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Environmental Impacts of Reservoirs
Abstract
The construction of reservoirs is one of the most important practices for the development and management of water resources. Many large reservoirs were built without a thorough or systematic evaluation of the long-term environmental, social, and economic interactions of different alternatives.
Up to the last quarter of the twentieth century, those responsible for the construction of dams and creation of reservoirs – entrepreneurs, decision makers, engineers, investors – were praised for the acknowledged benefits of their works: water supply, irrigated agriculture, flood control, improved navigation and firm hydroelectric generation (considered clean and unequivocally renewable energy). However, on the other hand, alarmist, especially environmental groups and organizations, have been exaggeratedly stating that infrastructure works, in general, and dams and reservoirs, in particular, cause serious and intolerable environmental impacts. Reservoir construction leads to a number of environmental issues, both during building and following completion. The physical, chemical character and water quality of rivers draining into lakes and reservoirs are governed in part by the velocity and the volume of river water. In these last decades of industrialization and rapid population increase, human intervention on the balance of nature has never been so various and so extensive as it is today.
This chapter reviews a large range of potential impacts linked to the exploitation of reservoirs and dams, such as: (1) Climate-changing greenhouse gases emissions; (2) Changes in the Temperature Regime (3) Reservoir sedimentation; (4) Water pollution; (5) Destruction of Eco-systems, and (6) Planning and reservoir management.
... where the hydro plants with large reservoirs in tropical regions have usually a much greater impact on global warming than fossil fuel plants generating equivalent amounts of electricity (Devic, 2015). Therefore, there is growing concern regarding increasing greenhouse gas emissions due to GERD reservoir. ...
... Generally, the carbon sink potential of a reservoir is determined by a number of factors including for example reservoir depth, and local climate, where shallow reservoirs in hot climates have high levels of GHGs emissions (Devic, 2015). ...
Despite the benefits of big project dams, their reservoirs may have significant environmental impacts. The main objective of this paper is to develop an integrated analysis framework of remotely-sensed data ad GIS techniques for delineating surface area of the dam reservoir, simulating their capacities and assessing associated environmental impacts with application to Grand Ethiopian Renaissance Dam (GERD). For this purpose, a methodology of four main steps was applied. The methodology involved delineating the up-to-date reservoir using remotely sensed data, simulating reservoir at full capacity, estimating current and potential reservoir capacity and finally assessing environmental impacts of the reservoir. The results revealed that the up-to-date reservoir covers a total area of 330.3 km2 billion m3 total area of 1650.9 km2 with a gross storage capacity of 12 billion m3. Under full capacity scenario, the reservoir is estimated to cover a , with a storage capacity of 63.4 billion m3. The GERD reservoir may lead to dramatic changes in the local environment with significant implications at both regional and global scales. In this respect, it was found that the reservoir will lead to destruction of ecosystems in a total area of 1300 km2 expected to have significant impacts on GHGs emissions and global warming. Moreover, a massive quantity of water is expected to be lost by surface evaporation.
... One of the main industries of human economic activity, which is developed at large surface water bodies is hydropower. Despite certain economic advantages, dams give rise to various environmental transformations: changes in the amount of regional precipitation, river discharge from different locations along the river, biodiversity, etc. [9][10][11]. The water hydrochemical composition of reservoirs, including the concentrations of major ions and trace elements, relies on natural (weathering processes, lithology of the basin, the composition of water in tributaries, etc.), and anthropogenic factors [12,13]. ...
The Irkutsk Reservoir, belonging to the largest unified freshwater Baikal–Angara system, is an important source of drinking water in the region. Therefore, studies of its hydrochemical characteristics are of prime importance in deciding on the role of anthropogenic activity in water quality. The water samples were collected across the reservoir in 2007, 2012, and 2021 and then were analyzed for major ions and trace elements. The data revealed that the distribution of HCO3−, SO42−, Cl−, Ca2+, Mg2+, Na+ and K+ is stable across the reservoir. Trace element concentrations varied from 1.13 to 15.39 µg L−1 for Al, from <DL to 0.39 µg L−1 for Cr, from 0.39 to 23.12 µg L−1 for Mn, from 1.25 to 53.22 µg L−1 for Fe, from 0.005 to 0.100 µg L−1 for Co, from 0.20 to 1.98 µg L−1 for Cu, from <DL to 13.40 µg L−1 for Zn, from 0.25 to 0.48 µg L−1 for As, from 0.004 to 0.127 µg L−1 for Cd, from <DL to 0.195 µg L−1 for Sn, from <DL to 0.0277 µg L−1 for Cs, from <DL to 1.13 µg L−1 for Pb, from <DL to 0.0202 µg L−1 for Th, and from 0.27 to 0.75 µg L−1 for U. The concentrations of all major ions and trace elements in water were below the drinking water standards. CF values showed considerable and high contamination of samples with Al, Mn, Fe, Co, Cu, Cd, Sn, Pb, and Th. PLI values classified the majority of water samples as water with baseline levels of pollutants, and part of the samples was classified as either polluted or highly polluted.
... Atualmente, no Brasil, existem mais de 1.300 usinas hidrelétricas que produzem mais de 60% de toda a energia elétrica do país e estão distribuídas nas principais bacias hidrográficas brasileira (Agostinho et al., 2016;Aneel, 2020). A implantação desses empreendimentos é caracterizada pela formação de imensos reservatórios e acarretam uma série de alterações nas condições físico-químicas da água, no fluxo de correntes, no regime de cheias e, consequentemente, geram a destruição e modificação de habitats, com influência direta no ciclo de vida de muitos organismos (Araújo et al., 2013;Dević, 2015;Fearnside, 2019). Tais modificações da paisagem natural ocasionam, ainda, mudanças nos padrões e/ou perda de heterogeneidade biótica (Ziober;Zanirato, 2014;Anderson, Jenkins & Heilpern, 2018). ...
O estudo investiga a influência do gradiente rio-barragem na composição taxonômica e a abundância das larvas de peixes ao longo de um reservatório na bacia do rio Curuá-Una, Pará. As larvas de peixes foram capturadas por meio de uma rede de plâncton com malha de 300 µm acoplada com um fluxômetro, durante os meses de abril de 2016 a março de 2017 em 12 estações de coletas distribuídas entre as zonas fluvial (lótica), transição e lacustre (lêntico) à montante da barragem. Na ocasião, foram capturadas 3.864 larvas de peixes, classificadas em 27 espécies. Microphilypnus tapajosensis contribuiu com o maior número de indivíduos e ocorrência em todas as zonas e períodos amostrados, indicando ampla distribuição. Registrou-se uma perda de espécies e diminuição da densidade ao longo do gradiente longitudinal, o que apontou um impacto causado pelo barramento do rio e, consequentemente, afetou a ictiofauna local. No entanto, a captura de espécies de diferentes categorias ecológicas e reprodutivas, porém, com traços oportunistas, indica que o reservatório não alcançou sua resiliência suportada pela ausência de larvas de espécies migradoras de longa distância e de grande porte. Monitoramentos contínuos da biota e delimitação de áreas de desova e berçário, na região adjacente, são fundamentais para servirem como base de uma proposta de manejo e conservação dos recursos pesqueiros, podendo auxiliar na manutenção das relações ecológicas e no bom funcionamento do reservatório. Palavras-Chaves: Peixes neotropicais, Desenvolvimento inicial, Variação longitudinal, Impacto ambiental, Barragem. Does the composition of fish larvae assemblage affect by the longitudinal gradient (dam-river) of the Curuá-Una reservoir? A B S T R A C T This study investigates the influence of the river-dam gradient on the taxonomic composition and abundance of fish larvae along a reservoir in the Curuá-Una river basin, Pará. The fish larvae were captured using a plankton net with a 300 µm mesh coupled with a flow meter, during the months of April 2016 to March 2017 in 12 collection stations distributed among the fluvial (lotic), transition and lacustrine (lentic) zones upstream of the dam. In that occasion, 3,864 fish larvae were captured, classified into 27 species. Microphilypnus tapajosensis contributed with the largest number of individuals, occurring in all zones and sampled periods, indicating a wide distribution. It recorded a species loss and a decrease in density along the longitudinal gradient, indicating that the impact caused by the river dam affected the local ichthyofauna. However, the capture of species from different ecological and reproductive categories, but with opportunistic features, indicates that the reservoir has not reached its resilience supported by the absence of larvae of long-distance and large migratory species. Continuous monitoring of the biota and the delimitation of spawning and nursery areas in the adjacent region are essential to serve as the basis for a proposal for the management and conservation of fisheries resources in the region, which can assist in the maintenance of ecological relations and the smooth functioning of the reservoir.
... In contrast to natural water, reservoir basins are speci c ecosystems, formed under the in uence of both natural and technogenic factors, which leads to irreversible changes in their hydrological, hydrochemical and hydrobiological regimes [1,2]. The addition of technogenic organic and inorganic matter, which enter the reservoir with wastewater, surface runoff and through the atmospheric deposition from contaminated areas, could bring about even more undesirable negative changes [3,4]. ...
This study was aimed at identifying the processes responsible for the major ion composition of pore water from the bottom sediments of the Bratsk water reservoir, which is a part of the largest freshwater Baikal-Angara water system. The pore water ionic composition varies both along the sediment depth profile and across the water area. In pore water, the difference between the highest and lowest values is remarkably large: 5.1 times for K+, 13 times for Mg2+, 16 times for HCO3-, 20 times for Ca2+, 23 times for Na+, 80 times for SO42-, 105 times for Cl-. Such a variability suggests that the dominant factors, influencing pore water chemistry, depend on the location. At the first stages of the sedimentation process, the chemistry of the pore water in the Bratsk reservoir is dependent on HCO3-Ca of the overlying water. Later on, due to the interaction with the sedimentary terrigenous material, they changed to SO4, SO4-HCO3, HCO3-SO4, HCO3-Cl-SO4-water types with exchangeable cations, mainly Ca. Some of pore waters may have a complex genesis associated with subaqueous groundwater discharge. The change in the redox potential observed in the pore water is the indicator of early-diagenetic transformations taking place in bottom sediments.
... However, on the other side, alarmist groups and organizations have been exaggeratedly stating that the infrastructure, in general, and dams and reservoirs, in particular, have serious and intolerable environmental impacts. Reservoir construction leads to number of environmental issues, both during building and following completion (Devic, 2015). ...
Surface water quality is currently matter of serious concern in developing countries, due to growing populations, rapid industrialization, urbanization and agricultural modernization. Since contaminants are primarily related to anthropogenic activities, pollution by heavy metals in surface water bodies
... Another example of water control measures is provided by dams and reservoirs, which have increased dramatically in number and scale globally since the 1950s (Chao, 1995), to the point that water impounded in artificial reservoirs since the 1950s is by far the most significant anthropogenic hydrological change in terms of water volume (Vö rö smarty et al., 2003(Vö rö smarty et al., , 2004.These structures are built for irrigation purposes, water for human consumption, agricultural use, power generation, land drainage and reclamation, flood mitigation and recreational use (Castelletti et al., 2008;FAO, 2001;Gordon and Meentemeyer, 2006;Hall and Shelby, 2000;Le et al., 2007). These functions are, however, accompanied by environmental changes, including subsequent impacts on lowland rivers and coastal systems, climate-changing greenhouse gases emissions, changes in the temperature regime, sedimentation, water pollution and destruction of ecosystems due to the reservoir effect on downstream environmental flows and sediment supply (Dević, 2015). Artificial wetlands have also become ubiquitous in recent decades, and are a distinctive form of water management system created for the purpose of treating municipal or industrial wastewater, greywater or stormwater, to act as a biofilter and remove pollutants from the water and for land reclamation after mining, refineries or other ecological disturbances (ElZein et al., 2016;Vymazal and Kröpfelová, 2008;Zhang et al., 2009). ...
Human societies have been reshaping the geomorphology of landscapes for thousands of years, producing anthropogenic geomorphic features ranging from earthworks and reservoirs to settlements, roads, canals, ditches and plough furrows that have distinct characteristics compared with landforms produced by natural processes. Physical geographers have long recognized the widespread importance of these features in altering landforms and geomorphic processes, including hydrologic flows and stores, to processes of soil erosion and deposition. In many of the same landscapes, archaeologists have also utilized anthropogenic geomorphic features to detect and analyse human societal activities, including symbolic formations, agricultural systems, settlement patterns and trade networks. This paper provides a general framework aimed at integrating geophysical and archaeological approaches to observing, identifying and interpreting the full range of anthropogenic geomorphic features based on their structure and functioning, both individually and as components of landscape-scale management strategies by different societies, or “sociocultural fingerprints”. We then couple this framework with new algorithms developed to detect anthropogenic geomorphic features using precisely detailed three-dimensional reconstructions of landscape surface structure derived from LiDAR and computer vision photogrammetry. Human societies are now transforming the geomorphology of landscapes at increasing rates and scales across the globe. To understand the causes and consequences of these transformations and contribute to building sustainable futures, the science of physical geography must advance towards empirical and theoretical frameworks that integrate the natural and sociocultural forces that are now the main shapers of Earth’s surface processes.
Ageing dams and the rising efforts to restore stream ecosystems are increasing the number of dam decommissioning programs. Although dam decommissioning aims at improving in‐stream habitat, biodiversity, and ecosystem functioning in the long‐term, it might also cause ecological impacts in the short‐term due to the mobilization of the sediment accumulated in the reservoir. Benthic biofilm in particular can be impaired by episodes of high turbidity and scouring. We conducted a mBACI (multiple Before‐After/Control‐Impact) experiment to assess the effects of the drawdown of a large dam (42‐m tall), a first step to its decommissioning, on biofilm structure (biomass and chlorophyll‐a) and functioning (metabolism, nutrient uptake, and organic matter breakdown). Our results show that the reservoir drawdown reduced the autotrophic biofilm biomass (chlorophyll‐a) downstream from the dam, which in turn lowered metabolism. However, nitrogen and phosphorus uptake by the biofilm was not affected. Organic matter breakdown was slower below the dam than in nearby undammed reaches before and during drawdown. All drawdown effects quickly disappeared and reaches downstream from the dam approached values found in nearby undammed reaches. Thus, our results indicate that the effects of reservoir drawdown on stream biofilms exist but may be small and disappear rapidly. This article is protected by copyright. All rights reserved.
The physico-chemical water quality of Lake Tiga was monitored over a two-year period (March 2009- March 2011) in order to bridge the information gap on its limnology and assess its physico-chemical condition. Turbidity, Dissolved Oxygen (DO) saturation and organic matter were significantly higher (p<0.05) in the rainy
season than in the dry season, while pH and Biological Oxygen Demand were significantly higher (p<0.05) in the dry season than in the rainy season. Apparent colour, Total Solids (TS), Total Suspended Solids (TSS), K+, Cl-, total acidity, total hardness, NO3- and PO43- decreased (p<0.05) from the riverine section towards the dam site, while water transparency, Dissolved Oxygen (DO), SO42- and Mg2+ showed an increase (p<0.05) from the riverine section towards the dam site. Apparent colour, TS, TSS, total acidity, total hardness, Ca2+, NO3- and PO43- increased (p<0.05) from the surface down to the bottom, while pH, Mg2+ and DO decreased (p<0.05) from the surface down to the bottom at the lacustrine section of the lake. Cluster analysis of the parameters showed major clusters between the major ions (Ca2+, Na+, K+, Cl-, HCO3-) and the general chemical characteristics (TDS, alkalinity, conductivity, acidity and hardness) and also between the nutrient compounds (Organic matter, NO3- and PO43-) and the hydrophysical parameters (TS, TSS, apparent colour, true colour and turbidity). The water quality indices and sodium absorption ratio values in the sampled stations indicated that the water is most suitable for probable applications at the lacustrine section, towards the dam site.
One of the major impediments to the integration of lentic ecosystems into global environmental analyses has been fragmentary data on the extent and size distribution of lakes, ponds, and impoundments. We use new data sources, enhanced spatial resolution, and new analytical approaches to provide new estimates of the global abundance of surface-water bodies. A global model based on the Pareto distribution shows that the global extent of natural lakes is twice as large as previously known (304 million lakes; 4.2 million km 2 in area) and is dominated in area by millions of water bodies smaller than 1 km2. Similar analyses of impoundments based on inventories of large, engineered dams show that impounded waters cover approximately 0.26 million km2. However, construction of low-tech farm impoundments is estimated to be between 0.1 % and 6% of farm area worldwide, dependent upon precipitation, and represents >77,000 km 2 globally, at present. Overall, about 4.6 million km2 of the earth's continental "land" surface (>3%) is covered by water. These analyses underscore the importance of explicitly considering lakes, ponds, and impoundments, especially small ones, in global analyses of rates and processes. © 2006, by the American Society of Limnology and Oceanography, Inc.
Water samples from five sampling points on four rivers, Owabi, Akyeampomene, Pumpunase and Sukobri, representing the main streams serving the Owabi reservoir were analysed for some pollution indicators using standard methods. Heavy metals (Zn, Cu, Mn, Cu, Pb and As) concentrations and some physical parameters of the water samples were determined. Electrical conductivity and pH of waters from all the streams were found to be within the acceptable limits of the World Health Organization (WHO). All the streams showed high turbidity values above WHO limits. Of the heavy metals determined in the water samples, Fe, Mn, Zn and Cu concentrations in all the streams were within the acceptable WHO limits, whiles Pb and As appeared to be higher than the acceptable limits in all the streams. The highest concentrations of most of the heavy metals were recorded at the Kronum site on Owabi stream. There was a statistically significant positive correlation between pH and some metals at all the sample points (p = 0.05). The results showed that all the streams were polluted and must be treated before consumption. It was also recommended that, human activities within the catchments should be monitored closely to minimise their polluting impacts on the water quality.
This paper focuses on sediment bypass tunnels for reservoir sedimentation management. Worldwide, number of constructed sediment bypass tunnels is very small because of topographical, hydrological or economical conditions. Bypass tunnels, however, have many advantages such as they can be constructed even at existing dams and prevent a loss of stored reservoir water caused by the lowering of the reservoir water level. They are also considered to have a relatively small impact on environment downstream because inflow discharge can pass through tunnels very naturally during flood times. In Japan, sediment bypass tunnels of the Nunobiki Dam completed in 1908, and of the Asahi Dam completed in 1995, have been successfully introduced to realize sustainable reservoir management. Sediment bypasses of the Miwa Dam, Koshibu Dam and Matsukawa Dam on the Tenryu River are expected to be next leading projects in Japan. In this paper, we discuss design criteria and lessons learned from existing facilities, and future challenges of planning projects. The focus is on tunnel geometries such as diameter, slope, bottom shape etc., and an abrasion-resistance design of the tunnel invert.
By means of a theoretical model, bootstrap resampling and data provided by the International Commission On Large Dams (ICOLD
(2003) World register of dams. http://www.icold-cigb.org) we found that global large dams might annually release about 104±7.2Tg
CH4 to the atmosphere through reservoir surfaces, turbines and spillways. Engineering technologies can be implemented to avoid
these emissions, and to recover the non-emitted CH4 for power generation. The immediate benefit of recovering non-emitted CH4 from large dams for renewable energy production is the mitigation of anthropogenic impacts like the construction of new large
dams, the actual CH4 emissions from large dams, and the use of unsustainable fossil fuels and natural gas reserves. Under the Clean Development
Mechanism of the Kyoto Protocol, such technologies can be recognized as promising alternatives for human adaptations to climate
change concerning sustainable power generation, particularly in developing nations owning a considerable number of large dams.
In view of novel technologies to extract CH4 from large dams, we estimate that roughly 23±2.6, 2.6±0.2 and 32±5.1Tg CH4 could be used as an environmentally sound option for power generation in Brazil, China and India, respectively. For the whole
world this number may increase to around 100±6.9Tg CH4.
The creation of large freshwater reservoirs is one of the most dramatic anthropogenic impacts on the natural environment.
With worldwide rising demand for water, the construction of more reservoirs is inevitable. Although the effects of reservoir
construction on many medically important parasites are well known and appreciated, changes to aquatic wildlife host–parasite
interactions have been largely undervalued even though a large body of literature exists. The present review examines changes
in the wildlife parasite fauna during the impoundment of reservoirs, focusing on the parasites of invertebrates, fish, and
birds, the effects both upstream and downstream of the reservoir, parasitic zoonoses, the associated pollution generated,
and assesses the impact of the recently completed Three Gorges Dam in China on the Yangtze River’s parasite fauna.
In this paper, we develop and apply a framework for estimating the potential global-scale impact of reservoir construction on riverine sediment transport to the ocean. Using this framework, we discern a large, global-scale, and growing impact from anthropogenic impoundment. Our study links information on 633 of the world's largest reservoirs (LRs) (≥0.5 km3 maximum storage capacity) to the geography of continental discharge and uses statistical inferences to assess the potential impact of the remaining >44,000 smaller reservoirs (SRs). Information on the LRs was linked to a digitized river network at 30′ (latitude×longitude) spatial resolution. A residence time change (ΔτR) for otherwise free-flowing river water is determined locally for each reservoir and used with a sediment retention function to predict the proportion of incident sediment flux trapped within each impoundment. The discharge-weighted mean ΔτR for individual impoundments distributed across the globe is 0.21 years for LRs and 0.011 years for SRs. More than 40% of global river discharge is intercepted locally by the LRs analyzed here, and a significant proportion (≈70%) of this discharge maintains a theoretical sediment trapping efficiency in excess of 50%. Half of all discharge entering LRs shows a local sediment trapping efficiency of 80% or more. Analysis of the recent history of river impoundment reveals that between 1950 and 1968, there was tripling from 5% to 15% in global LR sediment trapping, another doubling to 30% by 1985, and stabilization thereafter. Several large basins such as the Colorado and Nile show nearly complete trapping due to large reservoir construction and flow diversion. From the standpoint of sediment retention rates, the most heavily regulated drainage basins reside in Europe. North America, Africa, and Australia/Oceania are also strongly affected by LRs. Globally, greater than 50% of basin-scale sediment flux in regulated basins is potentially trapped in artificial impoundments, with a discharge-weighted sediment trapping due to LRs of 30%, and an additional contribution of 23% from SRs. If we consider both regulated and unregulated basins, the interception of global sediment flux by all registered reservoirs (n≈45,000) is conservatively placed at 4–5 Gt year−1 or 25–30% of the total. There is an additional but unknown impact due to still smaller unregistered impoundments (n≈800,000). Our results demonstrate that river impoundment should now be considered explicitly in global elemental flux studies, such as for water, sediment, carbon, and nutrients. From a global change perspective, the long-term impact of such hydraulic engineering works on the world's coastal zone appears to be significant but has yet to be fully elucidated.
Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH4) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets.
Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least
103 teragrams of CH4 year−1, corresponding to 0.65 petagrams of C as carbon dioxide (CO2) equivalents year−1, offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and
freshwaters need to be recognized as important in the global carbon cycle.
The need to understand and minimize negative environmental outcomes associated with large dams has both contributed to and benefited from the introduction and subsequent improvements in the Environmental Impact Assessment (EIA) process. However, several limitations in the EIA process remain, including those associated with the uncertainty and significance of impact projections. These limitations are directly related to the feedback between science and policy, with information gaps in scientific understanding discovered through the EIA process contributing valuable recommendations on critical focus areas for prioritizing and funding research within the fields of ecological conservation and river engineering.
This reports starts by assessing the scale of the problem of reservoir sedimentation. It assesses the volume of storage that is likely to be lost to sedimentation and compares this volume with the net volume of storage that is likely to be required to meet continuing demand. The report provides a review of the current state of knowledge of reservoir flushing.
Concentrations of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in the water column and their exchange at the water/air interface were studied during the open water period in two freshwater ponds with different catchment characteristics in the northern boreal zone in Finland; either peatlands or coniferous upland forests dominated the catchment of the ponds. Both ponds were supersaturated with dissolved CO2 and CH4 with respect to the equilibrium with the atmosphere, but were close to the equilibrium with N2O. The mean CO2 efflux from the pond was higher in the peatland-dominated catchment (22 mg m−2 h−1) than in the forested catchment (0.7 mg m−2 h−1), whereas the mean CH4 emissions were similar (7.6 and 3.5 mg m−2 d−1, respectively). The fluxes of N2O were generally negligible. The higher CO2 concentrations and efflux in the pond with the peatland-dominated catchment were attributed to a greater input of allochthonous carbon to that pond from its catchment due to its higher water colour and higher total organic carbon (TOC) concentration. The water pH, which also differed between the ponds, could additionally affect the CO2 dynamics. Since the catchment characteristics can regulate aquatic carbon cycles, catchment-scale studies are needed to attain a deeper understanding of the aquatic greenhouse gas dynamics.
Alton Water, Suffolk, UK, is a linear reservoir, with input water pumped into the northwest end and drawoff tower in the main basin at the southeast end. The reservoir had an eutrophic to mesotrophic gradient in 1995 and 1996, primarily due to differences in summer. In 1995 mean summer chlorophyll a concentration at the northwest end was 95±34 μg l−1, 24 times that in the main basin. Total phosphorus, orthophosphate, nitrate and ammonium concentrations significantly decreased along the length of the reservoir, whilst Secchi depth increased. The first two components of principal component analysis (PCA) explained 37.4% of the variation in the data set, with ordination of sample sites along opposing gradients of TP and Secchi depth. The northwest end of the reservoir had high suspended solids and algal biomass whilst the main basin was a clear water site with high Secchi depth. Phosphorus was more limiting than nitrogen (DIN:OP>16:1), however Si:TP fell below 16:1 during spring (March–May) and summer (July–September) indicating possible silica limitation to diatoms. In situ nutrient addition experiments (September 1996–August 1997) indicated phosphorus limitation, with response to phosphate addition significantly increasing along the length of the reservoir. Co-limitation did not occur as addition of phosphate, ammonium and silicate together produced the same response as phosphate addition alone. Alkaline phosphatase activity assay supported the pattern of phosphorus limitation with highest activity in the main basin. Manipulation of zooplankton grazing did not control the algal biomass response to phosphate addition. Ferric dosing of the pumped input coupled with the topography of the reservoir limited algal biomass in the main basin through bottom-up nutrient limitation.
Sediment deposition in reservoirs has caused the loss of 66% of the reservoir capacity in China. The main sedimentation control strategies are: 1) storing the clear water and releasing the turbid water; 2) releasing turbidity currents; 3) Draw-down flushing and empty flushing; and 4) dredging. The paper summarizes these strategies with examples. Sediment transport in many Chinese rivers occurs mostly during the 2-4 month flood season, that is, 80-90% of the annual sediment load is transported with 50-60% of the annual runoff. By storing the clear water after the flood season and releasing the turbid water during the flood season, less sediment deposits in the reservoir while the reservoir is still able to store enough water for power generation in the low flow season. The Three Gorges and Sanmenxia reservoirs apply this strategy and control sedimentation effectively. Turbidity currents have become the main sedimentation control strategy for the Xiaolangdi Reservoir. Empty flushing involves reservoir draw-down to temporarily establish riverine flow along the impound reach, flushing the eroded sediment through the outlets. Case studies with the Hengshan Reservoir and Zhuwo Reservoir are presented. Jet dredgers have been used to agitate the reservoir deposit so that the deposit is released from the reservoir with currents. The sediment releasing efficiency is 30-100% for storing the clear and releasing the turbid; 6-40 % for turbidity current; and 2,400-5,500% for empty flushing. Empty flushing causes high ecological stress on the ecosystem to the downstream reaches. Storing the clear and releasing the turbid is the best strategy to control reservoir sedimentation while achieving hydro-power benefit and maintain ecological stability. © 2009 International Research and Training Centre on Erosion and Sedimentation and the World Association for Sedimentation and Erosion Research.
H Abstract Tropical Asian rivers support a rich but incompletely known biota, including a host of fishes, a diverse array of benthic invertebrates, and an assem- blage of mammals adapted to riverine wetlands. River ecology is dominated by flow seasonality imposed by monsoonal rains with profound consequences for fishes and zoobenthos. Information on life histories, feeding, and the trophic base of production of these animals is summarized. Widespread use of allochthonous foods by fishes and zoobenthos is apparent. Migration by fishes is often associated with breeding and results in seasonal occupation of different habitats. Riverine biodiversity is threatened by habitat degradation (pollution, deforestation. of drainage basins), dams and flow regulation, as well as over-harvesting. Conservation efforts in tropical Asia are con- strained by a variety of factors, including lack of ecological information, but the extent of public awareness and political commitment to environmental protection are likely determinants of the future of riverine biodiversity.
This review provides an in-depth survey of the recorded incidences in aquatic organisms of mortality and disease events suspected or known to be caused by microalgal or ciliate blooms, their biotoxins, or their harmful mechanisms. Some 200 species of dinoflagellates, diatoms, raphidophytes, prymnesiophytes, silicoflagellates, cilliates, and cyanobacteria are currently known to be, suspected to be, or have the potential to be toxic or harmful to a wide spectrum of organisms. This review summarizes the current information on toxic or harmful microalgal species that affect aquatic organisms (and, when relevant, those that affect terrestrial organisms, including humans), provides an updated list of such species, cites pertinent case histories, and includes relevant information on harmful or toxic species from freshwater, brackish, and marine ecosystems. It is hoped that this review will provide documentation and reference material suitable for researchers, students, managers, and resource and health professionals alike and that it will stimulate future research questions critical to our understanding of harmful algal bloom (HAB) species and the significant effects they have upon aquatic systems.
IntroductionMaterials and methodsResultsWater temperature effects on troutDiscussionAcknowledgementsReferences
1] We report original data on nitrous oxide (N 2 O) fluxes from two tropical reservoirs, their rivers below the dam, and from natural aquatic ecosystems and rainforest soils in French Guiana and Panama. We also review published N 2 O fluxes from other tropical reservoirs and natural environments. We show that: (1) N 2 O emissions from tropical reservoirs occur mainly at the reservoir surface, fluxes downstream of dams being minor; (2) Because pre-flooding natural N 2 O fluxes are significant, the net N 2 O emissions from reservoirs are less than $50– 70% of gross N 2 O emissions; (3) the contribution of N 2 O to the global warming potential of emissions from reservoirs could be significant for gross emissions, but less than 10% for net emissions, disregarding N 2 O degassing emissions.
1. The thermal regime of rivers plays an important role in the overall health of aquatic ecosystems, including water quality issues and the distribution of aquatic species within the river environment. Consequently, for conducting environmental impact assessments as well as for effective fisheries management, it is important to understand the thermal behaviour of rivers and related heat exchange processes.
2. This study reviews the different river thermal processes responsible for water temperature variability on both the temporal (e.g. diel, daily, seasonal) and spatial scales, as well as providing information related to different water temperature models currently found in the literature.
3. Water temperature models are generally classified into three groups: regression, stochastic and deterministic models. Deterministic models employ an energy budget approach to predict river water temperature, whereas regression and stochastic models generally rely on air to water temperature relationships.
4. Water temperature variability can occur naturally or as a result of anthropogenic perturbations, such as thermal pollution, deforestation, flow modification and climate change. Literature information is provided on the thermal regime of rivers in relation to anthropogenic impacts and such information will contribute to the better protection of fish habitat and more efficient fisheries management.
Environmental problems resulting from human displacement and resettlement are considered to be secondary impacts of hydro projects. There is a significant gap in knowledge concerning the environmental consequences of resettlement of the Three Gorges project (TGP), China. This study examines critical environmental problems associated with the TGP resettlement. It reveals that the contradiction between the land inundation and demand for land in resettling rural residents is a critical environmental issue. On the positive side, countermeasures that are discussed include: engineering works for farmland protection, developing eco-agriculture, reforestation and constructing a green belt in the peripheral zone of the reservoir, and adjustments to resettlement policy.
The Malter Reservoir is situated about 30 km south of Dresden (eastern Germany) in a historical mining area of the eastern
Erzgebirge. It was built in 1913 for the protection from floodwaters, droughts and for generating electricity. The river Rote
Weißeritz is the main source of clastic input into the lake. Geochemical and sedimentological data of gravity-and piston-cores,
recovered from the deepest point of the lake, document the environmental history of the drainage area since 1963. 137Cs dating gives an average sedimentation rate of ∼2.9 cm/year. Within the whole core, heavy metals are strongly enriched (parentheses
refer to enrichment factors as compared with average shale): cadmium (290), silver (140), bismuth (90), antimony (25), lead
(21), zinc (14), tin (13), uranium (9), tungsten (9), molybdenum (5), copper (4), thallium (3) and chromium (2). Enrichments
are detectable for the whole registered time-period of 81 years. Peaks of up to 27 mg/kg silver, 37 mg/kg bismuth, 91 mg/kg
cadmium, 410 mg/kg chromium, 240 mg/kg copper, 20 mg/kg molybdenum, 14000 mg/kg phosphorus, 740 mg/kg lead, 6,5 mg/kg antimony,
74 mg/kg tin, 52 mg/kg tungsten and 1900 mg/kg zinc reflect local events caused by human impact. Inputs from different pollution
sources at different times are represented by highly variable elemental concentrations and ratios within the core. High pH
values within the water and the sediment column, the large adsorption capacity of the fine-grained Corg.-rich sediment, and the presence of low Eh-values and sulphide ions in the sediment prevent the remobilisation of the toxic
elements. Erosion of these contaminated sediments during floods, channel flows or resuspension during removal of the sediments
may lead to a downstream transfer of pollutants. Contents of P and Corg., as well as diatom abundance, indicate a change from oligotrophic to eutrophic conditions in the lake during ∼1940–1950.
This was mainly caused by high agricultural activity in the drainage area. Reduced contents of Cu, Zn, Cd and Cr since the
reunification of East and West Germany are obviously caused by increasing environmental protection measures, such as wastewater
purification and especially the closing of contaminating industries.
Although integrated simulation and optimization approaches under stochastic uncertainty have been applied to eutrophication management problems, few studies are reported in eutrophication control planning where multiple formats of uncertainties and nonlinearities are addressed in forms of intervals and probabilistic distributions within an integrated framework. Since the impounding of Three Gorges Reservoir (TGR), China in 2003, the hydraulic conditions and aquatic environment of the Xiangxi Bay (XXB) have changed significantly. The resulting emergence of eutrophication and algal blooms leads to its deteriorated water quality. The XXB becomes an ideal case study area. Thus, a simulation-based inexact chance-constrained nonlinear programming (SICNP) model is developed and applied to eutrophication control planning in the XXB of the TGR under uncertainties. In the SICNP, the wastewater treatment costs for removing total phosphorus (TP) are set as the objective function; effluent discharge standards, stream water quality standards and eutrophication control standards are considered in the constraints; a steady-state simulation model for phosphorus transport and fate is embedded in the environmental standards constraints; the interval programming and chance-constrained approaches are integrated to provide interval decision variables but also the associated risk levels in violating the system constraints. The model results indicate that changes in the violating level (q) will result in different strategy distributions at spatial and temporal scales; the optimal value of cost objective is from [2.74, 13.41] million RMB to [2.25, 13.08] million RMB when q equals from 0.01 to 0.25; the required TP treatment efficiency for the Baisha plant is the most stringent, which is followed by the Xiakou Town and the Zhaojun Town, while the requirement for the Pingyikou cement plant is the least stringent. The model results are useful for making optimal policies on eutrophication control planning and water quality improvement in the XXB.
Sustainability of Alpine reservoirs is severely threatened by sedimentation resulting from natural geomorphologic processes. Management of sedimentation in Alpine reservoirs cannot be apprehended by a standard generalized rule or procedure. The paper aims at identifying, measuring technique to assess the risk of reservoir siltation with and without countermeasures in Japanese and European Alps. Furthermore, analyzing how human interventions and climate changes may alter sediment fluxes, morphological patterns and in river basin system. Maintaining the “Healthy Life of the River Basin” is the ultimate goal of the paper by applies integrated sediment management, to realize the sustainable utilization of water resources and ecological environment protection, and achieve harmony between humans and nature. The results show that, the successful reservoir sediment management proceeds from a permanent change in river management. This may involve strategies to enhance water and sediment release by a combination of several countermeasures. In big Alpine reservoirs, turbidity currents are often the governing process in reservoir sedimentation by transporting fine materials in high concentrations.
En la actualidad, es bastante común identificar los embalses como causantes de efectos negativos sobre los tramos de río regulados. Los embalses y los ríos regulados guardan una relación intensa y unidireccional, río abajo, de modo que la forma de gestionar el embalse, además de condicionar sus propias características eco lógicas, determina también la organización, el funcionamiento y las posibilidades del ecosistema fluvial regulado. En España, los cuatro principales problemas ambientales que afectan al sistema embalse-río regulado son la alteración del régimen de caudales, la eutrofización, la interrupción del transporte de sedimentos y la creciente introducción de especies exóticas. Se puede continuar indefinidamente con las preocupaciones en medir y criticar los impactos de los embalses sobre los ríos, incluso se puede proponer la eliminación de presas, pero también se puede pensar en el valor estratégico de los embalses para garantizar la disponibilidad de agua y la preservación de los niveles de calidad de vida alcanzados gracias a ellos, y promover una gestión ambiental que reduzca sus impactos negativos sobre los ríos. Las opciones de manejo de niveles y caudales que ofrece prácticamente cualquier presa, junto con la inclusión dentro del programa de explotación de cada embalse, de unos objetivos ambientales para el mismo y para el tramo de río regulado río abajo, es un campo de aplicación de la limnología que no por conocido, se haya prodigado hasta donde sería deseable. Quedan muchos tópicos por demoler -aunque quizás no tantos como presas propuestas- y mucho margen para la mejora de los ríos regulados. Las opciones de gestión ambiental son inabordables en un solo artículo, de modo que no se pretende más que exponer una serie de reflexiones básicas sobre las que " poder elaborar un enfoque de gestión ambiental de los embalses, integrable con los usos para los que fueron construidos y con las demandas sociales actuales en materia de preservación de los ecosistemas acuáticos continentales.
The Lot-Garonne fluvial system is known for its historic heavy metal pollution resulting from mining and smelting activities since the late 19th century. Here, we report 137Cs activities and heavy metal (Cd, Zn, Cu, Pb and V) concentration-depth profiles from sediment cores retrieved in 2001 from three reservoirs in the Lot River. High mean sedimentation rates of 2.4-2.8 cm a(-1) are indicated by 137Cs dating. The reservoir sediments have recorded the heavy metal deposition and thus allow establishing a connection between the temporal evolution of the heavy metal pollution and historical changes in smelting and waste-treatment proceedings. Based on heavy metal concentrations in sediments upstream of the anthropogenic inputs and bottom-sediments of the furthest downstream core (interpreted as old soil or riverbed), concentrations of approximately 17, approximately 82, approximately 0.33 and approximately 28 mg kg(-1) for Cu, Zn, Cd and Pb, respectively, are proposed as natural background values for the Lot fluvial system. The geoaccumulation index (Igeo [Müller, G., 1979. Schwermetalle in den Sedimenten des Rheins-Veränderungen seit. Umschav 79, 133-149.]) revealed that the Lot River sediments must be considered as "severely polluted" in Cd and Zn. Moreover, despite remediation efforts undertaken in the former smelting site, the Lot River is still "severely" (Igeo approximately 4) and "moderately to severely" (Igeo>2) impacted by Cd and Zn inputs, respectively.
Biogeochemical distinction of methane emissions to the atmosphere may essentially rely on the surface area and morphometry of Amazon hydroreservoirs. Tucurui (deep) and Samuel (shallow) reservoirs released in average 13.82+/-22.94 and 71.19+/-107.4 mg CH4 m(-2)d(-1), respectively. delta13C-CH4 values from the sediments to the atmosphere indicate that the deep reservoir has extended methanotrophic layer, oxidizing large quantities of light isotope methane coming from the sediments, while sediment-generated methane can easily evade the shallow reservoir.
In this research we examined the hypothesis that upper reaches of rivers and streams can experience eutrophication as a consequence of deep releases from dams. Field studies were conducted in four mountain rivers (Tormes, Riaza, Eresma and Miraflores Rivers) of Central Spain. The watersheds of these rivers are underlain by siliceous rocks. A small deep-release storage reservoir is found in the upper reaches of each river. Two sampling sites, upstream and downstream from the reservoir, were established in stony riffles of each impounded river. Significant (P < 0.01) increases in conductivity and nutrient (NO3-N, NH4-N, PO4-P) concentrations downstream from the reservoirs were measured. Significant (P < 0.01) increases in periphyton chlorophyll a and ash-free dry biomass were also quantified at downstream sites. Significant (P < 0.01) correlation coefficients indicated that phosphate would play a more important role as the limiting nutrient for periphyton. Relative abundances of macroinvertebrate scrapers and collector-gatherers increased downstream from the reservoirs. Furthermore, taxon dominance, total density and total biomass of macroinvertebrates tended to be higher at downstream sites than at upstream sites. In contrast, taxon diversity and relative abundance of macroinvertebrate shredders decreased downstream from the reservoirs. It is concluded that small deep-release storage reservoirs, located in upper reaches of siliceous rivers, can act as nutrient sources, causing eutrophication downstream. Nutrients would ultimately come from land/forest runoff. The fact that terrestrial vegetation was not completely removed before filling reservoirs could also contribute to the eutrophication process.
Mercury (Hg) concentrations in fish in lakes are elevated due to increased global cycling of Hg. A special case of elevated Hg concentrations in fish occurs in new hydroelectric reservoirs because of increased rates of converting Hg in the environment into methyl mercury (MeHg). People and wildlife that eat fish from hydroelectric reservoirs have an elevated risk of accumulating too much MeHg. Demand for electrical energy is leading to the creation of new reservoirs. In 2005, Canada derived 60% of its electricity from hydroelectric reservoirs. As a result, hydroelectric companies and governing agencies are exploring strategies to lower MeHg contamination. Strategies may involve lowering the source of Hg before flooding, the rate of Hg methylation, or MeHg bioaccumulation and biomagnification. Possible strategies reviewed in this article include selecting a site to minimize impacts, intensive fishing, adding selenium, adding lime to acidic systems, burning before flooding, removing standing trees, adding phosphorus, demethylating MeHg by ultraviolet light, capping and dredging bottom sediment, aerating anoxic bottom sediment and waters, and water level management. A preventative strategy is to limit the flooded area, especially wetland areas. Flooded upland areas that contain less carbon produce MeHg for a shorter time than wetland areas. Run-of-the-river reservoirs contain lower MeHg concentrations than reservoirs that flood vast areas, at the cost of exporting MeHg downstream. Managing water levels to flush systems during times of peak MeHg production may have benefits for the reservoir, but also transports MeHg downstream. Intensive fishing can lower MeHg in food webs by increasing fish growth rate. Additions of selenium can lower MeHg bioaccumulation, but the mechanisms are not well established and excess selenium causes toxicity. Liming can lower fish Hg concentrations in lakes acidified with sulphuric and nitric acid. Burning before flooding can lower the production of MeHg, but MeHg bioaccumulation may increase. The most promising strategy will be one that is agreeable to all affected people.
An equilibrator system connected to an infrared photo acoustic gas analyzer was used in order to measure directly in situ the concentrations of dissolved CO2 and CH4 in waters of a tropical reservoir (Petit Saut, French Guiana). The performance of the system was tested both on a vertical profile in the stratified water body of the reservoir and in the surface waters of the river downstream the dam. Results agreed with conventional GC analysis at +/-15% in a wide range of concentrations (CO2:50-400 micromol l-1 and CH4:0.5-350 micromol l-1 corresponding to gas partial pressures of respectively 1700-13,000 and 12-8800 microatm). The time needed for in situ measurements was equivalent to water sampling, time for GC analysis in the laboratory being suppressed. The continuous monitoring of gas concentrations for 24 h in the reservoir surface waters revealed rapid changes in concentrations highly significant in the daily emission budget. The system opens new perspectives for the monitoring of gas concentrations in highly dynamic systems like tropical reservoirs.
A geochemical survey of the northwestern part of the Thailand Gulf (Inner Gulf) was carried out in order to define concentrations and distribution patterns of selected heavy metals (V, Cr, Co, Ni, Cu, Zn, and U) in the coastal system and estuarine area of the Mae Klong river. The results indicate the presence of two different sources of heavy metals in the studied environment and allowed us to identify a lithogenic component that significantly influences the composition of coastal waters and suspended particulate matter (SPM). Comparison of the normalized heavy metals concentrations both in the studied samples and in those reported for the Sn-W ores present in the surrounding areas suggests an important anthropogenic contribution to the chemistry of the seafloor sediments. Vanadium and nickel enrichment factors (EF) calculated for coastal waters indicate that contamination by hydrocarbons discharge took place in the investigated area.
Mercury (Hg) is a global pollutant and poses a worldwide concern due to its high toxicity. Guizhou province is recognized as a heavily Hg-polluted area in China due to both the special geochemical background and human activities. Here an integrated overview of current knowledge on the behavior of Hg in environments, as well as human health risk with respect to Hg contaminations in Guizhou was presented. Two key anthropogenic Hg emission sources in Guizhou were coal combustion and metals smelting, which dominantly contributed to the high levels of Hg in local ecosystems and high fluxes of Hg deposition. The annual Hg emission from anthropogenic sources ranged between 22.6 and 55.5 t, which was about 6.3-10.3% of current total Hg emissions in China. Meanwhile, Hg Hg-enriched soil in the province serves an important natural Hg emission source to the ambient air. The local environment of Hg mining and zinc smelting areas are seriously contaminated with Hg. It is demonstrated that rice growing in Hg Hg-contaminated soil can accumulate methylmercury (MeHg) to a level to pose health threat to local inhabitants whose staple food is rice. Local inhabitants in Hg mining areas are exposed to Hg through inhalation of Hg vapor and consumption of rice with high level of MeHg. Rice intake is indeed the main MeHg exposure pathway to local inhabitants in Hg mining areas in Guizhou, which is contrary to the general point of view that fish and fish products are the main pathway of MeHg exposure to humans.
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