Major Dams Research Articles

Impact of dam flushing operations on sediment dynamics and quality in the upper Rhône River, France

The Rhône River (France) has been used for energy production for decades and 21 dams have been built. To avoid problems due to sediment storage, dam flushing operations are periodically organized. The impacts of such operations on suspended particulate matter (SPM) dynamics (resuspension and fluxes) and quality (physico-chemical characteristics and contamination), were investigated during a flushing operation performed in June 2012 on 3 major dams from the Upper Rhône River. The concentrations of major hydrophobic organic contaminants (polychlorinated biphenyls, polycyclic aromatic hydrocarbons - PAHs, bis(2-ethylhexyl)phthalate [DEHP] and 4-n-nonylphenol), trace metal elements, particulate organic carbon (POC) and particle size distribution were measured on SPM samples collected during this event as well as on those obtained from 2011 to 2016 at a permanent monitoring station (150 km downstream). This allows to compare the SPM and contaminant concentrations and fluxes during the 2012 dam flushing operations with those during flood events and baseflow regime. At equal water discharge, mean SPM concentrations during flushing were on average 6–8 times higher than during flood events recorded from 2011 to 2016. While of short duration (19 days), the flushing operations led to the resuspension of SPM and contributed to a third of the mean annual SPM flux. The SPM contamination was generally lower during flushing than during baseflow or flood, probably due to the fact that flushing transports SPM only issued from resuspended sediment, with no autochtonous particles nor eroded soil. The only exception are PAHs and DEHP with higher concentrations during flushing, which must be issued from the resuspension of legacy-contaminated sediments stored behind the dams before the implementation of emission regulations. During flushing, the variations of POC and contaminant concentrations are also mostly driven by particle size. Finally, we propose a list of recommendations for the design of an adequate monitoring network to evaluate the impact of dam flushing operations on large river systems.

Discovering Dependencies, Trade‐Offs, and Robustness in Joint Dam Design and Operation: An Ex‐Post Assessment of the Kariba Dam

AbstractGlobally, many countries are actively seeking to maximize the hydropower potential of major river basins, yielding proposals for constructing approximately 3,700 major dams in the near future. At present, economic cost‐benefit analyses are the dominant approach for evaluating candidate dam designs. Yet they typically fail to explore the interdependence of dam design and operation by (i) monetizing and aggregating potentially conflicting and heterogeneous objectives into a single metric and (ii) using predefined operating rules aimed at maximizing specific performance objectives for the dams to be designed. Careful consideration of alternative reservoir operating schemes can help to avoid biases in how optimal dam sizes are identified while also clarifying their capacity to adapt to changing hydroclimatic conditions and human demands. This paper presents an integrated framework to solve coupled dam sizing and operation design problems. The framework combines Multiobjective Robust Decision Making and Evolutionary Multiobjective Direct Policy Search into a novel approach to dam sizing, which internalizes the operation design problem and explicitly considers uncertainty in external drivers. We demonstrate the potential of this integrated dam design framework through an ex‐post design analysis of the Kariba dam in the Zambezi river basin. Our results show that careful exploration of the coupled planning/operation search space yields designs that significantly outperform the existing Kariba system. Moreover, we demonstrate that our framework leads to a significant reduction in capital costs (i.e., smaller reservoir sizes) while simultaneously improving system robustness with respect to changing hydroclimatology and human irrigation demands.

Morphometric diversity of supply-limited and transport-limited river systems in the Himalayan foreland

The Indo-Gangetic basin exhibits highly diverse hydro-geomorphic settings that influence the hydrology, sediment production, and transport rates of the rivers draining this region, and this, in turn, is manifested in morphometric diversity of river systems. The rivers draining the western Gangetic plains (WGP) show incised channels attributable to high stream power and low sediment yield. In contrast, the rivers draining the Eastern Gangetic Plains (EGP) have formed aggradational landforms such as megafans due to low stream power and high sediment yield. For a better process understanding of the causal factors of such spatial inhomogeneities in a river basin, a morphometric characterization of its hinterland is necessary. In this work, a set of morphometric parameters such as stream network, longitudinal profile, and hypsometric curve have been integrated with data on sediment connectivity and stream power index to establish the form-process relationships in two contrasting basins, the upper Ganga basin (UGB) and the upper Kosi basin (UKB). The results of this study suggest that high sediment flux in the UKB is attributed to high rainfall, steep topography, unstable channel longitudinal profiles, and high sediment connectivity. A large part of these sediments gets deposited within the channel belt in the alluvial reaches and is remobilized during high flow events. However, the UGB produces fewer sediments due to low rainfall, mild topography, stable channel longitudinal profile, and low sediment connectivity. Also, the presence of a major dam at Tehri further reduces the functional sediment connectivity in the Upper Ganga Basin.

Associations among Fish Length, Dam Passage History, and Survival to Adulthood in Two At‐Risk Species of Pacific Salmon

AbstractThreatened or endangered salmon and steelhead originating in the Snake River basin must pass through a series of eight major hydroelectric dams during their seaward migration. Understanding the effects of specific dam passage routes on lifetime survival for these stocks is essential for successful management. Juvenile fish may pass these dams via three primary routes: (1) spillways, (2) turbines, or (3) juvenile bypass systems, which divert fish away from turbines and route them downstream. Bypass systems may expose fish to trauma, increased stress, or disease. However, numerous studies have indicated that direct survival through bypass systems is comparable to and often higher than that through spillways. Some researchers have suggested that the route of dam passage affects mortality in the estuary or ocean, but this is complicated by studies finding that fish size affects the route of passage. We tested whether passage through bypass systems was associated with the probability of adult return after accounting for fish length and other covariates for two species of concern. We also investigated the association between fish length and the probability of bypass at dams and how this relationship could lead to spurious conclusions regarding effects of bypass systems on survival if length is ignored. We found that (1) larger fish had lower bypass probabilities at six of seven dams; (2) larger fish had a higher probability of surviving to adulthood; (3) bypass history had little association with adult return after accounting for fish length; and (4) simulations indicated that spurious effects of bypass on survival may arise when no true bypass effect exists, especially in models without length. Our results suggest that after fish leave the hydropower system, bypass passage history has little effect on mortality. Our findings underscore the importance of accounting for fish size in studies of dam passage or survival.

Estimation of irrigation return flow on monthly time resolution using SWAT model under limited data availability

ABSTRACT This study is an assessment of the return flow ratio of an irrigation abstraction using the flow records of a downstream stream-gauging station, with the example of the Kozluk scheme irrigated by diverted water from Garzan Creek flowing through the southeastern region of Turkey. In the planning reports of the major dam projects of the region, an unverified return ratio was assumed in eliminating the influence of this irrigation on the flow measurements of Garzan Creek. The correctness of this assumed return ratio is evaluated by analysing the monthly streamflow measurements of the Besiri station through a Soil and Water Assessment Tool (SWAT) model constructed with the coarse-scale topography, land use and soil data from open source databases. The results show the necessity of irrigation project-based return flow analyses using regional fine-scale datasets, instead of rule-of-thumb assumptions, to determine the effects of irrigation activities on flow regimes more accurately.

The evolution of the transboundary Evros river delta (Northeast Aegean Sea) under human intervention: a seven-decade analysis

ABSTRACT The Evros deltaic plain (North Aegean Sea, Greece) covers an area of 188 km2 and is shared by Greece and Turkey by its current main channel. This paper investigates deltaic plain evolution during the last seven decades (1945–2017), taking into consideration human interventions and their impacts on deltaic processes. Outcomes indicate that the construction of more than 25 major dams in the Evros River catchment resulted in >80% reduction in fluvial suspended load. Moreover, the alignment and relocation of the main distributary channel to the southeast was accompanied by the transformation of >40% of the deltaic plain to agricultural land. The combination of human interventions supports the coastline advance of the active main mouth (current rate of 3.9 *10−3 km2/yr), retreat of the old (abandoned) Evros mouth (current rate 7.7 *10−3 km2/yr), and signs of remarkable vulnerability in the middle mouth area.

Major dams and the challenge of achieving “No Net Loss” of biodiversity in the tropics

AbstractDam construction is booming across tropical regions critical for global biodiversity and ecosystem service provision. The principle of “No Net Loss” (NNL)—under which biodiversity impacts of development projects are quantified and fully mitigated—is being increasingly applied to large infrastructure development worldwide, including dams. We discuss the impacts of major tropical dams and associated implementation of NNL policies and outline three major challenges in achieving NNL: (1) overcoming practicalities implementing NNL in highly connected river systems over large spatio‐temporal scales; (2) the stakes are high if NNL fails because tropical regions are hyper‐diverse, rich in species endemism, and difficult to restore; and (3) inclusion of ecosystem services in NNL design is necessary due to the importance of tropical biodiversity for ecosystem service provision at multiple spatial scales. Overcoming these challenges is crucial when hundreds of dams are planned and under construction across the tropics, many potentially subject to NNL policies.

Changes perceived by traditional fishing communities after a major dam disaster in Brazil

ABSTRACT The paper reports a study of the responses of fishing communities, Regência and Povoação, located at the mouth of the Doce River, to the collapse of the Fundão dam, owned by Samarco Mineração, in 2015. After the disaster, the fishermen’s social and cultural practices have undergone drastic changes. The arrival of tailings in the river has impaired their routines and income. The fishermen and their families indicate a sense of loss of identity and insecurity because of the uncertainty. They do not know if they will be able to resume fishing in these waters. This feeling contrasts with the results of a study conducted before the disaster.

Accounting for tailings dam failures in the valuation of mining projects

The number of major tailings dam failures has doubled over the past 20 years, culminating in the tragic accident at Brumadinho in Brazil where about 300 people lost their lives. In this context, there is a growing demand from mining companies, institutional investors and policymakers alike for updated mining project assessment tools taking account of such risks. As part of this research, this paper develops a real option framework for evaluating mining projects involving tailings dams and their associated risk. Two options are considered beyond standard business-as-usual safety measures: reinforced dam maintenance, and retrofitting a treatment process that reduces the volume of unconsolidated tailings. A closed-form expression was obtained for the expected value of the business-as-usual case; semi-analytic formulas were obtained for the two options for evaluation by dynamic programming with quantization of the price factor. When applied to an iron ore deposit with characteristics similar to the Samarco deposit, the method shows that both options are financially superior to business-as-usual for the mining company, with the dry processing retrofitting option being the most attractive. The sensitivity of the expected values was evaluated over a range of values of the key parameters. This research provides senior decision-makers with tools to evaluate different options regarding tailings dam safety from a financial point of view, and provides financial evidence in favour of safer treatment processes for mining waste.

Human-Induced Alterations to Land Use and Climate and Their Responses for Hydrology and Water Management in the Mekong River Basin

The Mekong River Basin (MRB) is one of the significant river basins in the world. For political and economic reasons, it has remained mostly in its natural condition. However, with population increases and rapid industrial growth in the Mekong region, the river has recently become a hotbed of hydropower development projects. This study evaluated these changing hydrological conditions, primarily driven by climate as well as land use and land cover change between 1992 and 2015 and into the future. A 3% increase in croplands and a 1–2% decrease in grasslands, shrublands, and forests was evident in the basin. Similarly, an increase in temperature of 1–6 °C and in precipitation of 15% was projected for 2015–2099. These natural and climate-induced changes were incorporated into two hydrological models to evaluate impacts on water budget components, particularly streamflow. Wet season flows increased by up to 10%; no significant change in dry season flows under natural conditions was evident. Anomaly in streamflows due to climate change was present in the Chiang Saen and Luang Prabang, and the remaining flow stations showed up to a 5% increase. A coefficient of variation <1 suggested no major difference in flows between the pre- and post-development of hydropower projects. The results suggested an increasing trend in streamflow without the effect of dams, while the inclusion of a few major dams resulted in decreased river streamflow of 6% to 15% possibly due to irrigation diversions and climate change. However, these estimates fall within the range of uncertainties in natural climate variability and hydrological parameter estimations. This study offers insights into the relationship between biophysical and anthropogenic factors and highlights that management of the Mekong River is critical to optimally manage increased wet season flows and decreased dry season flows and handle irrigation diversions to meet the demand for food and energy production.

The Avifauna of the Rio Branco, an Amazonian evolutionary and ecological hotspot in peril

SummaryThe Rio Branco is a river with unique biogeographic and ecological features, threatened by the Brazilian Government’s plan to build a major hydroelectric dam and associated hydroway along its course. The river crosses one of Amazonia’s largest rainfall gradients and a major geomorphological boundary along a savanna/forest ecotone, marked by the Bem Querer rapids. Above the rapids, the upper Rio Branco runs through the Boa Vista sedimentary formation and crosses the crystalline rocks of the Guiana Shield, and its margins are flanked by gallery forests. Downriver, it runs through a low-lying sedimentary basin, with Amazonian floodplain forests along its margins. Here, we present the results of ∼ 15 years of ornithological research on the Branco and its major tributaries, providing baseline data and evaluating potential threats to the riverine avifauna. Our surveys included opportunistic observations and standardized surveys along the entire length of the river in 16 systematically distributed localities. We catalogued 439 bird species, 87% of which are documented by physical evidence (specimens, recordings, photographs). Forty-six percent are restricted to single habitats, suggesting a high degree of habitat specialisation. A third of the species are widely distributed along the river, whereas 45% are restricted to either the upper or the lower Rio Branco, including 40 and 30 Indicator Species, respectively. Twenty-five species are threatened at global or national levels, including two ‘Critically Endangered’, nine ‘Vulnerable’, and 14 ‘Near Threatened’. We present a list of 50 bird species that are candidates for monitoring studies. Threats to the avifauna from dam construction include permanent flooding above the dam, eliminating gallery forests, river islands, and sandy beaches, and the disruption of the flood pulse along the river, affecting river island and floodplain forest specialists, many of which are globally threatened with extinction. If built, the Bem Querer dam will wipe out the ecotone region and affect dramatically the river’s avifauna.

South Devon, UK

Where can you teach the fundamental principles of geology in three short field days? In this feature article, I introduce South Devon as a classic area of geology, useful for introducing basic concepts relevant to school and first‐year degree curricula. That this region remains a catalyst for developing young geologists is especially fitting given that it was here that Henry de la Beche embarked on the first mapping project of what would later become the British Geological Survey. In South Devon, a novice geologist can learn about plate tectonics, the unifying theory of our subject, through a visit to two quarries. At Chipley Quarry, near Newton Abbott, sea‐floor spreading is well illustrated by Devonian pillow‐lavas extruded within the back‐arc margins of the Rheic Ocean. At Burrator Quarry, near Yelverton, the aftermath of continental collision is represented by the north‐verging Variscan fold belt, intruded and thermally metamorphosed by the Dartmoor granite. A trip along the coast to Paignton provides an informative lesson about the distinctive stratigraphic imprint that is created by this plate tectonic cycle. Here, tightly folded Devonian slates are unconformably overlain by near‐horizontal Permian breccia‐conglomerates at Waterside Cove. The ‘abyss of time’ at their junction represents the tens of millions of years involved in the uplift and denudation of Rheic Ocean sediments in the course of the Variscan Orogen. The Devonian and Permian successions of South Devon additionally serve as an excellent training ground for interpreting ancient environments with both marine and terrestrial facies spectacularly represented. Fossils abound in these strata, too, including the stromatoporoid life assemblage at Triangle Point, Torquay, where students have the opportunity to do a virtual scuba‐dive over a Devonian reef. Finally, given current discussions about employability in UK universities, there is even room in an excursion to instill the practical importance of geology: for example, a trip to the scenic Burrator Reservoir on Dartmoor reveals what can go wrong for geotechnical engineers when a major dam is sited on a granite weakened by chemical weathering. In summary, South Devon has it all—a brilliant natural laboratory for training and inspiring the next generation of geologists.

Mobilizing Water Actors and Bodies of Knowledge. The Multi-Scalar Movement against the Río Grande Dam in Málaga, Spain

Just as in other parts of Spain, the Guadalhorce Valley, Málaga, has a long history of policies based on ‘hydraulic utopianism’ (regenerationist and Franco-ist), bent on ‘reorganizing’ political, geographic, and human nature. Residents of the neighboring sub-basin, the Río Grande valley, have seen how these policies, designed to transfer rural water to modern urban centers, have turned the Guadalhorce hydrosocial territory into a ‘hydraulic dystopia’. In this article, we examine how Río Grande valley residents mobilized to maintain control over the development and use of their resources, livelihoods, and knowledge systems, when modernist-urbanist policies planned to take their water from a major dam on the Río Grande. Interviewing actors at different scales we examined how this anti-dam movement organized massively in a creative, multi-actor, and multi-scale network. Our results also show that this unified, successful fight against the ‘common enemy’, the mega-hydraulic construction, has become more complex, as threats crop up not only from the ‘city over there’ but also from ‘internal’ hydro-territorial transformations. These sprout from policies to modernize traditional irrigation systems, supposedly to ‘save water’, but critical voices assume that it is all about passing on the ‘surplus’ to Málaga city, or using that water to expand agribusiness. We conclude that the challenge lies in critically integrating multiple forms of knowledge, stakeholders, and scales to both defend collective water management and creatively construct anti-hegemonic alternatives.

Political Borders, Epistemological Boundaries, and Contested Knowledges: Constructing Dams and Narratives in the Mekong River Basin

The Mekong River Basin of mainland Southeast Asia is confronting a series of intertwined social, political, and biophysical crises. The ongoing construction of major hydroelectric dams on the river’s main channel and tributary systems—particularly in the basin’s lower and more populated reaches—is leading to significant socioecological changes. Multiple scientific studies have suggested that proceeding with the planned dam construction will disrupt the region’s incredibly productive fisheries and threaten the livelihoods of millions of basin residents. These effects will almost certainly be exacerbated by global and regional climate change. Yet increased understanding of the adverse consequences of dams for the Mekong’s hydrological and ecological processes is having minimal impact on decision-making around hydropower development. While local communities, non-governmental organizations (NGOs), and certain scientists draw on this knowledge to oppose or question accelerated dam building, state officials and hydropower developers have turned to the expertise of engineering and technological assessments in order to justify dam construction. Drawing on work in political geography, political ecology, and science and technology studies (STS), we ask two primary questions. First, why does engineering/technological knowledge retain so much legitimacy and authority in the face of mounting scientific knowledge about ecological change? Secondly, how are narratives of progress deployed and co-produced in the contested epistemologies of large dams as development? We conclude with some examples of how contestations over dams seem to be shifting epistemological boundaries in meaningful ways, creating new spaces for knowledge production and transfer. To answer these questions, we focus on three contested dams that are at various stages of construction in the basin: the nearly complete Xayaburi Dam, the under-construction Don Sahong Dam, and the planned Pak Beng Dam. The research advances understandings of the politics of contested knowledges as they become manifest in the conceptualization and governance of large dams in transboundary basins.

Climate‐Induced Changes in the Risk of Hydrological Failure of Major Dams in California

AbstractExisting major reservoirs in California, with average age above 50 years, were built in the previous century with limited data records and flood hazard assessment. Changes in climate and land use are anticipated to alter statistical properties of inflow to these infrastructure systems and potentially increase their hydrological failure probability. Because of large socioeconomic repercussions of infrastructure incidents, revisiting dam failure risks associated with possible shifts in the streamflow regime is fundamental for societal resilience. Here we compute historical and projected flood return periods as a proxy for potential changes in the risk of hydrological failure of dams in a warming climate. Our results show that hydrological failure probability is likely to increase for most dams in California by 2100. Noticeably, the New Don Pedro, Shasta, Lewiston, and Trinity Dams are associated with highest potential changes in flood hazard.

Patch‐scale biodiversity retention in fragmented landscapes: Reconciling the habitat amount hypothesis with the island biogeography theory

AbstractAimTo test whether the species richness of understorey insectivorous birds on forest islands induced by a major hydroelectric dam is best explained by either the island biogeography theory (IBT) or the habitat amount hypothesis (HAH). Given the low dispersal ability of the focal species group and the hostile water matrix, we predict that the species richness will be predominantly driven by an island effect as posited by the IBT, rather than a sample area effect as posited by the HAH.LocationForest islands within the Balbina Hydroelectric Reservoir, central Brazilian Amazonia.TaxonBirds.MethodsWe mist‐netted birds at 33 forest islands (0.63–1,699 ha), totalling 874 individuals of 59 species. The size of the local landscape used to calculate the habitat amount was determined by a multi‐scale analysis in which buffers around mist‐net lines ranged from 50 to 2,000 m. We applied four tests to examine whether the species richness on forest islands is predominantly driven by either an island effect (island size) or a sample area effect (habitat amount).ResultsFrom the four tests applied, one was consistent with an island effect, two were regarded as inappropriate to test the HAH, and one could not be adequately addressed due to island size being highly correlated with habitat amount in the local landscape (200‐m buffer).Main conclusionsSome of the proposed ways of testing the HAH may lead to misleading conclusions. The relative importance of island size in determining the species richness of understorey insectivorous birds on forest islands is higher than that of surrounding habitat amount, thereby providing stronger support for IBT. We propose a conceptual framework, based on the degree of matrix permeability and species dispersal ability, to determine to what extent a patch‐ or landscape‐centric worldview in landscape ecology provides the most appropriate framework to assess the effects of habitat fragmentation on biodiversity.

Assessment of Physico-Chemical Parameters and Their Pollution Implications on the Major Dams in Ekiti State

The study was aimed at assessing the Physico-chemical parameters namely, temperature, electrical conductivity (EC), pH, turbidity, total alkalinity (TA), total hardness (TH), total dissolved solids (TDS), dissolved oxygen (DO2); total solids (TS), total suspended solids (TSS) colour, potassium, Zinc, Copper, total Iron, BOD, COD etc. in three dams in Ekiti State, South-West Nigeria. The seasonal variations in the physicochemical parameters of water of the dams were studied from November, 2017 to October, 2018. Water samples were collected from the dams on monthly basis and analyzed for 26 water physico-chemical parameters by using standard methods. The standards for the drinking water recommended by the Indian Council of Medical Research (ICMR), World Health Organization (WHO), Nigerian Industrial Standard (NIS), National Environmental Standards and Regulations Enforcement Agency (NESREA) and Bureau of Indian standards (BIS) were used in this study. The comparison of the physico-chemical parameters values with the standard values of WHO guidelines and other international standards revealed the high level of BOD, COD, turbidity, DO2, pH, colour, K, Fe, Mn, Cu, Zn, Pb and Cd in the water content. There were significant differences (p > 0.05) between the seasons (dry and wet) values of some of the physicochemical parameters in Egbe dam, Ureje dam and Ero dam. pH, DO2, TSS, EC, TDS and TS had higher values in the rainy season while Temperature, BOD, COD, NO3, Alkalinity, NO2 and PO4 had higher values during the dry season in the dams with few exemptions. The accumulation of these parameters in high values may render the dams’ water unsuitable for drinking. In this study, it was observed that most of the physico-chemical parameters except metals were higher in Ureje dam than Egbe dam and Ero dam. This might be due to population increase, indiscriminate dumping of refuse around the dam, urbanization, domestic effluents and other attendant problems of the State capital where the dam is located and thus indicate that Ureje dam was more contaminated than Egbe and Ero dams in terms of anthropogenic contamination. Conclusively, the water from Egbe, Ureje and Ero dams may support fish production but is not fit for domestic and drinking purpose without adequate treatment.

Determination of Water Quality Index and Suitability of Three Major Dams in Ekiti State, Nigeria

Water Quality of Egbe, Ureje and Ero dams in Ekiti State was studied for a period of one year from November 2017 to October 2018. Twenty-four physicochemical parameters (temperature, conductivity, turbidity, pH, DO2, BOD, COD, alkalinity, turbidity, total dissolved solids, hardness, colour, phosphates, nitrates, nitrite, Cu, Pb, Mg, K, Mn, Fe, Na, Ca and Zn) were considered in the computation of Water Quality Index (WQI) based on Weighted Arithmetic Water Quality Index Method. ANOVA was used to evaluate the significant differences between water quality variables at the dams. T-test was used to show the variations of physico-chemical parame-ters and WQI between the two seasons. WQI in Egbe dam ranges from 118.00 - 164.67 (dry season) with a seasonal value of 145.69 and from 89.39 - 161.86 (rainy season) with a seasonal value of 120.59. In Ureje dam, WQI ranges from 101.88 - 164.76 (dry season) with seasonal value of 134.08 and from 96.61 - 138.36 (rainy season) with a seasonal value of 123.39 while in Ero, WQI ranges from 32.28 - 45.13 (dry season) with a seasonal value of 39.43 and from 52.12 - 106.22 (rainy season) with a seasonal value of 81.84. WQI of Egbe dam and Ureje dam during the dry and rainy seasons indicated poor water quality that is unfit for drinking while in Ero dam, the WQI during the dry season indicated good quality water while during the rainy season, the water in the dam was polluted. Our findings highlighted the deterioration of the dams due to anthropogenic activities and urbanization. There is an urgent need for proper management measures and suitable tools to restore the water quality of these dams. The formulas used to calculate the WQIs are easy to use thus providing a valuable tool for the accurate monitoring of water pollution in water bodies.

PRESENT STATUS OF STURGEON IN THE LOWER SAKARYA RIVER IN TURKEY

The Hydro development started in the 1960s with building 3 major dams in the upstream section of the Sakarya River. During the 1980s the development of the floodplain sections of the river had its onset. Under these altered conditions Huso huso, Acipenser nudiventris , and Acipenser sturio disappeared from the river until the 1980s but Acipenser gueldenstaedtii, as well as Acipenser stellatus, were shown to still reproduce in the remaining section of the river by 2013. The construction of three additional HEPPs begun in the river section below Pamukova, blocking migration and cutting off major spawning sites. While fish passage facilities were included in the construction of the HEPPs since the 1980s, their design and location, as well as the maintenance rendered them completely dysfunctional. A survey was carried out in the remaining free flowing section of the lower river in 2014 to determine fish commun ity composition and water quality at 4 stations below Adasu HEPP. While a few A. gueldenstaedtii juveniles were observed in Sakarya River mouth close to the Black Sea, only one young-of-the- (YOY) ( A. stellatus ; W:25g; TL:28cm) was reported which was captured from the Lower Sakarya River.

Development of an Earthen Dam Break Database

AbstractEarthen embankment dams comprise 85% of all major operational dams in the United States. Assessment of peak flow rates for these earthen dams and the impacts on dam failure are of high interest to engineers and planners. Regression analysis is a frequently used risk assessment approach for earthen dams. In this paper, we present a decision support tool for assessing the applicability of nine regression equations commonly used by practitioners. Using data from 108 case studies, six parameters were observed to be significant factors predicting for peak flow as a metric for risk analysis. We present our work on an expanded earthen dam break database that relates the regression equations and underlying data. A web application, regression selection tool, is also presented to assess the appropriateness of a given model for a given test point. This graphical display allows users to visualize how their data point compares with the data used for the regression equation. These contributions improve estimates and better inform decision makers regarding operational and safety decisions.