropogenic deposit prograded into the reservoir behind the Flix dam. • More than 3.6 × 10{sup 5} t of anthropogenic waste was accumulated in less than 4 decades. • A waste deposit with extreme levels of Hg and Cd was trapped in the Flix Reservoir. • The main pollution was related to

Earth's portfolio of extreme sediment transport events

Science.gov (United States)

Korup, Oliver

2012-05-01

Quantitative estimates of sediment flux and the global cycling of sediments from hillslopes to rivers, estuaries, deltas, continental shelves, and deep-sea basins have a long research tradition. In this context, extremely large and commensurately rare sediment transport events have so far eluded a systematic analysis. To start filling this knowledge gap I review some of the highest reported sediment yields in mountain rivers impacted by volcanic eruptions, earthquake- and storm-triggered landslide episodes, and catastrophic dam breaks. Extreme specific yields, defined here as those exceeding the 95th percentile of compiled data, are ~ 104 t km- 2 yr- 1 if averaged over 1 yr. These extreme yields vary by eight orders of magnitude, but systematically decay with reference intervals from minutes to millennia such that yields vary by three orders of magnitude for a given reference interval. Sediment delivery from natural dam breaks and pyroclastic eruptions dominate these yields for a given reference interval. Even if averaged over 102-103 yr, the contribution of individual disturbances may remain elevated above corresponding catchment denudation rates. I further estimate rates of sediment (re-)mobilisation by individual giant terrestrial and submarine mass movements. Less than 50 postglacial submarine mass movements have involved an equivalent of ~ 10% of the contemporary annual global flux of fluvial sediment to Earth's oceans, while mobilisation rates by individual events rival the decadal-scale sediment discharge from tectonically active orogens such as Taiwan or New Zealand. Sediment flushing associated with catastrophic natural dam breaks is non-stationary and shows a distinct kink at the last glacial-interglacial transition, owing to the drainage of very large late Pleistocene ice-marginal lakes. Besides emphasising the contribution of high-magnitude and low-frequency events to the global sediment cascade, these findings stress the importance of sediment storage

Rapid reservoir erosion, hyperconcentrated flow, and downstream deposition triggered by breaching of 38 m tall Condit Dam, White Salmon River, Washington

Science.gov (United States)

Wilcox, Andrew C.; O'Connor, James E.; Major, Jon J.

2014-01-01

Condit Dam on the White Salmon River, Washington, a 38 m high dam impounding a large volume (1.8 million m3) of fine-grained sediment (60% sand, 35% silt and clay, and 5% gravel), was rapidly breached in October 2011. This unique dam decommissioning produced dramatic upstream and downstream geomorphic responses in the hours and weeks following breaching. Blasting a 5 m wide hole into the base of the dam resulted in rapid reservoir drawdown, abruptly releasing ~1.6 million m3 of reservoir water, exposing reservoir sediment to erosion, and triggering mass failures of the thickly accumulated reservoir sediment. Within 90 min of breaching, the reservoir's water and ~10% of its sediment had evacuated. At a gauging station 2.3 km downstream, flow increased briefly by 400 m3 s−1during passage of the initial pulse of released reservoir water, followed by a highly concentrated flow phase—up to 32% sediment by volume—as landslide-generated slurries from the reservoir moved downstream. This hyperconcentrated flow, analogous to those following volcanic eruptions or large landslides, draped the downstream river with predominantly fine sand. During the ensuing weeks, suspended-sediment concentration declined and sand and gravel bed load derived from continued reservoir erosion aggraded the channel by >1 m at the gauging station, after which the river incised back to near its initial elevation at this site. Within 15 weeks after breaching, over 1 million m3 of suspended load is estimated to have passed the gauging station, consistent with estimates that >60% of the reservoir's sediment had eroded. This dam removal highlights the influence of interactions among reservoir erosion processes, sediment composition, and style of decommissioning on rate of reservoir erosion and consequent downstream behavior of released sediment.

The internal strength of rivers: autogenic processes in control of the sediment load (Tana River, Kenya)

Science.gov (United States)

Geeraert, Naomi; Ochieng Omengo, Fred; Tamooh, Fredrick; Paron, Paolo; Bouillon, Steven; Govers, Gerard

2014-05-01

The construction of sediment rating curves for monitoring stations is a widely used technique to budget sediment fluxes. Changes in the relationship between discharge and sediment concentrations over time are often attributed to human-induced changes in catchment characteristics, such as land use change, dam construction or soil conservation measures and many models have been developed to quantitatively link catchment characteristics and river sediment load. Conversely, changes in river sediment fluxes are often interpreted as indications of major changes in the catchment. By doing so, autogenic processes, taking place within the river channel, are overlooked despite the increasing awareness of their importance. We assessed the role of autogenic processes on the sediment load of Tana River (Kenya). The Tana river was impacted by major dam construction between 1968 and 1988, effectively blocking at least 80% of the sediment transfer from the highlands to the lower river reaches. However, a comparison of pre-dam sediment fluxes at Garissa (located 250 km downstream of the dams) with recent measurements shows that sediment fluxes have not changed significantly. This suggests that most of the sediment in the post-dam period has to originate from inside the alluvial plain of the river, as tributaries downstream of the dams are scarce and intermittent. Several observations are consistent with this hypothesis. We observed that, during the wet season, sediment concentrations rapidly increased below the dams and are not controlled by inputs from tributaries. Also, sediment concentrations were high at the beginning of the wet season, which can be attributed to channel adjustment to the higher discharges. The river sediment does not contain significant amounts of 137Cs or 210Pbxs, suggesting that sediments are not derived from topsoil erosion. Furthermore, we observed a counter clockwise hysteresis during individual events which can be explained by the fact that sediment

Turbid releases from Glen Canyon Dam, Arizona, following rainfall-runoff events of September 2013

Science.gov (United States)

Wildman, Richard A.; Vernieu, William

2017-01-01

Glen Canyon Dam is a large dam on the Colorado River in Arizona. In September 2013, it released turbid water following intense thunderstorms in the surrounding area. Turbidity was >15 nephelometric turbidity units (NTU) for multiple days and >30 NTU at its peak. These unprecedented turbid releases impaired downstream fishing activity and motivated a rapid-response field excursion. At 5 locations upstream from the dam, temperature, specific conductance, dissolved oxygen, chlorophyll a, and turbidity were measured in vertical profiles. Local streamflow and rainfall records were retrieved, and turbidity and specific conductance data in dam releases were evaluated. Profiling was conducted to determine possible sources of turbidity from 3 tributaries nearest the dam, Navajo, Antelope, and Wahweap creeks, which entered Lake Powell as interflows during this study. We discuss 4 key conditions that must have been met for tributaries to influence turbidity of dam releases: tributary flows must have reached the dam, tributary flows must have been laden with sediment, inflow currents must have been near the depth of dam withdrawals, and the settling velocity of particles must have been slow. We isolate 2 key uncertainties that reservoir managers should resolve in future similar studies: the reach of tributary water into the reservoir thalweg and the distribution of particle size of suspended sediment. These uncertainties leave the source of the turbidity ambiguous, although an important role for Wahweap Creek is possible. The unique combination of limnological factors we describe implies that turbid releases at Glen Canyon Dam will continue to be rare.

Wood and Sediment Dynamics in River Corridors

Science.gov (United States)

Wohl, E.; Scott, D.

2015-12-01

Large wood along rivers influences entrainment, transport, and storage of mineral sediment and particulate organic matter. We review how wood alters sediment dynamics and explore patterns among volumes of instream wood, sediment storage, and residual pools for dispersed pieces of wood, logjams, and beaver dams. We hypothesized that: volume of sediment per unit area of channel stored in association with wood is inversely proportional to drainage area; the form of sediment storage changes downstream; sediment storage correlates most strongly with wood load; and volume of sediment stored behind beaver dams correlates with pond area. Lack of data from larger drainage areas limits tests of these hypotheses, but analyses suggest a negative correlation between sediment volume and drainage area and a positive correlation between wood and sediment volume. The form of sediment storage in relation to wood changes downstream, with wedges of sediment upstream from jammed steps most prevalent in small, steep channels and more dispersed sediment storage in lower gradient channels. Use of a published relation between sediment volume, channel width, and gradient predicted about half of the variation in sediment stored upstream from jammed steps. Sediment volume correlates well with beaver pond area. Historically more abundant instream wood and beaver populations likely equated to greater sediment storage within river corridors. This review of the existing literature on wood and sediment dynamics highlights the lack of studies on larger rivers.

Evaluation of heavy metals (Cr, Fe, Ni, Cu, Zn, Cd, Pb and Hg) in water, sediments and water lily (Eichornia crassipes) from Jose Antonio Alzate dam

International Nuclear Information System (INIS)

Avila P, P.

1995-01-01

Water, sediments and water lily (Eichornia crassipes) from the Jose Antonio Alzate Dam were analyzed in order to determine concentrations of chromium, iron, nickel, copper, zinc, cadmium, lead and mercury. Mercury, lead, chromium and iron were found in concentrations above permissible limits in water, and in high concentrations in sediments. Cadmium, nickel, copper and zinc never were found in concentrations above permissible limits in water. The highest concentrations of heavy metals in water lily were found in the root. Accumulation factors decreased in the following order: Zn> Cr> Fe> Ni> Cu> Pb> Hg and Cd. Statistical differences (α < 0.5) between the collection samples dates was observed. High correlations between metals concentrations in superficial water, sediment and water hyacinth were also observed. These correlations could indicate that the heavy metals studied here, are originated from a natural source such as sediments or from an industrial source. (Author)

The morphodynamics of sediment movement through a reservoir during dam removal

OpenAIRE

Bromley, Chris

2008-01-01

Dam removal has recently emerged as a growing trend in river rehabilitation in the United States. The rate of dam removal has been increasing rapidly since 2000, but is doing so with large gaps in our understanding of how the fluvial system will respond to this disturbance. Most of the structures removed to date have been relatively small and, in the vast majority of cases, have not received any pre- or post-removal monitoring. Very few large structures have been removed but, when such remova...

New element for optimizing the functioning of sediment traps

Science.gov (United States)

Schwindt, Sebastian; Franca, Mário; Schleiss, Anton

2017-04-01

Sediment traps protect urban areas against excessive sediment transport during hazardous floods and consist typically of a retention basin with an open sediment check dam at the downstream end. The design, as well as the morphological processes within the retention basin, were analyzed by several authors. With regard to open sediment check dams two types of triggering mechanisms for the initiation of sediment retention can be distinguished: (1) mechanical and (2) hydraulic clogging of the structure. Recent studies have shown that outlet structures combining both clogging principles may be considered to avoid undesired self-flushing. Further elements of check dams are conceivable, e.g. for retaining or conveying driftwood. This study analyses experimentally working principles and design criteria of standard elements of sediment traps. Furthermore, it introduces a new structural element to the sediment trap design with a guiding channel in the retention reservoir. Taking into account the natural shape of mountain rivers, the guiding channel has a trapezoidal cross-section shape and a rough but fixed bed. The effect of the guiding channel on sediment deposition pattern and re-mobilization are studied by means of physical model experiments with a standardized hydrograph and variable sediment supply. The results are evaluated by means of zenithal pictures and bedload transport rate, measured at the downstream end of the model. Major advantages of the combined use of both clogging principles include an improved control of the initiation of sediment deposition in order to allow for sediment transfer for small floods and a reduction of hazards related to self-flushing.

Downstream ecological effects of dams: A geomorphic perspective

International Nuclear Information System (INIS)

Ligon, F.K.; Dietrich, W.E.; Trush, W.J.

1995-01-01

The damming of a river changes the flow of water, sediment, nutrients, energy, and biota, interrupting and altering most of a river's ecological processes. This article discusses the importance of geomorphological analysis in river conservation and management. To illustrate how subtle geomorphological adjustments may profoundly influence the ecological relationships downstream from dames, three case studies are presented. Then a geomorphically based approach for assessing and possibly mitigating some of the environmental effects of dams by tailoring dam designed and operation is outlined. The cases are as follows: channel simplification and salmon decline on the McKenzie River in Oregon; Channel incision and reduced floodplain inundation on the Oconee river in Georgia; Increased stability of a braided river in New Zealand's south island. 41 refs., 10 figs., 1 tab

Variability of streambed hydraulic conductivity in an intermittent stream reach regulated by Vented Dams: A case study

Science.gov (United States)

Naganna, Sujay Raghavendra; Deka, Paresh Chandra

2018-07-01

The hydro-geological properties of streambed together with the hydraulic gradients determine the fluxes of water, energy and solutes between the stream and underlying aquifer system. Dam induced sedimentation affects hyporheic processes and alters substrate pore space geometries in the course of progressive stabilization of the sediment layers. Uncertainty in stream-aquifer interactions arises from the inherent complex-nested flow paths and spatio-temporal variability of streambed hydraulic properties. A detailed field investigation of streambed hydraulic conductivity (Ks) using Guelph Permeameter was carried out in an intermittent stream reach of the Pavanje river basin located in the mountainous, forested tract of western ghats of India. The present study reports the spatial and temporal variability of streambed hydraulic conductivity along the stream reach obstructed by two Vented Dams in sequence. Statistical tests such as Levene's and Welch's t-tests were employed to check for various variability measures. The strength of spatial dependence and the presence of spatial autocorrelation among the streambed Ks samples were tested by using Moran's I statistic. The measures of central tendency and dispersion pointed out reasonable spatial variability in Ks distribution throughout the study reach during two consecutive years 2016 and 2017. The streambed was heterogeneous with regard to hydraulic conductivity distribution with high-Ks zones near the backwater areas of the vented dam and low-Ks zones particularly at the tail water section of vented dams. Dam operational strategies were responsible for seasonal fluctuations in sedimentation and modifications to streambed substrate characteristics (such as porosity, grain size, packing etc.), resulting in heterogeneous streambed Ks profiles. The channel downstream of vented dams contained significantly more cohesive deposits of fine sediment due to the overflow of surplus suspended sediment-laden water at low velocity

Endocrine-disruptor molecular responses, occurrence of intersex and gonado-histopathological changes in tilapia species from a tropical freshwater dam (Awba Dam) in Ibadan, Nigeria.

Science.gov (United States)

Adeogun, Aina O; Onibonoje, Kolawole; Ibor, Oju R; Omiwole, Roseline A; Chukwuka, Azubuike V; Ugwumba, Alex O; Ugwumba, Adiaha A A; Arukwe, Augustine

2016-05-01

In the present study, the occurrence of endocrine disruptive responses in Tilapia species from Awba Dam has been investigated, and compared to a reference site (Modete Dam). The Awba Dam is a recipient of effluents from University of Ibadan (Nigeria) and several other anthropogenic sources. A total of 132 Tilapia species (Sarotherodon malenotheron (n=57 and 32, males and females, respectively) and Tilapia guineensis (n=23 and 20, males and females, respectively)) were collected from June to September 2014. At the reference site, samples of adult male and female S. melanotheron (48 males and 47 females) and T. guineensis (84 males and 27 females) were collected. Gonads were morphologically and histologically examined and gonadosomatic index (GSI) was calculated. Hepatic mRNA transcriptions of vitellogenin (Vtg) and zona radiata protein (Zrp) genes were analyzed using validated RT-qPCR. Significant increase in Vtg and Zrp transcripts were observed in male tilapias from Awba Dam, compared to males from the reference site. In addition, male tilapias from Awba Dam produced significantly higher Vtg and Zrp mRNA, compared to females in June and July. However, at the natural peak spawning period in August and September, females produced, significantly higher Vtg and Zrp mRNA, compared to males. Fish gonads revealed varying incidence of intersex with a striking presence of two (2) pairs of testes and a pair of ovary in S. melanotheron from Awba Dam. The entire fish population examined at Awba Dam showed a high prevalence of intersex (34.8%), involving phenotypic males and females of both species. Analysis of sediment contaminant levels revealed that As, Cd, Pb, Hg and Ni (heavy metals), monobutyltin cation, 4-iso-nonyphenol and PCB congeners (138, 153 and 180) were significantly higher in Awba Dam, compared to the reference site. Principal component analysis (PCA) showed that fish variables were positively correlated with sediment contaminant burden at Awba Dam, indicating

Environmental-impact assessment of dams and reservoir projects (review and a case study)

International Nuclear Information System (INIS)

Shah, S.M.

2009-01-01

Dams and reservoirs are among one of the most sensitive of all development Project, in terms of pervasiveness of their influence in altering the environmental conditions and resources. In the present study, major dams and reservoir projects are reviewed, from the environmental point of view. Dams and Reservoir projects bring about major changes in the immediate environment, thus affecting public health, settlements, farmlands, roads and historical sites. Impacts on human population and wildlife may be profound. Tropical diseases, involving fresh-water hosts or vectors in their transmission, are often common around new reservoirs. Large lakes create limnological changes, excessive evaporation, seepage, disturbance in water-table and increased tendencies of landslides and earthquakes. Micro climatic changes are possible, such as fog formation, increased cloudiness and modified rainfall-patterns. Retention of sediment results in silting up of reservoirs. Water shortages on mountain rivers may leave unsightly dry river-beds below a dam. Sediment deposition and growth of vegetation in reservoir affects the water-extraction for navigation power-generation and fishing. Various dams and reservoir projects in the world are critically studied, in terms of creating environmental impacts. The Kala Bagh Dam project (Pakistan), which is ready for construction, has been analysed as a case study, by matrix method. Analyses show that adverse effects of this dam are less than the benefits. It is recommended that based on the experience, appropriate lines and strategies may be drawn up to evaluate the local projects. Multidisciplinary experts need to be involved, for assessing environmental impacts and suggesting mitigation measures, to combat the adverse effects. (author)

Long-Term Changes in Sediment and Nutrient Delivery from Conowingo Dam to Chesapeake Bay: Effects of Reservoir Sedimentation.

Science.gov (United States)

Zhang, Qian; Hirsch, Robert M; Ball, William P

2016-02-16

Reduction of suspended sediment (SS), total phosphorus (TP), and total nitrogen is an important focus for Chesapeake Bay watershed management. The Susquehanna River, the bay's largest tributary, has drawn attention because SS loads from behind Conowingo Dam (near the river's mouth) have been rising dramatically. To better understand these changes, we evaluated histories of concentration and loading (1986-2013) using data from sites above and below Conowingo Reservoir. First, observed concentration-discharge relationships show that SS and TP concentrations at the reservoir inlet have declined under most discharges in recent decades, but without corresponding declines at the outlet, implying recently diminished reservoir trapping. Second, best estimates of mass balance suggest decreasing net deposition of SS and TP in recent decades over a wide range of discharges, with cumulative mass generally dominated by the 75∼99.5th percentile of daily Conowingo discharges. Finally, stationary models that better accommodate effects of riverflow variability also support the conclusion of diminished trapping of SS and TP under a range of discharges that includes those well below the literature-reported scour threshold. Overall, these findings suggest that decreased net deposition of SS and TP has occurred at subscour levels of discharge, which has significant implications for the Chesapeake Bay ecosystem.

The influence of controlled floods on fine sediment storage in debris fan-affected canyons of the Colorado River basin

Science.gov (United States)

Mueller, Erich R.; Grams, Paul E.; Schmidt, John C.; Hazel, Joseph E.; Alexander, Jason S.; Kaplinski, Matt

2014-01-01

Prior to the construction of large dams on the Green and Colorado Rivers, annual floods aggraded sandbars in lateral flow-recirculation eddies with fine sediment scoured from the bed and delivered from upstream. Flows greater than normal dam operations may be used to mimic this process in an attempt to increase time-averaged sandbar size. These controlled floods may rebuild sandbars, but sediment deficit conditions downstream from the dams restrict the frequency that controlled floods produce beneficial results. Here, we integrate complimentary, long-term monitoring data sets from the Colorado River in Marble and Grand Canyons downstream from Glen Canyon dam and the Green River in the Canyon of Lodore downstream from Flaming Gorge dam. Since the mid-1990s, several controlled floods have occurred in these canyon rivers. These controlled floods scour fine sediment from the bed and build sandbars in eddies, thus increasing channel relief. These changes are short-lived, however, as interflood dam operations erode sandbars within several months to years. Controlled flood response and interflood changes in bed elevation are more variable in Marble Canyon and Grand Canyon, likely reflecting more variable fine sediment supply and stronger transience in channel bed sediment storage. Despite these differences, neither system shows a trend in fine-sediment storage during the period in which controlled floods were monitored. These results demonstrate that controlled floods build eddy sandbars and increase channel relief for short interflood periods, and this response may be typical in other dam-influenced canyon rivers. The degree to which these features persist depends on the frequency of controlled floods, but careful consideration of sediment supply is necessary to avoid increasing the long-term sediment deficit.

Reaching the end of the road [guidelines for decommissioning dams

International Nuclear Information System (INIS)

Austin, R.J.

1998-01-01

Some hydroelectric power plants in the United States date back as far as the last century when they were constructed to generated power and provide water, recreation and flood control for the growing economy. As these early dams age, an increasing number of retirement evaluations are needed. This article reviews the recently published ''''Guidelines for the Retirement of Dams and Hydroelectric Facilities'''' and explains its technical method of assessing the engineering, sediment management and environmental aspects of retirement evaluations. (UK)

Montgomery Point Lock and Dam, White River, Arkansas

Science.gov (United States)

2016-01-01

the time of this study was James E. Walker, Chief, Navigation Branch, HQUSACE. W. Jeff Lillycrop, CHL, was the ERDC Technical Director for... Fischer , and J. Mewes. 2011. Montgomery Point Lock and Dam HSR model, White River miles 4.0 – 0.0; Hydraulic sediment response model investigation

Dam construction as an engineering solution for water supply problem : environmental thrusts

Energy Technology Data Exchange (ETDEWEB)

Hosseini, A.H. [Alberta Univ., Edmonton, AB (Canada). Dept. of Civil and Environmental Engineering

2004-09-01

Water supply management and the potential impacts associated with engineering practices in water supply systems were examined. Global aspects of increasing water demand were presented and compared with populations, urbanization and water demand. Engineering practices in waterworks developments such as dam construction, river intakes, infiltration galleries, wells, boreholes and adits were also discussed. Construction of large dams and the problems associated with damming the rivers were studied as large dams generally have substantial impacts on rivers, watersheds and aquatic ecosystems, leading to the irreversible loss of species populations and ecosystems. These problems include negative impacts on the terrestrial ecosystem, greenhouse gas emissions from reservoirs due to decaying vegetation and carbon inflows from the catchment, changes in flow regimes, trapping of sediments and nutrients behind a dam, blocking migration of aquatic organisms, as well as negative impacts on flood plain ecosystems and fisheries. In addition, a case study, on the environmental impacts associated with damming in Three Gorges Valley in China was presented. 9 refs., 8 figs.

Sediment transfer dynamics in the Illgraben

Science.gov (United States)

Bennett, G. L.; Molnar, P.; McArdell, B. W.; Schlunegger, F.; Burlando, P.

2012-04-01

Quantification of the volumes of sediment removed by rock-slope failure and debris flows and identification of their coupling and controls are pertinent to understanding mountain basin sediment yield and landscape evolution. We analyzed photogrammetrically-derived datasets of hillslope and channel erosion and deposition along with hydroclimatic variables from the Illgraben, an active debris flow catchment in the Swiss Alps, spanning 1963 - 2010. Two events in the recent history of the catchment make it particularly interesting and challenging to study: a large rock avalanche in 1961, which filled the channel with sediment, and the construction of check dams along the channel in the late 1960s and 1970s. We aimed to (1) identify the nature of hillslope-channel coupling, (2) identify the dominant controls of hillslope sediment production, channel sediment transfer and total sediment yield, (3) observe the response of the channel system to the 1961 rock avalanche and check dam construction, and (4) develop a conceptual model with which to investigate sediment transfer dynamics in various scenarios, including the absence of check dams along the channel. The study captures a multi-decadal period of channel erosion in response to the 1961 rock avalanche, punctuated by shorter cut-and-fill cycles that occur in response to changes in hillslope sediment supply and changes in transport capacity. Hillslopes eroded rapidly at an average rate of 0.34 myr¯ 1, feeding the channel head with sediment. A near doubling of hillslope erosion in the 1980s coincided with a significant increase of air temperature and reduction in snow cover duration and depth, whilst precipitation variables did not change significantly. We find that the main influence of check-dam construction on channel sediment transfer was an initial reduction in sediment transport and a drop in debris flow activity between 1963 and 1986. After 1986 sediment storages in the channel were filled and debris flow activity

Sedimentation Impacts Modeling for the Lower Elwha River

Science.gov (United States)

Beggs, M.; Kosaka, M.; Sigel, A.; Vandermause, R.; Lauer, J. W.

2012-12-01

The removal of Glines Canyon and Elwha Dams from the Elwha River, northwest Washington, is intended to restore natural geomorphic and ecological processes to the Elwha River basin. Prior to the start of dam removal, over 16 million cubic meters of sediment had accumulated in the reservoirs above the two dams. As dam removal progresses, a portion of this sediment will erode and then be deposited on the downstream river bed and floodplain. To address uncertainty in downstream response to the project, the United States Bureau of Reclamation is implementing an adaptive management plan that relies upon continuous monitoring of water levels at a set of stream gages along the river. To interpret the monitoring data and allow for rapid assessment of the rate of downstream sedimentation, we developed rating curves at several locations along the lower Elwha River. The curves consider a range of possible sedimentation scenarios, each involving different sedimentation levels and/or locations. One scenario considers sedimentation primarily in the river channel, another considers sedimentation primarily on the floodplain, and a third considers both possibilities in tandem. We modeled these scenarios using two separate approaches. First, we modified the cross sections in an existing U.S. Army Corps of Engineers HEC-RAS model to represent possible changes associated with geomorphic adjustment to the dam removals. In-channel sedimentation was assumed to occur as a constant fraction of the bankfull depth at any given section, thereby focusing geomorphic change in relatively deep pool areas. In the HEC-RAS model, off-channel sedimentation was assumed uniform. The HEC-RAS model showed that both low-flow and flood hydraulics are much more sensitive to plausible levels of in-channel sedimentation than to plausible levels of overbank sedimentation. The wide floodplain, complex secondary channels, and geomorphic evolution since the original cross sections were surveyed raise some

Developing Sediment Transport and Dredging Prediction Model of Ohio River at Olmsted Locks and Dams Area using HEC-RAS (1D/2D)By Ganesh Raj Ghimire1 and Bruce A. Devantier 2

Science.gov (United States)

Ghimire, G. R.

2015-12-01

Sediment deposition is a serious issue in the construction and operation of large reservoir and inland navigation projects in the United States and around the world. Olmsted Locks and Dams in the Ohio River navigation system is facing similar challenges of huge sediment deposition during the ongoing in-wet construction methodology since 1993. HEC-RAS 5.0 integrated with ArcGIS, will be used to yield unsteady 2D hydrodynamic model of Ohio River at Olmsted area. Velocity, suspended sediment, bed sediment and hydrographic survey data acquired from public archives of USGS and USACE Louisville District will be input into the model. Calibration and validation of model will be performed against the measured stage, flow and velocity data. It will be subjected to completely unsteady 1D sediment transport modeling new to HEC-RAS 5.0 which incorporates sediment load and bed gradation via a DSS file, commercial dredging and BSTEM model. Sediment model will be calibrated to replicate the historical bed volume changes. Excavated cross-sections at Olmsted area will also be used to predict the sediment volume trapped inside the ditch over the period between excavations and placement of dam shells at site. Model will attempt to replicate historical dredging volume data and compare with the deposition volume from simulation model to formulate the dredging prediction model. Hence, the results of this research will generate a model that can form a basis for scheduling the dredging event prior to the placement of off-shore cast shells replacing the current as and when required approach of dredging plan. 1 Graduate Student, Department of Civil Engineering, Southern Illinois University Carbondale Carbondale, Illinois, 62901-6603 2 Professor, Department of Civil Engineering, Southern Illinois University Carbondale Carbondale, Illinois, 62901-6603

Velocity field measurements in tailings dam failure experiments using a combined PIV-PTV approach

Science.gov (United States)

Tailings dams are built to impound mining waste, also called tailings, which consists of a mixture of fine-sized sediments and water contaminated with some hazardous chemicals used for extracting the ore by leaching. Non-Newtonian flow of sediment-water mixture resulting from a failure of tailings d...

Hydrogeophysical investigations at Hidden Dam, Raymond, California

Science.gov (United States)

Minsley, Burke J.; Burton, Bethany L.; Ikard, Scott; Powers, Michael H.

2011-01-01

Self-potential and direct current resistivity surveys are carried out at the Hidden Dam site in Raymond, California to assess present-day seepage patterns and better understand the hydrogeologic mechanisms that likely influence seepage. Numerical modeling is utilized in conjunction with the geophysical measurements to predict variably-saturated flow through typical two-dimensional dam cross-sections as a function of reservoir elevation. Several different flow scenarios are investigated based on the known hydrogeology, as well as information about typical subsurface structures gained from the resistivity survey. The flow models are also used to simulate the bulk electrical resistivity in the subsurface under varying saturation conditions, as well as the self-potential response using petrophysical relationships and electrokinetic coupling equations.The self-potential survey consists of 512 measurements on the downstream area of the dam, and corroborates known seepage areas on the northwest side of the dam. Two direct-current resistivity profiles, each approximately 2,500 ft (762 m) long, indicate a broad sediment channel under the northwest side of the dam, which may be a significant seepage pathway through the foundation. A focusing of seepage in low-topography areas downstream of the dam is confirmed from the numerical flow simulations, which is also consistent with past observations. Little evidence of seepage is identified from the self-potential data on the southeast side of the dam, also consistent with historical records, though one possible area of focused seepage is identified near the outlet works. Integration of the geophysical surveys, numerical modeling, and observation well data provides a framework for better understanding seepage at the site through a combined hydrogeophysical approach.

Trends and evolution of contamination in a well-dated water reservoir sedimentary archive: the Brno Dam, Moravia, Czech Republic

Czech Academy of Sciences Publication Activity Database

Sedláček, J.; Bábek, O.; Matys Grygar, Tomáš

2013-01-01

Roč. 69, č. 8 (2013), s. 2581-2593 ISSN 1866-6280 Institutional support: RVO:61388980 Keywords : Brno Dam * Dam sediments * Cs-137 dating * Heavy metals * Eutrophication Subject RIV: DD - Geochemistry Impact factor: 1.572, year: 2013

Importance of measuring discharge and sediment transport in lesser tributaries when closing sediment budgets

Science.gov (United States)

Griffiths, Ronald E.; Topping, David J.

2017-11-01

Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a river reach is in a state of sediment accumulation, deficit or stasis. Many sediment-budget studies have estimated the sediment loads of ungaged tributaries using regional sediment-yield equations or other similar techniques. While these approaches may be valid in regions where rainfall and geology are uniform over large areas, use of sediment-yield equations may lead to poor estimations of loads in regions where rainfall events, contributing geology, and vegetation have large spatial and/or temporal variability. Previous estimates of the combined mean-annual sediment load of all ungaged tributaries to the Colorado River downstream from Glen Canyon Dam vary by over a factor of three; this range in estimated sediment loads has resulted in different researchers reaching opposite conclusions on the sign (accumulation or deficit) of the sediment budget for particular reaches of the Colorado River. To better evaluate the supply of fine sediment (sand, silt, and clay) from these tributaries to the Colorado River, eight gages were established on previously ungaged tributaries in Glen, Marble, and Grand canyons. Results from this sediment-monitoring network show that previous estimates of the annual sediment loads of these tributaries were too high and that the sediment budget for the Colorado River below Glen Canyon Dam is more negative than previously calculated by most researchers. As a result of locally intense rainfall events with footprints smaller than the receiving basin, floods from a single tributary in semi-arid regions can have large (≥ 10 ×) differences in sediment concentrations between equal magnitude flows. Because sediment loads do not

Assessment of the Physicochemical Quality of Challawa Gorge Dam ...

African Journals Online (AJOL)

Dr Maimuna

Water and sediment samples were collected from Challawa Gorge dam during the wet and dry seasons and analyzed for some physicochemical parameters, heavy metals (Cd, Cr, Mn, Pb, Zn) and minerals (Na and K) using Atomic Absorption Spectrophotometric and Flame Photometric techniques. The results showed the.

Geological And Geotechnical Investigations Of Axum Dam Site Tigray Northern Ethiopia

Directory of Open Access Journals (Sweden)

Leulalem

2015-08-01

Full Text Available Geological and geotechnical study was conducted in concrete gravity dam which is planned to be constructed in the Maychew River 40 km south of Axum town for the purpose of water supply for the town. The objectives of this research were to map geology of the area to characterize geological defects within and around dam site to evaluate the water tightness of the dam site and to determine the bearing capacity of the dam foundation. The research involved review of different literatures lithological and structural mapping characterizing rock masses by using different rock mass classification methods interpretation of subsurface data geophysical core drilled data test pit data etc.. Results of the study indicate that the area is underlain by Quaternary sediments metasedimentary and metavolcanic rocks. The Quaternary sediments are characterized by low permeability low plasticity and are poorly graded nature. Metasedimentary rocks are found covering the right abutment of the dam whereas at reservoir area it is found intercalating with metavolcanic rocks. These rocks are moderately jointed and sheared with faulting and folding noticed due to these they have a relatively high permeability. Metavolcanic rocks which are found covering the left abutment are strong less permeable and fractured. Most of discontinuities such as fractures bedding and foliation in the study area are oriented E-W NNW-SSE and NNE-SSW. The VES tomography and drilled core result revealed that the potential problems seepageleakage could occur due to presence of faults joints karstified black limestone lithological variations groundwater depth and topography at right abutment. Differential settlements may also occur because empirically estimated moduli of deformation Ed of rock masses indicate that for right abutment much less than left abutment and different geological defects across the dam axis. To minimize these problems contact grouting and consolidation grouting are recommended

Sedimentation and Its Impacts/Effects on River System and Reservoir Water Quality: case Study of Mazowe Catchment, Zimbabwe

Science.gov (United States)

Tundu, Colleta; Tumbare, Michael James; Kileshye Onema, Jean-Marie

2018-04-01

Sediment delivery into water sources and bodies results in the reduction of water quantity and quality, increasing costs of water purification whilst reducing the available water for various other uses. The paper gives an analysis of sedimentation in one of Zimbabwe's seven rivers, the Mazowe Catchment, and its impact on water quality. The Revised Universal Soil Loss Equation (RUSLE) model was used to compute soil lost from the catchment as a result of soil erosion. The model was used in conjunction with GIS remotely sensed data and limited ground observations. The estimated annual soil loss in the catchment indicates soil loss ranging from 0 to 65 t ha yr-1. Bathymetric survey at Chimhanda Dam showed that the capacity of the dam had reduced by 39 % as a result of sedimentation and the annual sediment deposition into Chimhanda Dam was estimated to be 330 t with a specific yield of 226 t km-2 yr-1. Relationship between selected water quality parameters, TSS, DO, NO3, pH, TDS, turbidity and sediment yield for selected water sampling points and Chimhanda Dam was analyzed. It was established that there is a strong positive relationship between the sediment yield and the water quality parameters. Sediment yield showed high positive correlation with turbidity (0.63) and TDS (0.64). Water quality data from Chimhanda treatment plant water works revealed that the quality of water is deteriorating as a result of increase in sediment accumulation in the dam. The study concluded that sedimentation can affect the water quality of water sources.

Quantifying the Effects of Near-Bed Concentration on the Sediment Flux after the Operation of the Three Gorges Dam, Yangtze River

Directory of Open Access Journals (Sweden)

Li He

2017-12-01

Full Text Available The regime of sediment transport in the Jingjiang Reach has significantly changed from quasi-equilibrium to sub-saturation since the impoundment of the Three Gorges Dam (TGD, and vertical profiles of suspended sediment concentration (SSC have changed accordingly. Vertical profiles of SSC data measured at three hydrological stations in the Jingjiang Reach (Zhicheng, Shaishi, and Jianli, before and after the impoundment of TGD, were collected and analyzed. Analytic results indicate a remarkably large concentration in the near-bed zone (within 10% of water depth from the river-bed in a sub-saturated channel. The maximum measured concentration was up to 15 times the vertical average concentration, while the ratio in quasi-equilibrium channel was less than four times that. Concentrations normalized with reference concentration at the same height, and may decrease with increasing values of suspension index (settling velocity over shear velocity. In addition, concentration near the water surface may be larger than concentration in the near-bed region when the suspension index is smaller than 0.01. Sediment flux transported in the near-bed zone may be up to 35% of the total sediment flux in unsaturated flows. The relationship between deviations of estimating sediment flux when ignoring the near-bed concentration and discharge in flood season and non-flood season are different in unsaturated and quasi-equilibrium channels. Analysis indicates that, in the quasi-equilibrium channel, more attention should be paid to near-bed concentration during non-flood season, the same as measurements during flood season with larger discharge.

SILTATION AND EROSION PROCESSES ON A TRIBUTARY OF LAKE ITAIPU DUE A DAM RESERVOIR

Directory of Open Access Journals (Sweden)

Cristiano Poleto

2012-12-01

Full Text Available It is known that sediments in the river have their origin from different sources. Therefore, the proportion that each source contributes to the mix varies over time and space, as a result of erosion processes that are ongoing in the basin of contribution. Within this context, both in human actions in urban and rural watersheds generate different rates of sediment production, but mainly with different characteristics or quality. Thus, the fluvial sedimentology should have a broad character within the study area and check all the possible influences of land use and soil. Hydrosedimentological processes are complex and include a disaggregation ("erosion" in the strict definition, transport, sedimentation, consolidation of sediments. Therefore, it is necessary more detailed studies of sediments and their interactions with the environment, considering it as a topic of interest to economic, social and ecological needs of a sustainable management, where they articulate an understanding of the physical and chemical properties of sediments with ecological and hydrological information of the water bodies receiver on a regional scale and thus evaluate the possible scenarios of pollution of water resources. This information will support in decision-making processes for managing the watershed and its water resources. Therefore, this project aims to determine the interference that a hydroelectric plant, together with the lack of proper management of the basin, can cause to the river morphology. The research is conducting a survey of sensitive areas to erode and the influence of a newly installed hydropower in a tributary of Lake Itaipu. Could notice that the removal of riparian vegetation is accelerating the erosion processes at various points of the river, but the agriculture system used in the rural area, without revolving of soil, has reduced the sediment load produced by this source. However, the retention of much of the coarse sediments by the new dam is

Modeling the capacity of riverscapes to support beaver dams

Science.gov (United States)

Macfarlane, William W.; Wheaton, Joseph M.; Bouwes, Nicolaas; Jensen, Martha L.; Gilbert, Jordan T.; Hough-Snee, Nate; Shivik, John A.

2017-01-01

The construction of beaver dams facilitates a suite of hydrologic, hydraulic, geomorphic, and ecological feedbacks that increase stream complexity and channel-floodplain connectivity that benefit aquatic and terrestrial biota. Depending on where beaver build dams within a drainage network, they impact lateral and longitudinal connectivity by introducing roughness elements that fundamentally change the timing, delivery, and storage of water, sediment, nutrients, and organic matter. While the local effects of beaver dams on streams are well understood, broader coverage network models that predict where beaver dams can be built and highlight their impacts on connectivity across diverse drainage networks are lacking. Here we present a capacity model to assess the limits of riverscapes to support dam-building activities by beaver across physiographically diverse landscapes. We estimated dam capacity with freely and nationally-available inputs to evaluate seven lines of evidence: (1) reliable water source, (2) riparian vegetation conducive to foraging and dam building, (3) vegetation within 100 m of edge of stream to support expansion of dam complexes and maintain large colonies, (4) likelihood that channel-spanning dams could be built during low flows, (5) the likelihood that a beaver dam is likely to withstand typical floods, (6) a suitable stream gradient that is neither too low to limit dam density nor too high to preclude the building or persistence of dams, and (7) a suitable river that is not too large to restrict dam building or persistence. Fuzzy inference systems were used to combine these controlling factors in a framework that explicitly also accounts for model uncertainty. The model was run for 40,561 km of streams in Utah, USA, and portions of surrounding states, predicting an overall network capacity of 356,294 dams at an average capacity of 8.8 dams/km. We validated model performance using 2852 observed dams across 1947 km of streams. The model showed

Classification of the alterations of beaver dams to headwater streams in northeastern Connecticut, U.S.A.

Science.gov (United States)

Burchsted, Denise; Daniels, Melinda D.

2014-01-01

Of the many types of barriers to water flow, beaver dams are among the smallest, typically lasting less than a decade and rarely exceeding 1.5 m in height. They are also among the most frequent and common obstructions in rivers, with a density often exceeding ten dams per km, a frequency of construction within a given network on a time scale of years, and a historic extent covering most of North America. Past quantification of the geomorphologic impact of beaver dams has primarily been limited to local impacts within individual impoundments and is of limited geographic scope. To assess the impact of beaver dams at larger scales, this study examines channel shape and sediment distribution in thirty river reaches in northeastern Connecticut, U.S.A. The study reaches fall within the broader categories of impounded and free-flowing segments, leaving a third segment class of beaver meadows requiring additional study. Each of the study reaches were classified at the reach scale as free-flowing, valley-wide beaver pond, in-channel beaver pond, and downstream of beaver dam. The bankfull channel width to depth ratios and channel widths normalized by watershed area vary significantly across the study reach classes. Additionally, reaches modified by beaver dams have finer sediment distributions. This paper provides the first quantitative geomorphic descriptions of the in-channel beaver pond and reaches downstream of beaver dams. Given the different channel shapes and sediment distributions, we infer that geomorphic processes are longitudinally decoupled by these frequent barriers that control local base level. These barriers generate heterogeneity within a river network by greatly increasing the range of channel morphology and by generating patches controlled by different processes. Therefore, in spite of the small size of individual beaver dams, the cumulative effect of multiple dams has the potential to modify processes at larger spatial scales. To improve assessment of the

Tailings dams from the perspective of conventional dam engineering

International Nuclear Information System (INIS)

Szymanski, M.B.

1999-01-01

A guideline intended for conventional dams such as hydroelectric, water supply, flood control, or irrigation is used sometimes for evaluating the safety of a tailings dam. Differences between tailings dams and conventional dams are often substantial and, as such, should not be overlooked when applying the techniques or safety requirements of conventional dam engineering to tailings dams. Having a dam safety evaluation program developed specifically for tailings dams is essential, if only to reduce the chance of potential errors or omissions that might occur when relying on conventional dam engineering practice. This is not to deny the merits of using the Canadian Dam Safety Association Guidelines (CDSA) and similar conventional dam guidelines for evaluating the safety of tailings dams. Rather it is intended as a warning, and as a rationale underlying basic requirement of tailings dam emgineering: specific experience in tailings dams is essential when applying conventional dam engineering practice. A discussion is included that focuses on the more remarkable tailings dam safety practics. It is not addressed to a technical publications intended for such dams, or significantly different so that the use of conventional dam engineering practice would not be appropriate. The CDSA Guidelines were recently revised to include tailings dams. But incorporating tailings dams into the 1999 revision of the CDSA Guidelines is a first step only - further revision is necessary with respect to tailings dams. 11 refs., 2 tabs

Evaluating temporal changes in hydraulic conductivities near karst-terrain dams: Dokan Dam (Kurdistan-Iraq)

Science.gov (United States)

Dafny, Elad; Tawfeeq, Kochar Jamal; Ghabraie, Kazem

2015-10-01

Dam sites provide an outstanding opportunity to explore dynamic changes in the groundwater flow regime because of the high hydraulic gradient rapidly induced in their surroundings. This paper investigates the temporal changes of the hydraulic conductivities of the rocks and engineered structures via a thorough analysis of hydrological data collected at the Dokam Dam, Iraq, and a numerical model that simulates the Darcian component of the seepage. Analysis of the data indicates increased seepage with time and suggests that the hydraulic conductivity of the rocks increased as the conductivity of the grout curtain decreased. Conductivity changes on the order of 10-8 m/s, in a 20-yr period were quantified using the numerical analysis. It is postulated that the changes in hydraulic properties in the vicinity of Dokan Dam are due to suspension of fine materials, interbedded in small fissures in the rocks, and re-settlement of these materials along the curtain. Consequently, the importance of the grout curtain to minimize the downstream seepage, not only as a result of the conductivity contrast with the rocks, but also as a barrier to suspended clay sediments, is demonstrated. The numerical analysis also helped us to estimate the proportion of the disconnected karstic conduit flow to the overall flow.

River system recovery following the Novat-Rosu tailings dam failure, Maramures County, Romania

International Nuclear Information System (INIS)

Bird, Graham; Brewer, Paul A.; Macklin, Mark G.; Balteanu, Dan; Serban, Mihaela; Driga, Basarab; Zaharia, Sorin

2008-01-01

The River Viseu catchment in Maramures County, northwestern Romania, has a long history of base and precious metal mining. Between 1994 and 2003 waste from mining activity at Baia Borsa was stored in the Novat-Rosu tailings pond in the upper Viseu catchment. However, in March 2000, the tailings dam failed releasing approximately 100,000 m 3 of contaminated water and 20,000 t of mineral-rich solid waste, which was routed downstream through the Rivers Novat, Vaser and Viseu into the River Tisa. Following the accident metal (Cd, Cu, Pb, Zn) concentrations in river water and river channel sediment were assessed in samples collected annually (July 2000, 2001, 2002 and 2003) from 29 sites in the Viseu catchment, downstream of the tailings pond. Additionally, the speciation of sediment-associated metals was established using a 4-stage sequential extraction procedure (SEP) and Pb isotope analysis ( 206/204 Pb and 207/204 Pb) was carried out to establish the provenance of contaminated sediments. Metal concentrations in river water were found to comply with EU directive 'target' values within four months of the failure. However, the impact of the spill upon river channel sediments was found to be much longer-lasting, with evidence of the delayed downstream remobilization of tailings stored within the narrow Novat valley following the dam failure, as well as continued inputs of contaminated sediment to the River Viseu from the River Tisla, another mining-affected tributary. Comparison with data from other recent tailings dam failures, indicates that river system recovery rates depend upon local geomorphological conditions, hydrological regimes, and the nature and scale of post-spill clean-up operations

Bank erosion along the dam-regulated lower Roanoke River, North Carolina

Science.gov (United States)

Hupp, C.R.; Schenk, E.R.; Richter, J.M.; Peet, Robert K.; Townsend, Phil A.

2009-01-01

Dam construction and its impact on downstream fluvial processes may substantially alter ambient bank stability and erosion. Three high dams (completed between 1953 and 1963) were built along the Piedmont portion of the Roanoke River, North Carolina; just downstream the lower part of the river flows across largely unconsolidated Coastal Plain deposits. To document bank erosion rates along the lower Roanoke River, >700 bank-erosion pins were installed along 66 bank transects. Additionally, discrete measurements of channel bathymetry, turbidity, and presence or absence of mass wasting were documented along the entire study reach (153 km). A bank-erosion- floodplain-deposition sediment budget was estimated for the lower river. Bank toe erosion related to consistently high low-flow stages may play a large role in increased mid- and upper-bank erosion. Present bank-erosion rates are relatively high and are greatest along the middle reaches (mean 63 mm/yr) and on lower parts of the bank on all reaches. Erosion rates were likely higher along upstream reaches than present erosion rates, such that erosion-rate maxima have since migrated downstream. Mass wasting and turbidity also peak along the middle reaches; floodplain sedimentation systematically increases downstream in the study reach. The lower Roanoke River isnet depositional (on floodplain) with a surplus of ??2,800,000 m3yr. Results suggest that unmeasured erosion, particularly mass wasting, may partly explain this surplus and should be part of sediment budgets downstream of dams. ?? 2009 The Geological Society of America.

Fe, Mn, P and S speciation in sediments from the Capivara Hydroelectric Dam Lake (Brazil) as an indicator of anthropogenic influences

Energy Technology Data Exchange (ETDEWEB)

Ishikawa, Dilson Norio [Department of Chemistry, CCE, Londrina State University, Londrina, Parana (Brazil); Spacino Scarminio, Ieda [Laboratory of Chemometrics in Natural Sciences, Department of Chemistry, CCE, Londrina State University, Londrina, Parana (Brazil); Souza Costa, Joao de; Santos Nora, Paulo dos; Fatima Soares, Miriam de; Mansano Nicolau, Romilaine; Esteves Goncalves, Adriana Celeste; Giancoli Barreto, Sonia Regina [Laboratory of Environmental Physical Chemistry, Department of Chemistry, CCE, Londrina State University, Londrina, Parana (Brazil); Barreto, Wagner Jose

2008-04-15

The conservation of large water resources is essential for the preservation of human life. The quantification and, more importantly, the speciation of chemical substances that indicate the presence of anthropogenic contamination in water resources are of great importance. This paper presents the results of analysis for the determination of organic, inorganic and total phosphorus, pseudo-sulfur, and iron and manganese, in five fractions, in water sediments collected from the Capivara Hydroelectric Power Plant, Brazil. A study on the seasonal variation of these parameters was conducted, with data having been collected in the winter and in the summer, at two sites along the dam, 5 km apart, close to the city of Primeiro de Maio. Phosphorous was found in sediments and adjacent soil in the organic form (OP), and was used as an indicator of anthropogenic influence on the reservoir banks. Speciation of potentially toxic Mn showed that it is present in the exchangeable fraction of the 0-5 cm depth layer (sediment/water interface), making its transfer to the water column possible. Results from this study showed that domestic and industrial effluent treatment measures are needed for the preservation of the quality of aquatic environments. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

Signatures of self-assembly in size distributions of wood members in dam structures of Castor canadensis

Directory of Open Access Journals (Sweden)

David M. Blersch

2014-12-01

Full Text Available Beavers (Castor canadensis construct dams on rivers throughout most of their historical range in North America, and their impact on water patterns in the landscape is considerable. Dam formation by beavers involves two processes: (1 intentional construction through the selection and placement of wood and sediment, which facilitates (2 the passive capture and accretion of suspended wood and sediment. The second process is a self-assembly mechanism that the beavers leverage by utilizing energy subsidies of watershed transport processes. The relative proportion of beaver activity to self-assembly processes in dam construction, however, is unknown. Here we show that lotic self-assembly processes account for a substantial portion of the work expended in beaver dam construction. We found through comprehensive measurement of the stick dimensions that the distributions for diameter, length, and volume are log-normal. By noting evidence of teeth markings, we determined that size distributions skewed significantly larger for wood handled by beavers compared to those that were not. Subsequent mass calculations suggest that beavers perform 50%–70% of the work of wood member placement for dam assembly, with riparian self-assembly processes contributing the remainder. Additionally, our results establish a benchmark for assessing the proportion of self-assembly work in similar riparian structures. Keywords: Beaver dam, Construction, Castor canadensis, Self-assembly, Distribution, Wood

Upstream effects of dams on alluvial channels: state-of-the-art and future challenges

Science.gov (United States)

Liro, Maciej

2017-04-01

More than 50,000 large dams (with the height above 15 m) operate all over the world and, thus, they significantly disturb water and sediment transport in river systems. These disturbances are recognized as one of the most important factors shaping river morphology in the Anthropocene. Downstream effects of dams have been well documented in numerous case studies and supported by predictions from existing models. In contrast, little is known on the upstream effects of dams on alluvial channels. This review highlights the lack of studies on sedimentological, hydromorphological and biogeomorphological adjustments of alluvial rivers in the base-level raised zones of backwater upstream of dam reservoirs where water level fluctuations occur. Up to date, it has been documented that backwater effects may facilitate fine and coarse sediment deposition, increase groundwater level, provide higher and more frequent channel and floodplain inundation and lead to significant morphological changes. But there have been no studies quantifying short- and long-term consequences of these disturbances for the hydromorphological and biogeomorphological feedbacks that control development of alluvial channels. Some recent studies carried out on gravel-bed and fine-grained bed rivers show that the above mentioned disturbances facilitate vegetation expansion on exposed channel sediments and floodplain influencing river morphology, which suggests that backwater area of alluvial rivers may be treated as the hotspot of bio-geomorphological changes in a fluvial system. To set the stage for future research on upstream effects of dams, this work presents the existing state-of-art and proposes some hypotheses which may be tested in future studies. This study was carried out within the scope of the Research Project 2015/19/N/ST10/01526 financed by the National Science Centre of Poland

Olympic Dam copper-uranium-gold deposit, South Australia

International Nuclear Information System (INIS)

Lalor, J.H.

1986-01-01

The Olympic Dam copper-uranium-gold deposit was discovered in July 1975. It is located 650 km north-northwest of Adelaide on Roxby Downs Station in South Australia. The first diamond drill hole, RD1, intersected 38 m of 1.05% copper. A further eight holes were drilled with only marginal encouragement to November 1976, when RD10 cored 170 m of 2.12% copper and 0.06% of uranium oxide, thus confirming an economic discovery. The discovery of Olympic Dam is an excellent example applying broad-scale, scientifically based conceptual studies to area selection. Exploration management supported its exploration scientists in testing their ideas with stratigraphic drilling. Geologic modeling, supported by geophysical interpretations and tectonic studies, was used to site the first hole. The discovery also illustrates the persistence required in mineral exploration. The deposit appears to be a new type of stratabound sediment-hosted ore. It has an areal extent exceeding 20 km 2 with vertical thicknesses of mineralization up to 350 m. It is estimated to contain more than 2000 million MT of mineralized material with an average grade of 1.6% copper, 0.06% uranium oxide, and 0.6 g/MT gold. The deposit occurs in middle Proterozoic basement beneath 350 m of unmineralized, flat upper Proterozoic sediments. The sediments comprising the local basement sequence are predominantly sedimentary breccias controlled by a northwest-trending graben

levels of heavy metals in gubi dam water bauchi, nigeria

African Journals Online (AJOL)

Ada

copper and lead were always highest in the suspended materials which indicate the dominant role played by ... essential. However, at high concentrations, these trace metals become toxic (Nurnberg, 1982). Heavy metals in .... mobilization of cobalt minerals into the dam. .... Interaction between sediments and fresh water ...

Estimated cumulative sediment trapping in future hydropower reservoirs in Africa

Science.gov (United States)

Lucía, Ana; Berlekamp, Jürgen; Zarfl, Christiane

2017-04-01

Despite a rapid economic development in Sub-Saharan Africa, almost 70% of the human population in this area remain disconnected from electricity access (International Energy Agency 2011). Mitigating climate change and a search for renewable, "climate neutral" electricity resources are additional reasons why Africa will be one key centre for future hydropower dam building, with only 8% of the technically feasible hydropower potential actually exploited. About 300 major hydropower dams with a total capacity of 140 GW are currently under construction (11.4%) or planned (88.6%) (Zarfl et al. 2015). Despite the benefits of hydropower dams, fragmentation of the rivers changes the natural flow, temperature and sediment regime. This has consequences for a high number of people that directly depend on the primary sector linked to rivers and floodplains. But sediment trapping in the reservoir also affects dam operation and decreases its life span. Thus, the objective of this work is to quantify the dimension of sediment trapping by future hydropower dams in African river basins. Soil erosion is described with the universal soil loss equation (Wischmeier & Smith 1978) and combined with the connectivity index (Cavalli et al. 2013) to estimate the amount of eroded soil that reaches the fluvial network and finally ends up in the existing (Lehner et al. 2011) and future reservoirs (Zarfl et al. 2015) per year. Different scenarios assuming parameter values from the literature are developed to include model uncertainty. Estimations for existing dams will be compared with literature data to evaluate the applied estimation method and scenario assumptions. Based on estimations for the reservoir volume of the future dams we calculated the potential time-laps of the future reservoirs due to soil erosion and depending on their planned location. This approach could support sustainable decision making for the location of future hydropower dams. References Cavalli, M., Trevisani, S., Comiti

After Three Gorges Dam: What have we learned?

Science.gov (United States)

Natali, J.; Williams, P.; Wong, R.; Kondolf, G. M.

2013-12-01

China is at a critical point in its development path. By investing heavily in large-scale infrastructure, the rewards of economic growth weigh against long-term environmental and social costs. The construction of Three Gorges Dam, the world's largest hydroelectric project, began in 1994. Between 2002 and 2010, its 660 kilometer reservoir filled behind a 181 meter dam, displacing at least 1.4 million people and transforming Asia's longest river (the Yangtze) while generating nearly 100 billion kWh/yr of electricity -- 2.85% of China's current electric power usage. As the mega-project progenitor in a cascade of planned dams, the Three Gorges Dam emerges as a test case for how China will plan, execute and mitigate its development pathway and the transformation of its environment. Post-Project Assessments (PPA) provide a systematic, scientific method for improving the practice of environmental management - particularly as they apply to human intervention in river systems. In 2012, the Department of Landscape Architecture and Environmental Planning at University of California, Berkeley organized a symposium-based PPA for the Three Gorges Dam on the Yangtze River. Prior to this symposium, the twelve invited Chinese scientists, engineers and economists with recent research on Three Gorges Dam had not had the opportunity to present their evaluations together in an open, public forum. With a 50-year planning horizon, the symposium's five sessions centered on impacts on flows, geomorphology, geologic hazards, the environment and socioeconomic effects. Three Gorges' project goals focused on flood control, hydropower and improved navigation. According to expert research, major changes in sediment budget and flow regime from reservoir operation have significantly reduced sediment discharge into the downstream river and estuary, initiating a series of geomorphic changes with ecological and social impacts. While the dam reduces high flow stages from floods originating above the

The Olympic Dam copper-uranium-gold deposit, Roxby Downs, South Australia

International Nuclear Information System (INIS)

Roberts, D.E.; Hudson, G.R.T.

1983-01-01

The Olympic Dam copper-uranium-gold deposit appears to be a new type of strata-bound sediment-hosted ore deposit. It is located 650 km north-northwest of Adelaide in South Australia and was discovered in 1975. It has an areal extent exceeding 20 km 2 with vertical thicknesses of mineralization up to 350 m. The deposit is estimated to contain in excess of 2,000 million metric tons of mineralized material with an average grade of 1.6 percent copper, 0.06 percent uranium oxide, and 0.6 g/metric ton gold. The deposit occurs in the basement beneath 350 m of unmineralized, flat-lying Adelaidean (late Proterozoic) to Cambrian sediments in the Stuart shelf region of South Australia. The host rocks of the deposit are unmetamorphosed and are probably younger than 1,580 m.y. The deposit is spatially related to coincident gravity and magnetic anomalies and the intersection of west-northwest- and north-northwest-trending lineaments. The Proterozoic sediments comprising the local basement sequence are predominantly sedimentary breccias ranging from matrix-poor granite breccias to matrix-rich polymict breccias containing clasts of a variety of rock types. This sequence is over 1 km thick and has been divided into two main units--the Olympic Dam Formation and the Greenfield Formation. The Olympic Dam Formation has five members, three of which are matrix rich. The Greenfield Formation has three members, the lower two being very hematite rich while the upper has a significant volcanic component. Pervasive hematite, chlorite, and sericite alteration of varying intensity affects all the basement sequence

Avoiding The Inevitable? Capacity Loss From Reservoir Sedimentation

Science.gov (United States)

Gray, John R.; Randle, Timothy J.; Collins, Kent L.

2013-01-01

The inexorable loss of capacity of the nation's reservoirs—sooner or later threatening water supplies for municipal, agricultural, and industrial uses—is but one of a number of deleterious effects wrought by sediment deposition. Trapped sediments can also damage or bury dam outlets, water intakes, and related infrastructure. Downstream effects of sediment capture and retention by reservoirs can include channel and habitat degradation and biotic alterations.

Surface and subsurface soils at the Pond B dam: July 1998

International Nuclear Information System (INIS)

Halverson, N.V.

1999-01-01

Pond B, 685-13G, is an inactive reactor cooling impoundment built in 1961 on the Savannah River Site (SRS). Between 1961 and 1964, Pond B received R-Reactor cooling water discharges that were contaminated with 137 Cs, 90 Sr and plutonium. Though the pond has not been used since 1964, radionuclides from the contaminated cooling water remain in the water and in the surface sediments of the pond. The current proposal to fix and repair the Pond B dam structure includes installing a new drain system and monitoring equipment. The dam will be reinforced with additional previous material on the downstream face of the dam. The objectives of this report are to describe the sampling methodology used during the July 1998 sampling event at the downstream face of the Pond B dam and in Pond B, present the results of the sampling event, and compare, where possible, these results to related risk-based standards

Sediment budget variation at watershed scale due to anthropogenic pressures, and its relationship to coastal erosion

Science.gov (United States)

Aiello, Antonello; Adamo, Maria; Canora, Filomena

2014-05-01

The transfer of sediments from hydrographic basins towards the coast is a significant pathway of material transfer on Earth. In sedimentary environment, the main portion of sediment that enters the coastal areas is derived originally from erosion in the coastal watersheds. Extensive anthropogenic pressures carried out within coastal basins have long shown negative impacts on littoral environments. In fluvial systems, sediments trapped behind dams and in-stream gravel mining cause the reduction in sediment supply to the coast. Along the Jonian littoral of the Basilicata Region (southern Italy), natural coastal processes have been severely disrupted since the second half of the 20th century as a result of riverbed sand and gravel mining and dam construction, when economic advantages were measured in terms of the development of infrastructure, water storage, and hydropower production for the agricultural, industrial and socio-economic development of the area. Particularly, the large numbers of dams and impoundments that have been built in the hydrographic basins have led a signi?cant reduction on river sediment loads. As a result, the Jonian littoral is experiencing a catalysed erosion phenomenon. In order to increase understanding of the morpho-dynamics of the Jonian littoral environment and more fully appreciate the amount of coastal erosion, an evaluation of the sediment budget change due to dam construction within the hydrographic basins of the Basilicata Region needs to be explored. Since quantitative data on decadal trends in river sediment supply before and after dam construction are lacking, as well as updated dam silting values, river basin assessment of the spatial patterns and estimated amount of sediment erosion and deposition are important in evaluating changes in the sediment budget. As coastal areas are being affected by an increasing number of population and socio-economic activities, the amount of sediment deficit at the littoral can permit to

River delta shoreline reworking and erosion in the Mediterranean and Black Seas: the potential roles of fluvial sediment starvation and other factors

Directory of Open Access Journals (Sweden)

Manon Besset

2017-09-01

Full Text Available The Mediterranean basin (including the Black Sea is characterized by a plethora of deltas that have developed in a wave-influenced setting. Many of these deltas are sourced in sediments by river catchments that have been variably dammed. The vulnerability status of a selection of ten deltas subject to different levels of reduction in fluvial sediment supply following damming was analysed by quantifying changes in delta protrusion area and protrusion angle over the last 30 years. The rationale for choosing these two metrics, which do not require tricky calculations of longshore bedload transport volumes and river ‘influence’, is that as sediment supply wanes, increasing relative efficiency of waves leads to longshore redistribution of reworked sediments and progressive ‘flattening’ of the delta protrusion. The results show that eight of the ten deltas (Nile, Rhône, Ebro, Ceyhan, Arno, Ombrone, Moulouya, Medjerda are in erosion, whereas two (Danube, Po show stability, but the statistical relationship between change in delta protrusion area and sediment flux reduction is poor, thus suggesting that the role of dams in causing delta shoreline erosion may have been over-estimated. But this poor relationship could also be due to a long temporal lag between dam construction and bedload removal and transport to the coast downstream of dams, and, where the delta protrusion is being eroded, to bedload trapping by shoreline engineering structures and by elongating delta-flank spits. Other potential influential factors in shoreline change include subsidence, sea-level rise, storminess, exceptional river floods, and managed sediment releases downstream of dams. A longer observation period and high-resolution sediment-budget studies will be necessary to determine more definitively to which extent continued trapping of sediment behind dams will impact overall delta stability in the Mediterranean and Black Seas. Mitigation of delta erosion is likely to

Enhancing mud supply from the Lower Missouri River to the Mississippi River Delta USA: Dam bypassing and coastal restoration

Science.gov (United States)

Kemp, G. Paul; Day, John W.; Rogers, J. David; Giosan, Liviu; Peyronnin, Natalie

2016-12-01

Sand transport to the Mississippi River Delta (MRD) remains sufficient to build wetlands in shallow, sheltered coastal bays fed by engineered diversions on the Mississippi River (MR) and its Atchafalaya River (AR) distributary. But suspended mud (silt & clay) flux to the coast has dropped from a mean of 390 Mt y-1 in the early 1950s, to 100 Mt y-1 since 1970. This fine-grained sediment travels deeper into receiving estuarine basins and plays a critical role in sustaining existing marshes. Virtually all of the 300 Mt y-1 of missing mud once flowed from the Missouri River (MOR) Basin before nearly 100 dams were built as part of the Pick-Sloan water development project. About 100 Mt y-1 is now intercepted by main-stem Upper MOR dams closed in 1953. But the remaining 200 Mt y-1 is trapped by impoundments built on tributaries to the Lower MOR in the 1950s and 1960s. Sediment flux during the post-dam high MOR discharge years of 1973, 1993 and 2011 approached pre-dam levels when tributaries to the Lower MOR, including the Platte and Kansas Rivers, contributed to flood flows. West bank tributaries drain a vast, arid part of the Great Plains, while those entering from the east bank traverse the lowlands of the MOR floodplain. Both provinces are dominated by highly erodible loess soils. Staunching the continued decline in MR fine-grained sediment flux has assumed greater importance now that engineered diversions are being built to reconnect the Lowermost MR to the MRD. Tributary dam bypassing in the Lower MOR basin could increase mud supply to the MRD by 100-200 Mt y-1 within 1-2 decades. Such emergency measures to save the MRD are compatible with objectives of the Missouri River Restoration and Platte River Recovery Programs to restore MOR riparian habitat for endangered species. Rapid mobilization to shunt fine-grained sediments past as many as 50 Lower MOR tributary dams in several U.S. states will undoubtedly require as much regional coordination and funding in the 21st

Geomorphic and vegetation changes in a meandering dryland river regulated by a large dam, Sauce Grande River, Argentina

Science.gov (United States)

Casado, Ana; Peiry, Jean-Luc; Campo, Alicia M.

2016-09-01

This paper investigates post-dam geomorphic and vegetation changes in the Sauce Grande River, a meandering dryland river impounded by a large water-conservation dam. As the dam impounds a river section with scarce influence of tributaries, sources for fresh water and sediment downstream are limited. Changes were inspected based on (i) analysis of historical photographs/imagery spanning pre- (1961) and post-dam (1981, 2004) channel conditions for two river segments located above and below the dam, and (ii) field survey of present channel conditions for a set of eight reference reaches along the river segments. Whilst the unregulated river exhibited active lateral migration with consequent adjustments of the channel shape and size, the river section below the dam was characterized by (i) marked planform stability (93 to 97%), and by (ii) vegetation encroachment leading to alternating yet localized contraction of the channel width (up to 30%). The present river displays a moribund, stable channel where (i) redistribution of sediment along the river course no longer occurs and (ii) channel forms constitute a remnant of a fluvial environment created before closing the dam, under conditions of higher energy. In addition to providing new information on the complex geomorphic response of dryland rivers to impoundment, this paper represents the very first geomorphic assessment of the regulated Sauce Grande and therefore provides an important platform to underpin further research assessing the geomorphic state of this highly regulated dryland river.

Characterization of landslide dams in the San Juan province (Argentina)

Science.gov (United States)

Penna, Ivanna; Longchamp, Celine; Derron, Marc-Henri; Jaboyedoff, Michel

2013-04-01

River blockages caused by landslide deposition are common phenomena in active mountain chains, influencing erosion-sedimentation patterns and acting as primary and secondary hazards. Regional scale analyses regarding their spatial distribution and morphometry allow establishing boundary conditions for their occurrence and stability, and determine differences among regions with different landscape and climatic conditions. Owing to the combination of endogenous and exogenous factors, landslide dams are frequent phenomena in the Andes. In the Argentinean NW and the Patagonian Andes, previous studies showed that stability of landslide dams determined by morphometric parameters generally matched satisfactorily with dam behavior, with some exceptions in which climatic component played an important role in dam longevity. Aiming to expand the knowledge of landslide dams in the Argentinean Andes, in this work we analyzed the stability of rock avalanche dams in the Pampeam flat slab subduction zone. In the study area, mountain dynamics creates suitable conditions for the occurrence of 34 rock avalanches with volumes up to 0.3 km3. They developed in deeply carved valleys (Cordillera) and Inter-thrust valleys (Precordillera). 22 impoundments of rivers resulted from channelized rock avalanches with long runouts (4-10 km) that blocked tributaries rivers, but most of them by rock avalanches that filled the valley bottom, with run up in the opposite slope and limited movement parallel to the valley axis. Most of the dams breached in unknown times, except for the last event that occurred on November 12th 2005. The quantification of morphometric parameters and contributing areas indicates the existence of dams with dimensionless blockage index above 2.75 (stable domain) and below 3.08 (instable domain). The Los Erizos dam in our study area and the Barrancas dam in the Patagonian Andes show that besides morphometric parameters, climatic conditions are decisive. Stable landslide dams

Synthesis of common management concerns associated with dam removal

Science.gov (United States)

Tullos, Desiree D.; Collins, Mathias J.; Bellmore, J. Ryan; Bountry, Jennifer A.; Connolly, Patrick J.; Shafroth, Patrick B.; Wilcox, Andrew C.

2016-01-01

Managers make decisions regarding if and how to remove dams in spite of uncertainty surrounding physical and ecological responses, and stakeholders often raise concerns about certain negative effects, regardless of whether or not these concerns are warranted at a particular site. We used a dam-removal science database supplemented with other information sources to explore seven frequently-raised concerns, herein Common Management Concerns (CMCs). We investigate the occurrence of these concerns and the contributing biophysical controls. The CMCs addressed are: degree and rate of reservoir sediment erosion, excessive channel incision upstream of reservoirs, downstream sediment aggradation, elevated downstream turbidity, drawdown impacts on local water infrastructure, colonization of reservoir sediments by non-native plants, and expansion of invasive fish. Biophysical controls emerged for some of the concerns, providing managers with information to assess whether a given concern is likely to occur at a site. To fully assess CMC risk, managers should concurrently evaluate site conditions and identify the ecosystem or human uses that will be negatively affected if the biophysical phenomenon producing the CMC occurs. We show how many CMCs have one or more controls in common, facilitating the identification of multiple risks at a site, and demonstrate why CMC risks should be considered in the context of other factors like natural watershed variability and disturbance history.

Plugs or flood-makers? the unstable landslide dams of eastern Oregon

Science.gov (United States)

Safran, Elizabeth B.; O'Connor, Jim E.; Ely, Lisa L.; House, P. Kyle; Grant, Gordon E.; Harrity, Kelsey; Croall, Kelsey; Jones, Emily

2015-01-01

data sets successfully separate dam sites in eastern Oregon that failed catastrophically from those that did not. Accumulated sediments upstream of about 50% of the dam sites indicate at least short-term persistence of landslide dams prior to eventual failure. Nevertheless, only three landslide dam remnants and one extant dam significantly elevate the modern river profile. We conclude that eastern Oregon's landslide dams are indeed floodmakers, but we lack clear evidence that they form lasting plugs.

Effects of removing Good Hope Mill Dam on selected physical, chemical, and biological characteristics of Conodoguinet Creek, Cumberland County, Pennsylvania

Science.gov (United States)

Chaplin, Jeffrey J.; Brightbill, Robin A.; Bilger, Michael D.

2005-01-01

The implications of dam removal on channel characteris-tics, water quality, benthic invertebrates, and fish are not well understood because of the small number of removals that have been studied. Comprehensive studies that document the effects of dam removal are just beginning to be published, but most research has focused on larger dams or on the response of a sin-gle variable (such as benthic invertebrates). This report, pre-pared in cooperation with the Conodoguinet Creek Watershed Association, provides an evaluation of how channel morphol-ogy, bed-particle-size distribution, water quality, benthic inver-tebrates, fish, and aquatic habitat responded after removal of Good Hope Mill Dam (a small 'run of the river' dam) from Conodoguinet Creek in Cumberland County, Pa. Good Hope Mill Dam was a 6-foot high, 220-foot wide concrete structure demolished and removed over a 3-day period beginning with the initial breach on November 2, 2001, at 10:00 a.m. eastern standard time. To isolate the effects of dam removal, data were collected before and after dam removal at five monitoring stations and over selected reaches upstream, within, and downstream of the impoundment. Stations 1, 2, and 5 were at free-flowing control locations 4.9 miles upstream, 2.5 miles upstream, and 5 miles downstream of the dam, respec-tively. Stations 3 and 4 were located where the largest responses were anticipated, 115 feet upstream and 126 feet downstream of the dam, respectively Good Hope Mill Dam was not an effective barrier to sedi-ment transport. Less than 3 inches of sediment in the silt/clay-size range (less than 0.062 millimeters) coated bedrock within the 7,160-foot (1.4-mile) impoundment. The bedrock within the impoundment was not incised during or after dam removal, and the limited sediment supply resulted in no measurable change in the thalweg elevation downstream of the dam. The cross-sec-tional areas at stations 3 and 4, measured 17 days and 23 months after dam removal, were within

Experiments on sediment pulses in mountain rivers

Science.gov (United States)

Y. Cui; T. E. Lisle; J. E. Pizzuto; G. Parker

1998-01-01

Pulses of sediment can be introduced into mountain rivers from such mechanisms as debris flows, landslides and fans at tributary confluences. These processes can be natural or associated with the activities of humans, as in the case of a pulse created by sediment derived from timber harvest or the removal of a dam. How does the river digest these pulses?

Particle size distribution of main-channel-bed sediments along the upper Mississippi River, USA

Science.gov (United States)

Remo, Jonathan; Heine, Ruben A.; Ickes, Brian

2016-01-01

In this study, we compared pre-lock-and-dam (ca. 1925) with a modern longitudinal survey of main-channel-bed sediments along a 740-km segment of the upper Mississippi River (UMR) between Davenport, IA, and Cairo, IL. This comparison was undertaken to gain a better understanding of how bed sediments are distributed longitudinally and to assess change since the completion of the UMR lock and dam navigation system and Missouri River dams (i.e., mid-twentieth century). The comparison of the historic and modern longitudinal bed sediment surveys showed similar bed sediment sizes and distributions along the study segment with the majority (> 90%) of bed sediment samples having a median diameter (D50) of fine to coarse sand. The fine tail (≤ D10) of the sediment size distributions was very fine to medium sand, and the coarse tail (≥ D90) of sediment-size distribution was coarse sand to gravel. Coarsest sediments in both surveys were found within or immediately downstream of bedrock-floored reaches. Statistical analysis revealed that the particle-size distributions between the survey samples were statistically identical, suggesting no overall difference in main-channel-bed sediment-size distribution between 1925 and present. This was a surprising result given the magnitude of river engineering undertaken along the study segment over the past ~ 90 years. The absence of substantial differences in main-channel-bed-sediment size suggests that flow competencies within the highly engineered navigation channel today are similar to conditions within the less-engineered historic channel.

Particle-borne radionuclides as tracers for sediment in the Susquehanna River and Chesapeake Bay

Energy Technology Data Exchange (ETDEWEB)

Donoghue, J F [Florida State Univ., Tallahassee, FL (USA). Dept. of Geology; Bricker, O P [Geological Survey, Reston, VA (USA). Water Resources Div.; Olsen, C R [Oak Ridge National Lab., TN (USA)

1989-10-01

The Chesapeake Bay receives nearly 1,000,000 tonnes of sediment annually from its major tributary, the Susquehanna River. The pattern of deposition of this sediment affects the lifetime of the estuarine resource and the fate of any sediment-borne contaminants. Previous estimates of the extent to which Susquehanna River sediment is transported down the Chesapeake have differed considerably. By use of reactor-generated radionuclides adsorbed on the river sediment, a sediment budget has been compiled for the upper Chesapeake Bay and the reservoirs on the lower Susquehanna. Reservoirs impound nearly 1,400,000 tonnes of sediment annually behind the power dams on the lower Susquehanna River. Without the dams, sediment delivery to the upper bay would more than double. The uppermost Chesapeake Bay, within and above the turbidity maximum, retains virtually all of the fluvial sediment delivered to it. The result is an annual sedimentation rate of approximately 3 mm yr{sup -1} in the upper bay, an infilling rate that is nearly equal to the regional rate of sea level rise. (author).

Particle-borne radionuclides as tracers for sediment in the Susquehanna River and Chesapeake Bay

International Nuclear Information System (INIS)

Donoghue, J.F.

1989-01-01

The Chesapeake Bay receives nearly 1,000,000 tonnes of sediment annually from its major tributary, the Susquehanna River. The pattern of deposition of this sediment affects the lifetime of the estuarine resource and the fate of any sediment-borne contaminants. Previous estimates of the extent to which Susquehanna River sediment is transported down the Chesapeake have differed considerably. By use of reactor-generated radionuclides adsorbed on the river sediment, a sediment budget has been compiled for the upper Chesapeake Bay and the reservoirs on the lower Susquehanna. Reservoirs impound nearly 1,400,000 tonnes of sediment annually behind the power dams on the lower Susquehanna River. Without the dams, sediment delivery to the upper bay would more than double. The uppermost Chesapeake Bay, within and above the turbidity maximum, retains virtually all of the fluvial sediment delivered to it. The result is an annual sedimentation rate of approximately 3 mm yr -1 in the upper bay, an infilling rate that is nearly equal to the regional rate of sea level rise. (author)

Sources and levels of concentration of metal pollutants in Kubanni dam, Zaria, Nigeria

Directory of Open Access Journals (Sweden)

Butu, A.W.

2013-06-01

Full Text Available The paper looked at the sources and levels of concentration of metal pollutants in Kubanni dam, Zaria, Nigeria. The main sources of data for the study were sediment from four different sections of the long profile of the dam. The samples were prepared in the laboratory according to standard methods and the instrumental Neutron Activation Analysis (INAA technique was adopted in the analysis using Nigeria Research Reactor – 1 (NIRR – 1. The results of the analysis showed that 29 metal pollutants; Mg, Al, Ca, Ti, V, Mn, Dy, Na, K, As, La, Sm, Yb, U, Br, Sc, Cr, Fe, Co, Rb, Zn,Cs, Ba, Eu, Lu, Hf, Ta, Sb and Th currently exist in Kubanni dam in various levels of concentrations. The results showed that most of the metal pollutants in the dam are routed to anthropogenic activities within the dam catchment area while few are routed to geologic formation. The results further revealed that metal pollutants that their sources are traceable to refuse dumps, farmlands, public drains and effluents showed higher levels of concentration in the dam than the ones that are gradually released from the soil regolith system.

Natural radioactivity levels in lake sediment samples

International Nuclear Information System (INIS)

Eroglu, H.; Kabadayi, O.

2013-01-01

The radioactivity concentrations of nuclides 238 U, 232 Th and 40 K in lake sediments collected from 15 different stations at Altinkaya dam lake and 12 different stations at Derbent dam lake in Turkey were measured using high-resolution gamma-ray spectrometry. The measurement was done using a coaxial HPGe detector system coupled to the Ortec-Dspect jr digital MCA system. The average measured activity concentrations of the nuclides 238 U, 232 Th and 40 K were found to be 19.5, 27.7 and 460 Bq kg -1 in Altinkaya dam, whereas the activity concentrations were 18.8, 25.5 and 365 Bq kg -1 in Derbent dam, respectively. The measured activity concentrations in the present study have been compared with similar measurements from different locations in the world. (authors)

Dam Safety Concepts

NARCIS (Netherlands)

Duricic, J.

2014-01-01

The majority of dams constructed in the world are dams that can be categorized as embankment dams. Throughout history we can point to many failures of dams, and embankment dams in particular. Nowadays it is clear that the goal to construct stable dams has not been achieved, even with advanced

Adjustments in channel morphology due to land-use changes and check dam installation in mountain torrents of Calabria (Southern Italy)

Science.gov (United States)

Fortugno, Diego; Zema, Demetrio Antonio; Bombino, Giuseppe; Tamburino, Vincenzo; Quinonero Rubio, Juan Manuel; Boix-Fayos, Carolina

2016-04-01

In Mediterranean semi-arid conditions the geomorphic effects of land-use changes and check dam installation on active channel headwater morphology are not completely understood. In such environments, the availability of specific studies, which monitor channel adjustments as a response to reforestation and check dams over representative observation periods, could help develop new management strategies and erosion control measures. This investigation is an integrated approach assessing the adjustments of channel morphology in a typical torrent (Sant'Agata, Calabria, Southern Italy) after land-use changes (e.g. fire, reforestation, land abandonment) and check dam construction across a period of about 60 years (1955-2012). A statistical analysis of historical rainfall records, an analysis of land-use change in the catchment area and a geomorphological mapping of channel adjustments were carried out and combined with field surveys of bed surface grain-size over a 5-km reach including 14 check dams. The analysis of the historical rainfall records showed a slight decrease in the amount and erosivity of precipitation. Mapping of land-use changes highlighted a general increase of vegetal coverage on the slopes adjacent to the monitored reaches. Together with the check dam network installation, this increase could have induced a reduction in water and sediment supply. The different erosional and depositional forms and adjustments showed a general narrowing between consecutive check dams together with local modifications detected upstream (bed aggradation and cross section expansion together with low-flow realignments) and downstream (local incision) of the installed check dams. Changes in the torrent bends were also detected as a response to erosional and depositional processes with different intensities. The study highlighted: (i) the efficiency of check dams against the disrupting power of the most intense floods by stabilising the active channel; and (ii) the influence of

Genome sequence of the acid-tolerant Desulfovibrio sp. DV isolated from the sediments of a Pb-Zn mine tailings dam in the Chita region, Russia

Directory of Open Access Journals (Sweden)

Anastasiia Kovaliova

2017-03-01

Full Text Available Here we report the draft genome sequence of the acid-tolerant Desulfovibrio sp. DV isolated from the sediments of a Pb-Zn mine tailings dam in the Chita region, Russia. The draft genome has a size of 4.9 Mb and encodes multiple K+-transporters and proton-consuming decarboxylases. The phylogenetic analysis based on concatenated ribosomal proteins revealed that strain DV clusters together with the acid-tolerant Desulfovibrio sp. TomC and Desulfovibrio magneticus. The draft genome sequence and annotation have been deposited at GenBank under the accession number MLBG00000000.

Interactions Study of Hydrodynamic-Morphology-Vegetation for Dam-Break Flows

Directory of Open Access Journals (Sweden)

Mingliang Zhang

2016-01-01

Full Text Available This study models a dam-break flow over a bed by using a depth-averaged numerical model based on finite-volume method and computes the dam-break flow and bed morphology characteristics. The generalized shallow water equations considering the sediment transport and bed change on dam-break flow are adopted in the numerical model, and the vegetation effects on the flow and morphological changes are considered. The model is verified against three cases from the laboratory and field data documented in the literature. The numerical results are consistent with the measured results, which show that the model could accurately simulate the evolution of the dam-break flows and the morphology evolution of bed within a computational domain with complex plant distribution. The results show that the riparian vegetation in the waterway narrows the channel and reduces the conveyance capacity of river. The flood flow is diverted away from the vegetation community toward two sides and forms a weak flow region behind the vegetation domain. The resistance of plants markedly reduces the flow velocity, which directly alters the fluvial processes and influences the waterway morphology.

Long-term Records of Trace Metal Elements in Core Sediments: Anthropogenic Impacts in The Eure River Watershed

Science.gov (United States)

Gardes, T.; Debret, M.; Copard, Y.; Patault, E.; Deloffre, J.; Marcotte, S.; Develle, A. L.; Sabatier, P.; Chaumillon, E.; Coulombier, T.; Revillon, S.; Nizou, J.; Laberdesque, Y.; Koltalo, F.

2017-12-01

The Martot Dam is located in the Eure River Watershed (Normandy, France), few hundred meters upstream the Eure-Seine Rivers confluence. In the context of the European Water Framework Directive (2000/60/EC), the French Authorities planned to remove this dam in 2017. Nevertheless, impacts of the removal remain poorly studied. Classically, dam blocked sedimentary transfers downstream, but here, sediments are not blocked behind the dam but stored three hundred meters upstream in a hydraulic annex, called the Martot Pond. Furthermore, this pond is submitted to the tidal flow from the Seine Estuary despite the Martot Dam. The aim of the study is to evaluate the dam removal impacts on sedimentary transfers and re-suspension of contaminated sediments stored in the Martot Pond and the Eure River's channel. Concerning past transfers and sediments accumulation in the Eure River Watershed, sedimentary archives have been cored, before dam removal, at the Martot Pond and the Les Damps Pond (located 10km upstream the latter). Dating of sedimentary cores for both ponds indicates a sedimentation rate around 1 cm y-1. Trace metal elements quantification showed a wide metallic contamination with highest concentrations evidenced during the 1950-1960's (As: 13-22 mg kg-1; Cd: 40-55 mg kg-1; Cr: 170-210 mg kg-1; Cu: 400-490 mg kg-1; Hg: 2.3 mg kg-1; Mn: 1,280-2,200 mg kg-1; Ni: 64-75 mg kg-1; Zn: 905-990 mg kg-1) and the 1990-2000's (Cr: 95-215 mg kg-1; Ni: 100 mg kg-1; Pb: 670-855 mg kg-1). These variations of concentrations along cores can be associated with industrial past of the Eure River Watershed and sources of contamination can be identified. Thereby, Zn, Ni or Hg contamination could be associated with wastes of battery factory released in the Eure River during the economic recovery, while Pb contamination is linked to the activities of a cathode-ray tubes factory. Metals quantification in core materials highlighted anthropogenic impacts in the Eure River Watershed. These

Geomorphic change and sediment transport during a small artificial flood in a transformed post-dam delta: The Colorado River delta, United States and Mexico

Science.gov (United States)

Mueller, Erich R.; Schmidt, John C.; Topping, David J.; Shafroth, Patrick B.; Rodríguez-Burgueño, Jesús Eliana; Ramírez-Hernández, Jorge; Grams, Paul E.

2017-01-01

The Colorado River delta is a dramatically transformed landscape. Major changes to river hydrology and morpho-dynamics began following completion of Hoover Dam in 1936. Today, the Colorado River has an intermittent and/or ephemeral channel in much of its former delta. Initial incision of the river channel in the upstream ∼50 km of the delta occurred in the early 1940s in response to spillway releases from Hoover Dam under conditions of drastically reduced sediment supply. A period of relative quiescence followed, until the filling of upstream reservoirs precipitated a resurgence of flows to the delta in the 1980s and 1990s. Flow releases during extreme upper basin snowmelt in the 1980s, flood flows from the Gila River basin in 1993, and a series of ever-decreasing peak flows in the late 1990s and early 2000s further incised the upstream channel and caused considerable channel migration throughout the river corridor. These variable magnitude post-dam floods shaped the modern river geomorphology. In 2014, an experimental pulse-flow release aimed at rejuvenating the riparian ecosystem and understanding hydrologic dynamics flowed more than 100 km through the length of the delta’s river corridor. This small artificial flood caused localized meter-scale scour and fill of the streambed, but did not cause further incision or significant bank erosion because of its small magnitude. Suspended-sand-transport rates were initially relatively high immediately downstream from the Morelos Dam release point, but decreasing discharge from infiltration losses combined with channel widening downstream caused a rapid downstream reduction in suspended-sand-transport rates. A zone of enhanced transport occurred downstream from the southern U.S.-Mexico border where gradient increased, but effectively no geomorphic change occurred beyond a point 65 km downstream from Morelos Dam. Thus, while the pulse flow connected with the modern estuary, deltaic sedimentary processes were not

梳子坝对土石流之防治效率%The Controlling Efficiency of Slit Dam for Debris Flow Disaster

Institute of Scientific and Technical Information of China (English)

连惠邦; 柴钫武; 柯志宗

2001-01-01

Using mass conservation law of debris flow which passing through a slit dam and laboratory experiments, this paper has established three primary efficiency parameters: the sediment flow-out ratio, sediment concentration ratio, and sediment storage rate behind the slit dam. These efficiency parameters are developed to evaluate the effectiveness of the slit dam in retarding the debris flow and to design the height and spacing of posts and the location of a slit dam or a series of slit dams.%梳子坝是一种透过性坝体，可以有效地防止土石流之危害。因此，本研究经由土石流通过梳子坝的质量守恒定律和渠槽试验，分别建立土砂流出率、泥砂体积浓度比及贮砂率等三种主要的效率参数，作为评估梳子坝防治土石流之效率，并据以发展出一种简单的设计模式，可以用来设计单一梳子坝的高度、开口间距及总开口宽度等坝体几何因子。

Dam Break Analysis of Embankment Dams Considering Breach Characteristics

Directory of Open Access Journals (Sweden)

Abolfazl Shamsaei

2004-05-01

Full Text Available The study of dam's break, needs the definition of various parameters such as the break cause, its type, its dimension and the duration of breach development. The precise forecast for different aspects of the breach is one of the most important factors for analyzing it in embankment dam. The characteristics of the breach and determination of their vulnerability has the most effect on the waves resulting from dam break. Investigating, about the parameters of the breach in "Silveh" earth dam have been determined using the suitable model. In Silve dam a trapezoid breach with side slope z=0.01m and the average base line b=80m was computed. The duration of the breaches development is 1.9 hour. Regarding the above results and the application of DAM Break software the consequences of the probable break of the dam was determined. The analysis of the results of water covering of the city of Piranshahr located 12km from silve dam confirms that in 3 hours the water will reach the height (level of 1425 meters.

Impacts of the dam-orientated water-sediment regulation scheme on the lower reaches and delta of the Yellow River (Huanghe): A review

Science.gov (United States)

Wang, Houjie; Wu, Xiao; Bi, Naishuang; Li, Song; Yuan, Ping; Wang, Aimei; Syvitski, James P. M.; Saito, Yoshiki; Yang, Zuosheng; Liu, Sumei; Nittrouer, Jeffrey

2017-10-01

The water-sediment regulation scheme (WSRS), beginning in 2002, is an unprecedented engineering effort to manage the Yellow River with the aims to mitigate the siltation both in the lower river channel and within the Xiaolangdi Reservoir utilizing the dam-regulated flood water. Ten years after its initial implementation, multi-disciplinary indicators allow us to offer a comprehensive review of this human intervention on a river-coastal system. The WSRS generally achieved its objective, including bed erosion in the lower reaches with increasing capacity for flood discharge and the mitigation of reservoir siltation. However, the WSRS presented unexpected disturbances on the delta and coastal system. Increasing grain size of suspended sediment and decreasing suspended sediment concentration at the river mouth resulted in a regime shift of sediment transport patterns that enhanced the disequilibrium of the delta. The WSRS induced an impulse delivery of nutrients and pollutants within a short period ( 20 days), which together with the altered hydrological cycle, impacted the estuarine and coastal ecosystem. We expect that the sediment yield from the loess region in the future will decrease due to soil-conservation practices, and the lower channel erosion will also decrease as the riverbed armors with coarser sediment. These, in combination with uncertain water discharge concomitant with climate change, increasing water demands and delta subsidence, will put the delta and coastal ocean at high environmental risks. In the context of global change, this work depicts a scenario of human impacts in the river basin that were transferred along the hydrological pathway to the coastal system and remotely transformed the different components of coastal environment. The synthesis review of the WSRS indicates that an integrated management of the river-coast continuum is crucially important for the sustainability of the entire river-delta system. The lessons learned from the WSRS in

Audit Technical of Kori Rubber Dam in the River of Keyang District of Ponorogo East Java Province

Science.gov (United States)

Murnianto, E.; Suprapto, M.; Ikhsan, C.

2018-03-01

The development of science and technology for the utilization and protection of rivers has embodied various types of river infrastructure. Without proper maintenance, rapid river sediments undergo physical degradation and function. Problems that occur in Kori Rubber Dam, among others, the damage to the body of the rubber dam that is made of rubber, so that the function of flower deflection is not optimal. This happens because of limited operational and maintenance activities (OM). A technical audit is a process of identifying problems, analyzing, and evaluating ones conducted independently, objectively and professionally on the basis of examination, to assess the truth, accuracy, credibility, and reliability of information about a job. In this case an assessment of the Kori Rubber Dam, which is basically a benchmarking activity. Assessment of rubber dam components includes the physical conditions and functions that affect the weir. This research is expected to know the performance of Kori rubber Dam as a recommendation material in the implementation of OM Rubber Dam activities.

Multi-timescale sediment responses across a human impacted river-estuary system

Science.gov (United States)

Chen, Yining; Chen, Nengwang; Li, Yan; Hong, Huasheng

2018-05-01

Hydrological processes regulating sediment transport from land to sea have been widely studied. However, anthropogenic factors controlling the river flow-sediment regime and subsequent response of the estuary are still poorly understood. Here we conducted a multi-timescale analysis on flow and sediment discharges during the period 1967-2014 for the two tributaries of the Jiulong River in Southeast China. The long-term flow-sediment relationship remained linear in the North River throughout the period, while the linearity showed a remarkable change after 1995 in the West River, largely due to construction of dams and reservoirs in the upland watershed. Over short timescales, rainstorm events caused the changes of suspended sediment concentration (SSC) in the rivers. Regression analysis using synchronous SSC data in a wet season (2009) revealed a delayed response (average 5 days) of the estuary to river input, and a box-model analysis established a quantitative relationship to further describe the response of the estuary to the river sediment input over multiple timescales. The short-term response is determined by both the vertical SSC-salinity changes and the sediment trapping rate in the estuary. However, over the long term, the reduction of riverine sediment yield increased marine sediments trapped into the estuary. The results of this study indicate that human activities (e.g., dams) have substantially altered sediment delivery patterns and river-estuary interactions at multiple timescales.

Sources of suspended-sediment loads in the lower Nueces River watershed, downstream from Lake Corpus Christi to the Nueces Estuary, south Texas, 1958–2010

Science.gov (United States)

Ockerman, Darwin J.; Heitmuller, Franklin T.; Wehmeyer, Loren L.

2013-01-01

The U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, Fort Worth District; City of Corpus Christi; Guadalupe-Blanco River Authority; San Antonio River Authority; and San Antonio Water System, developed, calibrated, and tested a Hydrological Simulation Program-FORTRAN (HSPF) watershed model to simulate streamflow and suspended-sediment concentrations and loads during 1958-2010 in the lower Nueces River watershed, downstream from Lake Corpus Christi to the Nueces Estuary in south Texas. Data available to simulate suspended-sediment concentrations and loads consisted of historical sediment data collected during 1942-82 in the study area and suspended-sediment concentration data collected periodically by the USGS during 2006-7 and 2010 at three USGS streamflow-gaging stations (08211000 Nueces River near Mathis, Tex. [the Mathis gage], 08211200 Nueces River at Bluntzer, Tex. [the Bluntzer gage], and 08211500 Nueces River at Calallen, Tex. [the Calallen gage]), and at one ungaged location on a Nueces River tributary (USGS station 08211050 Bayou Creek at Farm Road 666 near Mathis, Tex.). The Mathis gage is downstream from Wesley E. Seale Dam, which was completed in 1958 to impound Lake Corpus Christi. Suspended-sediment data collected before and after completion of Wesley E. Seale Dam provide insights to the effects of the dam and reservoir on suspended-sediment loads transported by the lower Nueces River downstream from the dam to the Nueces Estuary. Annual suspended-sediment loads at the Nueces River near the Mathis, Tex., gage were considerably lower for a given annual mean discharge after the dam was completed than before the dam was completed.

The role of Lake Dongting in regulating the sediment budget of the Yangtze River

Directory of Open Access Journals (Sweden)

Shi-bao Dai

2005-01-01

Full Text Available Lake Dongting, the second largest freshwater lake in China and located in the middle reaches of the River Yangtze catchment, was formed at the beginning of the Holocene period by sea level rise and has varied in size with changes in local weather patterns. The sedimentation rate in Lake Dongting during the Holocene is about 50×106 m3 yr-1, or 80×106 t yr-1 (a sand bulk density of 1.6×103 kg m-3, given the sediment deposition rate as 10 mm yr-1 and the average lake size as 5000 km2. By comparing the sediment import and export, it is estimated that the sediment deposition rate of Lake Dongting was 110.6×106 t yr-1 from 1956 to 2003. Siltation and raised embankments reduced the size of the lake and its capacity to accommodate floods. The sediment delivery ratio (SDR of the middle and lower Yangtze is about 0.92 (total sediment output divided by total sediment input given that the total sediment supply into the middle and lower Yangtze is 455.1×106 t yr-1 and the total sediment discharge into the sea is 419×106 t yr-1. Therefore, if it were not for Lake Dongting, the sediment flux at Datong would be 73.6×106 t yr-1 (80×106 t yr-1×0.92 more, an increase of 27% during the Holocene and an increase of 26% to 101.75×106 t yr-1 from 1956 to 2003. Historically, Lake Dongting had a considerable influence in regulating the sediment budget of the Yangtze. However, afforestation and the construction of large dams, such as the Three Gorges Dam, reduced significantly the sediment deposition in Lake Dongting. In 2003, the completion of the Three Gorges Dam and the subsequent impoundment of water reduced the sediment input from the Yangtze and net deposition in Lake Dongting dropped to 25% and 18% of the mean values of the historic records (1956-2003. During the same period, the amount of sediment deposited in Lake Dongting was only 10% of the sediment discharge at Datong. The influence of the sediment deposited in Lake Dongting on the sediment flux to

Impact of Watershed Development on Sediment Transport and Seasonal Flooding in the Main Stream of the Mekong River

Science.gov (United States)

Kameyama, S.; Nohara, S.; Sato, T.; Fujii, Y.; Kudo, K.

2009-12-01

The Mekong River watershed is undergoing rapid economic progress and population growth, raising conflicts between watershed development and environmental conservation. A typical conflict is between the benefits of dam construction versus the benefits of watershed ecological services. In developed countries, this conflict is changing to a coordinated search for outcomes that are mutually acceptable to all stakeholders. In the Mekong River, however, government policy gives priority to watershed development for ensuring steady energy supplies. Since the 1990s, a series of dams called “the Mekong Cascade” have been under construction. Dam construction has multiple economic values as electric power supply, irrigation water, flood control, etc. On the other hand, the artificial flow discharge controls of dam moderate seasonal hydrologic patterns of the Asian monsoon region. Dam operations can change the sediment transport regime and river structure. Furthermore, their impacts on watershed ecosystems and traditional economic activities of fisheries and agriculture in downstream areas may be severe. We focus on dam impacts on spatio-temporal patterns of sediment transport and seasonal flood in riparian areas downstream from Mekong River dams. Our study river section is located on 100 km down stream from the Golden Triangle region of Myanmar, Laos, and Thailand. We selected a 10-km section in this main channel to simulate seasonal flooding. We modeled the river hydrology in the years 1991 and 2002, before and after the Manwan dam construction (1986-1993). For this simulation, we adapted three models (distributed runoff model, 1-D hydrological model, and 2-D flood simulation with sediment movement algorithm.) Input data on river structure, water velocity, and flow volume were acquired from field survey data in November 2007 and 2008. In the step of parameter decision, we adopted the shuffled complex evolution method. To validate hydrologic parameters, we used annual

The Effects of Urbanization and Flood Control on Sediment Discharge of a Southern California River, Evidence of a Dilution Effect

Science.gov (United States)

Warrick, J. A.; Orzech, K. M.; Rubin, D. M.

2004-12-01

The southern California landscape has undergone dramatic urbanization and population growth during the past 60 years and currently supports almost 20 million inhabitants. During this time, rivers of the region have been altered with damming, channel straightening and hardening, and water transfer engineering. These changes have drastically altered water and sediment discharge from most of the region's drainage basins. Here we focus on changes in sediment discharge from the largest watershed of southern California, the Santa Ana River. Order-of-magnitude drops in the suspended sediment rating curves (the relationship between suspended sediment concentration and instantaneous river discharge) are observed between 1967 and 2001, long after the construction of a major flood control dam in 1941. These sediment concentration decreases do not, however, represent alteration of the total sediment flux from the basin (a common interpretation of sediment rating curves), but rather a dilution of suspended sediment by increases (approx. 4x) in stormwater discharge associated with urbanization. Increases in peak and total stormwater discharge are consistent with runoff patterns from urbanizing landscapes, supporting our hypothesis that the diluting water originated from stormwater runoff generated in urban areas both up- and downstream of dams. Our dilution hypothesis is further supported with water and sediment budgets, dilution calculations, and suspended and bed grain size information.

Qualitative simulation of bathymetric changes due to reservoir sedimentation: A Japanese case study.

Directory of Open Access Journals (Sweden)

Ahmed Bilal

Full Text Available Sediment-dynamics modeling is a useful tool for estimating a dam's lifespan and its cost-benefit analysis. Collecting real data for sediment-dynamics analysis from conventional field survey methods is both tedious and expensive. Therefore, for most rivers, the historical record of data is either missing or not very detailed. Available data and existing tools have much potential and may be used for qualitative prediction of future bathymetric change trend. This study shows that proxy approaches may be used to increase the spatiotemporal resolution of flow data, and hypothesize the river cross-sections and sediment data. Sediment-dynamics analysis of the reach of the Tenryu River upstream of Sakuma Dam in Japan was performed to predict its future bathymetric changes using a 1D numerical model (HEC-RAS. In this case study, only annually-averaged flow data and the river's longitudinal bed profile at 5-year intervals were available. Therefore, the other required data, including river cross-section and geometry and sediment inflow grain sizes, had to be hypothesized or assimilated indirectly. The model yielded a good qualitative agreement, with an R2 (coefficient of determination of 0.8 for the observed and simulated bed profiles. A predictive simulation demonstrated that the useful life of the dam would end after the year 2035 (±5 years, which is in conformity with initial detailed estimates. The study indicates that a sediment-dynamic analysis can be performed even with a limited amount of data. However, such studies may only assess the qualitative trends of sediment dynamics.

Qualitative simulation of bathymetric changes due to reservoir sedimentation: A Japanese case study.

Science.gov (United States)

Bilal, Ahmed; Dai, Wenhong; Larson, Magnus; Beebo, Qaid Naamo; Xie, Qiancheng

2017-01-01

Sediment-dynamics modeling is a useful tool for estimating a dam's lifespan and its cost-benefit analysis. Collecting real data for sediment-dynamics analysis from conventional field survey methods is both tedious and expensive. Therefore, for most rivers, the historical record of data is either missing or not very detailed. Available data and existing tools have much potential and may be used for qualitative prediction of future bathymetric change trend. This study shows that proxy approaches may be used to increase the spatiotemporal resolution of flow data, and hypothesize the river cross-sections and sediment data. Sediment-dynamics analysis of the reach of the Tenryu River upstream of Sakuma Dam in Japan was performed to predict its future bathymetric changes using a 1D numerical model (HEC-RAS). In this case study, only annually-averaged flow data and the river's longitudinal bed profile at 5-year intervals were available. Therefore, the other required data, including river cross-section and geometry and sediment inflow grain sizes, had to be hypothesized or assimilated indirectly. The model yielded a good qualitative agreement, with an R2 (coefficient of determination) of 0.8 for the observed and simulated bed profiles. A predictive simulation demonstrated that the useful life of the dam would end after the year 2035 (±5 years), which is in conformity with initial detailed estimates. The study indicates that a sediment-dynamic analysis can be performed even with a limited amount of data. However, such studies may only assess the qualitative trends of sediment dynamics.

NRC inventory of dams

International Nuclear Information System (INIS)

Lear, G.E.; Thompson, O.O.

1983-01-01

The NRC Inventory of Dams has been prepared as required by the charter of the NRC Dam Safety Officer. The inventory lists 51 dams associated with nuclear power plant sites and 14 uranium mill tailings dams (licensed by NRC) in the US as of February 1, 1982. Of the 85 listed nuclear power plants (148 units), 26 plants obtain cooling water from impoundments formed by dams. The 51 dams associated with the plants are: located on a plant site (29 dams at 15 plant sites); located off site but provide plant cooling water (18 dams at 11 additional plant sites); and located upstream from a plant (4 dams) - they have been identified as dams whose failure, and ensuing plant flooding, could result in a radiological risk to the public health and safety. The dams that might be considered NRC's responsibility in terms of the federal dam safety program are identified. This group of dams (20 on nuclear power plant sites and 14 uranium mill tailings dams) was obtained by eliminating dams that do not pose a flooding hazard (e.g., submerged dams) and dams that are regulated by another federal agency. The report includes the principal design features of all dams and related useful information

The modified swirl sedimentation tanks for water purification.

Science.gov (United States)

Ochowiak, Marek; Matuszak, Magdalena; Włodarczak, Sylwia; Ancukiewicz, Małgorzata; Krupińska, Andżelika

2017-03-15

This paper discusses design, evaluation, and application for the use of swirl/vortex technologies as liquid purification system. A study was performed using modified swirl sedimentation tanks. The vortex separators (OW, OWK, OWR and OWKR) have been studied under laboratory conditions at liquid flow rate from 2.8⋅10 -5 to 5.1⋅10 -4 [m 3 /s]. The pressure drop and the efficiency of purification of liquid stream were analyzed. The suspended particles of different diameters were successfully removed from liquid with the application of swirl chambers of proposed constructions. It was found that damming of liquid in the tank increases alongside liquid stream at the inlet and depends on the tank construction. The efficiency of the sedimentation tanks increases alongside the diameters of solid particles and decrease in the liquid flow rate. The best construction proved to be the OWR sedimentation tank due to smallest liquid damming, even at high flow rates, and the highest efficiency of the purification liquid stream for solid particles of the smallest diameter. The proposed solution is an alternative to the classical constructions of sedimentation tanks. Copyright © 2016 Elsevier Ltd. All rights reserved.

Freshwater mussel survey for the Columbia Dam removal, Paulins Kill, New Jersey

Science.gov (United States)

Galbraith, Heather S.; Blakeslee, Carrie J.; Cole, Jeffrey C.; Silldorff, Erik L.

2018-06-04

Semi-quantitative mussel surveys, conducted by the U.S. Geological Survey and the Delaware Riverkeeper Network in cooperation with The Nature Conservancy, were completed in the vicinity of the Columbia Dam, on the Paulins Kill, New Jersey, in August 2017 in order to document the mussel species composition and relative abundance prior to removal of the dam. Surveys were conducted from the Brugler Road Bridge downriver approximately 2,000 meters (m) to the Columbia Dam and downriver from the dam about 300 m to 75 m upriver from the confluence of the Paulins Kill with the Delaware River. Sixteen sections (average length=175 m) were surveyed by personnel snorkeling or SCUBA diving; 13 sections were upriver from the dam, and 3 were downriver from the dam. Mussels, as they were encountered by surveyors, were removed from the sediment, immediately identified to species, and replaced in their original collection locations. Habitat data were collected for each surveyed section. Upriver and downriver from the dam, river margins with dense vegetation were examined for mussels by personnel using snorkels in transects (approximately 25 meters) perpendicular to river flow every 50 m on both sides of the river. Only two species were found upriver from the dam, and those were present in relatively low numbers. Catch per unit effort is reported here within parentheses as the average across upriver sections in number of mussels per person hour of survey time: 42 Elliptio complanata (2.6) and 1 Pyganodon cataracta (0.1) were found upriver from the dam. No mussels were found in the dense vegetation either upriver or downriver of the dam by surveyors using snorkels. Significantly higher species richness and mussel catch per unit effort were found downriver from the dam than upriver, including 106 E. complanta (32.5), 27 Utterbackiana implicata (8.2), 1 Alasmidonta undulata (0.4), 2 Lampsilis cariosa (0.5), 6 Lampsilis radiata (2.1), 4 P. cataracta (1.1), and 1 Strophitus undulatus (0

The environmental impacts of one of the largest tailing dam failures worldwide.

Science.gov (United States)

Hatje, Vanessa; Pedreira, Rodrigo M A; de Rezende, Carlos Eduardo; Schettini, Carlos Augusto França; de Souza, Gabriel Cotrim; Marin, Danieli Canaver; Hackspacher, Peter Christian

2017-09-06

The impacts of the SAMARCO iron tailing spill along more than 650 km, between the dam and the plume of the Doce River in the Atlantic, were assessed by the determination of toxic metals. The tailing spill caused a substantial increase in suspended sediment loads (up to 33,000 mg L -1 ), in addition to large depositions of waste along the Doce basin. The highest estimated transport of dissolved metals was observed for Fe (58.8 μg s -1 ), Ba (37.9 μg s -1 ) and Al (25.0 μg s -1 ). Sediments reached the highest enrichment factors (EFs) for Hg (4,234), Co (133), Fe (43), and Ni (16), whereas As (55), Ba (64), Cr (16), Cu (17), Mn (41), Pb (38) and Zn (82) highest EFs were observed for suspended particulate matter (SPM). Iron, As, Hg, Mn exceeded sediment quality guidelines. Therefore, the risk of occurrence of adverse effects is highly possible, not only due to the dam failure, but also due to the Fe mining and the artisan Au mining. Heavy rain episodes will likely cause enhanced erosion, remobilization, and transport of contaminated particles, sustaining high inputs of SPM and metals for the years to come and threatening the ecosystem services.

Effects of catastrophic floods and debris flows on the sediment retention structure, North Fork Toutle River, Washington

Science.gov (United States)

Denlinger, Roger P.

2012-01-01

The eruption of Mount St. Helens in 1980 produced a debris avalanche that flowed down the upper reaches of the North Fork Toutle River in southwestern Washington, clogging this drainage with sediment. In response to continuous anomalously high sediment flux into the Toutle and Cowlitz Rivers resulting from this avalanche and associated debris flows, the U.S. Army Corps of Engineers completed a Sediment Retention Structure (SRS) on the North Fork Toutle River in May 1989. For one decade, the SRS effectively blocked most of the sediment transport down the Toutle River. In 1999, the sediment level behind the SRS reached the elevation of the spillway base. Since then, a higher percentage of sediment has been passing the SRS and increasing the flood risk in the Cowlitz River. Currently (2012), the dam is filling with sediment at a rate that cannot be sustained for its original design life, and the U.S. Army Corps of Engineers is concerned with the current ability of the SRS to manage floods. This report presents an assessment of the ability of the dam to pass large flows from three types of scenarios (it is assumed that no damage to the spillway will occur). These scenarios are (1) a failure of the debris-avalanche blockage forming Castle Lake that produces a dambreak flood, (2) a debris flow from failure of that blockage, or (3) a debris flow originating in the crater of Mount St. Helens. In each case, the flows are routed down the Toutle River and through the SRS using numerical models on a gridded domain produced from a digital elevation model constructed with existing topography and dam infrastructure. The results of these simulations show that a structurally sound spillway is capable of passing large floods without risk of overtopping the crest of the dam. In addition, large debris flows originating from Castle Lake or the crater of Mount St. Helens never reach the SRS. Instead, debris flows fill the braided channels upstream of the dam and reduce its storage

Modeling the Impact of controlled flow and sediment releases for the restoration of the Nile Delta, Egypt

Science.gov (United States)

Al-Zaidi, B. M.; Moussa, A.; Viparelli, E.

2017-12-01

The construction of the High and Old Aswan Dams and of barrages significantly altered the flow and the sediment transport regimes in the Egyptian reach of the Nile River. The field data collected by the Nile Research Institute show that the post-High Aswan Dam Nile River hydrology is characterized by reductions of more than 70% in flow discharge and 98% in sediment load compared to pre-High Aswan Dam conditions. A significant portion of discharge released from the dams is diverted at the barrages for agricultural ( 80%) and municipal ( 15%) uses. Thus, virtually no water is reaching the Nile Delta and the Mediterranean Sea. Consequently, the sediment load delivered to the Mediterranean Sea is negligible compared to pre-dam conditions. Consequences of the flow regulation are delta wide wetland loss and shoreline retreat, widespread delta pollution, reduction soil quality, salination of cultivated land, wetland losses, and saltwater intrusion in the groundwater. Here we present the second part of a feasibility study for the restoration of the Nile River-Delta system characterized by controlled flow releases and sediment augmentations downstream of the High Aswan Dam. The controlled flow releases are obtained by regulating the current releases from the High Aswan Dam at the Old Aswan Dam, which is located 6.5 km downstream of the High Aswan Dam. Previous studies showed that 10 billion m3 of water can be saved annually by improving the Egyptian irrigation system. Here we propose to use the saved water to increase the water discharge to the Nile Delta, i.e., the total volume of water released from the dams does not change, what changes is the water used and the imposed hydrograph. We modulate the river flow by storing the saved water during the agriculture season upstream of the Old Aswan Dam and releasing it in the months coinciding with the natural river flood season. It is important to note that here we are considering the simplest possible scenario for water storage

Anthropogenic impact on biogenic substance distribution and bacterial community in sediment along the Yarlung Tsangpo River on Tibet Plateau, China

Science.gov (United States)

Wang, C.; Peifang, W.; Wang, X.; Hou, J.; Miao, L.

2017-12-01

Lotic river system plays an important part in water-vapor transfer and biogenic substances migration and transformation. Anthropogenic activities, including wastewater discharging and river damming, have altered river ecosystem and continuum. However, as the longest alpine river in China and suffered from increasing anthropogenic activities, the Yarlung Tsangpo River has been rarely studied. Recently, more attention has also been paid to the bacteria in river sediment as they make vital contributions to the biogeochemical nutrient cycling. Here, the distribution of biogenic substances, including nitrogen, phosphorus, silicon and carbon, was explored in both water and sediment of the Yarlung Tsangpo River. By using the next generation 16S rRNA sequencing, the bacterial diversity and structure in river sediment were presented. The results indicated that the nutrient concentrations increased in densely populated sites, revealing that biogenic substance distribution corresponded with the intensity of anthropogenic activity along the river. Nitrogen, phosphorus, silicon and carbon in water and sediment were all retained by the Zangmu Dam which is the only dam in the mainstream of the river. Moreover, the river damming decreased the biomass and diversity of bacteria in sediment, but no significant alteration of community structure was observed upstream and downstream of the dam. The most dominant bacteria all along the river was Proteobacteria. Meanwhile, Verrucomicrobia and Firmicutes also dominated the community composition in upstream and downstream of the river, respectively. In addition, total organic carbon (TOC) was proved to be the most important environmental factor shaping the bacterial community in river sediment. Our study offered the preliminary insights into the biogenic substance distribution and bacterial community in sediment along an alpine river which was affected by anthropogenic activities. In the future, more studies are needed to reveal the

Major, trace and rate earth elements in sediments of the Julian Adame-Alatorre dam by instrumental neutron activation analysis

International Nuclear Information System (INIS)

Mireles, F.; Pinedo, J. L.; Davila, J. I.; Oliva, J. E.; Speakman, R. J.; Glascock, M. D.

2010-10-01

The rapid industrial development in regions of Mexico during recent years has had the side effect of introducing toxic metals, fertilizers, and pesticides into the ecosystem. Sediment cores were collected from eight locations around the Julian Adame-Alatorre dam located in Municipality of Villanueva in the Zacatecas State, Mexico. The cores were analyzed for 32 major, trace, and rare earth elements (As, La, Lu, Nd, Sm, U, Yb, Ce, Co, Cr, Cs, Eu, Fe, Hf, Rb, Sb, Sc, Sr, Ta, Tb, Th, Zn, Zr, Al, Ba, Ca, Dy, K, Mn, Na, Ti, V) in order to estimate the health risk. The samples were analyzed by instrument neutron activation analysis using thermal neutron fluxes of 8 x 10 13 and 5 x 10 13 n cm -2 s -1 for short and long irradiations, respectively. The results of the contamination levels for elements such as As, Ba, Cr, Fe, Mn, Ta, V, and Zn were compared with the Mexican regulations and the guidelines of US EPA. (Author)

Geomorphology of the Elwha River and its Delta: Chapter 3 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

Science.gov (United States)

Warrick, Jonathan A.; Draut, Amy E.; McHenry, Michael L.; Miller, Ian M.; Magirl, Christopher S.; Beirne, Matthew M.; Stevens, Andrew Stevens; Logan, Joshua B.; Duda, Jeffrey J.; Warrick, Jonathan A.; Magirl, Christopher S.

2011-01-01

The removal of two dams on the Elwha River will introduce massive volumes of sediment to the river, and this increase in sediment supply in the river will likely modify the shapes and forms of the river and coastal landscape downstream of the dams. This chapter provides the geologic and geomorphologic background of the Olympic Peninsula and the Elwha River with emphasis on the present river and shoreline. The Elwha River watershed was formed through the uplift of the Olympic Mountains, erosion and movement of sediment throughout the watershed from glaciers, and downslope movement of sediment from gravitational and hydrologic forces. Recent alterations to the river morphology and sediment movement through the river include the two large dams slated to be removed in 2011, but also include repeated bulldozing of channel boundaries, construction and maintenance of flood plain levees, a weir and diversion channel for water supply purposes, and engineered log jams to help enhance river habitat for salmon. The shoreline of the Elwha River delta has changed in location by several kilometers during the past 14,000 years, in response to variations in the local sea-level of approximately 150 meters. Erosion of the shoreline has accelerated during the past 80 years, resulting in landward movement of the beach by more than 200 meters near the river mouth, net reduction in the area of coastal wetlands, and the development of an armored low-tide terrace of the beach consisting primarily of cobble. Changes to the river and coastal morphology during and following dam removal may be substantial, and consistent, long-term monitoring of these systems will be needed to characterize the effects of the dam removal project.

A Bird's-eye View with X-ray Vision: Remote-sensing tools to Monitor Reach-scale Response to Dam Removal on the Elwha River

Science.gov (United States)

Ritchie, A. C.

2012-12-01

Repeat digital surface models, orthoimagery and sidescan sonar data are being generated to monitor river response to the largest dam removal and controlled sediment release in history on the Elwha River, on the Olympic Peninsula in Washington State. These products are generated using low-cost readily-available tools to collect data at a spatial and temporal scale that provides important insight into effects of base-level change, sediment release, and discrete hydrologic events on erosion of reservoir sediments, downstream sediment transport, and channel evolution above and below the dam sites. In combination, these products provide a view above and below the water surface to changes in sediment composition and morphology that other methods cannot capture at this spatial scale and both spatial and temporal resolution. Orthoimagery is developed from still images collected with a plane-mounted point-and-shoot camera using customized firmware from the open-source Canon Hack Development Kit (CHDK) with a total hardware cost of about $300 USD. Images are processed using structure-from-motion algorithms. Several software options are available. Sonar data are collected from a raft-mounted platform using a high-resolution 990 KHz Starfish sidescan sonar, with a water-resistant topside enclosure holding top-side electronics. A steerable pole-mount was developed for this application to allow the sidescan to to remain oriented in the direction of motion-over-ground.; Surface reconstruction from aerial images collected during Elwha dam removal project. ; bedforms near Elwha Sediment Treatment Plant from sediment released from Lake Aldwell, surveyed 12 July 2012.

Sediment transport and capacity change in three reservoirs, Lower Susquehanna River Basin, Pennsylvania and Maryland, 1900-2012

Science.gov (United States)

Langland, Michael J.

2015-01-01

The U.S. Geological Survey (USGS) has conducted numerous sediment transport studies in the Susquehanna River and in particular in three reservoirs in the Lower Susquehanna River Basin to determine sediment transport rates over the past century and to document changes in storage capacity. The Susquehanna River is the largest tributary to Chesapeake Bay and transports about one-half of the total freshwater input and substantial amounts of sediment and nutrients to the bay. The transported loads are affected by deposition in reservoirs (Lake Clarke, Lake Aldred, and Conowingo Reservoir) behind three hydropower dams. The geometry and texture of the deposited sediments in each reservoir upstream from the three dams has been a subject of research in recent decades. Particle size deposition and sediment scouring processes are part of the reservoir dynamics. A Total Maximum Daily Load (TMDL) for nitrogen, phosphorus, and sediment was established for Chesapeake Bay to attain water-quality standards. Six states and the District of Columbia agreed to reduce loads to the bay and to meet load allocation goals for the TMDL. The USGS has been estimating annual sediment loads at the Susquehanna River at Marietta, Pennsylvania (above Lake Clarke), and Susquehanna River at Conowingo, Maryland (below Conowingo Reservoir), since the mid-1980s to predict the mass balance of sediment transport through the reservoir system. Using streamflow and sediment data from the Susquehanna River at Harrisburg, Pennsylvania (upstream from the reservoirs), from 1900 to 1981, sediment loads were greatest in the early to mid-1900s when land disturbance activities from coal production and agriculture were at their peak. Sediment loads declined in the 1950s with the introduction of agricultural soil conservation practices. Loads were dominated by climatic factors in the 1960s (drought) and 1970s (very wet) and have been declining since the 1980s through 2012. The USGS developed a regression equation to

Lake sediment cores as indicators of historical metal(loid) accumulation – A case study in Mexico

International Nuclear Information System (INIS)

Hansen, Anne M.

2012-01-01

To examine and compare historical accumulation of metal(loid)s in Mexican lakes and reservoirs, 210 Pb and 137 Cs dated sediment cores were evaluated: two from the remote Zempoala and Miramar Lagoons and three from Lake Pátzcuaro, and the Intermedia and Silva dams that are affected by human activities. Sediment ecotoxicology was assessed using consensus-based sediment quality guidelines for freshwater ecosystems. The +100 a sediment core from the remote Miramar Lagoon had the highest concentrations of Cr and Ni these being higher than the Probable Effect Levels (PELs). Zinc concentrations were also higher in the Miramar Lagoon compared to the other lakes and reservoirs, with concentrations higher than the Threshold Effect Level (TEL). Mercury concentrations from this lagoon were comparable to those for the Intermedia dam that receives water from urban, industrial and agricultural areas. The higher metal concentrations in the core from the Miramar Lagoon suggest that metal concentrations in the rocks of the watershed are high. Another explanation for the higher metal concentrations is the slow sediment accumulation that causes metals to be accumulated over longer time-periods at the sediment–water interface. A decrease in the concentration of As in the Intermedia dam was observed in sediments corresponding to the last decades. This may be due to an increase in sediment accumulation rate or to the reduction in sources of this metalloid in the watershed. In the Miramar Lagoon, an increase was observed in concentrations of As and Cr in more recent sediments, probably related to increased deforestation in the area or the eruption of El Chichonal volcano in 1982. Concentrations of Pb showed a decreasing tendency over the past decades in the Lake Pátzcuaro, Miramar and Zempoala Lagoons sediment cores while such behavior was not be observed for the Intermedia dam. This reduction in concentrations of Pb was attributed to the decrease in use of leaded gasoline.

Dams

Data.gov (United States)

Vermont Center for Geographic Information — This dataset �is generated from from the Vermont Dam Inventory (VDI). The VDI is managed by the VT DEC's Dam Safety and Hydrology Section and contains information...

Numerical Simulation of Missouri River Bed Evolution Downstream of Gavins Point Dam

Science.gov (United States)

Sulaiman, Z. A.; Blum, M. D.; Lephart, G.; Viparelli, E.

2016-12-01

The Missouri River originates in the Rocky Mountains in western Montana and joins the Mississippi River near Saint Louis, Missouri. In the 1900s dam construction and river engineering works, such as river alignment, narrowing and bank protections were performed in the Missouri River basin to control the flood flows, ensure navigation and use the water for agricultural, industrial and municipal needs, for the production of hydroelectric power generation and for recreation. These projects altered the flow and the sediment transport regimes in the river and the exchange of sediment between the river and the adjoining floodplain. Here we focus on the long term effect of dam construction and channel narrowing on the 1200 km long reach of the Missouri River between Gavins Point Dam, Nebraska and South Dakota, and the confluence with the Mississippi River. Field observations show that two downstream migrating waves of channel bed degradation formed in this reach in response to the changes in flow regime, sediment load and channel geometry. We implemented a one dimensional morphodynamic model for large, low slope sand bed rivers, we validated the model at field scale by comparing the numerical results with the available field data and we use the model to 1) predict the magnitude and the migration rate of the waves of degradation at engineering time scales ( 150 years into the future), 2) quantify the changes in the sand load delivered to the Mississippi River, where field observations at Thebes, i.e. downstream of Saint Louis, suggest a decline in the mean annual sand load in the past 50 years, and 3) identify the role of the main tributaries - Little Sioux River, Platte River and Kansas River - on the wave migration speed and the annual sand load in the Missouri River main channel.

Spatial variation of sediment mineralization supports differential CO2 emissions from a tropical hydroelectric reservoir

Directory of Open Access Journals (Sweden)

Simone Jaqueline Cardoso

2013-04-01

Full Text Available Substantial amounts of organic matter (OM from terrestrial ecosystems are buried as sediments in inland waters. It is still unclear to what extent this OM constitutes a sink of carbon, and how much of it is returned to the atmosphere upon mineralization to carbon dioxide (CO2. The construction of reservoirs affects the carbon cycle by increasing OM sedimentation at the regional scale. In this study we determine the OM mineralization in the sediment of three zones (river, transition and dam of a tropical hydroelectric reservoir in Brazil as well as identify the composition of the carbon pool available for mineralization. We measured sediment OC mineralization rates and related them to the composition of the OM, bacterial abundance and pCO2 of the surface water of the reservoir. Terrestrial OM was an important substrate for the mineralization. In the river and transition zones most of the OM was allochthonous (56 % and 48 %, respectively while the dam zone had the lowest allochthonous contribution (7 %. The highest mineralization rates were found in the transition zone (154.80 ± 33.50 mg C m-2 d-1 and the lowest in the dam (51.60 ± 26.80 mg C m-2 d-1. Moreover, mineralization rates were significantly related to bacterial abundance (r2 = 0.50, p < 0.001 and pCO2 in the surface water of the reservoir (r2 = 0.73, p < 0.001. The results indicate that allochthonous OM has different contributions to sediment mineralization in the three zones of the reservoir. Further, the sediment mineralization, mediated by heterotrophic bacteria metabolism, significantly contributes to CO2 supersaturation in the water column, resulting in higher pCO2 in the river and transition zones in comparison with the dam zone, affecting greenhouse gas emission estimations from hydroelectric reservoirs.

PENCEMARAN KADMIUM DI SEDIMEN WADUK SAGULING PROVINSI JAWA BARAT (Cadmium Pollution in Saguling DAM Sediment West Java Province

Directory of Open Access Journals (Sweden)

Eka Wardhani

2016-09-01

Full Text Available ABSTRAK Sungai Citarum Hulu merupakan sumber air utama Waduk Saguling. Kualitas air sungai ini telah mengalami penurunan bahkan terpantau beberapa logam berat terkandung dalam air Sungai Citarum. Penelitian ini bertujuan untuk melihat pencemaran Cd di sedimen Waduk Saguling pada dua musim yang berbeda. Lokasi penelitian dilakukan di 10 titik di Waduk Saguling. Penelitian mengkaji perbedaan konsentrasi Cd pada Bulan Juli 2015 mewakili musim kemarau dan Bulan November 2015 mewakili musim hujan. Sedimen yang diperiksa merupakan sedimen permukaan pada kedalaman 0-10 cm pada dasar waduk. Konsentrasi Cd di sedimen dianalisis menggunakan ICP-MS. Tingkat pencemaran sedimen akibat Cd dinilai dengan menggunakan dua metode yaitu: faktor contaminasi/contamination factor, CF dan indeks pencemaran logam/Metal Pollution Index, MPI. Berdasarkan hasil penelitian konsentrasi Cd dalam air selama satu dekade mulai tahun 2008-2014 cenderung mengalami peningkatan, dengan konsentrasi berkisar antara 0 mg/L-0,14 mg/L. Konsentrasi rata-rata Cd di sedimen Waduk Saguling pada Bulan Juli 2015 mewakili musim kemarau sebesar 13,54 mg/kg, sedangkan pada Bulan November 2015 mewakili musim hujan sebesar 21,08 mg/kg. Konsentrasi Cd di sedimen Waduk Saguling tidak memenuhi baku mutu kualitas sedimen berdasarkan baku mutu yang berlaku di Australian dan New Zaeland mengingat Indonesia belum memiliki baku mutu kualitas sedimen yaitu sebesar 1,5 mg/kg. Hasil penilaian kualitas sedimen dengan menggunakan metode CF di semua titik penelitian di Waduk Saguling termasuk kategori terkontaminasi sangat tinggi sedangkan berdasarkan hasil penilaian dengan MPI kualitas sedimen Waduk Saguling termasuk kategori tercemar oleh logam berat Cd. Hasil penelitian ini dapat dijadikan bahan pertimbangan bagi pengelolaan Waduk Saguling mengenai kondisi pencemaran logam berat yang telah terjadi di waduk tersebut. ABSTRACT Citarum river is the main water source for Saguling Dam. The river waters quality

Legacy sediment storage in New England river valleys: anthropogenic processes in a postglacial landscape

Science.gov (United States)

Snyder, N. P.; Johnson, K. M.; Waltner, M.; Hopkins, A. J.; Dow, S.; Ames, E.; Merritts, D. J.; Walter, R. C.; Rahnis, M. A.

2016-12-01

Walter and Merritts (2008, and subsequent papers) show that legacy sediment associated with deposition in millponds is a common feature in river valleys of the Mid-Atlantic Piedmont region, with 1-5 m of fine sand and silt overlying Holocene soil and Pleistocene periglacial deposits. For this project, we seek to test the hypothesis that these field relationships are seen in New England, a formerly glaciated region with similar history and intensity of forest clearing and milldam construction during the 17-19th centuries. We study three watersheds, using field observations of bank stratigraphy, radiocarbon dating, and mapping of terraces and floodplains using lidar digital elevation models and other GIS datasets. The 68 km2 South River watershed in western Massachusetts exhibits the most extensive evidence for legacy sediment storage. We visited 17 historic dam sites in the watershed and found field evidence for fine sand and silt legacy sediment storage at 14, up to 2.2 m thick. In the 558 km2 Sheepscot River watershed in coastal Maine, we visited 12 historic dam sites, and found likely legacy sediment at six, up to 2.3 m thick. In the 171 km2 upper Charles River watershed in eastern Massachusetts, we investigated 14 dam sites, and found legacy sediment at two, up to 1.8 m thick. Stratigraphically, we identified the base of legacy sediment from a change in grain size to gravel at most sites, or to Pleistocene marine clay at some Sheepscot River sites. In the Sheepscot River, we observed cut timbers underlying historic sediment at several locations, likely associated with sawmill activities. Only at the Charles River were we able to radiocarbon date the underlying gravel (1281-1391 calibrated CE). At no site did we find a buried Holocene soil, in contrast to the field relations commonly observed in the Mid-Atlantic region. This may indicate that the New England sites have eroded to the pre-historic river bed, not floodplain surfaces. We attribute the variation in

Sediment Scaling for Mud Mountain Fish Barrier Structure

Science.gov (United States)

2017-06-28

River serves as a collection point of migratory fish. Operators at the structure collect the fish and transport them upstream of Mud Mountain Dam...fixed weir does not allow for structure operations to mobilize the sediment. Thus, a new structure is desired to both mitigate sediment accumulation...gradation, respectively. This analysis should be based on a representative prototype gradation taken from non- slack water areas (Einstein 1950). For this

Japan`s largest composition dam, aiming for harmony with nature. Chubetsu dam; Shizen tono chowa wo mezasu, Nippon ichi no fukugo dam. Chubetsu dam

Energy Technology Data Exchange (ETDEWEB)

Mizushima, T. [Hokkaido Development Bureau, Hokkaido Development Agency, Sapporo (Japan)

1994-08-15

This paper introduces Chubetsu Dam planned with a large-scale embankment having a river bed width of 600 m. Chubetsu Dam is being constructed with such objectives as flood control of Ishikari River, river flow rate maintenance, drinking water supply, irrigation water supply and power generation. The dam site is a gravel bed having a river bed width of 600 m and a maximum foundation rock thickness of 40 m, requiring evaluations as a dam foundation and discussions of water shielding methods. As a result of discussions at the Chubetsu Dam technical discussion committee, the dam type is decided to be a composition dam consisting of a gravity type concrete dam on the left river side and a central core type fill dam using a part of the gravel bed as the foundation on the right river side. A continuous underground wall system is planned to be used for shielding water in the gravel foundation. In discussing the anti-seismic properties, analyses for bank construction and water filling to derive stress and deformation conditions prior to an earthquake and a time-history response analysis to derive conditional changes during the earthquake are performed. According to the results thereof, evaluations are given on the safety by compounding the stress and the acceleration. In plans to improve the surrounding areas, an area will be provided upstream the reservoir where the water level is kept constant to serve as a bird sanctuary. 7 figs.

Sediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads

Science.gov (United States)

Dean, David; Topping, David; Schmidt, John C.; Griffiths, Ronald; Sabol, Thomas

2016-01-01

The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology; thus, it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change. We analyzed a suite of sediment transport and geomorphic data to determine the cumulative influence of different flood types on changing channel form. In this study, physically based analyses suggest that channel change in the Rio Grande is controlled by both changes in flow strength and sediment supply over different spatial and temporal scales. Channel narrowing is primarily caused by substantial deposition of sediment supplied to the Rio Grande during tributary-sourced flash floods. Tributary floods have large suspended-sediment concentrations, occur for short durations, and attenuate rapidly downstream in the Rio Grande, depositing much of their sediment in downstream reaches. Long-duration floods on the mainstem have the capacity to enlarge the Rio Grande, and these floods, released from upstream dams, can either erode or deposit sediment in the Rio Grande depending upon the antecedent in-channel sediment supply and the magnitude and duration of the flood. Geomorphic and sediment transport analyses show that the locations and rates of sand erosion and deposition during long-duration floods are most strongly controlled by spatial changes in flow strength, largely through changes in channel slope. However, spatial differences in the in-channel sediment supply regulate sediment evacuation or accumulation over time in long reaches (greater than a kilometer).

Comparing geological and statistical approaches for element selection in sediment tracing research

Science.gov (United States)

Laceby, J. Patrick; McMahon, Joe; Evrard, Olivier; Olley, Jon

2015-04-01

Elevated suspended sediment loads reduce reservoir capacity and significantly increase the cost of operating water treatment infrastructure, making the management of sediment supply to reservoirs of increasingly importance. Sediment fingerprinting techniques can be used to determine the relative contributions of different sources of sediment accumulating in reservoirs. The objective of this research is to compare geological and statistical approaches to element selection for sediment fingerprinting modelling. Time-integrated samplers (n=45) were used to obtain source samples from four major subcatchments flowing into the Baroon Pocket Dam in South East Queensland, Australia. The geochemistry of potential sources were compared to the geochemistry of sediment cores (n=12) sampled in the reservoir. The geochemical approach selected elements for modelling that provided expected, observed and statistical discrimination between sediment sources. Two statistical approaches selected elements for modelling with the Kruskal-Wallis H-test and Discriminatory Function Analysis (DFA). In particular, two different significance levels (0.05 & 0.35) for the DFA were included to investigate the importance of element selection on modelling results. A distribution model determined the relative contributions of different sources to sediment sampled in the Baroon Pocket Dam. Elemental discrimination was expected between one subcatchment (Obi Obi Creek) and the remaining subcatchments (Lexys, Falls and Bridge Creek). Six major elements were expected to provide discrimination. Of these six, only Fe2O3 and SiO2 provided expected, observed and statistical discrimination. Modelling results with this geological approach indicated 36% (+/- 9%) of sediment sampled in the reservoir cores were from mafic-derived sources and 64% (+/- 9%) were from felsic-derived sources. The geological and the first statistical approach (DFA0.05) differed by only 1% (σ 5%) for 5 out of 6 model groupings with only

Safety Aspects of Sustainable Storage Dams and Earthquake Safety of Existing Dams

Directory of Open Access Journals (Sweden)

Martin Wieland

2016-09-01

Full Text Available The basic element in any sustainable dam project is safety, which includes the following safety elements: ① structural safety, ② dam safety monitoring, ③ operational safety and maintenance, and ④ emergency planning. Long-term safety primarily includes the analysis of all hazards affecting the project; that is, hazards from the natural environment, hazards from the man-made environment, and project-specific and site-specific hazards. The special features of the seismic safety of dams are discussed. Large dams were the first structures to be systematically designed against earthquakes, starting in the 1930s. However, the seismic safety of older dams is unknown, as most were designed using seismic design criteria and methods of dynamic analysis that are considered obsolete today. Therefore, we need to reevaluate the seismic safety of existing dams based on current state-of-the-art practices and rehabilitate deficient dams. For large dams, a site-specific seismic hazard analysis is usually recommended. Today, large dams and the safety-relevant elements used for controlling the reservoir after a strong earthquake must be able to withstand the ground motions of a safety evaluation earthquake. The ground motion parameters can be determined either by a probabilistic or a deterministic seismic hazard analysis. During strong earthquakes, inelastic deformations may occur in a dam; therefore, the seismic analysis has to be carried out in the time domain. Furthermore, earthquakes create multiple seismic hazards for dams such as ground shaking, fault movements, mass movements, and others. The ground motions needed by the dam engineer are not real earthquake ground motions but models of the ground motion, which allow the safe design of dams. It must also be kept in mind that dam safety evaluations must be carried out several times during the long life of large storage dams. These features are discussed in this paper.

Damming evidence : Canada and the World Commission on Dams

Energy Technology Data Exchange (ETDEWEB)

Vert, P.; Parkinson, B.

2003-06-01

Large hydroelectric projects have been met with strong resistance from affected communities, particularly indigenous groups who have been displaced from their flooded communities following the damming of a river. The World Commission on Dams (WCD) was formed in 1998 to review the effectiveness of large dams and develop internationally acceptable guidelines and standards for large dams or hydro energy projects. The Canadian government, through the Canadian International Development Agency, was one of many governments to fund the WCD. However, the authors argue that despite the financial support, the Canadian government was absent from any effort to follow-up on the recommendations of the WCD. The seven strategic priorities in the decision making process include: (1) gaining public acceptance, (2) comprehensive option assessment of water, energy, food and development needs, (3) addressing existing dams to improve the benefits that can be derived from them, (4) sustaining livelihoods, (5) recognizing the entitlements and sharing benefits, (6) ensuring compliance, and (7) sharing rivers for peace, development and security. This report offers a means to assess planned or existing dams and presents a set of guidelines for good practices linked to the seven strategic priorities. Ten case studies from around the world were presented, including the Three Gorges Dam in China. 154 refs., 3 figs., 3 appendices.

Proceedings of the Canadian Dam Association's 2006 annual conference: dams: past, present and future

International Nuclear Information System (INIS)

2006-01-01

This conference addressed particular technical challenges regarding the operation of dams with particular focus on best practices for improving dam management and safety. It featured 4 workshops and a technical program led by experts on dams and tailings facilities that addressed topics such as dam construction, design and rehabilitation; dam management in a hydrological uncertainty context; monitoring, instrumentation and maintenance; dam behaviour; dam safety, dam failure and practical approaches to emergency preparedness planning for dam owners; historical aspects and environmental issues and conflicting water use. Recent developments in dam construction were reviewed along with discharge and debris management, tailings dam issues, asset management, seismic issues, public safety, seepage monitoring, flow control, dam rehabilitation, concrete testing, hydrotechnical issues, risk assessment methodology, and dam safety guidelines for extreme flood analyses and their applications. All 80 presentations from this conference have been catalogued separately for inclusion in this database. refs., tabs., figs

Proceedings of the 2010 Canadian Dam Association's public safety around dams workshop

Energy Technology Data Exchange (ETDEWEB)

NONE

2010-07-01

Nearly 30 people have drowned in dam-related incidents over the last 10 years in Canada. The Canadian public is now calling for improved safety guidelines. Public interaction with dams is increasing as a result of interest in extreme sports and perceived rights of access. However, many members of the public are not aware of the dangers posed by dams. This workshop provided a forum to discuss proposals for a draft publication of the Canadian Dam Association (CDA) guidelines for public safety and security around dams. Issues related to current legislation and liability were discussed. Methods of increasing public awareness of the hazards posed by dams included increased signage in dam locations, the use of audible and visual alert systems, and the use of booms and buoys. The responsibilities of dam owners in ensuring the safety of dams were also discussed. The conference featured 5 presentations, of which 2 have been catalogued separately for inclusion in this database. tabs., figs.

Expert-Opinion Elicitation for the Risk Analysis of Design-Improvement Alternatives to the Lindy Claiborne Boggs Lock and Dam

National Research Council Canada - National Science Library

Ayyub, Bilal M

2002-01-01

This report documents the expert-opinion elicitation performed to meet risk analysis needs of the lower lock approach sediment management improvement alternatives to the Lindy Claiborne Boggs Lock and Dam...

The Dams and Monitoring Systems and Case Study: Ataturk and Karakaya Dams

Science.gov (United States)

Kalkan, Y.; Bilgi, S.; Gülnerman, A. G.

2017-12-01

Dams are among the most important engineering structures used for flood controls, agricultural purposes as well as drinking and hydroelectric power. Especially after the Second World War, developments on the construction technology, increase the construction of larger capacity dams. There are more than 150.000 dams in the world and almost 1000 dams in Turkey, according to international criteria. Although dams provide benefits to humans, they possess structural risks too. To determine the performance of dams on structural safety, assessing the spatial data is very important. These are movement, water pressure, seepage, reservoir and tail-water elevations, local seismic activities, total pressure, stress and strain, internal concrete temperature, ambient temperature and precipitation. These physical data are measured and monitored by the instruments and equipment. Dams and their surroundings have to be monitored by using essential methods at periodic time intervals in order to determine the possible changes that may occur over the time. Monitoring programs typically consist of; surveillance or visual observation. These programs on dams provide information for evaluating the dam's performance related to the design intent and expected changes that could affect the safety performance of the dam. Additionally, these programs are used for investigating and evaluating the abnormal or degrading performance where any remedial action is necessary. Geodetic and non-geodetic methods are used for monitoring. Monitoring the performance of the dams is critical for producing and maintaining the safe dams. This study provides some general information on dams and their different monitoring systems by taking into account two different dams and their structural specifications with the required information. The case study in this paper depends on a comparison of the monitoring surveys on Atatürk Dam and Karakaya Dam, which are constructed on Firat River with two different structural

Estimation of annual suspended-sediment fluxes, 1931-95, and evaluation of geomorphic changes, 1950-2010, in the Arkansas River near Tulsa, Oklahoma

Science.gov (United States)

Lewis, Jason M.; Smith, S. Jerrod; Buck, Stephanie D.; Strong, Scott A.

2011-01-01

An understanding of fluvial sediment transport and changing channel morphology can assist planners in making responsible decisions with future riverine development or restoration projects. Sediment rating curves can serve as simple models and can provide predictive tools to estimate annual sediment fluxes. Sediment flux models can aid in the design of river projects by providing insight to past and potential future sediment fluxes. Historical U.S. Geological Survey suspended-sediment and discharge data were evaluated to estimate annual suspended-sediment fluxes for two stations on the Arkansas River located downstream from Keystone Dam in Tulsa County. Annual suspended-sediment fluxes were estimated from 1931-95 for the Arkansas River at Tulsa streamflow-gaging station (07164500) and from 1973-82 for the Arkansas River near Haskell streamflow-gaging station (07165570). The annual flow-weighted suspended-sediment concentration decreased from 1,970 milligrams per liter to 350 milligrams per liter after the completion of Keystone Dam at the Tulsa station. The streambed elevation at the Arkansas River at Tulsa station has changed less than 1 foot from 1970 to 2005, but the thalweg has shifted from a location near the right bank to a position near the left bank. There was little change in the position of most of the banks of the Arkansas River channel from 1950 to 2009. The most substantial change evident from visual inspection of aerial photographs was an apparent decrease in sediment storage in the form of mid-channel and meander bars. The Arkansas River channel between Keystone Dam and the Tulsa-Wagoner County line showed a narrowing and lengthening (increase in sinuosity) over the transition period 1950-77 followed by a steady widening and shortening of the river channel (decrease in sinuosity) during the post-dam (Keystone) periods 1977-85, 1985-2003, and 2003-10.

Assessing dam development, land use conversion, and climate change pressures on tributary river flows and water quality of the Mekong's Tonle Sap basin.

Science.gov (United States)

Cochrane, T. A.; Arias, M. E.; Oeurng, C.; Arnaiz, M.; Piman, T.

2016-12-01

The Tonle Sap Lake is Southeast Asia's most productive freshwater fishery, but the productivity of this valuable ecosystem is under threat from extensive development in the lower Mekong. With dams potentially blocking all major tributaries along the lower Mekong River, the role of local Tonle Sap basin tributaries for maintaining environmental flows, sediment loads, and fish recruitment is becoming increasingly critical. Development within the Tonle Sap basin, however, is not stagnant. Developers are proposing extensive dam development in key Tonle Sap tributaries (see Figure). Some dams will provide hydroelectricity and others will provide opportunities for large-scale irrigation resulting in agro-industrial expansion. There is thus an immediate need to assess the current situation and understand future effects of dam development and land use conversion under climate change on local riverine ecosystems. A combination of remote sensing, field visits, and hydro-meteorological data analyses enabled an assessment of water infrastructure and agricultural development in the basin. The application of SWAT for modelling flows and water quality combined with HEC-RESSIM for reservoir operations enabled for a holistic modelling approach. Initial results show that dams and land use change dominate flow and water quality responses, when compared to climate change. Large ongoing dam and irrigation development in the Pursat and Battambang subbasins will critically alter the natural river flows to the Tonle Sap Lake. Some of the observed dams did not have provisions for sediment flushing, clearing of flooded areas, fish passages, or other environmental protection measures. Poor planning and operation of this infrastructure could have dire consequences on the fragile riverine ecosystem of Tonle Sap tributaries, resulting in fish migration barriers, losses in aquatic habitats, and ecological degradation. The seemingly chaotic development in the Tonle Sap basin induces a great level

The effects of Hurricane Hugo on suspended-sediment loads, Lago Loiza Basin, Puerto Rico

Science.gov (United States)

Gellis, A.

1993-01-01

In the two main tributaries that enter Lago Loiza, Rio Grande de Loiza and Rio Gurabo, 99 600 tonnes of suspended sediment was transported by 58.2??106 m3 of runoff in a 48 h period. The storm-average suspended-sediment concentration in the Rio Grande de Loiza for Hurricane Hugo was 2290 mgl-1, the second lowest for the 12 storms that have been monitored at this site. In Rio Gurabo the storm-average suspended-sediment concentration was 1420 mg l -1, the sixth lowest recorded out of 15 monitored storms. In Quebrada Salvatierra, a small tributary to Rio Grande de Loiza, suspended-sediment concentrations were as low as 33 mg l-1 during peak runoff of 20m3s-1. Normally the suspended-sediment concentrations at this discharge are 300 mg l-1. Hurricane force winds seem to be the most important factor contributing to the lower than expected suspended-sediment loads. High winds caused vegetation and debris to be dislodged and displaced. Debris accumulated on hillslopes and in small channels, blocked bridges and formed debris dams. These dams caused local backwater effects that reduced stream velocities and decreased suspended-sediment loads. -from Author

Human impacts on sediment in the Yangtze River: A review and new perspectives

Science.gov (United States)

Yang, H. F.; Yang, S. L.; Xu, K. H.; Milliman, J. D.; Wang, H.; Yang, Z.; Chen, Z.; Zhang, C. Y.

2018-03-01

Changes in riverine suspended and riverbed sediments have environmental, ecological and social implications. Here, we provide a holistic review of water and sediment transport and examine the human impacts on the flux, concentration and size of sediment in the Yangtze River in recent decades. We find that most of the fluvial sediment has been trapped in reservoirs, except for the finest portion. Furthermore, soil-conservation since the 1990s has reduced sediment yield. From 1956-1968 (pre-dam period) to 2013-2015 (post-dams and soil-conservation), the sediment discharge from the sub-basins decreased by 91%; in the main river, the sediment flux decreased by 99% at Xiangjiaba (upper reach), 97% at Yichang (transition between upper and middle reaches), 83% at Hankou (middle reach), and 77% at Datong (tidal limit). Because the water discharge was minimally impacted, the suspended sediment concentration decreased to the same extent as the sediment flux. Active erosion of the riverbed and coarsening of surficial sediments were observed in the middle and lower reaches. Fining of suspended sediments was identified along the river, which was counteracted by downstream erosion. Along the 700-km-long Three Gorges Reservoir, which retained 80% of the sediment from upstream, the riverbed gravel or rock was buried by mud because of sedimentation after impoundment. Along with these temporal variations, the striking spatial patterns of riverine suspended and riverbed sediments that were previously exhibited in this large basin were destroyed or reversed. Therefore, we conclude that the human impacts on sediment in the Yangtze River are strong and systematic.

Sediment transport over sills at longitudinal training dams with unaligned main flow

NARCIS (Netherlands)

Jammers, S.M.M.; Paarlberg, AJ; Mosselman, E.; Uijttewaal, W.S.J.

2017-01-01

Longitudinal training dams (LTDs) are  constructed in the River Waal in the  Netherlands. They are aligned parallel to the  river shore and divide the river into a main and  side channel. The existing groynes are  removed yielding more discharge capacity at  high

Research on Safety Factor of Dam Slope of High Embankment Dam under Seismic Condition

Directory of Open Access Journals (Sweden)

Li Bin

2015-01-01

Full Text Available With the constant development of construction technology of embankment dam, the constructed embankment dam becomes higher and higher, and the embankment dam with its height over 200m will always adopt the current design criteria of embankment dam only suitable for the construction of embankment dam lower than 200m in height. So the design criteria of high embankment dam shall be improved. We shall calculate the stability and safety factors of dam slope of high embankment dam under different dam height, slope ratio and different seismic intensity based on ratio of safety margin, and clarify the change rules of stability and safety factors of dam slope of high embankment dam with its height over 200m. We calculate the ratio of safety margin of traditional and reliable method by taking the stable, allowable and reliability index 4.2 of dam slope of high embankment dam with its height over 200m as the standard value, and conduct linear regression for both. As a result, the conditions, where 1.3 is considered as the stability and safety factors of dam slope of high embankment dam with its height over 200m under seismic condition and 4.2 as the allowable and reliability index, are under the same risk control level.

Impact on sediments and water by release of copper from chalcopyrite bearing rock due to acidic mine drainage

Science.gov (United States)

Shukla, Anoop Kant; Pradhan, Manoj; Tiwari, Onkar Nath

2018-04-01

Mining activity causes transition of rock-mass from its original position in earth into open environment. The action of environmental elements such air, water, microorganisms leads to oxidation of minerals which constitute the rock. The oxidation of sulphide minerals in presence of moisture releases acidic mine discharge (AMD). The acidic nature of AMD causes leaching of metals from rock minerals. Dissolution of other minerals may occur upon reaction with AMD. Chalcopyrite (CuFeS2) undergoes oxidation in acidic condition releasing copper among other products. This study reveals contamination of copper in sediment samples and seepage water from the tailing dam of a large copper project in located in central India. Elevation was studied using GIS to ascertain to the topographic elevation of tailing dam area. It was located at relatively high altitude causing seepage to flow away from tailing dam. The seepage water from tailing dam was found to be acidic with mean pH value of 4.0 and elevated copper content. Similarly, sediments from seepage water flow displayed elevated copper concentration. The copper concentration in seepage water was found with a mean value of 10.73 mg/l. The sediments from seepage water flow also displayed elevated copper concentration with mean value of 26.92 g/kg. This indicates impact on sediments by release of copper due to acidic mine drainage.

Creating an Erosion Vulnerability Map for the Columbia River Basin to Determine Reservoir Susceptibility to Sedimentation Before and After Wildfires

Science.gov (United States)

Ren, J.; Robichaud, P. J. L.; Adam, J. C.

2017-12-01

Sedimentation is important issue to most rivers and reservoirs especially in watersheds with extensive agricultural or wildfire activity. These human and natural induced disturbances have the potential to increase runoff-induced erosion and sediment load to rivers; downstream sedimentation can decrease the life expectancy of reservoir and consequently the dam. This is particularly critical in snowmelt-dominant regions because, as rising temperatures reduce snowpack as a natural reservoir, humans will become more reliant on reservoir storage. In the Northwest U.S., the Columbia River Basin (CRB) has more than 60 dams, which were built for irrigation, hydropower, and flood control, all of which are affected by sediment to varying degrees. Determining what dams are most likely to be affected by sedimentation caused by post-fire erosion is important for future management of reservoirs, especially as climate change is anticipated to exacerbate wildfire and its impacts. The objective of this study is to create a sedimentation vulnerability map for reservoirs in the CRB. There are four attributes of a watershed that determine erosion potential; soil type, topography, vegetation (such as forests, shrubs, and grasslands), and precipitation (although precipitation was excluded in this analysis). In this study, a rating system was developed on a scale of 0-90 (with 90 having the greatest erosion potential). The different layers in a Graphical Information System were combined to create an erosion vulnerability map. Results suggest that areas with agriculture have more erosion without a wildfire but that forested areas are most vulnerable to erosion rates following a fire, particularly a high severity fire. Sedimentation in dams is a growing problem that needs to be addressed especially with the likely reduction in snowpack, this vulnerability map will help determine which reservoirs in the CRB are prone to high sedimentation. This information can inform managers where post

Radiometric survey of radioactive minerals in the Matias Romero dam, in Oaxaca; Exploracion radiometrica de minerales radiactivos en la presa Matias Romero, en Oaxaca

Energy Technology Data Exchange (ETDEWEB)

Flores, J H; Pena, P; Balcazar, M; Lopez, A M [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Juarez, S F; Cabrera, M O [IGEFUNAM, 04510 Mexico D.F. (Mexico); Huizar, R [IGEUNAM, 04510 Mexico D.F. (Mexico)

2006-07-01

Migration of radioactive Uranium and Thorium minerals from the old mine El Muerto, to the dam Matias Romero in Oaxaca was detected in dam sediments. The identified elements were Th and U, from the decay series of the last one; {sup 234}Th, {sup 234}Pa and {sup 214}Bi from the radioactive series of {sup 238}U. The mineral was in the past extracted from high fractured zones. Total activity measurements in sediments from the dam increases as the particle size decrease, which indicates that main reason of the movement is produced by erosion of small particles from high altitude deposits to lower parts where the dam is located. Geo statistical analysis gives a general picture of mineral distribution. ICP-MS, Ge(hp) detector, and X-ray diffraction techniques were used for associated minerals and radioactive content evaluation. Oaxaca State presents a complex geology. Pre cambric metamorphic rocks (600 ma) are present at the southern part, covering 25% of the state surface; intrusive metamorphic and igneous rocks form the Paleozoic (375 m.a.) cover 6 % of the surface. (Author)

Dams designed to fail

Energy Technology Data Exchange (ETDEWEB)

Penman, A. [Geotechnical Engineering Consultants, Harpenden (United Kingdom)

2004-09-01

New developments in geotechnical engineering have led to methods for designing and constructing safe embankment dams. Failed dams can be categorized as those designed to fail, and those that have failed unexpectedly. This presentation outlined 3 dam failures: the 61 m high Malpasset Dam in France in 1959 which killed 421; the 71 m high Baldwin Hills Dam in the United States in 1963 which killed 5; and, the Vajont Dam in Italy in 1963 which killed 2,600 people. Following these incidents, the International Commission for Large Dams (ICOLD) reviewed regulations on reservoir safety. The 3 dams were found to have inadequate spillways and their failures were due to faults in their design. Fuse plug spillways, which address this problem, are designed to fail if an existing spillway proves inadequate. They allow additional discharge to prevent overtopping of the embankment dam. This solution can only be used if there is an adjacent valley to take the additional discharge. Examples of fuse gates were presented along with their effect on dam safety. A research program is currently underway in Norway in which high embankment dams are being studied for overtopping failure and failure due to internal erosion. Internal erosion has been the main reason why dams have failed unexpectedly. To prevent failures, designers suggested the use of a clay blanket placed under the upstream shoulder. However, for dams with soft clay cores, these underblankets could provide a route for a slip surface and that could lead to failure of the upstream shoulder. It was concluded that a safe arrangement for embankment dams includes the use of tipping gates or overturning gates which always fail at a required flood water level. Many have been installed in old and new dams around the world. 14 refs., 19 figs.

Major, trace and rate earth elements in sediments of the Julian Adame-Alatorre dam by instrumental neutron activation analysis

Energy Technology Data Exchange (ETDEWEB)

Mireles, F.; Pinedo, J. L.; Davila, J. I.; Oliva, J. E. [Universidad Autonoma de Zacatecas, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Speakman, R. J. [Museum Conservation Institute, Smithsonian Institution, Suitland, MD 20746 (United States); Glascock, M. D., E-mail: fmireles@uaz.edu.m [Research Reactor Center, University of Missouri, Columbia, MO 65211 (United States)

2010-10-15

The rapid industrial development in regions of Mexico during recent years has had the side effect of introducing toxic metals, fertilizers, and pesticides into the ecosystem. Sediment cores were collected from eight locations around the Julian Adame-Alatorre dam located in Municipality of Villanueva in the Zacatecas State, Mexico. The cores were analyzed for 32 major, trace, and rare earth elements (As, La, Lu, Nd, Sm, U, Yb, Ce, Co, Cr, Cs, Eu, Fe, Hf, Rb, Sb, Sc, Sr, Ta, Tb, Th, Zn, Zr, Al, Ba, Ca, Dy, K, Mn, Na, Ti, V) in order to estimate the health risk. The samples were analyzed by instrument neutron activation analysis using thermal neutron fluxes of 8 x 10{sup 13} and 5 x 10{sup 13} n cm{sup -2} s{sup -1} for short and long irradiations, respectively. The results of the contamination levels for elements such as As, Ba, Cr, Fe, Mn, Ta, V, and Zn were compared with the Mexican regulations and the guidelines of US EPA. (Author)

Red River Waterway, Lock and Dam 3: Report 3 - Sedimentation Conditions Hydraulic Model Investigation

National Research Council Canada - National Science Library

McCollum, Randy

1997-01-01

...) To study tendency for scour and fill in the approaches to the lock and dam and determine training structures that would improve navigation conditions and minimize dredging requirements and scour problems.

Management of dams for the next Millennium: proceedings of the 1999 Canadian Dam Association

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-07-01

The meeting featured seven sessions with 18 papers abstracted/indexed therein as follows: keynote address: tailings dams safety - implications for the dam safety community; 1 - design and performance: performance monitoring of dams: are we doing what we should be doing?; tailings dams from the perspective of conventional dam engineering; and design overview of Syncrude's Mildred Lake east toe berm; 2 - design and modelling: use of a 2D model for a dam break study on the ALCAN hydroelectric complex in Quebec; and spillway design implications resulting from changes in rainfall extremes; 3 - risk and dam safety I: closing the gaps in the dam safety guidelines; the reality of life safety consequence classification; and surveillance practices for the next millenium; 4 - risk and dam safety II: quantitative risk-assessment using the capacity-demand analysis; and new guidelines for dam safety classification; 5 - millenium issues: expectations of immortality, dam safety management into the next millenium; 6 - rehabilitation techniques: the unconventional application of conventional materials; nondestructive testing technology to characterize concrete dam/bedrock interface; method and instrument for detecting crack in concrete; and grouting of the cracks in the Arch 5-6 - Daniel Johnson Dam; and 7 - case studies: rehabilitation of an 80 year old Ambursen type dam; and debris booms for the protection of spillways.

Dramatic decreases in runoff and sediment load in the Huangfuchuan Basin of the Middle Yellow River, China: historical records and future projections

Science.gov (United States)

LI, E.; Li, D.; Wang, Y.; Fu, X.

2017-12-01

The Yellow River is well known for its high sediment load and serious water shortage. The long-term averaged sediment load is about 1.6´103 million tons per year, resulting in aggrading and perched lower reaches. In recent years, however, dramatic decreases in runoff and sediment load have been observed. The annual sediment load has been less than 150 million tons in the last ten years. Extrapolation of this trend into the future would motivate substantial change in the management strategies of the Lower Yellow River. To understand the possible trend and its coevolving drivers, we performed a case study of the Huangfuchuang River, which is a tributary to the Middle Yellow River, with a drainage area of 3246 km2 and an annual precipitation of 365 mm. Statistical analysis of historical data from 1960s to 2015 showed a significantly decreasing trend in runoff and sediment load since 1984. As potential drivers, the precipitation does not show an obvious change in annual amount, while the vegetation cover and the number of check dams have been increased gradually as a result of the national Grain for Green project. A simulation with the Soil and Water Assessment Tool (SWAT) reproduced the historical evolution processes, and showed that human activities dominated the reduction in runoff and sediment load, with a contribution of around 80%. We then projected the runoff and sediment load for the next 50 years (2016-2066), considering typical scenarios of climate change and accounting for vegetation cover development subject to climate conditions and storage capacity loss of check dams due to sediment deposition. The differences between the projected trend and the historical record were analyzed, so as to highlight the coevolving processes of climate, vegetation, and check dam retention on a time scale of decades. Keywords: Huangfuchuan River Basin, sediment load, vegetation cover, check dams, annual precipitation, SWAT.

Heavy metals (Cd, Pb, Cu, Zn) in mudfish and sediments from three ...

African Journals Online (AJOL)

The percentage of uranium present in sediment samples (analysed by energy dispersive X-ray spectrometry) from the three dams was 9.0 % (SD 2.1%). In sediment it was found that cation exchange capacity measurements and the dolomitic hard water and high pH of the Mooi River water effectively \\'detoxified\\' Cd and Pb, ...

Evaluating safety of concrete gravity dam on weak rock: Scott Dam

International Nuclear Information System (INIS)

Goodman, R.E.; Ahlgren, C.S.

2000-01-01

Scott Dam is owned and operated by Pacific Gas and Electric Co. (PG and E) as part of the Potter Valley Project. Although it is an unimpressive concrete gravity dam [233 m (765 ft) long with maximum water surface 33.4 m (110 ft) above tail water], the dam has unusually complex and weak foundation rocks; thick condition caused design changes during construction, numerous subsequent special investigations, and several corrections and additions. A main stumbling block to clarification of the dam safety issue for Scott Dam has always been difficulty in characterizing the foundation material. This paper discusses an approach to this problem as well s how the safety of the dam was subsequently confirmed. Following a comprehensive program of research, investigations, and analysis from 1991 to 1997

Numerical modelling of solid transport caused by an extreme flood: Case of the Hamiz dam failure (Algeria

Directory of Open Access Journals (Sweden)

Haddad Ali

2017-07-01

Full Text Available Study of solid transport caused by the flow of an extreme flood such as the propagation of dam failure wave aims to simulate the hydrodynamics behaviour of the solid particles contained in the valley during the flood passage. With this intention, we have developed a numerical model which is based on the resolution of the one-dimensional Saint Venant–Exner equations by the implicit finite difference scheme. Numerical stability of liquid phase calculation is checked by the Courant number and De Vries condition for the solid phase. The model has been applied to the Hamiz dam (Algeria which is built in the semi arid zone and presents a major risk of failure. The simulation of several scenarios of dam failure has allowed us to trace the cartography of sediment transport in the valley which is induced by the flood of dam failure.

Public safety around dams

Energy Technology Data Exchange (ETDEWEB)

Bourassa, H. [Centre d' expertise hydrique du Quebec, Quebec, PQ (Canada)

2009-07-01

Fourty public dams are managed on a real-time basis by the Centre d'expertise hydrique du Quebec (CEHQ). This presentation described the public dams owned by the CEHQ and discussed the public safety measures at the dams. The dams serve various purposes, including protection against floods; industrial or drinking water supply; resort or recreational activities; hydroelectric development; and wildlife conservation. Trigger events were also discussed, such as the complaint at Rapides-des-Cedres dam and deaths that occurred in 2004 when water from a dam was released without warning. Several photographs were presented to illustrate that people were unaware of the danger. Initiatives aimed at raising awareness and studying public safety issues were discussed. A pilot project was launched and a permanent committee was created to evaluate all aspects of public safety at the dams owned by CEHQ. The first tasks of the committee were to establish requirements for waterway safety barriers, both upstream and downstream, for all public dams; to establish requirements for safety signage for all public dams; and to develop criteria to decide on safety signage at each dam. figs.

Public safety around dams

Energy Technology Data Exchange (ETDEWEB)

Bourassa, H [Centre d' expertise hydrique du Quebec, Quebec, PQ (Canada)

2009-07-01

Fourty public dams are managed on a real-time basis by the Centre d'expertise hydrique du Quebec (CEHQ). This presentation described the public dams owned by the CEHQ and discussed the public safety measures at the dams. The dams serve various purposes, including protection against floods; industrial or drinking water supply; resort or recreational activities; hydroelectric development; and wildlife conservation. Trigger events were also discussed, such as the complaint at Rapides-des-Cedres dam and deaths that occurred in 2004 when water from a dam was released without warning. Several photographs were presented to illustrate that people were unaware of the danger. Initiatives aimed at raising awareness and studying public safety issues were discussed. A pilot project was launched and a permanent committee was created to evaluate all aspects of public safety at the dams owned by CEHQ. The first tasks of the committee were to establish requirements for waterway safety barriers, both upstream and downstream, for all public dams; to establish requirements for safety signage for all public dams; and to develop criteria to decide on safety signage at each dam. figs.

Legacy effects of colonial millponds on floodplain sedimentation, bank erosion, and channel morphology, MID-Atlantic, USA

Science.gov (United States)

Schenk, E.R.; Hupp, C.R.

2009-01-01

Many rivers and streams of the Mid-Atlantic Region, United States (U.S.) have been altered by postcolonial floodplain sedimentation (legacy sediment) associated with numerous milldams. Little Conestoga Creek, Pennsylvania, a tributary to the Susquehanna River and the Chesapeake Bay, is one of these streams. Floodplain sedimentation rates, bank erosion rates, and channel morphology were measured annually during 2004-2007 at five sites along a 28-km length of Little Conestoga Creek with nine colonial era milldams (one dam was still in place in 2007). This study was part of a larger cooperative effort to quantify floodplain sedimentation, bank erosion, and channel morphology in a high sediment yielding region of the Chesapeake Bay watershed. Data from the five sites were used to estimate the annual volume and mass of sediment stored on the floodplain and eroded from the banks for 14 segments along the 28-km length of creek. A bank and floodplain reach based sediment budget (sediment budget) was constructed for the 28 km by summing the net volume of sediment deposited and eroded from each segment. Mean floodplain sedimentation rates for Little Conestoga Creek were variable, with erosion at one upstream site (-5 mm/year) to deposition at the other four sites (highest = 11 mm/year) despite over a meter of floodplain aggradation from postcolonial sedimentation. Mean bank erosion rates range between 29 and 163 mm/year among the five sites. Bank height increased 1 m for every 10.6 m of channel width, from upstream to downstream (R2 = 0.79, p channel and the floodplain. Floodplain sedimentation and bank erosion rates also appear to be affected by the proximity of the segments to one existing milldam, which promotes deposition upstream and scouring downstream. The floodplain and bank along the 28-km reach produced a net mean sediment loss of 5,634 Mg/year for 2004-2007, indicating that bank erosion was exceeding floodplain sedimentation. In particular, the three segments

A review of sediment quantity issues: examples from the River Ebro and adjacent basins (Northeastern Spain).

Science.gov (United States)

Batalla, Ramon J; Vericat, Damià

2011-04-01

Sediment flows naturally through the drainage network, from source areas to deposition zones. Sedimentary disequilibrium in rivers and coastlines is related to the imbalance within the fluvial system caused mostly by dams, instream mining, and changes in land use. This phenomenon is also responsible for ecological perturbations in rivers and streams. A broad need exists to establish comprehensive management strategies (soft measures) that would go beyond site-specific engineering practices (technical measures) typically taken to solve particular problems. Long-term programs are also required to monitor sediment transport in river basins, in order to assess the magnitude and variability of sediment transfer and potential deficits. This paper shows examples of rivers with important sediment disequilibrium in the Ebro and adjacent basins. These basins, like most in the Iberian Peninsula, experience sediment discontinuity in the catchment-river-coast system. Reservoir siltation is the main quantitative issue. Land use change and especially gravel mining downstream from dams accentuate the process. We also present and discuss recent developments on water and sediment management undertaken to improve the morphosedimentary dynamics of rivers. Copyright © 2010 SETAC.

Dam failure analysis for the Lago El Guineo Dam, Orocovis, Puerto Rico

Science.gov (United States)

Gómez-Fragoso, Julieta; Heriberto Torres-Sierra,

2016-08-09

The U.S. Geological Survey, in cooperation with the Puerto Rico Electric Power Authority, completed hydrologic and hydraulic analyses to assess the potential hazard to human life and property associated with the hypothetical failure of the Lago El Guineo Dam. The Lago El Guineo Dam is within the headwaters of the Río Grande de Manatí and impounds a drainage area of about 4.25 square kilometers.The hydrologic assessment was designed to determine the outflow hydrographs and peak discharges for Lago El Guineo and other subbasins in the Río Grande de Manatí hydrographic basin for three extreme rainfall events: (1) a 6-hour probable maximum precipitation event, (2) a 24-hour probable maximum precipitation event, and (3) a 24-hour, 100-year recurrence rainfall event. The hydraulic study simulated a dam failure of Lago El Guineo Dam using flood hydrographs generated from the hydrologic study. The simulated dam failure generated a hydrograph that was routed downstream from Lago El Guineo Dam through the lower reaches of the Río Toro Negro and the Río Grande de Manatí to determine water-surface profiles developed from the event-based hydrologic scenarios and “sunny day” conditions. The Hydrologic Engineering Center’s Hydrologic Modeling System (HEC–HMS) and Hydrologic Engineering Center’s River Analysis System (HEC–RAS) computer programs, developed by the U.S. Army Corps of Engineers, were used for the hydrologic and hydraulic modeling, respectively. The flow routing in the hydraulic analyses was completed using the unsteady flow module available in the HEC–RAS model.Above the Lago El Guineo Dam, the simulated inflow peak discharges from HEC–HMS resulted in about 550 and 414 cubic meters per second for the 6- and 24-hour probable maximum precipitation events, respectively. The 24-hour, 100-year recurrence storm simulation resulted in a peak discharge of about 216 cubic meters per second. For the hydrologic analysis, no dam failure conditions are

Legacy effects of colonial millponds on floodplain sedimentation, bank erosion, and channel morphology, MID-Atlantic, USA

Science.gov (United States)

Schenk, E.R.; Hupp, C.R.

2009-01-01

Many rivers and streams of the Mid-Atlantic Region, United States (U.S.) have been altered by postcolonial floodplain sedimentation (legacy sediment) associated with numerous milldams. Little Conestoga Creek, Pennsylvania, a tributary to the Susquehanna River and the Chesapeake Bay, is one of these streams. Floodplain sedimentation rates, bank erosion rates, and channel morphology were measured annually during 2004-2007 at five sites along a 28-km length of Little Conestoga Creek with nine colonial era milldams (one dam was still in place in 2007). This study was part of a larger cooperative effort to quantify floodplain sedimentation, bank erosion, and channel morphology in a high sediment yielding region of the Chesapeake Bay watershed. Data from the five sites were used to estimate the annual volume and mass of sediment stored on the floodplain and eroded from the banks for 14 segments along the 28-km length of creek. A bank and floodplain reach based sediment budget (sediment budget) was constructed for the 28 km by summing the net volume of sediment deposited and eroded from each segment. Mean floodplain sedimentation rates for Little Conestoga Creek were variable, with erosion at one upstream site (-5 mm/year) to deposition at the other four sites (highest = 11 mm/year) despite over a meter of floodplain aggradation from postcolonial sedimentation. Mean bank erosion rates range between 29 and 163 mm/year among the five sites. Bank height increased 1 m for every 10.6 m of channel width, from upstream to downstream (R2 = 0.79, p scouring downstream. The floodplain and bank along the 28-km reach produced a net mean sediment loss of 5,634 Mg/year for 2004-2007, indicating that bank erosion was exceeding floodplain sedimentation. In particular, the three segments between the existing dam and the confluence with the Conestoga River (32% of the studied reach) account for 97% of the measured net sediment budget. Future research directed at understanding channel

Particle-bound metal transport after removal of a small dam in the Pawtuxet River, Rhode Island, USA

Science.gov (United States)

The Pawtuxet River in Rhode Island, USA, has a long history of industrial activity and pollutant discharges. Metal contamination of the river sediments is well documented and historically exceeded toxicity thresholds for a variety of organisms. The Pawtuxet River dam, a low-head ...

Grain-size evolution in suspended sediment and deposits from the 2004 and 2008 controlled-flood experiments in Marble and Grand Canyons, Arizona

Science.gov (United States)

Draut, Amy E.; Topping, David J.; Rubin, David M.; Wright, Scott A.; Schmidt, John C.

2010-01-01

Since the closure of Glen Canyon Dam in 1963, the hydrology, sediment supply, and distribution and size of modern alluvial deposits in the Colorado River through Grand Canyon have changed substantially (e.g., Howard and Dolan, 1981; Johnson and Carothers, 1987; Webb et al., 1999; Rubin et al., 2002; Topping et al., 2000, 2003; Wright et al., 2005; Hazel et al., 2006). The dam has reduced the fluvial sediment supply at the upstream boundary of Grand Canyon National Park by about 95 percent. Regulation of river discharge by dam operations has important implications for the storage and redistribution of sediment in the Colorado River corridor. In the absence of natural floods, sediment is not deposited at elevations that regularly received sediment before dam closure. There has been a systemwide decrease in the size and number of subaerially exposed fluvial sand deposits since the 1960s, punctuated by episodic aggradation during the exceptional high-flow intervals in the early 1980s and by sediment input from occasional tributary floods (Beus and others, 1985; Schmidt and Graf, 1990; Kearsley et al., 1994; Schmidt et al., 2004; Wright et al., 2005; Hazel et al., 2006). Fluvial sandbars are an important component of riparian ecology that, among other functions, enclose eddy backwaters that form native-fish habitat, provide a source for eolian sand that protects some archaeological sites, and are used as campsites by thousands of river-runners annually (Rubin et al., 1990; Kearsley et al., 1994; Neal et al., 2000; Wright et al., 2005; Draut and Rubin, 2008).

Environmental Benefits of Restoring Sediment Continuity to the Kansas River

Science.gov (United States)

2016-06-01

quality and ecological effects of reservoir aging by sediment accumulation. The section titled “Downstream Channel Effects” cites specific ecological ...effects ( Wood and Armitage 1997; Karr and Yoder 2004). However, as noted by the National Research Council (2011), “Not all sediments and all rivers...National Research Council 2011). Dam construction , as discussed by Wohl et al. (2015), Juracek (2014), Kondolf et al. (2014), and the National Research

Estimating changes in riparian and channel features along the Trinity River downstream of Lewiston Dam, California, 1980 to 2011

Science.gov (United States)

Curtis, Jennifer A.

2015-01-01

Dam construction, flow diversion, and legacy landuse effects reduced the transport capacity, sediment supply, channel complexity and floodplain-connectivity along the Trinity River, CA below Lewiston Dam. This study documents the geomorphic evolution of the Trinity River Restoration Program’s intensively managed 65-km long restoration reach from 1980 to 2011. The nature and extent of riparian and channel changes were assessed using a series of geomorphic feature maps constructed from ortho-rectified photography acquired at low flow conditions in 1980, 1997, 2001, 2006, 2009, and 2011. Since 1980 there has been a general conversion of riparian to channel features and expansion of the active channel area. The primary mechanism for expansion of the active channel was bank erosion from 1980 to 1997 and channel widening was well distributed longitudinally throughout the study reach. Subsequent net bar accretion from 1997 to 2001, followed by slightly higher net bar scour from 2001 to 2006, occurred primarily in the central and lower reaches of the study area. In comparison, post-2006 bank and bar changes were spatially-limited to reaches with sufficient local transport capacity or sediment supply supported by gravel augmentation, mechanical channel rehabilitation, and tributary contributions to flow and sediment supply. A series of tributary floods in 1997, 1998 and 2006 were the primary factors leading to documented increases in channel complexity and floodplain connectivity. During the post-2006 period managed flow releases, in the absence of large magnitude tributary flooding, combined with gravel augmentation and mechanical restoration caused localized increases in sediment supply and transport capacity leading to smaller but measurable increases in channel complexity and floodplain connectivity primarily in the upper river below Lewiston Dam.

Design of a sediment-monitoring gaging network on ephemeral tributaries of the Colorado River in Glen, Marble, and Grand Canyons, Arizona

Science.gov (United States)

Griffiths, Ronald E.; Topping, David J.; Anderson, Robert S.; Hancock, Gregory S.; Melis, Theodore S.

2014-01-01

Management of sediment in rivers downstream from dams requires knowledge of both the sediment supply and downstream sediment transport. In some dam-regulated rivers, the amount of sediment supplied by easily measured major tributaries may overwhelm the amount of sediment supplied by the more difficult to measure lesser tributaries. In this first class of rivers, managers need only know the amount of sediment supplied by these major tributaries. However, in other regulated rivers, the cumulative amount of sediment supplied by the lesser tributaries may approach the total supplied by the major tributaries. The Colorado River downstream from Glen Canyon has been hypothesized to be one such river. If this is correct, then management of sediment in the Colorado River in the part of Glen Canyon National Recreation Area downstream from the dam and in Grand Canyon National Park may require knowledge of the sediment supply from all tributaries. Although two major tributaries, the Paria and Little Colorado Rivers, are well documented as the largest two suppliers of sediment to the Colorado River downstream from Glen Canyon Dam, the contributions of sediment supplied by the ephemeral lesser tributaries of the Colorado River in the lowermost Glen Canyon, and Marble and Grand Canyons are much less constrained. Previous studies have estimated amounts of sediment supplied by these tributaries ranging from very little to almost as much as the amount supplied by the Paria River. Because none of these previous studies relied on direct measurement of sediment transport in any of the ephemeral tributaries in Glen, Marble, or Grand Canyons, there may be significant errors in the magnitudes of sediment supplies estimated during these studies. To reduce the uncertainty in the sediment supply by better constraining the sediment yield of the ephemeral lesser tributaries, the U.S. Geological Survey Grand Canyon Monitoring and Research Center established eight sediment-monitoring gaging

Historical variations in the stable isotope composition of mercury in a sediment core from a riverine lake: Effects of dams, pulp and paper mill wastes, and mercury from a chlor-alkali plant

International Nuclear Information System (INIS)

Jackson, Togwell A.

2016-01-01

The Wabigoon River (Ontario, Canada) was affected by dams starting in 1898 and was polluted with pulp and paper mill wastes starting in 1913 and mercury from a chlor-alkali plant from 1962 to 1975. A dated sediment core from a riverine lake was analysed to investigate resultant changes in the biogeochemistry of mercury as revealed by variations in mercury isotope ratios and sediment chemistry. A total mercury maximum formed by the mercury pollution coincided with minimums in the δ-values of the 198 Hg/ 202 Hg, 199 Hg/ 202 Hg, 200 Hg/ 202 Hg, and 201 Hg/ 202 Hg ratios, and the δ-values decreased in the order δ 201 Hg > δ 200 Hg > δ 199 Hg > δ 198 Hg. Thus, mass-dependent fractionation caused depletion in lighter isotopes, implying evaporation of Hg(0) and pollution of the atmosphere as well as the river-lake system. Concurrently, mass-independent fractionation caused 199 Hg enrichment, possibly reflecting an independently documented upsurge in methylmercury production, and 201 Hg depletion, suggesting removal of methylmercury with anomalously high 201 Hg/ 199 Hg ratios by aquatic organisms and accumulation of 201 Hg-depleted inorganic Hg(II) in sediments. The δ 201 Hg/δ 199 Hg ratio rose abruptly when mercury pollution began, reflecting the resultant increase in methylmercury production, and remained high but gradually declined as the pollution abated, paralleling trends shown by methylmercury in aquatic organisms. The δ 201 Hg/δ 199 Hg ratio of pre-1962 background mercury increased ca. 1898 and ca. 1913–1929, suggesting accelerated methylmercury production due to stimulation of microbial activities by the damming of the river and the input of pulp and paper mill wastes, respectively. Other variations were linked to economic and technological factors that affected pulp and paper manufacture. - Highlights: • A core from a lake polluted by Hg and organic wastes was analysed for Hg isotopes. • Hg from a chlor-alkali plant was depleted in lighter

Spatial variation of sediment mineralization supports differential CO2 emissions from a tropical hydroelectric reservoir.

Science.gov (United States)

Cardoso, Simone J; Vidal, Luciana O; Mendonça, Raquel F; Tranvik, Lars J; Sobek, Sebastian; Fábio, Roland

2013-01-01

Substantial amounts of organic matter (OM) from terrestrial ecosystems are buried as sediments in inland waters. It is still unclear to what extent this OM constitutes a sink of carbon, and how much of it is returned to the atmosphere upon mineralization to carbon dioxide (CO2). The construction of reservoirs affects the carbon cycle by increasing OM sedimentation at the regional scale. In this study we determine the OM mineralization in the sediment of three zones (river, transition, and dam) of a tropical hydroelectric reservoir in Brazil as well as identify the composition of the carbon pool available for mineralization. We measured sediment organic carbon mineralization rates and related them to the composition of the OM, bacterial abundance and pCO2 of the surface water of the reservoir. Terrestrial OM was an important substrate for the mineralization. In the river and transition zones most of the OM was allochthonous (56 and 48%, respectively) while the dam zone had the lowest allochthonous contribution (7%). The highest mineralization rates were found in the transition zone (154.80 ± 33.50 mg C m(-) (2) d(-) (1)) and the lowest in the dam (51.60 ± 26.80 mg C m(-) (2) d(-) (1)). Moreover, mineralization rates were significantly related to bacterial abundance (r (2) = 0.50, p hydroelectric reservoirs.

Teton Dam failure

Energy Technology Data Exchange (ETDEWEB)

Snorteland, N. [United States Dept. of the Interior, Washington, DC (United States). Bureau of Reclamation

2009-07-01

This case summary discussed an internal erosion failure that occurred at the embankment foundation of Teton Dam. The project was designed as a run-of-the-river power generation facility and to provide irrigation, flood protection, and power generation to the lower Teton region of southern Idaho. The dam site was located next to the eastern Snake River plain, a volcanic filled depression. The foundation's cutoff trench was excavated into the bedrock along the length of the dam. The dam was designed as a zoned earthfill with a height of 305 feet. A trench made of low plasticity windblown silt was designed to connect the embankment core to the rock foundation. Seeps were noted in 1976, and a leak was observed near the toe of the dam. A wet spot appeared on the downstream face of the dam at elevation 5200. A sinkhole then developed. The embankment crest collapsed, and the dam breached. Peak outflow was estimated at 1,000,000 cfs. The failure was attributed to a lack of communication between designers, a failure to understand geologic information about the region, and an insufficient review of designs and specifications by designers and field personnel. No monitoring instrumentation was installed in the embankment. Approximately 300 square miles were inundated, and 25,000 people were displaced. Eleven people were killed. A review group noted that the rock surface was not adequately sealed, and that the dam failed as a result of inadequate protection of the impervious core material from internal erosion. 42 figs.

Integrating isotopic tracer techniques with Bayesian modelling for improved assessment and management of sedimentation problems in the Gilgel-Gibe catchment, Ethiopia

Science.gov (United States)

Dume, Bayu; Amsalu, Nebiyu; Bode, Samuel; Mtei, Kelvin; Munishi, Linus; Navas, Ana; Semmens, Brice; Smith, Hugh; Stock, Brian; Blake, Will; Boeckx, Pascal

2017-04-01

Soil erosion and associated downstream siltation of dams and lakes is becoming serious threat to catchment ecosystem services supporting water, food and energy security in Ethiopia. Sediments originate on catchment hillslopes but mobilisation processes vary depending on land use and terrain. The Gilgel Gibe hydroelectric dam is one of a series of development projects launched by the Federal Government of Ethiopia. The catchment is characterised by erodible, deforested agricultural land which is also overgrazed. Siltation and nutrient enrichment are significant issues given 'hotspot' sheet erosion estimates of 2210 ton per square km. The annual contribution of sediment from the Gilgel Gibe River to the dam was estimated at 277 thousand tons per year leading to accumulations of 3.75 x 107 cubic metres per year of silt behind the dam. The primary driver for mobilisation and translocation to downstream is believed to be erosion on agricultural lands and collapse of steep banks, through landsliding into river channels in the highland headwaters. The relative importance of specific sources of siltation are unknown and sediment source apportionment has been identified as a first essential step before soil conservation measures can be implemented. Knowledge of sediment source and transfer dynamics is critical to inform management policy decisions to maintain and enhance future food, water and energy security To test the applicability of a new combination of Bayesian unmixing modelling with sediment fingerprinting in this terrain (IMIXSED approach) a demonstration sub-catchment was selected through field assessment in the upper Gilgel-Gibe water-supply catchments (Unta River) and sampling strategies designed. Accordingly, sources, i.e. soil samples from landslides (n=40), eroding channel bank (n = 5), cultivated land (n = 30), grasslands (n = 30), wooded areas (n = 10), homestead plots (n = 10) were collected alongside 10 spatially-integrated sediment deposits from the

Enhancing sediment flux control and natural hazard risk mitigation through a structured conceptual planning approach

Science.gov (United States)

Simoni, S.; Vignoli, G.; Mazzorana, B.

2017-08-01

Sediment fluxes from mountain rivers contribute to shape the geomorphologic features of lowland rivers and to establish the physical basis for an optimal set of ecosystem functions and related services to people. Through significant public funding, the hydro-morphological regimes of mountain rivers in the European Alps have been progressively altered over the last century, with the aim to provide a safe dwelling space, to boost transport, mobility and to support economic growth. We claim that the underlying planning weaknesses contribute to determine these inefficient resource allocations, since flood risk is still high and the ecosystem services are far from being optimal. Hence, with the overall aim to enhance sediment flux control and hazard risk mitigation in such heavily modified alpine streams, we propose a structured design workflow which guides the planner through system analysis and synthesis. As a first step the proposed workflow sets the relevant planning goals and assesses the protection structure functionality. Then a methodology is proposed to achieve the goals. This methodology consists in characterising the hydrologic basin of interest and the sediment availability and determining the sediment connectivity to channels. The focus is set on the detailed analysis of existing river cross sections where the sediment continuity is interrupted (e.g. slit and check dams). By retaining relevant sediment volumes these structures prevent the reactivation of hydro-morphological and associated ecological functionalities. Since their actual performance can be unsatisfying with respect to flood risk mitigation (e.g. mainly old structures), we introduce specific efficiency indicators as a support for the conceptual design stage to quantify effects related to sediment flux control and risk management. The proposed planning approach is then applied to the Gadria system (stream, slit dam, retention basin and culvert), located in South Tyrol, Italy. This case study

How big of an effect do small dams have? Using geomorphological footprints to quantify spatial impact of low-head dams and identify patterns of across-dam variation

Science.gov (United States)

Fencl, Jane S.; Mather, Martha E.; Costigan, Katie H.; Daniels, Melinda D.

2015-01-01

Longitudinal connectivity is a fundamental characteristic of rivers that can be disrupted by natural and anthropogenic processes. Dams are significant disruptions to streams. Over 2,000,000 low-head dams (research and conservation is impaired by not knowing the magnitude of low-head dam impacts. Based on the geomorphic literature, we refined a methodology that allowed us to quantify the spatial extent of low-head dam impacts (herein dam footprint), assessed variation in dam footprints across low-head dams within a river network, and identified select aspects of the context of this variation. Wetted width, depth, and substrate size distributions upstream and downstream of six low-head dams within the Upper Neosho River, Kansas, United States of America were measured. Total dam footprints averaged 7.9 km (3.0–15.3 km) or 287 wetted widths (136–437 wetted widths). Estimates included both upstream (mean: 6.7 km or 243 wetted widths) and downstream footprints (mean: 1.2 km or 44 wetted widths). Altogether the six low-head dams impacted 47.3 km (about 17%) of the mainstem in the river network. Despite differences in age, size, location, and primary function, the sizes of geomorphic footprints of individual low-head dams in the Upper Neosho river network were relatively similar. The number of upstream dams and distance to upstream dams, but not dam height, affected the spatial extent of dam footprints. In summary, ubiquitous low-head dams individually and cumulatively altered lotic ecosystems. Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network. For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic approach that has been applied to larger dams.

Mechanics of slide dams

International Nuclear Information System (INIS)

Young, G.A.

1970-01-01

Studies which promote the use of nuclear energy for peaceful projects in engineering are sponsored by the Atomic Energy Commission under the Plowshare program. Specific projects being considered include the construction of harbors, canals, and dams. Of these projects, perhaps the most difficult to accomplish will be the latter. This paper which is in two parts considers the problems which are associated with the construction of slide dams with nuclear explosives. It examines first the characteristics of conventional earth and rock-fill dams which are based upon proven techniques developed after many years of experience. The characteristics of natural landslide dams are also briefly considered to identify potential problems that must be overcome by slide dam construction techniques. Second, the mechanics of slide dams as determined from small-scale laboratory studies are presented. It is concluded that slide dams can be constructed and that small-scale field tests and additional laboratory studies are justified. (author)

Mechanics of slide dams

Energy Technology Data Exchange (ETDEWEB)

Young, G A [Engineering, Agbabian-Jacobsen Associates, Los Angeles (United States)

1970-05-15

Studies which promote the use of nuclear energy for peaceful projects in engineering are sponsored by the Atomic Energy Commission under the Plowshare program. Specific projects being considered include the construction of harbors, canals, and dams. Of these projects, perhaps the most difficult to accomplish will be the latter. This paper which is in two parts considers the problems which are associated with the construction of slide dams with nuclear explosives. It examines first the characteristics of conventional earth and rock-fill dams which are based upon proven techniques developed after many years of experience. The characteristics of natural landslide dams are also briefly considered to identify potential problems that must be overcome by slide dam construction techniques. Second, the mechanics of slide dams as determined from small-scale laboratory studies are presented. It is concluded that slide dams can be constructed and that small-scale field tests and additional laboratory studies are justified. (author)

Dam break analysis and flood inundation map of Krisak dam for emergency action plan

Science.gov (United States)

Juliastuti, Setyandito, Oki

2017-11-01

The Indonesian Regulation which refers to the ICOLD Regulation (International Committee on Large Dam required have the Emergency Action Plan (EAP) guidelines because of the dams have potential failure. In EAP guidelines there is a management of evacuation where the determination of the inundation map based on flood modeling. The purpose of the EAP is to minimize the risk of loss of life and property in downstream which caused by dam failure. This paper will describe about develop flood modeling and inundation map in Krisak dam using numerical methods through dam break analysis (DBA) using hydraulic model Zhong Xing HY-21. The approaches of dam failure simulation are overtopping and piping. Overtopping simulation based on quadrangular, triangular and trapezium fracture. Piping simulation based on cracks of orifice. Using results of DBA, hazard classification of Krisak dam is very high. The nearest village affected dam failure is Singodutan village (distance is 1.45 kilometer from dam) with inundation depth is 1.85 meter. This result can be used by stakeholders such as emergency responders and the community at risk in formulating evacuation procedure.

Spruce Lake Dam reconstruction

Energy Technology Data Exchange (ETDEWEB)

Snyder, G. [SGE Acres Ltd., Fredericton, NB (Canada); Barnard, J. [SGE Acres Ltd., St. John' s, NF (Canada); Vriezen, C. [City of Saint John, NF (Canada); Stephenson, M. [Jacques Whitford Environment Ltd., Fredericton, NB (Canada)

2004-09-01

Spruce Lake Dam was constructed in 1898 as part of the water supply system for Saint John, New Brunswick. The original dam was a 6 meter high, 140 meter long concrete gravity dam with an intake structure at its mid point and an overflow spillway at the left abutment. A rehabilitation project was launched in 2001 to bring the deteriorated dam into conformance with the dam safety guidelines of the Canadian Dam Association. The project criteria included minimal disruption to normal operation of water supply facilities and no negative effect on water quality. The project involved installation of a new low level outlet, removal of a gate house and water intake pipes, replacement of an access road culvert in the spillway channel, and raising the earth dam section by 1.8 meters to allow for increased water storage. The new raised section has an impervious core. The project also involved site and geotechnical investigations as well as hydrotechnical and environmental studies. This presentation described the final design of the remedial work and the environmental permitting procedures. Raising the operating level of the system proved successful as demonstrated by the fewer number of pumping days required after dam rehabilitation. The dam safety assessment under the Canadian Environmental Assessment Act began in April 2001, and the rehabilitation was completed by the end of 2002. 1 tab., 8 figs.

Small dams need better management

Science.gov (United States)

Balcerak, Ernie

2012-03-01

Many small dams around the world are poorly maintained and represent a safety hazard, according to Pisaniello et al. Better oversight of small dams is needed, the authors argue. The researchers reviewed literature, conducted case studies in four states in Australia, and developed policy benchmarks and best practices for small-dam management. Small dams, often just several meters high and typically privately owned by individual farmers, have historically caused major damage when they fail. For instance, in China in 1975, 230,000 people died when two large dams failed because of the cumulative failure of 60 smaller upstream dams. In the United States, in 1977 the 8-meter-high Kelly Barnes Lake dam failed, killing 39 people. Many other small-dam failures around the world have resulted in casualties and severe ecological and economic damage.

Sediment accumulation rate and radiological characterisation of the sediment of Palmones River estuary (southern of Spain)

International Nuclear Information System (INIS)

Rubio, L.; Linares-Rueda, A.; Duenas, C.; Fernandez, M.C.; Clavero, V.; Niell, F.X.; Fernandez, J.A.

2003-01-01

Chemical analyses and radioecological methods were combined in order to estimate the sediment accumulation rate in the upper 20 cm depth of the Palmones River estuary. Organic matter, total carbon, C:N and 137 Cs vertical profiles showed changes at 13 cm depth. These changes could be associated with the decrease in river input since 1987 when a dam situated in the upper part of the estuary started to store water. Using 1987 as reference to date the sediment, accumulation rate was 1.2 cm yr -1 . As alternative method, two layer model of 210 Pb xs vertical distribution showed a sedimentation rate of 0.7 cm yr -1 with a surface mixing layer of 7 cm thickness. The high ammonium, potassium and sodium content in pore water and the strong correlation between 137 Cs activities and organic matter in dry sediment suggests that 137 Cs (the only anthropogenic product detected) is mainly accumulated in the estuary associated with the particulate organic material from the catchment area

Meta-analysis of environmental effects of beaver in relation to artificial dams

Science.gov (United States)

Ecke, Frauke; Levanoni, Oded; Audet, Joachim; Carlson, Peter; Eklöf, Karin; Hartman, Göran; McKie, Brendan; Ledesma, José; Segersten, Joel; Truchy, Amélie; Futter, Martyn

2017-11-01

Globally, artificial river impoundment, nutrient enrichment and biodiversity loss impair freshwater ecosystem integrity. Concurrently, beavers, ecosystem engineers recognized for their ability to construct dams and create ponds, are colonizing sites across the Holarctic after widespread extirpation in the 19th century, including areas outside their historical range. This has the potential to profoundly alter hydrology, hydrochemistry and aquatic ecology in both newly colonized and recolonized areas. To further our knowledge of the effects of beaver dams on aquatic environments, we extracted 1366 effect sizes from 89 studies on the impoundment of streams and lakes. Effects were assessed for 16 factors related to hydrogeomorphology, biogeochemistry, ecosystem functioning and biodiversity. Beaver dams affected concentrations of organic carbon in water, mercury in water and biota, sediment conditions and hydrological properties. There were no overall adverse effects caused by beaver dams or ponds on salmonid fish. Age was an important determinant of effect magnitude. While young ponds were a source of phosphorus, there was a tendency for phosphorus retention in older systems. Young ponds were a source methylmercury in water, but old ponds were not. To provide additional context, we also evaluated similarities and differences between environmental effects of beaver-constructed and artificial dams (767 effect sizes from 75 studies). Both are comparable in terms of effects on, for example, biodiversity, but have contrasting effects on nutrient retention and mercury. These results are important for assessing the role of beavers in enhancing and/or degrading ecological integrity in changing Holarctic freshwater systems.

The Impact of Dam-Reservoir-Foundation Interaction on Nonlinear Response of Concrete Gravity Dams

International Nuclear Information System (INIS)

Amini, Ali Reza; Motamedi, Mohammad Hossein; Ghaemian, Mohsen

2008-01-01

To study the impact of dam-reservoir-foundation interaction on nonlinear response of concrete gravity dams, a two-dimensional finite element model of a concrete gravity dam including the dam body, a part of its foundation and a part of the reservoir was made. In addition, the proper boundary conditions were used in both reservoir and foundation in order to absorb the energy of outgoing waves at the far end boundaries. Using the finite element method and smeared crack approach, some different seismic nonlinear analyses were done and finally, we came to a conclusion that the consideration of dam-reservoir-foundation interaction in nonlinear analysis of concrete dams is of great importance, because from the performance point of view, this interaction significantly improves the nonlinear response of concrete dams

Investigation of quality of storage dam in Ilam, identifying of pollutant resources and pollutants attitude

Directory of Open Access Journals (Sweden)

Moayed Avazpour

2013-12-01

Full Text Available Water quality of dam storage is highly affected by upstream environment and basin. Regarding other conducted studies, there exist various reasons such as some studies and general monitoring of dams which cause some main problems including salinity, chemical and microbial pollution eutrophication, and sedimentation. Chame-Gerdalan storage dam in Ilam Province is one of the storages which have many environmental issues because of discharge upstream rural wastewaters, animal excreta, agricultural drainage, and leachate. The aim of this study is to signify the quality of Ilam’s storage dam and also to recognize the pollutant resources and to analyze the pollutants’ behavior at different times and sites in order to determine dam properties for agricultural and domestic usages. Regarding the importance of the topic, the present study (in the year 2012 is based on the collected information of water quality of the basin, recognition of pollutant resources and measurement of qualitative parameters such as temperature, TDS, EC, BOD5, COD, nitrogen, phosphor, and pH in seven periods of time (from May to November. The results show that the total increase in the concentration of all variables along the basin are over double, in particular, Nitrat, Sulfat, BOD, and COD. After analyzing data with some water quality indexes, we analyzed water quality of the storage and some strategies were applied in order to control the effect decrease in the dam storage which, a management program was presented to improve water quality.

Estimating Sediment Delivery to The Rio Maranon, Peru Prior to Large-Scale Hydropower Developments Using High Resolution Imagery from Google Earth and a DJI Phantom 3 Drone

Science.gov (United States)

Goode, J. R.; Candelaria, T.; Kramer, N. R.; Hill, A. F.

2016-12-01

As global energy demands increase, generating hydroelectric power by constructing dams and reservoirs on large river systems is increasingly seen as a renewable alternative to fossil fuels, especially in emerging economies. Many large-scale hydropower projects are located in steep mountainous terrain, where environmental factors have the potential to conspire against the sustainability and success of such projects. As reservoir storage capacity decreases when sediment builds up behind dams, high sediment yields can limit project life expectancy and overall hydropower viability. In addition, episodically delivered sediment from landslides can make quantifying sediment loads difficult. These factors, combined with remote access, limit the critical data needed to effectively evaluate development decisions. In the summer of 2015, we conducted a basic survey to characterize the geomorphology, hydrology and ecology of 620 km of the Rio Maranon, Peru - a major tributary to the Amazon River, which flows north from the semi-arid Peruvian Andes - prior to its dissection by several large hydropower dams. Here we present one component of this larger study: a first order analysis of potential sediment inputs to the Rio Maranon, Peru. To evaluate sediment delivery and storage in this system, we used high resolution Google Earth imagery to delineate landslides, combined with high resolution imagery from a DJI Phantom 3 Drone, flown at alluvial fan inputs to the river in the field. Because hillslope-derived sediment inputs from headwater tributaries are important to overall ecosystem health in large river systems, our study has the potential to contribute to the understanding the impacts of large Andean dams on sediment connectivity to the Amazon basin.

Modeling Anthropogenic Impact on Sediment Balance and Relative Sea-Level Rise in Contemporary and Future Deltas

Science.gov (United States)

Tessler, Z. D.; Vorosmarty, C. J.; Overeem, I.; Syvitski, J. P.

2017-12-01

Modern deltas are dependent on human-mediated freshwater and sediment fluxes. Changes to these fluxes impact delta biogeophysical functioning, and affect the long-term sustainability of these landscapes for both human and natural systems. Here we present contemporary estimates of long-term mean sediment balance and relative sea-level rise across 46 global deltas. We model ongoing development and scenarios of future water resource management and hydropower infrastructure in upstream river basins to explore how changing sediment fluxes impact relative sea-level in coastal delta systems. Model results show that contemporary sediment fluxes, anthropogenic drivers of land subsidence, and sea-level rise result in relative sea-level rise rates in deltas that average 6.8 mm/year. Currently planned or under-construction dams can be expected to increase rates of relative sea-level rise on the order of 1 mm/year. Some deltas systems, including the Magdalena, Orinoco, and Indus, are highly sensitive to future impoundment of river basins, with RSLR rates increasing up to 4 mm/year in a high-hydropower-utilization scenario. Sediment fluxes may be reduced by up to 60% in the Danube and 21% in the Ganges-Brahmaputra-Megnha if all currently planned dams are constructed. Reduced sediment retention on deltas due to increased river channelization and local flood controls increases RSLR on average by nearly 2 mm/year. Long-term delta sustainability requires a more complete understanding of how geophysical and anthropogenic change impact delta geomorphology. Strategies for sustainable delta management that focus on local and regional drivers of change, especially groundwater and hydrocarbon extraction and upstream dam construction, can be highly impactful even in the context of global climate-induced sea-level rise.

Study of Dam-break Due to Overtopping of Four Small Dams in the Czech Republic

Directory of Open Access Journals (Sweden)

Zakaraya Alhasan

2015-01-01

Full Text Available Dam-break due to overtopping is one of the most common types of embankment dam failures. During the floods in August 2002 in the Czech Republic, several small dams collapsed due to overtopping. In this paper, an analysis of the dam break process at the Luh, Velký Bělčický, Melín, and Metelský dams breached during the 2002 flood is presented. Comprehensive identification and analysis of the dam shape, properties of dam material and failure scenarios were carried out after the flood event to assemble data for the calibration of a numerical dam break model. A simple one-dimensional mathematical model was proposed for use in dam breach simulation, and a computer code was compiled. The model was calibrated using the field data mentioned above. Comparison of the erodibility parameters gained from the model showed reasonable agreement with the results of other authors.

Investigation of geophysical methods for assessing seepage and internal erosion in embankment dams : a study of through-dam seismic testing at WAC Bennett Dam

Energy Technology Data Exchange (ETDEWEB)

Gaffran, P.; Jeffries, M. [BC Hydro, Burnaby, BC (Canada)

2005-07-15

Crosshole tomography is used to establish the distribution of seismic velocity between drill holes. The through-dam mode takes advantage of the triangular cross-section of earth embankments, obviating the need for drill holes. Seismic energy, generated on one face of the dam, passes underneath the crest and is detected by sensors arrayed on the opposite face. The sinkholes discovered at WAC Bennett Dam in 1996 provided an opportunity to test the procedure. Using p-wave energy, two series of measurements were conducted, notably one immediately before remediation of one sinkhole, and a second one shortly after the sinkhole was repaired. The known defect was successfully imaged by the first round of measurements. This report presented the results of an investigation of the through-dam seismic method using propagation of seismic waves through a dam from upstream to downstream, or vice-versa. The purpose of the study was to determine if this procedure could characterize the distribution of seismic velocity within a dam in an accurate and cost effective manner. The report presented the methods of velocity testing such as crosshole and downhole, and tomography; and through-dam measurements. Background to the Bennett Dam studies was also provided, with particular reference to the Bennett Dam sinkholes; sinkhole investigations; working hypothesis for sinkhole development; sinkhole number one characterization; and sinkhole remediation. An analysis of compression wave testing at Bennett Dam and shear wave testing was then offered. Other topics that were discussed included field test procedures; methodologies for data processing; p-waves versus s-waves; applicability of the research; and costs of through-dam surveys. It was concluded that under the right circumstances, through-dam seismic testing was capable of detecting changed conditions in an embankment dam. 15 refs., 2 tabs., 41 figs., 1 appendix.

Geologic Hazards Associated With a Proposed Dam on the Yarlung-Tsangpo River in SE Tibet

Science.gov (United States)

Zeitler, P. K.; Meltzer, A. S.; Hallet, B.; Kidd, W. S.; Koons, P. O.

2007-12-01

For a decade anecdotes and media reports have been circulating about a proposed dam on the Yarlung- Tsangpo River in SE Tibet. The proposed site is in the deep canyon of the Yarlung-Tsangpo where the river leaves the Tibetan Plateau across an immense knickpoint, falling ~2000 m along an irregular U-shaped reach ~100 km in length. The fundamental purpose of the dam is generation of ~40,000 MW of hydropower, to be used in diverting a portion of the impounded river to water-starved regions of northern China. Offsetting benefits that would accrue from improved water supply in the north, debate has centered on the water-flow and sediment-flux impacts that would be felt downstream in the Brahmaputra system in northeastern India and Bangladesh, as well as the impact of a dam and large lake on the pristine, ecologically and ethnographically diverse area around the Yarlung-Tsangpo canyon, an area of great significance to Tibetan Buddhists. We have been examining the geodynamic evolution of eastern Tibet, and have gathered considerable geophysical and geological data on the knickpoint region. The knickpoint traverses the Namche Barwa-Gyala Peri massif, one of the most geologically active regions on Earth. In this region, very rapid bedrock exhumation at rates of 7 mm/yr or more has exposed granites as young as 1 Ma, and these rates have been ongoing for at least the past 3 m.y. Detrital-dating evidence shows that these high rates continue at present and that erosion within the massif contributes fully 50% of the suspended-sediment load in the Yarlung-Tsangpo at the point where it enters the Brahmaputra (this would be about 100 Mt/yr derived from the massif). The steep slopes in the massif fail by pervasive landsliding and suggest a steady-state topography where the high erosion rates are balanced by equivalent rates of rock uplift accommodated by numerous active structures. At a more regional scale, GPS results show that steep three-dimensional velocity gradients exist

Negligible contribution of reservoir dams to organic and inorganic transport in the lower Mimi River, Japan

Science.gov (United States)

Nukazawa, Kei; Kihara, Kousuke; Suzuki, Yoshihiro

2017-12-01

Rivers fulfill an essential ecological role by forming networks for material transport from upland forests to coastal areas. The way in which dams affect the organic and inorganic cycles in such systems is not well understood. Herein, we investigated the longitudinal profiles of the various components of the water chemistry across three cascade dams in Japan: the Yamasubaru Dam, Saigou Dam, and Ohuchibaru Dam, which are situated along the sediment-productive Mimi River in different flow conditions. We analyzed the following water quality components: suspended solids (SS), turbidity, total iron (TFe), dissolved iron (DFe), total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), humic substance (HS), and major ionic components (Na+, Mg2+, Ca2+, Cl-, NO3-, and SO42-) in the downstream channels of the three dams during the low-intermediate-flow and high-flow events from 2012 to 2014. We estimated hourly loads of each component using hourly turbidity data and discharge data (i.e., L-Q model) separately, and the results are integrated to estimate the annual fluxes. The annual fluxes between the methods were compared to verify predictability of the conventional L-Q models. Annual flux of TOC, TN, DFe, and HS estimated by the turbidity displayed similar values, whereas the flux of SS, TFe, and TP tended to increase downstream of the dams. Among the dams, estimated flux proportions for TP and TFe were higher during high-flow events (74%-94%). Considering geographic conditions (e.g., absence of major tributary between the dams), the result implies that accumulated TP and TFe in the reservoirs may be flushed and transported downstream with SS over the short height dams during flood events. Assuming this process, the reservoir dams probably make only a fractional contribution to the organic and inorganic transport in the catchment studied. The percent flux errors for SS, TFe, and TP fluxes ranged from -7.2% to -97% (except for the TP flux in 2013), which

Sediment transport modelling in wadi Chemora during flood flow events

Directory of Open Access Journals (Sweden)

Berghout Ali

2016-12-01

Full Text Available The sediment transport is a complex phenomenon by its intermittent nature, randomness and by its spatiotemporal discontinuity. By reason of its scale, it constitutes a major constraint for development; it decreases storage capacity of dams and degrades state of ancillary structures.

Influence of Beaver-Induced Complexity on Storage of Organic Carbon and Sediment in Colorado Mountain Streams

Science.gov (United States)

Laurel, D.; Wohl, E.

2016-12-01

Beaver meadows (complexes of multiple different aged beaver dams and ponds) influence the storage of water, sediment, and nutrients. Although beaver meadows compose only a small fraction of catchment area, they provide a potentially large role in retaining these fluxes in mountain watersheds. Multiple dams and ponds in beaver meadows increase overbank flows leading to an anastomosing stream channel planform, and deposition of fine sediment along with particulate organic carbon. An earlier study estimated a range of cumulative carbon stored in 27 beaver meadows east of the continental divide in Rocky Mountain National Park. Storage ranged from 735,800 to 2.8 x 106 Mg carbon, with the high value estimating storage if all the meadows had active beaver (historic conditions pre-European settlement) and the lower value estimating current conditions where many of the meadows are abandoned. We combined geomorphic surveys, soil depth probing by rebar, and soil cores analyzed for carbon content to investigate the influence of beaver activity, meadow size, and meadow placement within the drainage on catchment-scale fluxes of fine sediment and organic carbon. We found carbon storage in floodplain soils to be highly variable across both active and abandoned meadows; however, active beaver meadows store more carbon on average than abandoned meadows. In addition, active meadows with high levels of beaver activity (multiple colonies) stored greater volumes of fine sediment behind dams and in ponds. These results have implications for the restoration potential of abandoned beaver meadows in mountain environments to store greater volumes of sediment and more organic carbon if beaver are successfully reintroduced.

Th, U and trace elements determination in Egyiptian Lake sediments by INAA and laser fluorimetry

International Nuclear Information System (INIS)

Ismail, S.S.; Grass, F.; Ghods, A.

1995-01-01

A study was undertaken to determine element concentrations in Aswan High Dam Lake sediments. Sediment samples were collected from 40 to 500 km upstream of the dam to follow the sedimentation process and the distribution of Th, U and the trace elements in the lake. INAA was applied for the determination of Sm, Ce, Lu, Th, Cr, Yb, Au, Hf, Ba, Nd, Cs, Tb, Sc, Rb, Fe, Zn, Co, Eu, and Sb, while Laser Fluorimetry was applied for U determination. The accuracy and the reproducibility of the techniques were tested with IAEA standard materials (SL, Soil-7). The U values ranged from 4 ppm to 18 ppm, Th values were between 2 and 10 ppm, and showed a very good correlation with the rare earth elements and Fe. The distribution of most of the elements in the lake follows the same trend as the distribution of the clays in the sediments. Ba showed a negative correlation with most of the elements under investigation. (author) 5 refs.; 4 figs.; 7 tabs

Perspectives on dam safety in Canada

International Nuclear Information System (INIS)

Halliday, R.

2004-01-01

Canadian dam safety issues were reviewed from the perspective of a water resources engineer who is not a dam safety practitioner. Several external factors affecting dam safety were identified along with perceived problems in dam safety administration. The author claims that the main weakness in safety practices can be attributed to provincial oversights and lack of federal engagement. Some additions to the Canadian Dam Safety Guidelines were proposed to address these weaknesses. Canada has hundreds of large dams and high hazard dams whose failure would result in severe downstream consequences. The safety of dams built on boundary waters shared with the United States have gained particular attention from the International Joint Commission. This paper also examined safety criteria for concerns such as aging dams, sabotage and global climate change that may compromise the safety of a dam. 26 refs

78 FR 53494 - Dam Safety Modifications at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams

Science.gov (United States)

2013-08-29

... Bar Dams AGENCY: Tennessee Valley Authority. ACTION: Issuance of Record of Decision. SUMMARY: This... the dam safety modifications at Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams. The notice of... Loudoun, Tellico, and Watts Bar Dams was published in the Federal Register on May 31, 2013. This...

Characterization and evaluation of potential reuse options for wastewater sludge and combined sewer system sediments in Mexico

Energy Technology Data Exchange (ETDEWEB)

Jimenez, B.; Mendez, J.M.; Barrios, J.A.; Salgado, G.; Sheinbaum, C.

2003-07-01

Combined sewer systems generate sediments that have characteristics similar to those of primary sludge. Mexico City has such a system composed of a network of pipes, regulation structures (dams, basins) and open channels. The annual generation of sediments is estimated in 2.8 Mm{sup 3}, which includes 0.41 Mm{sup 3} of sludge. As a result, the total capacity for transporting water is reduced considerably, making necessary to extract yearly an approximate 0.85 Mm{sup 3} of those materials and to send them to a final disposal site with a capacity that is being exhausted. As part of the local Governmental effort, this project evaluates the quality of sediments from 6 dams, 4 regulation basins, 2 open channels, and 3 transfer stations. Also, sludge from 20 wastewater treatment plants was sampled. The results showed an important presence of lead and hydrocarbons in some sediments, and some sludge samples contained arsenic and nickel above the limits. Moreover, microbial levels exceeded the limits in all the sediments and sludge samples. Erosion was linked to the generation of an important amount of sediments based on lead concentration. A classification was established to determine the degree of contamination of the sediments as well as the required treatment to allow their potential reuse. (author)

Changes in sediment volume in Alder Lake, Nisqually River Basin, Washington, 1945-2011

Science.gov (United States)

Czuba, Jonathan A.; Olsen, Theresa D.; Czuba, Christiana R.; Magirl, Christopher S.; Gish, Casey C.

2012-01-01

The Nisqually River drains the southwest slopes of Mount Rainier, a glaciated stratovolcano in the Cascade Range of western Washington. The Nisqually River was impounded behind Alder Dam when the dam was completed in 1945 and formed Alder Lake. This report quantifies the volume of sediment deposited by the Nisqually and Little Nisqually Rivers in their respective deltas in Alder Lake since 1945. Four digital elevation surfaces were generated from historical contour maps from 1945, 1956, and 1985, and a bathymetric survey from 2011. These surfaces were used to compute changes in sediment volume since 1945. Estimates of the volume of sediment deposited in Alder Lake between 1945 and 2011 were focused in three areas: (1) the Nisqually River delta, (2) the main body of Alder Lake, along a 40-meter wide corridor of the pre-dam Nisqually River, and (3) the Little Nisqually River delta. In each of these areas the net deposition over the 66-year period was 42,000,000 ± 4,000,000 cubic meters (m3), 2,000,000 ± 600,000 m3, and 310,000 ± 110,000 m3, respectively. These volumes correspond to annual rates of accumulation of 630,000 ± 60,000 m3/yr, 33,000 ± 9,000 m3/yr, and 4,700 ± 1,600 m3/yr, respectively. The annual sediment yield of the Nisqually (1,100 ± 100 cubic meters per year per square kilometer [(m3/yr)/km2]) and Little Nisqually River basins [70 ± 24 (m3/yr)/km2] provides insight into the yield of two basins with different land cover and geomorphic processes. These estimates suggest that a basin draining a glaciated stratovolcano yields approximately 15 times more sediment than a basin draining forested uplands in the Cascade Range. Given the cumulative net change in sediment volume in the Nisqually River delta in Alder Lake, the total capacity of Alder Lake since 1945 decreased about 3 percent by 1956, 8 percent by 1985, and 15 percent by 2011.

A model of water and sediment balance as determinants of relative sea level rise in contemporary and future deltas

Science.gov (United States)

Tessler, Zachary D.; Vörösmarty, Charles J.; Overeem, Irina; Syvitski, James P. M.

2018-03-01

Modern deltas are dependent on human-mediated freshwater and sediment fluxes. Changes to these fluxes impact delta biogeophysical functioning and affect the long-term sustainability of these landscapes for human and for natural systems. Here we present contemporary estimates of long-term mean sediment balance and relative sea level rise across 46 global deltas. We model scenarios of contemporary and future water resource management schemes and hydropower infrastructure in upstream river basins to explore how changing sediment fluxes impact relative sea level rise in delta systems. Model results show that contemporary sediment fluxes, anthropogenic drivers of land subsidence, and sea level rise result in delta relative sea level rise rates that average 6.8 mm/y. Assessment of impacts of planned and under-construction dams on relative sea level rise rates suggests increases on the order of 1 mm/y in deltas with new upstream construction. Sediment fluxes are estimated to decrease by up to 60% in the Danube and 21% in the Ganges-Brahmaputra-Meghna if all currently planned dams are constructed. Reduced sediment retention on deltas caused by increased river channelization and management has a larger impact, increasing relative sea level rise on average by nearly 2 mm/y. Long-term delta sustainability requires a more complete understanding of how geophysical and anthropogenic change impact delta geomorphology. Local and regional strategies for sustainable delta management that focus on local and regional drivers of change, especially groundwater and hydrocarbon extraction and upstream dam construction, can be highly impactful even in the context of global climate-induced sea level rise.

Metal pollution assessment in the surface sediment of Lake Nasser, Egypt

Directory of Open Access Journals (Sweden)

Mohamed E. Goher

2014-01-01

Full Text Available Eight heavy metals were measured seasonally in the sediment of Lake Nasser during 2013. 27 sites were chosen through 9 sectors across the main channel of the lake from Abu-Simbel to Aswan High Dam to assess the levels of the selected metals. The abundance of these metals was in the order of Fe > Mn > Zn > Cr > Ni > Cu > Pb > Cd, with mean concentrations of 12.41 mg/g, 279.56, 35.38, 30.79, 27.56, 21.78, 11.21 and 0.183 μg/g, respectively. Heavy metals are positively correlated with fine particles (mud fractions and organic matter accumulation. The results showed perspicuous spatial high significant differences (P < 0.01 for all the measured metals. Fe, Cr, Ni, Pb and Cd exhibited temporally high significant differences (P < 0.01 before and after the flood period. Four Pollution Indices were used for the environmental assessment of Lake Nasser sediment. The indices included three single indices, Enrichment Factor (EF, Index of Geo-accumulation (Igeo and Contamination Factor (CF. While the fourth, Pollution Load Index (PLI was an integrated index. The pollution indexes confirmed that the Lake Nasser sediment was not contaminated with these elements. Sediments of Lake Nasser may be represented as a reference for the pre-industrial background of River Nile Sediments downstream Aswan High Dam.

Fluvial wood function downstream of beaver versus man-made dams in headwater streams in Massachusetts, USA

Science.gov (United States)

David, G. C.; DeVito, L. F.; Munz, K. T.; Lisius, G.

2014-12-01

Fluvial wood is an essential component of stream ecosystems by providing habitat, increasing accumulation of organic matter, and increasing the processing of nutrients and other materials. However, years of channel alterations in Massachusetts have resulted in low wood loads despite the afforestation that has occurred since the early 1900s. Streams have also been impacted by a large density of dams, built during industrialization, and reduction of the beaver population. Beavers were reintroduced to Massachusetts in the 1940s and they have since migrated throughout the state. Beaver dams impound water, which traps sediment and results in the development of complex channel patterns and more ecologically productive and diverse habitats than those found adjacent to man-made dams. To develop better management practices for dam removal it is essential that we understand the geomorphic and ecologic function of wood in these channels and the interconnections with floodplain dynamics and stream water chemistry. We investigate the connections among fluvial wood, channel morphology, floodplain soil moisture dynamics, and stream water chemistry in six watersheds in Massachusetts that have been impacted by either beaver or man-made dams. We hypothesize that wood load will be significantly higher below beaver dams, subsequently altering channel morphology, water chemistry, and floodplain soil moisture. Reaches are surveyed up- and downstream of each type of dam to better understand the impact dams have on the fluvial system. Surveys include a longitudinal profile, paired with dissolved oxygen and ammonium measurements, cross-section and fluvial wood surveys, hydraulic measurements, and floodplain soil moisture mapping. We found that dissolved oxygen mirrored the channel morphology, but did not vary significantly between reaches. Wood loads were significantly larger downstream of beaver dams, which resulted in significant changes to the ammonium levels. Floodplain soil moisture

Flood effects provide evidence of an alternate stable state from dam management on the Upper Missouri River

Science.gov (United States)

Skalak, Katherine; Benthem, Adam J.; Hupp, Cliff R.; Schenk, Edward R.; Galloway, Joel M.; Nustad, Rochelle A.

2017-01-01

We examine how historic flooding in 2011 affected the geomorphic adjustments created by dam regulation along the approximately 120 km free flowing reach of the Upper Missouri River bounded upstream by the Garrison Dam (1953) and downstream by Lake Oahe Reservoir (1959) near the City of Bismarck, ND, USA. The largest flood since dam regulation occurred in 2011. Flood releases from the Garrison Dam began in May 2011 and lasted until October, peaking with a flow of more than 4200 m3 s−1. Channel cross-section data and aerial imagery before and after the flood were compared with historic rates of channel change to assess the relative impact of the flood on the river morphology. Results indicate that the 2011 flood maintained trends in island area with the loss of islands in the reach just below the dam and an increase in island area downstream. Channel capacity changes varied along the Garrison Segment as a result of the flood. The thalweg, which has been stable since the mid-1970s, did not migrate. And channel morphology, as defined by a newly developed shoaling metric, which quantifies the degree of channel braiding, indicates significant longitudinal variability in response to the flood. These results show that the 2011 flood exacerbates some geomorphic trends caused by the dam while reversing others. We conclude that the presence of dams has created an alternate geomorphic and related ecological stable state, which does not revert towards pre-dam conditions in response to the flood of record. This suggests that management of sediment transport dynamics as well as flow modification is necessary to restore the Garrison Segment of the Upper Missouri River towards pre-dam conditions and help create or maintain habitat for endangered species. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Investigation on the Causes of Cracking in Earth Dams (Case study: Mahmood-Abad Earth Dam

Directory of Open Access Journals (Sweden)

H. Rahimi

2016-09-01

Full Text Available Introduction: Cracking of earth dams is a one of the main threat causes of stability of embankment dams. In this research by modeling of the behavior of an embankment dam and employing conditions of the earthquake, the reasons of cracking were inspected using by modeling of earth dam behavior. Based on the literature, one of the main causes of dam failures is sliding and cracking of the dam structure during earthquake. Localized liquefaction of foundation soils was one of the causes of the observed post-earthquake distress within these dams. Material and Methods: In order to study the causes and the results of crack on earth dams, Mahmoodabad earthen dam with a height of 19 m, is located in Zanjan province, northwest of Iran, which suffered a longitudinal crack on the crest and slight sliding of the upstream slope due to 2001 Avaj earthquake was studied. This dam has faced earthquake two times with an interval of two years. During the first earthquake with the magnitude about 6.6 in Richter scale small longitudinal cracks had created on the crest. The developed cracks had been repaired by injecting the cement and then has been hidden by passing the time. After the second earthquake with the magnitude about 6.5 in Richter scale the hidden cracks had been appeared again and the slight movement of the upper slopes of dam reported. Based on the site investigation and documented information about dam, including maps and parameter data, the behavior of the dam has modeled by using Plaxis as a finite element model. In order to check the accuracy of the design of dam, the stability analysis has been conducted using by Xslope as a limit equilibrium model. The foundation conditions and the Geotechnical properties of the layer beneath the dam has been inspected by open excavation. Results and Discussion: Underground investigation about Geotechnical properties of dam foundation has showed that there is a thin sandy layer confined in alluvium material of the

A Late Pleistocene linear dune dam record of aeolian-fluvial dynamics at the fringes of the northwestern Negev dunefield

Science.gov (United States)

Roskin, Joel; Bookman, Revital; Friesem, David; Vardi, Jacob

2017-04-01

The paper presents a late Pleistocene aeolian-fluvial record within a linear dune-like structure that partway served as a dune dam. Situated along the southern fringe of the northwestern Negev desert dunefield (Israel) the structure's morphology, orientation, and some of its stratigraphic units partly resemble adjacent west-east extending vegetated linear dunes. Uneven levels of light-colored, fine-grained fluvial deposits (LFFDs) extend to the north and south from the flanks of the studied structure. Abundant Epipalaeolithic sites line the fringes of the LFFDs. The LFFD microstructures of fine graded bedding and clay blocky peds indicate sorting and shrinking of saturated clays in transitional environments between low energy flows to shallow standing water formed by dunes damming a mid-sized drainage system. The structure's architecture of interchanging units of sand with LFFDs indicates interchanging dominances between aeolian sand incursion and winter floods. Sand mobilization associated with powerful winds during the Heinrich 1 event led to dune damming downstream of the structure and within the structure to in-situ sand deposition, partial fluvial erosion, reworking of the sand, and LFFD deposition. Increased sand deposition led to structure growth and blockage of its drainage system that in turn accumulated LFFD units up stream of the structure. Extrapolation of current local fluvial sediment yields indicate that LFFD accretion up to the structure's brim occurred over a short period of several decades. Thin layers of Geometric Kebaran (c. 17.5-14.5 ka cal BP) to Harifian (12-11 ka BP) artifacts within the structure's surface indicates intermittent, repetitive, and short term camping utilizing adjacent water along a timespan of 4-6 kyr. The finds directly imply that the NW Negev LFFDs formed in dune-dammed water bodies which themselves were formed following events of vegetated linear dune elongation. LFFD accumulation persisted as a result of dune dam

Riparian plant succession in the dam-regulated Colorado River: Why is saltcedar losing?

International Nuclear Information System (INIS)

Stevens, L.

1993-01-01

Three modes of plant succession (inhibition, facilitation and tolerance) were tested to explain the replacement of exotic saltcedar (Tamarix ramosissima) by naive phreatophytes in the Colorado River corridor in the Grand Canyon. Dam construction reduced flood frequency and sediment transport, interrupting the open-quotes perpetual successionclose quotes of the pre-dam riparian vegetation and initially allowing saltcedar to proliferate. Inhibition results from direct or indirect competition, but field measurements and experiments demonstrate limited evidence of competitive superiority by naive species over saltcedar in three life stages. Field observations and experiments on germination, physiological responses to gradients and comparative life history analyses demonstrate that saltcedar is a stress tolerant, disturbance specialist in an ecologically stabilized river corridor where safe germination sites are increasingly rare. Altered flood frequency, increased soil coarseness and differential herbivory contribute to succession in this system

Dynamic decision making for dam-break emergency management - Part 2: Application to Tangjiashan landslide dam failure

Science.gov (United States)

Peng, M.; Zhang, L. M.

2013-02-01

Tangjiashan landslide dam, which was triggered by the Ms = 8.0 Wenchuan earthquake in 2008 in China, threatened 1.2 million people downstream of the dam. All people in Beichuan Town 3.5 km downstream of the dam and 197 thousand people in Mianyang City 85 km downstream of the dam were evacuated 10 days before the breaching of the dam. Making such an important decision under uncertainty was difficult. This paper applied a dynamic decision-making framework for dam-break emergency management (DYDEM) to help rational decision in the emergency management of the Tangjiashan landslide dam. Three stages are identified with different levels of hydrological, geological and social-economic information along the timeline of the landslide dam failure event. The probability of dam failure is taken as a time series. The dam breaching parameters are predicted with a set of empirical models in stage 1 when no soil property information is known, and a physical model in stages 2 and 3 when knowledge of soil properties has been obtained. The flood routing downstream of the dam in these three stages is analyzed to evaluate the population at risk (PAR). The flood consequences, including evacuation costs, flood damage and monetized loss of life, are evaluated as functions of warning time using a human risk analysis model based on Bayesian networks. Finally, dynamic decision analysis is conducted to find the optimal time to evacuate the population at risk with minimum total loss in each of these three stages.

Colonial Era Impoundment of the Northeastern United States: Beaver Trapping and Low- head Dam Construction

Science.gov (United States)

Salant, N.; Bain, D.; Brandt, S.

2008-12-01

Hydrologic systems of the northeastern United States were transformed by European settler activities. The colonial economy shifted engineered water structures from beaver dams to human dams built for power generation. While the geomorphic effects of human-constructed dams have recently garnered considerable attention, few studies have investigated how intensive trapping for the fur trade, the near extermination of the Northeast beaver population, and the consequent loss of beaver ponds altered the regional water balance. Although reconstructions of colonial beaver populations have been made, none link the decline in beavers to its hydrologic impact. Beaver population models based on pre-colonial population estimates, historic harvest rates, and current-day population dynamics were used to simulate the corresponding decrease in pond numbers over time. Beaver populations declined dramatically during the seventeenth century, with harvest rates estimated at 2,000-10,000 beavers per year, resulting in expatriation in some sub-regions by the early 1700s. Using contemporary estimates of beaver pond volumes, the calculated loss in pond storage between 1600 and 1840 was approximately 17 million cubic meters of water and sediment, considerably larger than estimated storage gains from dam construction in the same period, suggesting that beaver eradication was a major driver of hydrologic change during the colonial era.

Technical background information for the environmental and safety report, Volume 4: White Oak Lake and Dam

International Nuclear Information System (INIS)

Oakes, T.W.; Kelly, B.A.; Ohnesorge, W.F.; Eldridge, J.S.; Bird, J.C.; Shank, K.E.; Tsakeres, F.S.

1982-03-01

This report has been prepared to provide background information on White Oak Lake for the Oak Ridge National Laboratory Environmental and Safety Report. The paper presents the history of White Oak Dam and Lake and describes the hydrological conditions of the White Oak Creek watershed. Past and present sediment and water data are included; pathway analyses are described in detail

Technical background information for the environmental and safety report, Volume 4: White Oak Lake and Dam

Energy Technology Data Exchange (ETDEWEB)

Oakes, T.W.; Kelly, B.A.; Ohnesorge, W.F.; Eldridge, J.S.; Bird, J.C.; Shank, K.E.; Tsakeres, F.S.

1982-03-01

This report has been prepared to provide background information on White Oak Lake for the Oak Ridge National Laboratory Environmental and Safety Report. The paper presents the history of White Oak Dam and Lake and describes the hydrological conditions of the White Oak Creek watershed. Past and present sediment and water data are included; pathway analyses are described in detail.

Variations of Runoff and Sediment Load in the Middle and Lower Reaches of the Yangtze River, China (1950-2013).

Science.gov (United States)

Li, Na; Wang, Lachun; Zeng, Chunfen; Wang, Dong; Liu, Dengfeng; Wu, Xutong

2016-01-01

On the basis of monthly runoff series obtained in 1950-2013 and annual sediment load measured in 1956--2013 at five key hydrological stations in the middle and lower reaches of the Yangtze River basin, this study used the Mann-Kendall methods to identify trend and abrupt changes of runoff and sediment load in relation to human activities. The results were as follows: (1) The annual and flood season runoffs showed significant decreasing trends at Yichang station, and showed slight downward trends at Hankou and Datong stations, while the abrupt changes of dry season runoff at Yichang, Hankou and Datong stations occurred in about 2007 and the change points were followed by significant increasing trends. The construction of the Three Gorges Dam, which began to operate in 2003, influenced the variations of runoff in the mainstream of Yangtze River, but the effect weakened with the distance along the downstream direction from TGD. (2) Since the 1990s, annual sediment loads at Yichang, Hankou, and Datong stations have been decreasing significantly, and after 2002, the annual sediment load at Yichang dropped below that of Hankou and Datong. The dams and deforestation/forestation contributed to the significant decreasing trend of the sediment load. In addition, the Three Gorges Dam aggravated the downward trend and caused the erosion of the riverbed and riverbanks in the middle and lower reaches. (3) The runoff and sediment load flowing from Dongting Lake into the mainstream of the Yangtze River showed significant decreasing trends at Chenglingji station after 1970s, and in contrast, slight increase in the sediment flow from Poyang Lake to the mainstream of the Yangtze River at Hukou station were detected over the post-TGD period (2003-2013). The result of the study will be an important foundation for watershed sustainable development of the Yangtze River under the human activities.

Variations of Runoff and Sediment Load in the Middle and Lower Reaches of the Yangtze River, China (1950-2013)

Science.gov (United States)

Li, Na; Wang, Lachun; Zeng, Chunfen; Wang, Dong; Liu, Dengfeng; Wu, Xutong

2016-01-01

On the basis of monthly runoff series obtained in 1950–2013 and annual sediment load measured in 1956–-2013 at five key hydrological stations in the middle and lower reaches of the Yangtze River basin, this study used the Mann-Kendall methods to identify trend and abrupt changes of runoff and sediment load in relation to human activities. The results were as follows: (1) The annual and flood season runoffs showed significant decreasing trends at Yichang station, and showed slight downward trends at Hankou and Datong stations, while the abrupt changes of dry season runoff at Yichang, Hankou and Datong stations occurred in about 2007 and the change points were followed by significant increasing trends. The construction of the Three Gorges Dam, which began to operate in 2003, influenced the variations of runoff in the mainstream of Yangtze River, but the effect weakened with the distance along the downstream direction from TGD. (2) Since the 1990s, annual sediment loads at Yichang, Hankou, and Datong stations have been decreasing significantly, and after 2002, the annual sediment load at Yichang dropped below that of Hankou and Datong. The dams and deforestation/forestation contributed to the significant decreasing trend of the sediment load. In addition, the Three Gorges Dam aggravated the downward trend and caused the erosion of the riverbed and riverbanks in the middle and lower reaches. (3) The runoff and sediment load flowing from Dongting Lake into the mainstream of the Yangtze River showed significant decreasing trends at Chenglingji station after 1970s, and in contrast, slight increase in the sediment flow from Poyang Lake to the mainstream of the Yangtze River at Hukou station were detected over the post-TGD period (2003–2013). The result of the study will be an important foundation for watershed sustainable development of the Yangtze River under the human activities. PMID:27479591

Variations of Runoff and Sediment Load in the Middle and Lower Reaches of the Yangtze River, China (1950-2013.

Directory of Open Access Journals (Sweden)

Na Li

Full Text Available On the basis of monthly runoff series obtained in 1950-2013 and annual sediment load measured in 1956--2013 at five key hydrological stations in the middle and lower reaches of the Yangtze River basin, this study used the Mann-Kendall methods to identify trend and abrupt changes of runoff and sediment load in relation to human activities. The results were as follows: (1 The annual and flood season runoffs showed significant decreasing trends at Yichang station, and showed slight downward trends at Hankou and Datong stations, while the abrupt changes of dry season runoff at Yichang, Hankou and Datong stations occurred in about 2007 and the change points were followed by significant increasing trends. The construction of the Three Gorges Dam, which began to operate in 2003, influenced the variations of runoff in the mainstream of Yangtze River, but the effect weakened with the distance along the downstream direction from TGD. (2 Since the 1990s, annual sediment loads at Yichang, Hankou, and Datong stations have been decreasing significantly, and after 2002, the annual sediment load at Yichang dropped below that of Hankou and Datong. The dams and deforestation/forestation contributed to the significant decreasing trend of the sediment load. In addition, the Three Gorges Dam aggravated the downward trend and caused the erosion of the riverbed and riverbanks in the middle and lower reaches. (3 The runoff and sediment load flowing from Dongting Lake into the mainstream of the Yangtze River showed significant decreasing trends at Chenglingji station after 1970s, and in contrast, slight increase in the sediment flow from Poyang Lake to the mainstream of the Yangtze River at Hukou station were detected over the post-TGD period (2003-2013. The result of the study will be an important foundation for watershed sustainable development of the Yangtze River under the human activities.

EVALUASI KEAMANAN DAM JATILUHUR BERBASIS INDEKS RESIKO

Directory of Open Access Journals (Sweden)

Avazbek Ishbaev

2014-12-01

Full Text Available The dams have very important roles to agricultural activities. Especially, West Java with 240,000 hectares of agricultural land, needs a good dam structure that can be used sustainably. Jatiluhur dam in Purwakarta, West Java is one of big dams in Indonesia which has important rules not only for Purwakarta but also for Jakarta, Karawang and Bekasi residents. A study and observation about safety and dam stability is needed to prevent any damage. The purpose of this research were to identify parameters that influenced dam safety and to evaluate dam reliability based on index tools. Analysis was done using risk index tools. The result showed that the condition of the dam of Jatiluhur is still satisfied with indicators, "Idam"-750. The total index risk was 127.22 and the safety factor was 83.04 out of 100. Therefore, Jatiluhur dam could be classified as safe and no need for particular treatments. Jatiluhur dam can be operated in normal condition or abnormal condition with periodic monitoring. Keywords: dam safety, evaluation, Jatiluhur Dam, risk index tools

Dam safety operating guidelines

International Nuclear Information System (INIS)

Elsayed, E.; Leung, T.; Kirkham, A.; Lum, D.

1990-01-01

As part of Ontario Hydro's dam structure assessment program, the hydraulic design review of several river systems has revealed that many existing dam sites, under current operating procedures, would not have sufficient discharge capacity to pass the Inflow Design Flood (IDF) without compromising the integrity of the associated structures. Typical mitigative measures usually considered in dealing with these dam sites include structural alterations, emergency action plans and/or special operating procedures designed for extreme floods. A pilot study was carried out for the Madawaska River system in eastern Ontario, which has seven Ontario Hydro dam sites in series, to develop and evaluate the effectiveness of the Dam Safety Operating Guidelines (DSOG). The DSOG consist of two components: the flood routing schedules and the minimum discharge schedules, the former of which would apply in the case of severe spring flood conditions when the maximum observed snowpack water content and the forecast rainfall depth exceed threshold values. The flood routing schedules would identify to the operator the optimal timing and/or extent of utilizing the discharge facilities at each dam site to minimize the potential for dam failures cased by overtopping anywhere in the system. It was found that the DSOG reduced the number of structures overtopped during probable maximum flood from thirteen to four, while the number of structures that could fail would be reduced from seven to two. 8 refs., 4 figs., 3 tabs

Dam risk reduction study for a number of large tailings dams in Ontario

Energy Technology Data Exchange (ETDEWEB)

Verma, N. [AMEC Earth and Environmental Ltd., Mississauga, ON (Canada); Small, A. [AMEC Earth and Environmental Ltd., Fredericton, NB (Canada); Martin, T. [AMEC Earth and Environmental, Burnaby, BC (Canada); Cacciotti, D. [AMEC Earth and Environmental Ltd., Sudbury, ON (Canada); Ross, T. [Vale Inco Ltd., Sudbury, ON (Canada)

2009-07-01

This paper discussed a risk reduction study conducted for 10 large tailings dams located at a central tailings facility in Ontario. Located near large industrial and urban developments, the tailings dams were built using an upstream method of construction that did not involve beach compaction or the provision of under-drainage. The study provided a historical background for the dam and presented results from investigations and instrumentation data. The methods used to develop the dam configurations were discussed, and remedial measures and risk assessment measures used on the dams were reviewed. The aim of the study was to address key sources of risk, which include the presence of high pore pressures and hydraulic gradients; the potential for liquefaction; slope instability; and the potential for overtopping. A borehole investigation was conducted and piezocone probes were used to obtain continuous data and determine soil and groundwater conditions. The study identified that the lower portion of the dam slopes were of concern. Erosion gullies could lead to larger scale failures, and elevated pore pressures could lead to the risk of seepage breakouts. It was concluded that remedial measures are now being conducted to ensure slope stability. 6 refs., 1 tab., 6 figs.

Soil erosion planning using sediment yield index method in the Nun Nadi watershed, India

Directory of Open Access Journals (Sweden)

Hasan Raja Naqvi

2015-06-01

Full Text Available The study identifies the extent of soil loss and proposes a method for prioritization of micro-watershed in the Nun Nadi watershed. The study used the Sediment Yield Index (SYI method, based on weighted overlays of soil, topography, rainfall erosivity and land use parameters in 24 micro watersheds. Accordingly the values and thematic layers were integrated as per the SYI model, and minimum and maximum sediment yield values were calculated. The priority ranks as per the sediment yield values were assigned to all micro-watersheds. Then the values were classified into four priority zones according to their composite scores. Almost 14 percent area of three micro-watersheds (SW5b, SW6a and SW7b showed very high priority; approximately 30.57 percent of the study area fell under the high priority zones. These areas require immediate attention. Conservation methods are suggested, and the locations of check dams are proposed after considering drainage, slope and soil loss. Keywords: Check dam, Prioritization, Nun Nadi watershed, Soil loss, SYI

Impact of water and sediment discharges on subaqueous delta evolution in Yangtze Estuary from 1950 to 2010

Directory of Open Access Journals (Sweden)

Yun-ping Yang

2014-07-01

Full Text Available In order to determine how the subaqueous delta evolution depends on the water and sediment processes in the Yangtze Estuary, the amounts of water and sediment discharged into the estuary were studied. The results show that, during the period from 1950 to 2010, there was no significant change in the annual water discharge, and the multi-annual mean water discharge increased in dry seasons and decreased in flood seasons. However, the annual sediment discharge and the multi-annual mean sediment discharge in flood and dry seasons took on a decreasing trend, and the intra-annual distribution of water and sediment discharges tended to be uniform. The evolution process from deposition to erosion occurred at the −10 m and −20 m isobaths of the subaqueous delta. The enhanced annual water and sediment discharges had a silting-up effect on the delta, and the effect of sediment was greater than that of water. Based on data analysis, empirical curves were built to present the relationships between the water and sediment discharges over a year or in dry and flood seasons and the erosion/deposition rates in typical regions of the subaqueous delta, whose evolution followed the pattern of silting in flood seasons and scouring in dry seasons. Notably, the Three Gorges Dam has changed the distribution processes of water and sediment discharges, and the dam's regulating and reserving functions can benefit the subaqueous delta deposition when the annual water and sediment discharges are not affected.

The Effects of Dams on Downstream Channel Characteristics in Pennsylvania and Maryland: Assessing the Potential Consequences of Dam Removal

Science.gov (United States)

Skalak, K. J.; Pizzuto, J. E.; Jenkins, P.

2003-12-01

The potential downstream effects of dam removal were assessed on fifteen sites of varying dam size and characteristics in Pennsylvania and Maryland. The dams ranged in size from a 30 cm high fish weir to a water supply dam 57 m high. Stream order ranged from 1 to 4. The dams are located in watersheds with varying degrees of human disturbance and urbanization. The dams are also operated differently, with significant consequences for hydraulic residence time and downstream flow variability. Most streams were alluvial, but 6 of the reaches were clearly bedrock channels. We hypothesize that the channel upstream, which is unaffected by the dam, will provide an accurate model for the channel downstream of the dam long after dam removal. Therefore, reaches upstream and downstream of the dam were compared to determine the effects of the dam as well as the condition of the stream that will ultimately develop decades after dam removal. Surprisingly, the dams had no consistent influence on channel morphology. However, the percentage of sand is significantly lower downstream than upstream: the mean % sand downstream is 11.47%, while the mean % sand upstream is 21.39%. The coarser fractions of the bed, as represented by the 84th percentile grain diameter, are unaffected by the presence of the dam. These results imply that decades after dam removal, the percentage of sand on the bed will increase, but the coarse fraction of the bed will remain relatively unchanged.

Public safety around dams guidelines

Energy Technology Data Exchange (ETDEWEB)

Bennett, T [Canadian Dam Association, Edmonton, AB (Canada)

2010-07-01

This presentation discussed Canadian and international initiatives for improving dam safety and described some of the drivers for the development of new Canadian Dam Association (CDA) public safety guidelines for dams. The CDA guidelines were divided into the following 3 principal sections: (1) managed system elements, (2) risk assessment and management, and (3) technical bulletins. Public and media responses to the drownings have called for improved safety guidelines. While the public remains unaware of the hazards of dams, public interaction with dams is increasing as a result of interest in extreme sports and perceived rights of access. Guidelines are needed for dam owners in order to provide due diligence. Various organizations in Canada are preparing technical and public safety dam guidelines. CDA guidelines have also been prepared for signage, booms and buoys, and audible and visual alerts bulletins. Working groups are also discussing recommended practices for spill procedures, spillways and the role of professional engineers in ensuring public safety. Methods of assessing risk were also reviewed. Managed system elements for risk assessment and public interactions were also discussed, and stepped control measures were presented. tabs., figs.

Odelouca Dam Construction: Numerical Analysis

OpenAIRE

Brito, A.; Maranha, J. R.; Caldeira, L.

2012-01-01

Odelouca dam is an embankment dam, with 76 m height, recently constructed in the south of Portugal. It is zoned with a core consisting of colluvial and residual schist soil and with soil-rockfill mixtures making up the shells (weathered schist with a significant fraction of coarse sized particles). This paper presents a numerical analysis of Odelouca Dam`s construction. The material con-stants of the soil model used are determined from a comprehensive testing programme carried out in the C...

Effect of a dam on epilithic algal communities of a mountain stream: before-after dam construction comparison

Directory of Open Access Journals (Sweden)

Luciana Cibils Martina

2013-02-01

Full Text Available In this study we evaluated the effect of a dam on epilithic algal communities by analyzing community response after dam construction and by comparing community composition, structure and biomass upstream and downstream of the dam. Samples of epilithic algae and environmental data were collected at each site during high and low water periods before and after dam construction in Achiras Stream (Córdoba, Argentina. Ordinations showed modifications in algal assemblages after dam construction and downstream of the dam. Ordinations also suggested a loss of seasonality at the downstream site since the assemblages were similar between hydrological periods after dam construction. Indicator species, obtained by the Indicator Value method, showed that, after dam construction, there could have been an increase in nutrient concentration and a release of plankton from the impoundment. Abundance, richness and diversity were altered after dam construction as assessed by ANOVAs derived from a modified BACI Design. Proportion of early-successional species was higher at the upstream site while late-successional species were dominant at the downstream site, as predicted. Lower fluctuations in discharge downstream of the dam may have helped succession advance, whereas at the upstream site, mainly during the high water period, floods could have caused sloughing of life forms from the outer layers of the biofilm, resetting the algal community to early successional stages. It may be concluded that the dam affected algal community and favored succession advance mainly by reducing current velocity and flow fluctuations.

78 FR 77397 - Flood Control Regulations, Marshall Ford Dam (Mansfield Dam and Lake Travis), Colorado River, Texas

Science.gov (United States)

2013-12-23

... Regulations, Marshall Ford Dam (Mansfield Dam and Lake Travis), Colorado River, Texas AGENCY: U.S. Army Corps... Marshall Ford Dam (Mansfield Dam and Lake Travis), Colorado River, Texas. In 1997, the Lower Colorado River... regulations to reflect changes in ownership and responsibilities of flood control management of Marshall Ford...

7 CFR 1724.55 - Dam safety.

Science.gov (United States)

2010-01-01

... 7 Agriculture 11 2010-01-01 2010-01-01 false Dam safety. 1724.55 Section 1724.55 Agriculture... § 1724.55 Dam safety. (a) The provisions of this section apply only to RUS financed electric system... for Dam Safety,”(Guidelines), as applicable. A dam, as more fully defined in the Guidelines, is...

New guidelines for dam safety classification

International Nuclear Information System (INIS)

Dascal, O.

1999-01-01

Elements are outlined of recommended new guidelines for safety classification of dams. Arguments are provided for the view that dam classification systems should require more than one system as follows: (a) classification for selection of design criteria, operation procedures and emergency measures plans, based on potential consequences of a dam failure - the hazard classification of water retaining structures; (b) classification for establishment of surveillance activities and for safety evaluation of dams, based on the probability and consequences of failure - the risk classification of water retaining structures; and (c) classification for establishment of water management plans, for safety evaluation of the entire project, for preparation of emergency measures plans, for definition of the frequency and extent of maintenance operations, and for evaluation of changes and modifications required - the hazard classification of the project. The hazard classification of the dam considers, as consequence, mainly the loss of lives or persons in jeopardy and the property damages to third parties. Difficulties in determining the risk classification of the dam lie in the fact that no tool exists to evaluate the probability of the dam's failure. To overcome this, the probability of failure can be substituted for by a set of dam characteristics that express the failure potential of the dam and its foundation. The hazard classification of the entire project is based on the probable consequences of dam failure influencing: loss of life, persons in jeopardy, property and environmental damage. The classification scheme is illustrated for dam threatening events such as earthquakes and floods. 17 refs., 5 tabs

War damages and reconstruction of Peruca dam

International Nuclear Information System (INIS)

Nonveiller, E.; Sever, Z.

1999-01-01

The paper describes the heavy damages caused by blasting in the Peruca rockfill dam in Croatia in January 1993. Complete collapse of the dam by overtopping was prevented through quick action of the dam owner by dumping clayey gravel on the lowest sections of the dam crest and opening the bottom outlet of the reservoir, thus efficiently lowering the water level. After the damages were sufficiently established and alternatives for restoration of the dam were evaluated, it was decided to construct a diaphragm wall through the damaged core in the central dam part as the impermeable dam element and to rebuild the central clay core at the dam abutments. Reconstruction works are described

33 CFR 208.19 - Marshall Ford Dam and Reservoir (Mansfield Dam and Lake Travis), Colorado River, Tex.

Science.gov (United States)

2010-07-01

... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Marshall Ford Dam and Reservoir... Marshall Ford Dam and Reservoir (Mansfield Dam and Lake Travis), Colorado River, Tex. The Secretary of the Interior, through his agent, the Lower Colorado River Authority (LCRA) shall operate the Marshall Ford Dam...

Excavation of the Surikamigawa dam diversion tunnel. Surikamigawa dam karihaisui tunnel kantsu

Energy Technology Data Exchange (ETDEWEB)

Ikeda, T.; Konno, T. (Ministry of Construction, Tokyo (Japan))

1994-04-01

A bypass tunnel construction has been completed at the Surikamigawa dam (Japan). This paper describes the summary of the construction. The full-swing dam construction work is scheduled to begin in 1995. The soils distributed near the dam site consist of lapillus tuff containing andesite-based light stones and tuff-based conglomerates containing large gravels. Excavation of the dam diversion tunnel has used a blasting method, and the tunnel construction has adopted an automatic tunnel cross section marking system and a non-electric explosion method. This marking system is a system to irradiate a laser beam onto the facing to depict excavation lines that realizes labor saving and high-accuracy excavation. The error at the tunnel completion was found 20 mm. The non-electric explosion method ignites a coated explosive layer with an impact wave, which is electrostatically safe, and reduces blasting vibration. Electric detonators have also been used because of using ANFO explosives. The result obtained from measurements of inner space displacement necessary for the blasting process has indicated that the area near the dam site consists of stable mountains. 6 figs., 4 tabs.

Three Sisters Dam modifications and performance

Energy Technology Data Exchange (ETDEWEB)

Courage, L.J.R. [Monenco AGRA Inc., Calgary, AB (Canada)

1995-12-31

Recent modifications and maintenance carried out at the Three Sisters Dam, in the Alberta Rockies south of the town of Canmore, were described. A detailed account was given of the dam`s geological setting, its abnormally high leakage through the foundation and its sinkhole activity. Results of studies aimed at finding the cause of leakage and sinkhole occurrences were reviewed. Modifications made to the dam since 1951 were detailed, as were modifications to handle probable maximum flood levels. Three approaches for estimating failure probabilities after identification of failure modes were described. The overall conclusion was that based on constant leakage, no settlement in the dam, penstocks, or the powerhouse since construction, the Three Sisters Dam was stable. 1 ref.

Dams and Levees: Safety Risks

Science.gov (United States)

Carter, N. T.

2017-12-01

The nation's flood risk is increasing. The condition of U.S. dams and levees contributes to that risk. Dams and levee owners are responsible for the safety, maintenance, and rehabilitation of their facilities. Dams-Of the more than 90,000 dams in the United States, about 4% are federally owned and operated; 96% are owned by state and local governments, public utilities, or private companies. States regulate dams that are not federally owned. The number of high-hazard dams (i.e., dams whose failure would likely result in the loss of human life) has increased in the past decade. Roughly 1,780 state-regulated, high-hazard facilities with structural ratings of poor or unsatisfactory need rehabilitation. Levees-There are approximately 100,000 miles of levees in the nation; most levees are owned and maintained by municipalities and agricultural districts. Few states have levee safety programs. The U.S. Army Corps of Engineers (Corps) inspects 15,000 miles of levees, including levees that it owns and local levees participating in a federal program to assist with certain post-flood repairs. Information is limited on how regularly other levees are inspected. The consequence of a breach or failure is another aspect of risk. State and local governments have significant authority over land use and development, which can shape the social and economic impacts of a breach or failure; they also lead on emergency planning and related outreach. To date, federal dam and levee safety efforts have consisted primarily of (1) support for state dam safety standards and programs, (2) investments at federally owned dams and levees, and (3) since 2007, creation of a national levee database and enhanced efforts and procedures for Corps levee inspections and assessments. In Public Law 113-121, enacted in 2014, Congress (1) directed the Corps to develop voluntary guidelines for levee safety and an associated hazard potential classification system for levees, and (2) authorized support for the

Health impacts of large dams

International Nuclear Information System (INIS)

Lerer, L.B.

1999-01-01

Large dams have been criticized because of their negative environmental and social impacts. Public health interest largely has focused on vector-borne diseases, such as schistosomiasis, associated with reservoirs and irrigation projects. Large dams also influence health through changes in water and food security, increases in communicable diseases, and the social disruption caused by construction and involuntary resettlement. Communities living in close proximity to large dams often do not benefit from water transfer and electricity generation revenues. A comprehensive health component is required in environmental and social impact assessments for large dam projects

Flux of nitrogen, phosphorus, and suspended sediment from the Susquehanna River Basin to the Chesapeake Bay during Tropical Storm Lee, September 2011, as an indicator of the effects of reservoir sedimentation on water quality

Science.gov (United States)

Hirsch, Robert M.

2012-01-01

Concentrations of nitrogen, phosphorus, and suspended sediment are measured at the U.S. Geological Survey streamgage at Conowingo Dam at the downstream end of the Susquehanna River Basin in Maryland, where the river flows into the Chesapeake Bay. During the period September 7-15, 2011, in the aftermath of Tropical Storm Lee, concentrations of these three constituents were among the highest ever measured at this site. These measurements indicate that sediment-storage processes behind the three dams on the lower Susquehanna River are evolving. In particular, they indicate that scouring of sediment (and the nitrogen and phosphorus attached to that sediment) may be increasing with time. Trends in flow-normalized fluxes at the Susquehanna River at Conowingo, Maryland, streamgage during 1996-2011 indicate a 3.2-percent decrease in total nitrogen, but a 55-percent increase in total phosphorus and a 97-percent increase in suspended sediment. These large increases in the flux of phosphorus and sediment from the Susquehanna River to the Chesapeake Bay have occurred despite reductions in the fluxes of these constituents from the Susquehanna River watershed upstream from the reservoirs. Although the Tropical Storm Lee flood event contributed about 1.8 percent of the total streamflow from the Susquehanna River to the Chesapeake Bay over the past decade (water years 2002-11), it contributed about 5 percent of the nitrogen, 22 percent of the phosphorus, and 39 percent of the suspended sediment during the same period. These results highlight the importance of brief high-flow events in releasing nitrogen, phosphorus, and sediment derived from the Susquehanna River watershed and stored in the Conowingo Reservoir to the Chesapeake Bay.

Deformation performance of Waba Dam

Energy Technology Data Exchange (ETDEWEB)

Salloum, T.; Bhardwaj, V.; Hassan, P. [Ontario Power Generation, Niagara-on-the-Lake, ON (Canada); Cragg, C. [Cragg Consulting Services, Toronto, ON (Canada)

2009-07-01

This paper described the performance of the Waba Dam which is being monitored as part of Ontario Power Generation's Dam Safety Program. It described the deformations that have been observed in this 3600 ft long earthfill dam which lies on marine clay in eastern Ontario. An extensive instrumentation program, including foundation settlement gauges, surface monuments, slope inclinometers, load cells and piezometers has been in effect since the construction of the dam in 1975. Significant settlement has occurred at Waba Dam since its construction. Wide berms were provided upstream and downstream beyond the slopes of the main fill to ensure stability of the dyke on the soft clay foundation and the crest elevations were designed to allow for the expected settlement in the foundation which would be overstressed by the dam loading. Based on current settlements, future settlements are predicted based on Asaoka's method. Inclinometer measurements have shown a foundation lateral spreading of 12 in. The lateral versus vertical deformations were found to be comparable to well behaving embankments reported in the literature. These analyses indicate that Waba Dam is performing well and should continue to perform well into the future. 8 refs., 1 tab., 14 figs.

DAM-LAKEFRONT PLAZA: Revitalization of an Agriculture Reservoir Dam in Kashar-Tirana/Albania

Directory of Open Access Journals (Sweden)

Valbona Koçi

2014-12-01

Full Text Available The Dam-Lakefront Plaza in Kashar-Tirana/Albania is a research project that proposes not only the re-consideration and reinforcement of the artificial Reservoirs Dams built during Socialism in Albania, but envisions the maintenance of dams and revitalization of the lakeside area promoting the public-private collaboration. In addition, it envisions the generation of qualitative and lively public spaces in sub-urban areas as well. Admitting the artificial lakes as specific nodes of man-made infrastructure in the landscape, and consequently the dams (together with the drainage channels as important hydrotechnic elements of the flood protection infrastructure, this research intends to elaborate on one type of landscape infrastructure - the vertical screens, offering a mediation between the natural and built landscape.

Influences of Dam Operations in Groundwater-Surface Water Mixing Zones: Towards Multiscale Understanding

Science.gov (United States)

Stegen, J.; Scheibe, T. D.; Chen, X.; Huang, M.; Arntzen, E.; Garayburu-Caruso, V. A.; Graham, E.; Johnson, T. C.; Strickland, C. E.

2017-12-01

The installation and operation of dams have myriad influences on ecosystems, from direct effects on hydrographs to indirect effects on marine biogeochemistry and terrestrial food webs. With > 50000 existing and > 3700 planned large dams world-wide there is a pressing need for holistic understanding of dam impacts. Such understanding is likely to reveal unrecognized opportunities to modify dam operations towards beneficial outcomes. One of the most dramatic influences of daily dam operations is the creation of `artificial intertidal zones' that emerge from short-term increases and decreases in discharge due to hydroelectric power demands; known as hydropeaking. There is a long history of studying the influences of hydropeaking on macrofauna such as fish and invertebrates, but only recently has significant attention been paid to the hydrobiogeochemical effects of hydropeaking. Our aim here is to develop an integrated conceptual model of the hydrobiogeochemical influences of hydropeaking. To do so we reviewed available literature focusing on hydrologic and/or biogeochemical influences of hydropeaking. Results from these studies were collated into a single conceptual model that integrates key physical (e.g., sediment transport, hydromorphology) and biological (e.g., timescale of microbiome response) processes. This conceptual model highlights non-intuitive impacts of hydropeaking, the presence of critical thresholds, and strong interactions among processes. When examined individually these features suggest context dependency, but when viewed through an integrated conceptual model, common themes emerge. We will further discuss a critical next step, which is the local to regional to global evaluation of this conceptual model, to enable multiscale understanding. We specifically propose a global `hydropeaking network' of researchers using common methods, data standards, and analysis techniques to quantify the hydrobiogeochemical effects of hydropeaking across biomes. We

What are the contemporary sources of sediment in the Mississippi River?

Science.gov (United States)

Hassan, M. A.; Roberge, L.; Church, M.; More, M.; Donner, S. D.; Leach, J.; Ali, K. F.

2017-09-01

Within the last two centuries, the Mississippi River basin has been transformed by changes in land use practices, dam construction, and training of the rivers for navigation. Here we analyze the contemporary patterns of fluvial sediment yield in the Mississippi River basin using all available data in order to assess the influence of regional land condition on the variation of sediment yield within the basin. We develop regional-scale relations between specific sediment yield (yield per unit area) and drainage area to reveal contemporary regional sediment yield patterns and source areas of riverine sediments. Extensive upland erosion before the development of soil conservation practices exported large amounts of sediment to the valleys and floodplains. We show that sediment today is sourced primarily along the river valleys from arable land, and from stream bank and channel erosion, with sediment yields from areas dominated by arable land 2 orders of magnitude greater than that of grassland dominated areas. Comparison with the "T factor," a commonly quoted measure of agricultural soil resilience suggests that the latter may not reflect contemporary soil loss from the landscape.

Reservoir Sedimentation and Upstream Sediment Sources: Perspectives and Future Research Needs on Streambank and Gully Erosion

Science.gov (United States)

Fox, G. A.; Sheshukov, A.; Cruse, R.; Kolar, R. L.; Guertault, L.; Gesch, K. R.; Dutnell, R. C.

2016-05-01

The future reliance on water supply and flood control reservoirs across the globe will continue to expand, especially under a variable climate. As the inventory of new potential dam sites is shrinking, construction of additional reservoirs is less likely compared to simultaneous flow and sediment management in existing reservoirs. One aspect of this sediment management is related to the control of upstream sediment sources. However, key research questions remain regarding upstream sediment loading rates. Highlighted in this article are research needs relative to measuring and predicting sediment transport rates and loading due to streambank and gully erosion within a watershed. For example, additional instream sediment transport and reservoir sedimentation rate measurements are needed across a range of watershed conditions, reservoir sizes, and geographical locations. More research is needed to understand the intricate linkage between upland practices and instream response. A need still exists to clarify the benefit of restoration or stabilization of a small reach within a channel system or maturing gully on total watershed sediment load. We need to better understand the intricate interactions between hydrological and erosion processes to improve prediction, location, and timing of streambank erosion and failure and gully formation. Also, improved process-based measurement and prediction techniques are needed that balance data requirements regarding cohesive soil erodibility and stability as compared to simpler topographic indices for gullies or stream classification systems. Such techniques will allow the research community to address the benefit of various conservation and/or stabilization practices at targeted locations within watersheds.

Fragility Analysis of Concrete Gravity Dams

Science.gov (United States)

Tekie, Paulos B.; Ellingwood, Bruce R.

2002-09-01

Concrete gravity dams are an important part ofthe nation's infrastructure. Many dams have been in service for over 50 years, during which time important advances in the methodologies for evaluation of natural phenomena hazards have caused the design-basis events to be revised upwards, in some cases significantly. Many existing dams fail to meet these revised safety criteria and structural rehabilitation to meet newly revised criteria may be costly and difficult. A probabilistic safety analysis (PSA) provides a rational safety assessment and decision-making tool managing the various sources of uncertainty that may impact dam performance. Fragility analysis, which depicts fl%e uncertainty in the safety margin above specified hazard levels, is a fundamental tool in a PSA. This study presents a methodology for developing fragilities of concrete gravity dams to assess their performance against hydrologic and seismic hazards. Models of varying degree of complexity and sophistication were considered and compared. The methodology is illustrated using the Bluestone Dam on the New River in West Virginia, which was designed in the late 1930's. The hydrologic fragilities showed that the Eluestone Dam is unlikely to become unstable at the revised probable maximum flood (PMF), but it is likely that there will be significant cracking at the heel ofthe dam. On the other hand, the seismic fragility analysis indicated that sliding is likely, if the dam were to be subjected to a maximum credible earthquake (MCE). Moreover, there will likely be tensile cracking at the neck of the dam at this level of seismic excitation. Probabilities of relatively severe limit states appear to be only marginally affected by extremely rare events (e.g. the PMF and MCE). Moreover, the risks posed by the extreme floods and earthquakes were not balanced for the Bluestone Dam, with seismic hazard posing a relatively higher risk.

The role of dams in development

International Nuclear Information System (INIS)

Cakmak, C.

2001-01-01

Although the amounts of water resources are enough for the entire world, the distribution of them in time and space shows uneven pattern. The water need is increasing with heavy industrial and agricultural requirements, while available water in the world remains as a fixed source. Economic growth, socio-cultural, and environmental developments are being realized following these changes. In order to achieve sustainable management of water resources, these changes have to be taken into consideration in water-related development projects. Demand for water is steadily increasing through out the world, even though the fresh water resources are limited and unevenly distributed, during the past three centuries, the amount of water withdrawn from fresh water resources has increased by a factor of 35, whereas world population by a factor 8. The engineering of dams, which provides regular water from reservoirs of dams to be used in case of demand pattern, is a vital part of the civilization. Dams have played a key rote in the development since the third millennium B C when the first great civilizations evolved on major rivers, such as Tigris-Euphrates, the Nile and the Indus. From these early times dams were built for flood control, water supply, irrigation and navigation. Dams also had been built to produce motive power and electricity since the industrial revolution. Development priorities changed, experience accumulated with the construction and operation of dams. Although the importance of water is well known in the human life and civilization around the world, still various groups argue that expected economic benefits are not being produced and that major environmental, economic and social costs are not being taken into account. By the end of 20th century, there were 45000 large dams in over 150 countries. According to the same classification there are 625 large dams in Turkey. All over the world, 50 % of the large dams were built mainly for irrigation. It is estimated

Levels of potentially toxic metals in water, sediment and peat from Wonderfonteinspruit, North West Province, South Africa.

Science.gov (United States)

Nsaka, Ntumba C; McCrindle, Robert I; Ambushe, Abayneh A

2018-04-30

Environmental monitoring of the levels of potentially toxic metals is of importance because of possible adverse effects on living species. This study was conducted to assess the levels of Cd, Cr, Cu, Hg, Mn, Pb, U and V in water, sediment and peat samples collected from the region of Wonderfonteinspruit. Water samples were simply filtered and acidified with HNO 3 prior to analysis. Sediment and peat were oven-dried, ground, sieved and mineralised using a microwave digestion system. Concentrations of the selected elements in all samples were determined by inductively coupled plasma-mass spectrometry. A Zeeman mercury analyser was also used for quantification of Hg in the same sediment and peat samples. The method validation was carried out using SRM 1643e water and BCR 320R sediment certified reference materials. The results showed no significant difference at 95% level of confidence between the certified and measured values after using the Student's t-test. The levels of Cd, Cr, Cu, Pb, V and U found in rivers and dams were lower than the tentative South African water quality range guideline for domestic and irrigation purposes. However, water from dams and certain rivers was unsuitable for irrigation and domestic use.

Dam-breach analysis and flood-inundation mapping for selected dams in Oklahoma City, Oklahoma, and near Atoka, Oklahoma

Science.gov (United States)

Shivers, Molly J.; Smith, S. Jerrod; Grout, Trevor S.; Lewis, Jason M.

2015-01-01

Dams provide beneficial functions such as flood control, recreation, and storage of water supplies, but they also entail risk; dam breaches and resultant floods can cause substantial property damage and loss of life. The State of Oklahoma requires each owner of a high-hazard dam, which the Federal Emergency Management Agency defines as dams for which failure or improper operation probably will cause loss of human life, to develop an emergency action plan specific to that dam. Components of an emergency action plan are to simulate a flood resulting from a possible dam breach and map the resulting downstream flood-inundation areas. The resulting flood-inundation maps can provide valuable information to city officials, emergency managers, and local residents for planning an emergency response if a dam breach occurs.

Technical bulletin : structural considerations for dam safety

Energy Technology Data Exchange (ETDEWEB)

NONE

2007-07-01

This technical bulletin discussed issues related to the safety assessment of concrete water-retaining structures and timber dams. Structures reviewed in the paper included gravity dams; buttress dams; arch dams; spillway structures; intake structures; power plants; roller compacted concrete dams; and timber dams. A variety of issues related to the loss of cohesive bond and discontinuities in bedrock foundations were reviewed with reference to issues related to compressive strength, tensile strength, and shear strength. Static failure modes and failure mechanisms related to dam failures were also described. Visual indicators for potential failures include abutment and foundation movement, seepage, and structure movements. Loading combinations were discussed, and performance indicators for gravity dams were provided. Methods of analysis for considering load characteristics, structure types and geological conditions were also discussed. Modelling techniques for finite element analysis were also included. 16 refs., 3 tabs., 5 figs.

Assessing Risks of Mine Tailing Dam Failures

Science.gov (United States)

Concha Larrauri, P.; Lall, U.

2017-12-01

The consequences of tailings dam failures can be catastrophic for communities and ecosystems in the vicinity of the dams. The failure of the Fundão tailings dam at the Samarco mine in 2015 killed 19 people with severe consequences for the environment. The financial and legal consequences of a tailings dam failure can also be significant for the mining companies. For the Fundão tailings dam, the company had to pay 6 billion dollars in fines and twenty-one executives were charged with qualified murder. There are tenths of thousands of active, inactive, and abandoned tailings dams in the world and there is a need to better understand the hazards posed by these structures to downstream populations and ecosystems. A challenge to assess the risks of tailings dams in a large scale is that many of them are not registered in publicly available databases and there is little information about their current physical state. Additionally, hazard classifications of tailings dams - common in many countries- tend to be subjective, include vague parameter definitions, and are not always updated over time. Here we present a simple methodology to assess and rank the exposure to tailings dams using ArcGIS that removes subjective interpretations. The method uses basic information such as current dam height, storage volume, topography, population, land use, and hydrological data. A hazard rating risk was developed to compare the potential extent of the damage across dams. This assessment provides a general overview of what in the vicinity of the tailings dams could be affected in case of a failure and a way to rank tailings dams that is directly linked to the exposure at any given time. One hundred tailings dams in Minas Gerais, Brazil were used for the test case. This ranking approach could inform the risk management strategy of the tailings dams within a company, and when disclosed, it could enable shareholders and the communities to make decisions on the risks they are taking.

The socio-economics dynamics of Dam on Rural Communities: A case study of Oyan Dam, Nigeria

Science.gov (United States)

Ayeni, Amidu; Ojifo, Lawrence

2018-06-01

Dams construction and operations have many benefits, nevertheless, they have also led to lots of negative social, health and human impacts. It is based on this that this study assesses the potential and socio-economics dynamics of Oyan dam between 1980 and 2016. The data used for this study include water level and discharge records of the dam between 2007 and 2016, Landsat imageries of 1984 and 2016 and socio-economic datasets for the period. Analysis of the dam potentials (water supply, agriculture and hydropower) and socio-economic impacts of the dam were carried out using basic statistical tools, land use change anaysis and field survey using questionnaire, structured interview with major stakeholders and personal observation. The results revealed that the water level and storage of the Oyan dam had a relative reduction of about 2 % as well as non-stationarity pattern of water abstraction and production for the period. The landuse classes show all classes decreased in extent except the cultivated landuse that acrued an increased of 19.9 % between 1984 and 2016. Furthermore, commercial water supply varied significantly between 2010 and 2016 while irrigation scheme is grossly under-utilized from the inception in 1983 to 2016. Finally, the result of socio-economic impacts revealed that majority of the selected communities' members are actually not benefiting from the dam and their livelihoods are not from the dam.

Dam that social networking: connecting South Africa's major dams to social media

CSIR Research Space (South Africa)

Butgereit, L

2011-10-01

Full Text Available where four major South African dams are connected to Twitter and Facebook (and other social media such as MXit and Google Chat) in a mechanism which would be easy to replicate for additional dams or rivers. Data is supplied by the South African...

Case Study: Effects of a Partial-Debris Dam on Riverbank Erosion in the Parlung Tsangpo River, China

Directory of Open Access Journals (Sweden)

Clarence Edward Choi

2018-02-01

Full Text Available This paper examines two successive debris flows that deposited a total of 1.4 million m3 of sediment into the Parlung Tsangpo River in China in 2010. As a result of these deposits, a partial-debris dam was formed in the river. This dam rerouted the discharge in the river along one of the riverbanks, which supported a highway. The rerouted discharge eroded the riverbank and the highway eventually collapsed. To enhance our understanding of the threat posed by partial-debris dams, a field investigation was carried out to measure the discharge in the river and to collect soil samples of the collapsed riverbank. Findings from the field investigation were then used to back-analyze fluvial erosion along the riverbank using a combined erosion framework proposed in this study. This combined framework adopts a dam-breach erosion model which can capture the progressive nature of fluvial erosion by considering the particle size distribution of the soil being eroded. The results from the back-analysis were then evaluated against unique high-resolution images obtained from satellites. This case study not only highlights the consequences of the formation of partial-debris dams on nearby infrastructure, but it also proposes the use of a combined erosion framework to provide a first-order assessment of riverbank stability. Unique high-resolution satellite images are used to assess the proposed erosion framework and key challenges in assessing erosion are discussed.

Contaminants of emerging concern in the Hartbeespoort Dam catchment and the uMngeni River estuary 2016 pollution incident, South Africa.

Science.gov (United States)

Rimayi, Cornelius; Odusanya, David; Weiss, Jana M; de Boer, Jacob; Chimuka, Luke

2018-06-15

A quantitative assessment of pollutants of emerging concern in the Hartbeespoort Dam catchment area was conducted using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to establish the occurrence, source and distribution of 15 environmental pollutants, including 10 pharmaceuticals, 1 pesticide and 4 steroid hormones. Seasonal sampling was conducted in the Hartbeespoort Lake using sub-surface grab sampling to determine the lake's ecological status and obtain data for establishment of progressive operational monitoring. The Jukskei River, which lies upstream of the Hartbeespoort Dam, was sampled in the winter season. Five year old carp (Cyprinus carpio) and catfish (Clarias gariepinus) were also sampled from the Hartbeespoort Dam to study bioaccumulation in biota as well as to estimate risk associated with fish consumption. In the Jukskei River, the main source of 11 emerging pollutants (EPs) was identified as raw sewage overflow, with the highest ∑11 EP concentration of 593ngL -1 being recorded at the Midrand point and the lowest ∑11 EP concentration of 164ngL -1 at the N14 site located 1km downstream of a large wastewater treatment plant. The Jukskei River was found to be the largest contributor of the emerging contaminants detected in the Hartbeespoort Dam. In the Hartbeespoort Dam EP concentrations were generally in the order efavirenz>nevirapine>carbamazepine>methocarbamol>bromacil>venlafaxine. Water and sediment were sampled from the uMngeni River estuary within 24h after large volumes of an assortment of pharmaceutical waste had been discovered to be washed into the river estuary after flash rainfall on 18 May 2016. Analytical results revealed high levels of some emerging pollutants in sediment samples, up to 81ngg -1 for nevirapine and 4ngg -1 for etilefrine HCL. This study shows that efavirenz, nevirapine, carbamazepine, methocarbamol, bromacil and venlafaxine are contaminants that require operational monitoring in South African urban waters

DEFORMATION EFFECTS OF DAMS ON COASTAL REGIONS USING SENTINEL-1 IW TOPS TIME SERIES: THE WEST LESVOS, GREECE CASE

Directory of Open Access Journals (Sweden)

K. Karamvasis

2017-11-01

Full Text Available Coastal zones are vulnerable to erosion and loss by level sea rise. Subsidence caused by the reduction of fluvial sediments in coastal zones found close to dams, is another important deformation factor. Quantification of the deformation rate of coastal region is essential for natural and anthropogenic activities. The study utilizes Interferometric SAR (Synthetic Aperture Radar techniques and exploits the archive of Sentinel-1 TOPS data for the period 2014–2016. The freely available, wide ground coverage (250 × 170 km and small temporal resolution Sentinel-1 TOPS datasets are promising for coastal applications. Persistent Scatterer Interferometry (PSI methodologies are considered state-of-the-art remote sensing approaches for land deformation monitoring. The selected PSI method is the Small Baseline Subset (SBAS multitemporal InSAR technique. The study area of this study is the coastal zone of west region of Lesvos Island, Greece. The main characteristic of the area is the reduction of the fluvial sediment supply from the coastal drainage basins due to construction of dams and the abstraction of riverine sediments. The study demonstrates the potentials of the SBAS method for measuring and mapping the dynamic changes in coastal topography in terms of subsidence rates and discusses its advantages and limitations. The results show that natural and rural environments appear to have diverse ground deformation patterns.

Sedimentation studies at MUDA catchment area, Kedah, Malaysia

International Nuclear Information System (INIS)

Kamarudin Samuding; Juhari Yusuf; Wan Abdul Aziz; Juhari Latiff

2000-01-01

A study on the sediment size distribution and determination of sediment density profile in the selected area of Muda dam catchment area, Kedah is presented. The objective of the study was to establish a base line data of the input sedimentation with regards to the effects of development within the catchment in the future. Three main sampling locations were identified namely at Sungai Teliang, Sungai Muda and Muda reservoir. Measurement of sediment thickness was performed by using nuclear gauges i.e. direct transmission and backscattering methods. Results showed that the grain size distribution of sediment ranges from gravel to clay sizes. In the reservoir and downstream of the river, most of the samples studied consisting of fine sediment i.e silt and clay sizes (<63,um). However, sediment distribution in the upstream section of Sungai Teliang mainly consist of fine to coarse sand. Sediment density profiles in the reservoir showed little changes, whereas bed sediment profiles in the river cross-sectional areas exhibit some changes. The results also showed that thickness of bedload sediment were different from one location to another, in which the thickness may achieve up to 0.75 metre in some areas. Based on the sediment distribution profile analysis, the study site could be divided into two parts comprising of dynamic area (region) covering selected locations along the river and deposited sediment in the reservoir. Basic information derived from this study may provide as one of the important inputs for the MADA reservoir management authority in monitoring, supervising y and identifying rate and source of sediment in the catchment area

TYPOLOGY OF LARGE DAMS. A REVIEW

Directory of Open Access Journals (Sweden)

Gheorghe ROMANESCU

2015-06-01