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"Reservoirs Design and construction."
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Small Dams : Planning, Construction, and Maintenance
\"A practial guide to determining catchment yield and the amount of water required in a dam. Also advises on working with engineers and contractors, and outlines the causes of dam failures and how to remedy problems quickly. It further covers relevant legislation, as well as environmental and ecological issues from a global perspective, with explicit reference to various countries around the world. An invaluable reference resource for anyone who owns or plans to own a dam, and a useful reference for agencies, contractors and engineers\"-- Provided by publisher.
Book
Sustainable sediment management in reservoirs and regulated rivers: Experiences from five continents
By trapping sediment in reservoirs, dams interrupt the continuity of sediment transport through rivers, resulting in loss of reservoir storage and reduced usable life, and depriving downstream reaches of sediments essential for channel form and aquatic habitats. With the acceleration of new dam construction globally, these impacts are increasingly widespread. There are proven techniques to pass sediment through or around reservoirs, to preserve reservoir capacity and to minimize downstream impacts, but they are not applied in many situations where they would be effective. This paper summarizes collective experience from five continents in managing reservoir sediments and mitigating downstream sediment starvation. Where geometry is favorable it is often possible to bypass sediment around the reservoir, which avoids reservoir sedimentation and supplies sediment to downstream reaches with rates and timing similar to pre‐dam conditions. Sluicing (or drawdown routing) permits sediment to be transported through the reservoir rapidly to avoid sedimentation during high flows; it requires relatively large capacity outlets. Drawdown flushing involves scouring and re‐suspending sediment deposited in the reservoir and transporting it downstream through low‐level gates in the dam; it works best in narrow reservoirs with steep longitudinal gradients and with flow velocities maintained above the threshold to transport sediment. Turbidity currents can often be vented through the dam, with the advantage that the reservoir need not be drawn down to pass sediment. In planning dams, we recommend that these sediment management approaches be utilized where possible to sustain reservoir capacity and minimize environmental impacts of dams. Key Points Reservoirs trap sediment, losing storage capacity Downstream reaches can become sediment starved Many dams can be designed/operated to pass sediment
Journal Article
Experimental study on the influence of sandstone gradation on the water storage capacity of a pore-space reservoir in a waste dump of an open-pit coal mine
Poor water management can result in water shortages that greatly impact the production capacity of open-pit coal mines in arid and semiarid areas. Additionally, the improper handling of mine pit wastewater can exacerbate the overall loss of water resources. To mitigate the imbalance between the seasonal supply and demand for water resources, and the scarcity and low utilization rate of the water resources associated with open-pit coal mines, underground reservoirs with rock-mass pore space can be established in on-site waste dumps to store water. Here, the Baorixile open-pit coal mine, located in a semiarid area of China, was selected as the research area. Pebbly sandstone material was divided into three grain sizes in order to study these pore-space reservoirs. Considering the water storage characteristics of the aquifers in their original undisturbed state, and with reference to similarity theory, a similarity simulation experiment was set up. The experimental design can facilitate simulation of the influence of overburden pressure on the water storage capacity of underground pore-space reservoirs constructed in different stages, repeated pumping/storage on the reservoir water storage capacity, and underground reservoir establishment on ground surface settlement. It was found that pebbly sandstone with a larger grain size is more suitable for use as a water storage material in underground pore-space reservoirs of open-pit coal mines. This study provides a reliable material grading system for underground reservoir construction in open-pit coal mine waste dumps in arid and semiarid areas, to improve the water resources situation in mining areas.
Journal Article
A bivariate return period based on copulas for hydrologic dam design: accounting for reservoir routing in risk estimation
A multivariate analysis on flood variables is needed to design some hydraulic structures like dams, as the complexity of the routing process in a reservoir requires a representation of the full hydrograph. In this work, a bivariate copula model was used to obtain the bivariate joint distribution of flood peak and volume, in order to know the probability of occurrence of a given inflow hydrograph. However, the risk of dam overtopping is given by the maximum water elevation reached during the routing process, which depends on the hydrograph variables, the reservoir volume and the spillway crest length. Consequently, an additional bivariate return period, the so-called routed return period, was defined in terms of risk of dam overtopping based on this maximum water elevation obtained after routing the inflow hydrographs. The theoretical return periods, which give the probability of occurrence of a hydrograph prior to accounting for the reservoir routing, were compared with the routed return period, as in both cases hydrographs with the same probability will draw a curve in the peak-volume space. The procedure was applied to the case study of the Santillana reservoir in Spain. Different reservoir volumes and spillway lengths were considered to investigate the influence of the dam and reservoir characteristics on the results. The methodology improves the estimation of the Design Flood Hydrograph and can be applied to assess the risk of dam overtopping.
Journal Article
Long-term trends in study duration of lakes and reservoirs over recent decades
Owing to increased awareness of the value of long-term ecological studies, there have been numerous calls for long-term data. Natural lakes and reservoirs provide ecosystem services and serve as sentinels of change but differ in origin, water movement, and location. We conducted a meta-analysis of study duration for lake and reservoir studies from 1975 to 2015 (6362 studies were initially identified, and 801 met study criteria). Study duration increased among longer studies (> 0.5 quantile) with increases of 20 years for the highest (0.9) quantile, and there were no changes among short-term studies. Increased study duration was inversely related to number of focal areas or metrics (e.g., phytoplankton, zooplankton, vertebrates) with few focal areas or metrics (< 2 metrics) indicating few focal areas for long-term studies. Surprisingly, despite continued construction of reservoirs, the ratio of studies of lakes to reservoirs was 5 to 1 with no change over time, with the dearth of data on reservoirs making it difficult to characterize long-term trends. Increased duration in high quantiles concurrent with static duration of short-term studies suggests limnologists have fundamentally altered the way they approach questions that are influenced by study duration, but also that gaps remain in multifaceted studies and in reservoir studies.
Journal Article
Classification of Management Alternatives to Combat Reservoir Sedimentation
Sedimentation is steadily depleting reservoir capacity worldwide, threatening the reliability of water supplies, flood control, hydropower energy and other benefits that form the basis of today’s water-intensive society. The strategies available to combat reservoir sedimentation may be classed into four broad categories. Three proactive categories seek to improve the sediment balance across reservoirs by: (a) reducing sediment yield from the watershed, (b) routing sediment-laden flows around or through the storage pool, and (c) removing deposited sediment following deposition. The fourth category (d) consists of strategies that adapt to capacity loss, without addressing the sediment balance. Successful management will typically combine multiple strategies. This paper presents a comprehensive classification of both proactive and adaptive strategies, consistent with current international practice. Functional descriptions and examples are given for each strategy, and criteria are provided to differentiate between them when there is potential for ambiguity. The classification categories can be used as a checklist of strategies to consider in evaluating sediment management alternatives for new designs as well as remedial work at existing sediment-challenged reservoirs. This will also help practitioners to more clearly describe and communicate the nature of their management activities. Widespread application of both active and adaptive strategies is required to bring sedimentation under control to sustain benefits of water storage for today’s and future generations.
Journal Article
Optimization design and assessment of the effect of seepage control at reservoir sites under karst conditions: a case study in Anhui Province, China
Seepage analysis and assessment of the effect of seepage control at reservoir sites are essential parts of dam design and operations, and of considerable significance for the safe and economic design of the masses and hydraulic structures associated with reservoir sites. In this study, a systematic process is provided for the optimal design and assessment of seepage control of reservoir dams under karst development conditions. A reservoir dam planned for construction in the middle-upper reaches of the Huayang River in China is selected as a case example for illustration. A three-dimensional equivalent continuum seepage finite-element numerical model is applied to investigate the effectiveness of the proposed and optimized seepage-control schemes, and it is calibrated by an inversion analysis of the initial seepage field based on the flexible tolerance method and field penetration test data. By analyzing the sensitivity of seepage discharge to the length and depth of the grouting curtain, a safe and economic seepage-control optimization scheme is suggested. Additionally, the sensitivity of seepage discharge to the hydraulic conductivity of the limestone layer is analyzed, and the results show that the hydraulic conductivity of the limestone layer has a significant impact on the seepage discharge of the reservoir site. The methodology and results derived from this study can provide technical support and reference for the optimal design and assessment of seepage control for reservoir dam engineering under karst conditions.
Journal Article
Fisheries and biotic homogenization of freshwater fish in the Brazilian semiarid region
The construction of dams in Brazilian semiarid regions has been a common governmental practice since the early 1900s, initially with the aim of providing water to meet the needs of humans and animals, and, later, to improve fisheries. Along with dams, several nonnative fish species were introduced with the intention of supplying new fisheries. We used a dataset compiled since the 1950s for the following: (i) evaluate fisheries for native and nonnative species across space–time scales and (ii) quantify the spatial and temporal changes in taxonomic and functional similarity of freshwater fish assemblages in semiarid reservoirs. Overall, fisheries for native species decreased over time, while fisheries for nonnative species increased during the early periods, which then, for the most part, decreased after 2000. At the Inter-region scale, we recorded a transition from homogenization to differentiation over time, both in taxonomic and functional terms. At the Intra-region scale, we also found a transition phase from taxonomic homogenization to differentiation over time, while functional differentiation was recorded for most of the regions. This study highlights the variation in fisheries for native and nonnative species over a period of ~ 70 years, and the homogenization dynamics of Brazil’s semiarid freshwater fish resulting from the construction of dams, stocking programs, and aquaculture using nonnative species.
Journal Article
Modelling hazards impacting the flow regime in the Hranice Karst due to the proposed Skalička Dam
This study examines the hydrogeological hazard associated with the construction of the proposed Skalička Dam in the vicinity of the Hranice Karst. Prompted by the catastrophic regional floods in 1997 and 2010, the design of the dam aims to mitigate floods along the Bečva River downstream of the reservoir. However, concerns have been raised regarding the potential disturbance of the natural groundwater regime in the Hranice Karst and the source of mineral waters for the Teplice spa. This is due in particular to the dam's location in an area with limestone outcrops potentially susceptible to surface-water infiltration. Previous studies have also highlighted the strong correlation between the water level in the Bečva River and the water level in karst formations such as the Hranice Abyss, Zbrašov Aragonite Caves, and other caves in the locality. To address these concerns, a nonlinear reservoir-pipe groundwater flow model was employed to simulate the behaviour of the Hranice Karst aquifer and specifically the effects of the dam reservoir's impoundment. The study concluded that the lateral variant of the dam would have a practically negligible impact on the karst water system, with the rise in water level being only a few centimetres. The through-flow variant was found to have a more significant potential impact on water levels and the outflow of mineral water to the spa, with a piezometric rise of about 1 m and an increase in the karst water discharge to the Bečva River of more than 50 %. Based on these results, recommendations for further investigations concerning the design of the dam and its eventual construction have been formulated to reduce geological uncertainties and to minimize the potential impact of the hydraulic scheme on the hydrogeology of the karstic system.
Journal Article
Dams and reservoirs in karst? Keep away or accept the challenges
The distribution and flow of groundwater in karstified rocks can be extremely complex and not readily predictable, a far from friendly environment for constructing dams and reservoirs. There have been many expensive failures such as unacceptable leakage rates at and around dams, and/or reservoirs that could not be filled to the design levels. This is never the fault of site geology but always of human mistakes due to inadequate investigation programmes and/or erroneous interpretation of the karst processes at work. Remedial works are expensive, time-consuming and frequently do not justify the money invested. As a result, those undertaking engineering works in karst terrains may approach with two fears—of the exceptional risk and/or of a failure. The key question, so often, is whether to build the dam in karstified rocks or keep away from such a risky environment. However, construction of water storage reservoirs is essential in many karst regions for socio-economic development. The challenge must be accepted. Based on much field experience, the best practices for selection of adequate dam and reservoir sites are defined and illustrated with specific examples from many different climatic, topographic, lithologic and hydrogeologic settings in Europe and Asia. This work emphasises that the amount of certainty or uncertainty in the crucial parameters—geological structure, groundwater regime, intensity and depth of karstification—should be recognized.
Journal Article