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In Quebec, the fluvial dynamics of the Escoumins River have been disturbed by the forestry industry for over a century. Most specifically, a dam was built near the mouth of the river in 1846 and dismantled in 2013. These disturbances had significant repercussions on the equilibrium of the river and Atlantic salmon habitat. This study therefore proposes to characterize the fluvial dynamics of the Escoumins River and to analyze the impacts of the dam dismantling from the perspective of restoring hydrogeomorphological processes and improving Atlantic salmon habitat. The results suggest that the trajectory of the river evolved differently depending on the fluvial style and the grain size composition of each of its homogeneous segments. However, log drive activities in river and dam removal appear to have been the most important controlling factors on the evolution of the stream trajectory. The dismantling notably allowed the restoration of hydrogeomorphological processes and the free movement of salmonids. A better procedure for dam removal and monitoring should be put in place in Canada to encourage this practice. [ABSTRACT FROM AUTHOR]

The study of flow over various steps behind the hydraulic structures, such as weirs, dams, spillways, barrages, and flood gates, is still of particular interest to researchers due to the complexity of flow characteristics and sediment behaviors at near-bed region. This study investigates the effect of various inclined backward-facing step (BFS) angles on near-bed turbulent flow structures and bedload transport rate in surface jet flow regime. A combined numerical technique of large eddy simulation and discrete element method, based on the open sources package OpenFOAM, is employed. The validation of the numerical model shows a good agreement between the simulation results and observed data obtained from different experiments. The simulation results reveal that the flow does not form a separation zone when the BFS angle is less than 20 ° , wherein the near-bed turbulence intensity is insufficient to induce substantial sediment movements. As the step angle is increased to a certain value (20 °), the separation flow is formed. Consequently, the near-bed turbulence intensity is significantly increased due to the splat effect, and the sediment flux is also drastically increased. As the BFS angle further increases to 30 ° and 90 ° , the reattachment length is extended without notable changes in maximum turbulence intensity near the bed. The peaks of the mean bedload transport rate are located further downstream along the extended reattachment length. The quadrant analysis for bedload transport is performed to quantify the interactions between the flow and sediment movement. The results demonstrate that the sweep event plays significant role in moving most sediment to downstream of the reattachment point. On the other hand, right upstream of the reattachment point, the burst becomes the dominant turbulence event to move the majority of the sediment backward in the upstream direction. [ABSTRACT FROM AUTHOR]

Physiographic and hydrologic complexities play major role in determining the habitat suitability for river dolphins. However, dams and other water development structures alter hydrologic regimes that degrade habitat conditions. For the three extant species of obligate freshwater dolphins, namely: Amazon dolphin (Inia geoffrensis), Ganges dolphin (Platanista gangetica), and Indus dolphin (Platanista minor), the threat is high as dams and water‐based infrastructure dotted throughout their distribution range impact dolphin populations by restricting their movement. But there is also evidence of localized increase in dolphin population in certain segments of habitats affected by such hydrologic alterations. Hence, the impacts of hydrologic alterations on dolphin distribution are not as binary as it seems. We aimed to ascertain the role of hydrologic and physiographic complexities in determining the distribution of the dolphins in their geographic ranges using density plot analysis and also to understand how hydrologic alterations in the rivers affect their distribution using a combination of density plot analysis and review of literature. The influence of some of the study variables such as distance to confluence and sinuosity was similar across species—for instance, all three dolphin species preferred slightly sinuous river segments and habitats near confluences. However, varying influences across species were observed for some other variables such as river order and river discharge. We assessed 147 cases of impacts of hydrological alterations on dolphin distribution by categorizing the reported impacts in nine broad types out of which habitat fragmentation accounted for the majority of the impacts (35%) followed by habitat reduction (24%). These endangered species of freshwater megafauna will experience further intensified pressures as more large‐scale hydrologic modifications such as damming and diversion of rivers are underway. In this context, basin‐scale water‐based infrastructural development planning should take into consideration the salient ecological requirements of these species to ensure their long‐term survival. [ABSTRACT FROM AUTHOR]

The article reports that civil engineering projects such as the Cardiff Bay Barrage have obscured the Welsh capital relationship with its nearby expanse of open water. Topics include examines that the secret shoreline of Splott Beach would never find itself displayed on the postcards for sale at the cultural venues of Cardiff Bay.

Water shortage has been a problem in Algeria for a long time. The State’s strategy aims to raise water stocks by adopting several solutions, including the construction of dams. However, even this last solution is faced with meteorological conditions which favour water losses by evaporation, especially in arid areas. This article aims to present the first Algerian trials on preservation of water bodies by reducing evaporation using long-chain organic chemicals that form a thin, “mono-molecular layer” at the air/water interface. The results obtained show significant rates of evaporation reduction that depend on the chemical substance used, the duration between two applications of chemicals, and the meteorological conditions.Editeur Z.W. Kundzewicz; Editeur Associe B. Touaibia [ABSTRACT FROM PUBLISHER]

Seeing Like a State (1998), anthropologist James C. Scott's critique of twentieth-century development and the ideology of "high modernism" that animates it, has shaped the writing of Canadian history, as it has in so many other fields. Environmental historians of Canada, particularly those who study hydroelectric development in the postwar period, have found it especially useful because it links social and environmental change to political power, putting nature at the core of the project of modernization. This article reviews some of that literature to illustrate and critique Scott's key concepts and arguments. Specifically, it takes issue with Scott's contention that high modernist development pitted local knowledge against the expertise of the state's agents. The article also challenges the declensionist narrative offered in the book, which portrays the nature of high modernist change solely in terms of degradation. Finally, it suggests that adopting the very way of seeing that Scott criticizes - an imperial, encompassing, reductive vision - has, and can hold out, the promise for a better kind of development. [ABSTRACT FROM AUTHOR]

We used tree-ring analysis to examine the radial growth response of a common, moderately flood-tolerant species ( Fraxinus pennsylvanica Marsh.) to hydrologic and climatic variability for >40 years before and after hydrologic modifications affecting two forest stands in the Mississippi River Alluvial Valley (USA): a stand without levees below dams and a stand within a ring levee. At the stand without levees below dams, spring flood stages decreased and overall growth increased after dam construction, which we attribute to a reduction in flood stress. At the stand within a ring levee, growth responded to the elimination of overbank flooding by shifting from being positively correlated with river stage to not being correlated with river stage. In general, growth in swales was positively correlated with river stage and Palmer Drought Severity Index (an index of soil moisture) for longer periods than flats. Growth decreased after levee construction, but swales were less impacted than flats likely because of differences in elevation and soils provided higher soil moisture. Results of this study indicate that broadscale hydrologic processes differ in their effects on the flood regime, and the effects on growth of moderately flood-tolerant species such as F. pennsylvanica can be mediated by local-scale factors such as topographic position, which affects soil moisture. [ABSTRACT FROM AUTHOR]

Compensation to indigenous communities forced to relocate as a result of a development project is examined in this study. A survey of 379 families displaced by the construction of the Bakun Dam in Sarawak, Malaysia, reveals a high level of dissatisfaction with the compensation provided. The compensation given by the government to the relocated indigenous communities was lower than they had expected. The average compensation gap (the difference between the expected compensation and the actual compensation received for land) is 20 acres per study household. This has resulted in dissatisfaction among the indigenous communities. Greater participation of indigenous communities in the compensation process is needed to reduce the compensation gap. Indigenous communities' rights and freedom to participate in the compensation process is important and should be an integral part of compensation policy for large development projects. [ABSTRACT FROM AUTHOR]

The expansion of the Totora Khocha dam-based irrigation system in the Pucara watershed is a case of planned re-engineering of a closing watershed. This article shows how, when irrigation systems expand in space and across boundaries to capture new water, they also involve new claims by existing and emergent users. This results in complex processes of design, contestation and negotiated redesign, where irrigation projects are being produced by the negotiated construction of water networks. Therefore, the design process in a closing watershed is better approached as a dynamic and negotiated process of engineering than as a prescriptive mode of network building. [ABSTRACT FROM AUTHOR]

The Barriga Dam (Burgos, Spain) is a unique case study because its trapezoid spillway is located on the dam body and is composed of wedge-shaped concrete blocks (WSB) that include certain relevant improvements. This note summarizes the main features of the studies, the key aspects of the final design of the WSB and their placement on the dam, and important details of the spillway design. The design team concluded the study by showing the suitability of this enhanced technology for application to small dams and ponds in the short term, even with unit flows above 5 m2/s. [ABSTRACT FROM AUTHOR]

Hydrologic metrics have been used widely to quantify flow-ecology relationships; however, there are several challenges associated with their use, including the selection from a large number of available metrics and the limitation that metrics are a synthetic measure of a multi-dimensional flow regime. Using two case studies of fish species density and community composition, we illustrate the use of functional linear models to provide new insights into flow–ecology relationships and predict the expected impact of environmental flow scenarios, without relying on hydrologic metrics. The models identified statistically significant relationships to river flow over the 12 months prior to sampling (r2range 36–67%) and an environmental flow scenario that may enhance native species’ densities while controlling a non-native species. Hydrologic metrics continue to play an important role in ecohydrology and environmental flow management; however, functional linear models provide an approach that overcomes some of the limitations associated with their use.Editor Z.W. Kundzewicz; Guest editor M. AcremanCitation Stewart-Koster, B., Olden, J.D., and Gido, K.B., 2014. Quantifying flow–ecology relationships with functional linear models. Hydrological Sciences Journal, 59 (3–4), 629–644. [ABSTRACT FROM PUBLISHER]

River managers worldwide are increasingly addressing flow needs for ecosystem processes and services in their management plans for dams and reservoirs. However, while planning and scientific assessments have advanced substantially, successful re-operation of infrastructure to achieve environmental benefits has been more limited. The Sustainable Rivers Project (SRP) was formalized in 2002, as a national partnership between the United States Army Corps of Engineers and The Nature Conservancy to define and implement environmental flows through adaptive reservoir management. The project has focused on eight demonstration basins containing 36 Corps dams, but is designed to direct the collective experience from these sites to help guide agency-wide operational changes for as many as 600 dams to benefit up to 80 000 river kilometres and tens of thousands of hectares of related floodplain and estuarine habitat. This article summarizes the progress to date on defining and implementing environmental flows through the SRP, and evaluates the technical, social, legal, and institutional factors that act as dominant enabling conditions and constraints to implementation.Editor Z.W. Kundzewicz; Guest editor M. AcremanCitation Warner, A.T., Bach, L.B., and Hickey, J.T., 2014. Restoring environmental flows through adaptive reservoir management: planning, science, and implementation through the Sustainable Rivers Project. Hydrological Sciences Journal, 59 (3–4), 770–785. [ABSTRACT FROM PUBLISHER]

Predicting specific erosion at the basin scale is essential in order to help prevent or forecast soil loss problems, water-quality degradation and the impairment of riparian ecosystems. In this study, models were defined to predict specific erosion of an ungauged basin according to hydromorphometric parameters, climatic parameters and vegetation cover, at the sites of dams and small dams in a highly eroded basin, the Algérois-Hodna-Soummam. The governing characteristics were carefully selected based on literature survey, examined and grouped into two zones by principal component analysis. Two methods were used: multiple regression and static neural networks. Very satisfactory results were obtained in testing the validity of the neural networks model by cross-validation—the model being composed of: average annual flow, drainage density, average slope of basin, and average annual rainfall in the input layer—with a determination coefficient of 0.81 and a mean square error of 0.19. [ABSTRACT FROM AUTHOR]

Dams alter the geomorphology, water quality, temperature regime, and flow regime of lotic systems influencing the resources and habitat of fish, benthic invertebrates, and lower trophic levels. Since the inception of the river continuum concept and the serial discontinuity concept (SDC), biotic and abiotic impacts below impoundments have been the focus of many lotic studies. However, recovery gradients below dams are rarely examined in sufficient detail and no current synthesis of longitudinal impacts in regulated rivers exists. This understanding is needed to build ecological relationships in regulated rivers to inform environmental flows science and management. In this review, we provide evidence for SDC predictions on physical, chemical, and biological recovery in regulated rivers. Additionally, we determine how these changes are reflected in the benthic community. Our review suggests that two recovery gradients exist in regulated rivers: (1) a longer, thermal gradient taking up to hundreds of kilometres downstream; and (2) a shorter, resource subsidy gradient recovering within 1-4 km downstream of an impoundment. Total benthic invertebrate abundance varies considerably, with both increases and reductions observed at near-dam sites and varying in recovery downstream. Much of this variability stems from the degree of flow alteration and resource subsidies from the upstream reservoir. In contrast, benthic diversity is often reduced below dams irrespective of dam location and operation with little recovery observed downstream. The community at near-dam sites is largely composed of filter-feeding invertebrates which are quickly replaced downstream, while stoneflies are reduced below impoundments with limited downstream recovery. Despite a lack of formal testing, studies support SDC predictions. The SDC still provides a useful theoretical framework for hypothesis testing, and future studies should further expand the SDC to include empirical estimation within the context of the landscape. [ABSTRACT FROM AUTHOR]

A curious phenomenon of significant summertime downslope movements, observed at other sites where trees grow on the lower slope of clay fill embankments, has been recorded during 10 years of downstream slope monitoring at Aldenham embankment dam, UK. The data from four monitored sections of the slope are described. At two locations, downslope movements were observed in high soil moisture deficit (SMD) conditions, where it appeared that high SMD and shrinkage caused by trees growing on the lower slope allowed the grassed upper slope with lower SMD to slip downwards under its own weight. This led to a seasonal, ratcheting accumulation of crest settlement - a type of mechanism that presents a continual serviceability problem to infrastructure embankments as well as dams. This mechanism was simulated in a qualitative way by finite difference analysis. At a third monitored section, a sparser distribution of lower water-demand trees, lower plasticity clay fill, and a moisture content close to or below the plastic limit appeared to result in insignificant slope movements. At a fourth low-height monitored section, a slow accumulation of downslope movements, as well as tension cracking, was observed. [ABSTRACT FROM AUTHOR]

The hydrological regime of a river is defined by variables or representative curves that in turn have characteristics related to fluctuations in flow rates resulting from climate variability. Distinguishing between the causes of streamflow variations, i.e. those resulting from human intervention in the watershed and those due to climate variability, is not trivial. To discriminate the alterations resulting from climate variation from those due to regulation by dams, a reference hydrological regime was established using the classification of events based on mean annual streamflow anomalies and inferred climatic conditions. The applicability of this approach was demonstrated by analysis of the streamflow duration curves. An assessment of the hydrological regime in the lower reaches of the São Francisco River, Brazil, after the implementation of hydropower plants showed that the operation of the dams has been responsible for 59% of the hydrological changes, while the climate (in driest conditions) has contributed to 41% of the total changes. Editor Z.W. Kundzewicz Citation Genz, F. and Luz, L.D., 2012. Distinguishing the effects of climate on discharge in a tropical river highly impacted by large dams. Hydrological Sciences Journal, 57 (5), 1020–1034. [ABSTRACT FROM AUTHOR]

This paper presents a reach-scale sediment balance of a large impounded Mediterranean river (the lower Ebro, 1998–2008). Multi-temporal sediment storage and the influence of floods and tributaries on the sediment load were examined using continuous discharge and turbidity records. The mean annual suspended sediment load at the reach outlet (Xerta) is 0.12 × 106 t, corroborating previous results. Suspended sediment concentrations were low (SSCmean = 13 mg L-1), attaining a maximum of 274 mg L-1. Erosion processes (channel-scour, bank erosion) are dominant, and net export of sediment occurs over the long term. Unexpectedly, ephemeral tributaries were found to contribute significantly: sediment delivered during torrential events attained 5% of the Ebro annual load, and was even larger than that in flushing flows. Overall, most of the suspended sediment load is transported by floods (up to 65% in some years). The results constitute basic information to underpin current management actions aiming to achieve the sustainability of the riverine and deltaic system. Editor D. Koutsoyiannis; Associate editor D. Hughes Citation Tena, A., Batalla, R.J. and Vericat, D., 2012. Reach-scale suspended sediment balance downstream from dams in a large Mediterranean river. Hydrological Sciences Journal, 57 (5), 831–849. [ABSTRACT FROM AUTHOR]

Abstract: Data on temperature, major constituents and some trace elements, measured in the dissolved and particulate phases, were used to identify the hydrodynamics of a reservoir (the Bicaz reservoir, Romania). Results revealed that the reservoir experiences two thermal stratifications per year (summer and winter). However, the summer stratification is delayed by the high river inflow of June–July. Two layers were identified, a surface and a deep layer, whose location and impact vary with time. The surface layer originates from the river inflow (intrusion layer) and the deep current is produced by the outflow (velocity current). According to season, the river inflow either supplies the deep current or remains recordable up to the dam. Consequently, the structure of the water column, and thus the biogeochemical processes within it, are governed both by thermal stratification and by these layers. [Copyright &y& Elsevier]

The main cause of rockfill and embankment dam failures is overtopping due to insufficient outlet works. During the last 15 years, the Civil Engineering Department: Hydraulics and Energy of the Technical University of Madrid has been studying the overtopping failure process of rockfill dams. One of the aims of this research is to develop design criteria of cost-effective rockfill dam protections to avoid failure due to such overtopping. Among the different types of known protection, this analysis has focused on downstream rockfill toes. The objective of this study is to achieve stability of the downstream shell of rockfill dams to prevent mass slides. This article summarizes the results of the preliminary experimental and numerical tests developed during the year 2008. Preliminary conclusions show the feasibility of this protection to mitigate partially or totally the serious consequences of overtopping in rockfill dams. [ABSTRACT FROM AUTHOR]

This paper explores the spurt of dam-building in British Columbia from the 1960s to the 1980s, offering a different interpretation of high modernism and the changes it caused. It does so by focusing on the agents of high modernity: the engineers, geologists, and construction workers who designed, built, and drove the machinery of progress. By taking the synoptic seriously, we make three related arguments. First, dam-building was characterized by an intense engagement with place that generated a particular kind of knowledge, something we call 'high modernist local knowledge.' Second, the environmental and social changes that ensued from dam-building were a result of the presence, not the absence, of this local knowledge. Moreover, and finally, those changes were more than destructive. Big dams did not just destroy locales, they displaced and globalized them, and in so doing created new ones. [ABSTRACT FROM AUTHOR]

Ganga, the national river of India, is now sadly depleted in flow and utterly polluted due to construction of dams and barrages, discharge of untreated municipal and industrial wastes, floral offerings, cremation of dead bodies on its bank. Kanpur to Trighat is identified as the most polluted section of the river. This critical state of the river has been revealed in the paper based on an analysis of the published accounts and research results by various institutes and individuals. It also sheds light on the strategies and action plans to rejuvenate the Ganga to its pristine quality. [ABSTRACT FROM AUTHOR]

This paper reports on a set of laboratory experiments involving a layout that is common in irrigation diversion works. The layout involves a lateral intake channel with a diversion dam, positioned to allow the flow to be controlled and managed. Based on experimental measurements and observations, the effect of diversion angle (ranging from 90 to 120°) on the structure of the approaching flow to the lateral intake and amount of sediment entering the intake was investigated. Velocity fields both upstream of the intake in the main channel and in front of the intake in the sluiceway were measured under various discharge combinations of the river, intake and sluice gate. Analysis of sediment measurements showed that the intake with a diversion angle of 110° had the least amount of sediment entering the intake. Analysis of the streamlines in the main channel showed that the width of the bottom-diverted current in the main channel decreased as the diversion angle increased. Furthermore, analysis of the data showed that the product of the width of the diverted current and the mean shear stress decreased when the diversion angle increased from 90 to 110° before increasing again at 120°. [ABSTRACT FROM AUTHOR]

Abstract: This research investigated seepage under hydraulic structures considering flow through the banks of the canal. A computer model, utilizing the finite element method, was used. Different configurations of sheetpile driven under the floor of the structure were studied. Results showed that the transverse extension of sheetpile, driven at the middle of the floor, into the banks of the canal had very little effect on seepage losses, uplift force, and on the exit gradient at the downstream end of the floor. Likewise, confining the downstream floor with sheetpile from three sides was not found effective. When the downstream floor was confined with sheetpile from all sides, this has significantly reduced the exit gradient. Furthermore, all the different configurations of the sheetpile had insignificant effect on seepage losses. The most effective configuration of the sheetpile was the case when two rows of sheetpiles were driven at the middle and at the downstream end of the floor, with the latter sheetpile extended few meters into the banks of the canal. This case has significantly reduced the exit gradient and caused only slight increase in the uplift force when compared to other sheetpile configurations. The present study suggests that two-dimensional analysis of seepage problems underestimates the exit gradient and uplift force on hydraulic structures. [Copyright &y& Elsevier]

Several aspects of water resources and their links with food and energy supply, as well as with natural hazards, have been obscured due to political aims and ideological influences. At the same time, the involvement of politics and ideology testifies to the high importance of water-related issues internationally, and reflects the intensifying unresolved problems related to water, food and energy adequacy, as well as protection from floods and droughts. In an attempt to separate, as much as possible, the essence of problems from the political and ideological influences, several facts and fallacies about water and interrelated issues are discussed, based on data (numbers) rather than on dominant ideological views. The domain of the discussion is generally the entire globe, but, as a particular case, Greece, whose water resources are only partly developed, is discussed in more detail. From a pragmatic point of view, the water infrastructure in developed countries appears to be irreplaceable, although its management is adaptable toward more environmentally-friendly operation. For developing countries, no alternative to large-scale water resources development by engineering means appears plausible. The recent pursuit of renewable energy makes imperative the utilization of the existing and, where possible, the building of new, large hydropower plants, as only these can provide efficient energy storage, which is necessary for the renewable energy provided by nature in highly varying patterns. Citation Koutsoyiannis, D. (2011) Scale of water resources development and sustainability: small is beautiful, large is great. Hydrol. Sci. J. 56(4), 553-575. [ABSTRACT FROM AUTHOR]

During recent years, risk analysis has been introduced into infrastructure engineering, and has greatly improved the design, construction, and operation. In this paper, we study the risk of dams in the perspective of clustering analysis. Fuzzy c-means clustering (FCM) is widely used in many fields since it is simple and fast. However the result of FCM technique is sensitive to the initialization of clustering centres and is easily trapped into local optima. To improve the performance of FCM, an artificial bee colony algorithm (ABC) with FCM is proposed. By introducing ABC, the shortcomings of the original FCM method is overcome. The proposed clustering algorithm is demonstrated on a benchmark classification problem and two dam risk analysis problems. Results show that it is more accurate and robust than FCM, and it is an efficient tool for risk analysis of dams. [ABSTRACT FROM AUTHOR]

This paper describes a series of laboratory tests performed to characterize the mechanical and hydraulic properties of plastic concrete (PL-C). PL-C is used in the construction of seepage cut-off walls in dams and it comprises cement, aggregate, and water mixed with sodium bentonite. The addition of sodium bentonite causes a reduction in strength and improved ductility after failure compared with normal concrete. The mechanical properties of PL-C are studied using a series of unconfined compression tests and confined compression tests performed while simultaneously permeating water through PL-C specimens. Stress relaxation and controlled rate of loading tests are also performed to investigate the rate-sensitivity and time-dependency of plastic concrete. The test results show that the hydraulic conductivity of PL-C increases between two and three orders of magnitude during triaxial compression due to yielding, crack formation, and dilation of the cracks. Such changes in the behaviour of PL-C should be minimized during design by controlling the working strains and using erosion-resistant mixes. In addition to these findings, PL-C exhibits significant time-dependent behaviour similar to that observed for clays, and the variation of compressive strength versus confining stress is comparable to normal strength concrete. Cet article décrit une série d’essais en laboratoire effectués dans le but de caractériser les propriétés mécaniques et hydrauliques du béton plastique (BP). Le BP est utilisé dans la construction de systèmes de coupure dans les barrages. Il est constitué du ciment, de l’agrégat et de l’eau mélangé avec de la bentonite de sodium. L’ajout de bentonite de sodium entraîne une réduction de la résistance et une amélioration de la ductilité suite à la rupture, comparativement au béton standard. Les propriétés mécaniques du BP sont étudiées à l’aide d’essais en compression non confinés et confinés effectués en même temps que l’eau pénètre à travers les échantillons de BP. Des essais de relaxation des contraintes et de chargement à taux contrôlé ont aussi été effectués pour investiguer la sensibilité au taux et la dépendance au temps des BP. Les résultats des essais montrent que la conductivité hydraulique du béton plastique augmente de deux à trois ordres de grandeur durant la compression triaxiale en raison de l’écoulement, de la formation de fissures et de la dilatation dans les fissures. Ces changements dans le comportement du BP devraient être minimisés durant la conception par un contrôle des déformations et par l’utilisation de mélanges résistants à l’érosion. De plus, le béton plastique démontre un comportement dépendant du temps de façon significative, comme ce qui est observé pour les argiles, et la variation de la contrainte compressive versus la contrainte de confinement est comparable à la résistance normale d’un béton. [ABSTRACT FROM AUTHOR]

1. Hydropower is often presented as a clean and renewable energy source that is environmentally preferable to fossil fuels or nuclear power. Hydropower production, however, fundamentally transforms rivers and their ecosystems by fragmenting channels and altering river flows. These changes reduce flow velocity and the number of rapids, and reduce or alter wetland, floodplain and delta ecosystems. Dams disrupt dispersal of riverine organisms and sediment dynamics and may alter riverine biodiversity composition and abundance. Freshwater ecosystems now belong among the world’s most threatened ecosystems. 2. Water managers are beginning to recognise the need to combine demands for social and economic development with the protection of the resource base on which socio-economic benefits rely. Environmental flows can help to balance ecosystem and human needs for water, both when constructing new dams and in re-licensing existing dams. 3. We briefly review the impacts of hydropower generation on freshwater ecosystems by discussing different types of dams and development, and by providing examples from Sweden of how environmental effects of hydropower production could be mitigated. Special emphasis is given to flow regulation through re-operation of dams. 4. Regulated rivers in Sweden were developed with little consideration of ecological effects, with most dams lacking migration pathways or minimum flow releases. There is thus a substantial potential for improvement of ecological conditions, such as naturalisation of flow regimes and reestablishment of connectivity, in regulated river reaches but technical hurdles imply major challenges for rehabilitation and mitigation. Most regulated rivers consist of cascades of consecutive reservoirs and impoundments, further constraining possible actions to improve ecological conditions. 5. Most environmental mitigation measures require flow modifications to serve ecosystems, implying reduced power production. An important challenge for river management is to identify situations where measures involving relatively small production losses can have major ecological advantages. 6. Climate change during the 21st century is expected to increase runoff in northern and central Sweden and make the annual hydrograph more similar to variation in electricity demand, i.e. a lower spring flood and increased run-off during winter months. This could provide opportunities for operating dams and power stations to the benefit of riverine ecosystems. On the other hand, demands to produce hydropower are likely to increase as fossil fuels are phased out, leading to increased pressures on free-flowing rivers and aquatic ecosystems. [ABSTRACT FROM AUTHOR]

The article describes the potential of tidal barrage solutions for renewable energy generation in Great Britain. The installations on eight major estuaries has been demonstrated, in which they should be capable of meeting at least 10% of present electricity demand, and employing fully proven technology. Under favourable British Treasury discount rates, the demand must be achievable at unit electricity prices that are likely to be competitive against future costs of alternative sources.

The article describes a simplified approach to the design of impounded estuarine tidal power schemes based on the mean tidal amplitude and the surface area of the enclosed basin. The approach allows designs to be readily scaled down to the much smaller-scale schemes presently under consideration. Agreement is found in both theoretical designs and engineering schemes constructed at La Rance and proposed in the Bay of Fundy and Bristol Channel.

The labyrinth spillway is characterised by a broken axis in plan, generally triangular or trapezoidal, repeated periodically. Therefore, a labyrinth spillway will have longer crest length than a straight spillway and, for the same head the discharge per unit width, is substantially increased. The discharge over a labyrinth spillway is a function of the total head, the effective crest length and the discharge coefficient. The discharge coefficient depends on the total head, height of spillway, shape of crest and apex configuration of spillway. In this paper, results of experiments on a triangular labyrinth spillway are reported. The stage-discharge relationship for a triangular labyrinth spillway with different crest shapes is obtained. The discharge coefficient was related to the ratio of length of spillway to width of spillway, ratio of total head to spillway height and crest shape. [ABSTRACT FROM AUTHOR]

Filter design criteria predicated on no-erosion filter (NEF) test results are widely adopted for filter substantiation in earth dams. Hitherto, repetitions of NEF tests on various base-soil-filter combinations have suggested some anomalies between test results and accepted filter criteria. This treatment analyses a large database of NEF tests available in the literature, and carefully assesses the influences of different base-soil properties, including d85, fines content, clay content, plasticity index and sand content on the experimentally defined boundary filter (i.e. D15b). The parametric study presented, alongside the available criteria, may improve the design of optimum—that is, safe and economical—filters. [ABSTRACT FROM AUTHOR]

This paper examines the similarities and contrasts between environmental and water quality changes caused by the 1966 tidal power barrage at La Rance in North Brittany, France and those expected to result from construction of a tidal power barrage in the Severn estuary in the UK. Over the 40-year period since the opening of La Rance, a great deal of knowledge has been accumulated concerning the operation of such schemes and the way water quality and ecosystems have altered. Knowledge gained from experiences at Rance is consequently of great benefit in predicting the effects of the proposed Severn barrage. The nature of the changes anticipated in the Severn estuary is thus unambiguous, but whether this would make the estuary better or worse is a matter of perception. As at Rance, it would be different. [ABSTRACT FROM AUTHOR]

We used ultrasound imaging and passive integrated transponder (PIT)-tagging programs to assess maturation status and iteroparity patterns in summer-run steelhead (anadromous rainbow trout, Oncorhynchus mykiss) of the interior Columbia River Basin (Pacific Northwest, USA). Postspawn kelts examined in downstream fish bypass systems at Columbia River and Snake River dams were disproportionately female (>80%) and majorities were of wild origin, unlike prespawn steelhead at these sites. Annual repeat migration estimates varied from 2.9% to 9.0% for kelts tagged at lower Columbia River dams (n = 2542) and from 0.5% to 1.2% for Snake River kelts (n = 3762). Among-site differences reflected greater outmigration distance and additional dam passage hazards for Snake River kelts. There was also strong evidence for condition-dependent mortality, with returns an order of magnitude higher for good- versus poor-condition kelts. Disproportionately more females and wild fish also returned, providing potentially valuable genetic and demographic benefits for the Columbia River’s threatened steelhead populations. Results overall provide baseline data for evaluating kelt mortality mitigation efforts and basic life history information for steelhead conservation planning. [ABSTRACT FROM AUTHOR]

Small water storage dams are nowadays regarded as the ideal solution for the water-thirsty islands of the Greek Archipelago. Several of these dams have been already constructed and more are planned for the near future. However, dams can also create problems to coastal areas, particularly to the beaches found at the lower reaches of the dammed rivers. The present contribution reports the results of a study undertaken on the effects of such a dam located at Eressos, Lesbos (E. Mediterranean), using both morphological and sedimentological information and a GIS-based sediment erosion model. The results showed that Eressos Beach is currently under erosion, which however is spatially variable. The spatial variability of the beach erosion can only partly be explained by the patterns of longshore sediment transport, suggesting also a negative sedimentary balance. The results of the sediment erosion model showed that the dam retains more than half of the sediment produced in the basin, irrespective of the scenario used. Thus, it is likely that the effects of the dam on the downstream beach are already apparent. [ABSTRACT FROM AUTHOR]

Abstract: An AMF infectivity study and spore viability assessment was performed on substrata obtained from gold and uranium mine tailings dumps (‘slimes dams’) in the North West and Free State provinces of South Africa. Three slimes dams in each region were categorized as recently vegetated (RV), old vegetated (OV) and never vegetated (NV), and dams then divided into five zones based on elevation above ground level, steepness and broad chemical differences. Rhizosphere samples were collected from two of three plant species common to all sites; Eragrostis curvula, Atriplex semibaccata and Cynodon dactylon, as well as from bare areas, in order to allow comparisons across all site categories because of the rarity of the grasses on the lower slope of NV dams. Infectivity was determined by the mean infection percentage method from a bioassay of the substrata using Eragrostis curvula cv Ermelo as a host plant. There was no difference in total infectivity between North West and Free State substrata, but within regions, there were differences in infectivity between rehabilitation ages, between zones, and between rhizosphere and bare areas. Toepaddock substrata and veld soil produced the highest total infection levels overall. On both dams and veld, total arbuscular levels differed between rhizosphere and bare substrata, and the percentage of arbuscules (max. 15.4%) and vesicles (max. 22.0%) as a proportion of total infection structures was low. A low correlation between infectivity and total spore numbers was also found. Spore numbers and the numbers of viable spores increased with zone down the slimes dams to the veld, and also differed within zones between rhizosphere and bare substrata with marked interactive effects. Substratum organic matter (SOM) levels differed between regions, and between zones within the North West region increasing with distance down the slopes to the veld, and were strongly correlated with total spore numbers. Substratum pH values and most AMF parameters were positively correlated in the order of RV>OV>NV dams, indicating that natural colonization of acidic NV sites by AMF is at very low rates, and that AMF colonizing RV slopes are not surviving the transition from RV to OV, with the associated increase in acidity, conductivity and decline in plant cover. Substratum conductivity differed between zones in both regions, with minor interaction between region and zone, and was negatively correlated with pH, AMF infectivity and total spore numbers. Our findings demonstrate that the ameliorant effects of liming and irrigation on substratum pH and conductivity are short-lived, but despite the physico-chemical constraints, a significant measurable AMF inoculum potential does exist on all substrata. Amelioration of tailings with organic matter and use of acid and salt-tolerant AMF would be expected to contribute to more persistent AMF communities and vegetation on gold and uranium slimes dams. [Copyright &y& Elsevier]

In the 1980s, USAID (US Agency for International Development) funded an environmental assessment of dams on the Gambia River, which determined that construction of the Balingho anti-salinity barrage would result in adverse unmitigative environmental and social consequences. Attempts by host country politicians, USAID and UNDP (United Nations Development Programme) to discredit this process made it necessary to take the matter to the Natural Resource Defense Council. A case study of the events surrounding these dams and their potential construction illustrates the 'big dam' paradigm and its potential harm to people, their livelihoods and the environment in Sub-Saharan Africa. [ABSTRACT FROM AUTHOR]

Abstract: The impairments in the maternal behavior of ovariectomized sensitized females, relative to lactating dams, resemble those deficits found in lactating females after treatment with the D1/D2 DA receptor antagonist haloperidol, which interferes with maternal motivation. Therefore, it could be speculated that these behavioral deficits found in sensitized females and haloperidol-treated dams are due to a reduced motivation to interact with pups. In support of this hypothesis, we have found that both sensitized and haloperidol-treated lactating females exhibited remarkably similar impairments in the expression of all active maternal behaviors relative to lactating dams. Furthermore, these deficits were overridden when they were allowed to interact with 12h-isolated pups (demanding pups). Interestingly, lactating dams also improved their maternal behavior in the presence of demanding pups, and clearly chose demanding more than non-demanding pups in a preference paradigm. These data support the idea that the behavioral deficits of sensitized and haloperidol-treated lactating females are due to a reduced behavioral activation in response to the incentive cues from pups compared to lactating dams, and not because of a motor inability to express maternal behavior. These findings ultimately suggest that pups modulate the activity of DA system involved in the regulation of maternal behavior. [Copyright &y& Elsevier]

Abstract: Commercially farmed, hybrid striped bass – female white bass (Morone chrysops) crossed with male striped bass (Morone saxatilis) – represent a rapidly growing industry in the United States. Expanded production of hybrid striped bass, however, is limited because of uncontrolled variation in performance of fish derived from undomesticated broodstock. A 10×10 factorial mating design was employed to examine genetic effects and heritability of growth-related traits based on dam half-sib and sire half-sib families. A total of 881 offspring were raised in a common environment and body weight and length were recorded at three different times post-fertilization; parentage of each fish was inferred from genotypes at 10 nuclear-encoded microsatellites. Dam and sire effects on juvenile growth (weight and length) and growth rate were significant, whereas dam by sire interaction effect was not. The dam and sire components of variance for weight and length (at age) and growth rate were estimated using a Restricted Maximum Likelihood algorithm. Estimates of broad-sense heritability of weight, using a family-mean basis, ranged from 0.67±0.17 to 0.85±0.07 for dams; estimates for sires ranged from 0.43±0.20 to 0.77±0.10. Estimates of broad-sense heritability of growth rate (based on weight), using a family-mean basis, ranged from 0.69±0.12 to 0.82±0.09 for dams and from 0.69±0.13 to 0.81±0.08 for sires. Similar results were obtained with length data. Both genetic and phenotypic correlations between weight and length were close to unity. High genetic (0.98–0.99) and phenotypic (0.79) correlations between growth rates measured at two time intervals suggested that selection for growth rate at an early life stage could affect growth rate at a later life stage. Estimates of general combining ability (GCA) for growth rates differed significantly among dams and among sires, whereas estimates of specific combining ability (SCA) for each dam×sire combination did not differ significantly from zero. These results suggest that additive-effect genes contributed to the differences in juvenile growth. [Copyright &y& Elsevier]

Post-earthquake inspection is required by many dam safety regulations. Typically, based on the magnitude of the earthquake, the guidelines define an area within which dams should be inspected. The areas are established on ground-motion relations derived for the western United States. In eastern North America (ENA), the attenuation is slower with distance from the earthquake epicentre, and as a consequence the inspection area should be significantly larger than that recommended by the current guidelines. We review the state of knowledge on earthquake damage to dams, the factors used to define post-earthquake inspections, and the earthquake characteristics used to define the guidelines. We recommend new radii of inspections for dams applicable in ENA, including the Province of Quebec. Derived from historical earthquake information, the proposed new radii of inspections are twofold to sixfold larger than the 1988 guidelines of the International Commission on Large Dams. It is also suggested that a half-magnitude unit be added to every magnitude “rapidly” released by seismological organizations to include the intrinsic uncertainty in magnitude values and types. Our proposed approach is only one avenue that dam owners can follow to comply with dam safety regulations. Irrespective of the avenue chosen, however, this paper emphasizes the need for dam owners to consider the lower ground motion attenuation in ENA. [ABSTRACT FROM AUTHOR]

The Tapi is a major interstate, westerly flowing river with 14 tributaries, of which the left bank tributaries support large settlements in Maharashtra State. It has been identified as one of the water scarce basins of India. There are many dams and barrages in the basin to store and divert water for agricultural and industrial purposes. This results in low flow and deterioration of water quality in the region particularly in non‐monsoon months. This paper presents the details of a GIS‐based rainfall‐runoff modelling study carried out to assess the runoff flow in the sub‐catchments and at the outlet of the Tapi Basin. Using mean monthly rainfall data at seven gauging stations in the basin, and land use and soil characteristics as reported by the Central Pollution Control Board (CPCB), the annual runoff flow at the watershed outlet was estimated to be 18,814 MCM. A comparison of runoff generated in the sub‐catchments and the observed runoff at Central Water Commission (CWC) monitoring stations is presented. Results of the simulation indicate that the reduced river flows caused by the number of dams/reservoirs constructed upstream are useful as a guideline for the development of environmental flow regulations for rivers and streams in the Tapi Basin. [ABSTRACT FROM AUTHOR]

Quantitative investigations, including two aquifer tests and development of a three-dimensional (3D) groundwater flow model, were required to determine the hydraulic connection between an irrigation reservoir and a buried valley aquifer in southern Alberta. Evidence of seepage was detected in the buried valley aquifer 10 km east of the Pine Coulee reservoir at the onset of filling in 1999, when the reservoir level exceeded an elevation of 1035 m above sea level (a.s.l.). Concern for an increase in the local water table and the creation of artesian conditions in the aquifer prompted this study to determine the approximate location of a seepage window that appeared to be connecting the reservoir and aquifer. Observations of hydraulic head in the aquifer during the pumping tests revealed a barrier boundary when the reservoir level was at an elevation of 1035 m a.s.l. and a recharge boundary condition when the elevation exceeded 1039 m a.s.l. These data were used to calibrate a 3D groundwater flow model, which was needed to determine the hydraulic properties and approximate location of the leakage zone. The quantitative investigation showed that seepage likely occurred through the sideslopes of the flooded coulee, rather than through the low-permeability coulee floor sediments or the embankment dam. Further simulations illustrated the expected seepage rates at various reservoir supply levels and the pumping rates required for relief wells installed in the buried valley aquifer to maintain historic aquifer hydraulic head. A brief postanalysis indicated that the forecasted pumping rates were only 15% lower than have been required to maintain preconstruction water levels in the buried valley aquifer. [ABSTRACT FROM AUTHOR]

We assessed the effects of lowhead dams on the EPT group (ephemeropterans, plecopterans, and trichopterans) by sampling habitat and macroinvertebiates monthly from November 2000 to October 2001 at eight gravel bars centered around two lowhead dams on the Neosho River, Lyon County, Kansas. Sites included a reference and treatment site upstream and downstream from each dam. Percent EFF was greater at reference sites than upstream treatment sites, and was positively correlated with stream velocity and %gravel in the substrate, but negatively correlated with substrate compaction and %boulder in the substrate. These results are similar to those for large dams and suggest that differences in habitat around these lowhead dams are unfavorable for EPT taxa, a finding important to the conservation and restoration of biotic integrity in riverine ecosystems. [ABSTRACT FROM AUTHOR]

The analysis of stress–strain behaviour and the effects of submergence on quarried rock shells, used mainly in dams but also in road construction, is of major importance from both economic and safety points of view. The research work presented here starts with an in-depth review of the nonlinear elastic procedure widely used in rockfill analyses since 1970, its later application to simulate wetting effects, and the latest published modifications to the so-called hyperbolic stress–strain model. An update of the existing wetting simulation procedure has been formulated, calculation routines to analyze constructional behaviour and wetting effects on rockfills have been implemented, and the methodology developed has been applied to a structure 100 m high. Calculation routines have been written to run in FLAC, a finite difference based code that incorporates a programming language. The analyzed structure is part of a road rockfill located at the Contreras Reservoir in Spain and consists specifically of two shell-shaped cross sections subjected to the influence of submergence. The results are expected to be useful in estimating collapse settlements in the upstream shells of earth-core dams. [ABSTRACT FROM AUTHOR]

The seepage rate through homogeneous or zoned dikes includes saturated and unsaturated flow. The latter is often neglected but should be considered to obtain the positions of the water table and the seepage face that may develop either on the downstream slope of a homogeneous dike or within the filter layer behind the core of a zoned dike. Different dikes with heights of 5, 10, 20, and 50 m have been analyzed numerically with a two-dimensional finite element code. The cases investigated include the most frequent types of small dikes designed to retain municipal or industrial wastewater. Solutions are proposed to solve numerically two difficulties related to the representation of saturated and unsaturated physical flow conditions. One difficulty is treating a downstream seepage face. The other is treating the passage of water from the core into a draining layer. The paper presents simple expressions to predict the total (saturated and unsaturated) seepage flow rate through a dike and discusses precautions to be taken.Key words: dams, dikes, seepage, saturated soil, unsaturated soil, numerical modeling.Le débit de fuite des digues homogènes ou zonées inclut les écoulements saturés et non saturés. Ces derniers sont souvent négligés mais devraient être considérés pour avoir les positions de la nappe et de la surface de suintement qui peut se développer sur la pente aval d'une digue homogène ou dans le filtre à l'arrière du noyau d'une digue zonée. Différentes digues de hauteurs 5, 10, 20 et 50 m ont été analysées numériquement avec un code bidimensionnel d'éléments finis. Les cas étudiés comprennent les types les plus fréquents de petites digues conçues pour retenir des eaux usées municipales ou industrielles. On propose des solutions pour résoudre numériquement deux difficultés reliées à la représentation des conditions physiques d'écoulement saturé et non saturé. Une difficulté est le traitement d'une surface de suintement. L'autre est le traitement du passage de l'eau du noyau dans une couche drainante. L'article propose des expressions simples pour prédire le débit de fuite total (saturé et non saturé) à travers une digue et discute des précautions à prendre.Mots clés : barrages, digues, écoulement, sol saturé, sol non saturé, modèle numérique. [ABSTRACT FROM AUTHOR]

Salinity refers to the amount of salt in rivers, where the salt can be in many different forms. There are two main methods of defining the concentration of salt in water such as the total dissolved solid measurement (TDS) and the electrical conductivity measurement (EC). The salinity is measured by evaporating water to dryness and weighing the solid residue. The electrical conductivity measurement is measured by passing an electric current through the water and measuring how readily the current flows. The total amount of salt in the water can affect the taste of water. The World Health Organization's guideline on water palatability is that water with a salinity level of less than about 0.50–0.60 g/L is generally considered to be of a standard level. The drinking-water becomes significantly and increasingly unpalatable at salinity levels greater than about 1.0 g/L. In this research, a one-dimensional mathematical model of salinity measurement in a river is proposed. A modified model of salinity control in a river with a barrage dam is also introduced. An unconditionally stable explicit finite difference technique is used to approximate the salinity level under several conditions from the proposed model. The proposed computational technique gives good agreement results in realistic scenarios for water supply processes. [ABSTRACT FROM AUTHOR]