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Reservoir sedimentation management has become an important topic for large dams in the United States due to their historical design, current age, and increased environmental regulation. Less attention has been paid to small dams (hydraulic size < 0.01) in remote mountains with urgent sedimentation problems. In drier climates, such reservoirs may be frequently drained and trans-catchment flows routed over their sediment deposits heading from one mountain tunnel to another. This study asked an unexplored scientific question focusing on this special setting: how do different amounts of water transfers interact with different reservoir stages to affect sediment erosion and its redistribution in the backwater zone? Mindful timing and magnitude adjustment of water transfer, involving water diverted across watersheds by tunnels, through a reservoir were hypothesized to strategically redistribute sediment erosion for sites with water transfer/diversion facilities in the main channel. For a study site in the north-central Sierra Mountains of California, 2D hydrodynamic modeling revealed that sediment erosion within the backwater zone increased by > 100% when water transfer was maximized, involving a flow 12 times higher than mean annual discharge. With reservoir stage drawdown, the increment of sediment erosion was further increased by > 50% compared with water-transfer-only scenarios. The natural upstream inflow with daily flow occurrence of 5–25% was the optimal water transfer to avoid disturbing sediment. These results indicated that water transfer and stage drawdown optimization is a promising strategy to promote or abate redistribution of deposited sediment through a smaller reservoir. [ABSTRACT FROM AUTHOR]

Dams accumulate sediment by interrupting the continuity of rivers, resulting in a loss of reservoir water storage capacity and decreased productive life. These issues raise a growing concern about the decreasing benefits of projects. This paper contributes to the implementation of sediment transit strategies and operating rules of reservoirs to reduce overflows and recover the technical–economic viability of sedimented reservoirs by maintaining ecological flow. The main difficulty lies in the fact that sedimentation of the reservoir limits the mobility of dredging equipment and blocks the intake. To regain the viability of the reservoir, the commonly used strategies to manage water resources and reservoir sedimentation were analyzed. To control reservoir sedimentation and restore the generation capacity, different sediment management strategies were implemented and evaluated at the entrance, body of the reservoir and intake; these strategies included reduction of the entry of sediments, restoration of the storage capacity, clearing of the water intake for the turbines to restore power generation, trash rack cleaning during the power generation process and modification of the hydroelectric power plant operating rules to optimize the economic income. The implemented strategies successfully reduced overflows from 88 to 40% in 3 years and stabilized the reservoir storage capacity by balancing the inflow and removal of sediments. Although the water intake for the turbines was cleaned, accumulation increased in other areas of the reservoir. Finally, root cause analysis (RCA) was employed, and solutions were proposed to increase the capacity of the reservoir and reduce overflows to 15%. [ABSTRACT FROM AUTHOR]

Sedimentation in large reservoirs is a major concern in semi-arid regions characterized by severe seasonal water scarcity. As a contribution to improved sediment management, this study analyses the real case of the reservoir of Sidi Yacoub in the north of Algeria. First, a dynamic model of the reservoir was set up and used to estimate past water and sediment inflows (period 1990-2010) based on data recorded by the dam operator and measurements at a gauging station located downstream of the reservoir. Second, in a stochastic framework using the statistical characteristics of inflow and outflow discharges, a projection of future sedimentation was performed until 2030, assuming stationarity of the statistical distributions. Third, the model was used to investigate the influence of possible climate change and to quantify the positive effects of soil conservation measures upstream. [ABSTRACT FROM AUTHOR]

Importance of existing reservoirs for supplying fresh water has increased significantly due to population increase and enhanced living standards, while the reduced development of new reservoirs in recent decades has made it even more pertinent that the current battery of reservoirs be operated in a sustainable and efficient manner. In order to move a step towards the goal of sustainability, sediment evacuation must be considered when optimizing a reservoir's operations. The Reservoir Optimization-Simulation with Sediment Evacuation (ROSSE) model is a recently developed tool which internalizes sediment evacuation routines and the simulation module in a newly developed GA-based optimization module. This article applies the ROSSE model with the aim of minimizing irrigation shortages in the Tarbela Reservoir, Pakistan. The article also calculates the suitable values of various GA parameters required to run the model through a sensitivity analysis. Simulation results of three sets of rule curves-one existing and two optimized sets-are compared with each other for parameters like irrigation shortage, power generation, sediment evacuation and flood dis-benefits (damages). It is found that the optimized rule curves of scenario 1 reduce the irrigation shortages by 39 % while the optimized rule curves of scenario 2 can reduce the irrigation shortages by 24 % of that of the shortages by existing rule curves. The optimized rule curves of scenario 2 also ensure the current level of hydropower generation and sediment evacuation for the Tarbela reservoir. The study recommends a change in the reservoir's existing rule curves in order to reduce irrigation shortages. The incorporation of the sediment evacuation routine and availability of economic and hydro based objective functions in the optimization model will help achieving the goal of sustainability. [ABSTRACT FROM AUTHOR]

A limnological survey of a man-made reservoir in the central part of Albania was conducted from May 2006 to May 2008. This water body is being constructed 15 years ago for water supply of the Tirana, capital city of Albania. The physical and chemical quality of water in this reservoir was determined and compared against universally accepted water quality standards. Water quality parameters relevant to the study area are discussed considering the ecosystem function and interrelationship among physical and chemical parameters with the biological ones. The water quality of traditional and modern reservoir was not significantly different except for a bed odour that occurs throughout of the summer. Due to the reservoirs life the eutrophication in the nowadays is not a major problem in the reservoir, but due to an intensive sedimentation rate it is predicted that will seriously affect the water body in the near future. Management strategies to improve the water use efficiency with particular reference to eutrophication are proposed. On the other hand it is recommended that an integrated approach following the IRBM criteria will be the best way of management and administration. [ABSTRACT FROM AUTHOR]

In this study, we present a long-term water management model which can be an important tool for the ordinary management of a reservoir. The model can be made simple and applicable in a graphic form. The key point of the model is that the sedimentation rate of solids can be modeled according to a power law. The basic equation of the model is tested using bathymetric surveys of different dams located in different parts of the world. Robustness and predictive power are evaluated both numerically and by comparison with satellite results. Then the model is transformed into the form of a management plot and applied to the real case of the Camastra dam. [ABSTRACT FROM AUTHOR]

The aim of this study was to show the importance of exploiting the appropriate sites for construction of dams on the borders of riparian countries. To achieve this aim, a multi-reservoir system was designed across the border of two riparian countries. In addition, simulation models that express the possible operating mechanisms for this system were created. This storage system comprises two reservoirs along the border of Iraq and Turkey. One simulation model of a real reservoir was formulated to prove the model's validity by comparing its output with the observed output of the real counterpart. Three simulation models for the proposed reservoirs were developed by adopting the standard operating policy. The first and second of these three models were built to mimic the operation of the two proposed reservoirs separately, while the third simulation model was formulated to operate these two proposed reservoirs simultaneously as united multi-reservoir system. The results indicated the efficiency of the simulation model for an existing reservoir. In addition, the results of the three simulation models of the proposed multi-reservoir system demonstrated the flexibility of these simulation models in imitating the operation of a storage system, whether it was a single or a multi-reservoir system. According to the results of these three simulation models, the two proposed reservoirs could be significantly beneficial to Iraq and Turkey. [ABSTRACT FROM AUTHOR]

Although sediment is one of the most common causes of stream impairment in the United States, soil erosion is not integrated into many surface water management models. In this work, a module is developed to estimate fluvial erosion within an existing surface water optimization model. This model is applied to the Lower Republican River Basin in Kansas to demonstrate the effects of climate scenarios and water management strategies on water shortages and sediment loads. Results indicate water shortage varies most under different water management strategies, whereas fluvial erosion varies most under different climate scenarios. Fluvial erosion results are highly sensitive to streambank parameters, demonstrating the importance of measuring these parameters and quantifying their uncertainty. This novel modeling approach provides a computationally efficient method of estimating both water shortages and sediment load within one framework and demonstrates the benefit of considering water shortages and fluvial erosion when making water management decisions. [ABSTRACT FROM AUTHOR]

Long-term reservoir management often uses bounds on the reservoir level, between which the operator can work. However, these bounds are not always kept up-to-date with the latest knowledge about the reservoir drainage area, and thus become obsolete. The main difficulty with bounds computation is to correctly take into account the high uncertainty about the inflows to the reservoir. In this article, we propose a methodology to derive minimum bounds while providing formal guarantees about the quality of the obtained solutions. The uncertainty is embedded using either stochastic or robust programming in a model-predictive-control framework. We compare the two paradigms to the existing solution for a case study and find that the obtained solutions vary substantially. By combining the stochastic and the robust approaches, we also assign a confidence level to the solutions obtained by stochastic programming. The proposed methodology is found to be both efficient and easy to implement. It relies on sound mathematical principles, ensuring that a global optimum is reached in all cases. [ABSTRACT FROM AUTHOR]

Reservoirs play a strategic role in the rapid monetary growth of the world by providing numerous benefits. However, the reduction in appropriate sites along with environmental and social apprehensions has resulted in curtailment of new reservoirs around the world in twenty-first century. There is a potential of benefits available from existing reservoirs which can be best capitalized through their optimized operation. Reservoirs Operation Optimization considering Sediment Evacuation (RESOOSE), recently developed model which combines multiple reservoirs operation and sediment evacuation with Genetic Algorithm based optimization module, has been used in the study. The objective of the study was to optimize the irrigation deficit through cascade reservoirs with consideration to hydropower, sediment evacuation and flood damages reduction benefits. The RESOOSE model was applied to optimize the irrigation deficits of Tarbela and Diamer Basha Reservoirs in Pakistan using developed objective function. The article computed and compared the benefits of optimized and existing rule curves. The hydropower benefits of 36.92 Billion Kw, sediment evacuation benefits of 21.534 Million m3 and flood damages of 616.19 Million US$ due to existing rule curves were considered as minimum benefits for achieving the optimized rule curves to minimize irrigation deficits. The developed optimized rule curves reduced the irrigation shortages of case study reservoirs from 6.9 to 5.8 Billion m3 (16% enhancement) annually as compared to existing rule curves. The optimized rule curves minimized the irrigation deficits by maintaining the existing benefits and without lowering the minimum operating levels of case study reservoirs. The study suggests change in existing rule curves of Tarbela and Diamer Basha Reservoirs due to less irrigation shortages. The RESOOSE model can be applied to other cascade reservoirs for optimizing the rule curves. [ABSTRACT FROM AUTHOR]

Sediment flushing in many reservoirs of the world is accomplished with low efficiency. In this study, a new configuration was proposed for reservoir bottom outlet to increase the pressurized flushing efficiency. In the new configuration, a projecting semi-circular structure was connected to the upstream edge of bottom outlet. It was observed that by employing the projecting bottom outlet, the sediment removal efficiency increased significantly compared to the flushing via typical bottom outlet. In the case of new-configuration bottom outlet with L /D = 5.26 and D /D = 1.32, the dimensionless length, width and depth of flushing cone increased 280%, 45% and 14%, respectively, compared to the reference test. The proposed structure can ensure the sustainable use of reservoirs. [ABSTRACT FROM AUTHOR]

Freshwater reservoirs are under threat because of huge amounts of sediments deposited annually. Sediment flushing seems to be effective to preserve reservoir storage, but it may have negative environmental impacts on downstream ecosystems such as fish mortality. Therefore, providing a suitable flushing strategy that could be compatible with the river ecosystem downstream is of great importance. Two numerical models were developed in this paper to predict the suspended sediment concentration (SSC) on the reservoir-river system and effects of different flushing scenarios on aquatic life. Developed models were applied to the Dez Resevoir system in the southwest of Iran which has suffered from the sediment problems in two last decades. The suitable values for flushing time, concentration limits, and flushing discharge have been recommended in this research by use of the existing information and previous flushing records, as well as field measurement and modeling. Based on social, environmental and technical limitations, March is the appropriate time for flushing. After hydraulic simulation of different flushing scenarios and sediment routing along the river, flushing with 1275 and 800 cubic meter per second with 30 and 20 g per lit concentration in dry and wet season respectively are feasible and have minimum environmental impacts. [ABSTRACT FROM AUTHOR]

Sedimentation and erosion can significantly affect the performance of river regulated reservoirs. In the vicinity of flow control structures, the interaction between the hydrodynamics and sediment transport often induces complex morphological processes. It is generally very challenging to accurately predict these morphological processes in real applications. Details are given of the refinement and application of a three-dimensional (3-D) layer integrated model to predict the morphological processes in a river regulated reservoir. The model employs an Alternating Direction Implicit finite difference algorithm to solve the mass, momentum and suspended sediment transport conservation equations, and an explicit finite difference scheme for the bed sediment mass conservation equation for calculating bed level changes. The model is verified against experimental data reported in the literature. It is then applied to a scaled physical model of a regulated reservoir, including the associated intakes and sluice gates, to predict the velocity distributions, sediment transport rates and bed level changes in the vicinity of the hydraulic structures. It is found that the velocity distribution near an intake is non-uniform, resulting in a reduction in the suspended sediment flux through the intake and the formation of a sedimentation zone inside the reservoir. [ABSTRACT FROM AUTHOR]

The paper develops a new methodology and RESOOSE model for optimizing operation of multiple reservoirs considering sediment evacuation for multiple objectives consisting of maximization of irrigation, hydropower, storage conservation and minimization of flood damages. The optimization and sediment evacuation modules of the model are based on Genetic Algorithm and Tsinghua equation respectively. According to the criteria developed for selection of reservoirs, three reservoirs on Indus River of Pakistan have been selected. The model has been calibrated and validated for Tarbela and Chashma Reservoirs. The calibrated model has been applied to Diamer Basha (proposed) and Tarbela Reservoirs. Eight scenarios comprising of combined and individual objectives were developed. The optimized results of different scenarios have been compared with existing rule curves. The optimization results reveal that objective function for hydropower, irrigation, and storage conservation benefits would be enhanced by 11, 13 and 84 % respectively while flood damages would reduce by 80 %. Similarly the optimized rule curves will increase the benefits up to 579, 960, 533 and 648 million US$ per year (on 2012 prices) for all the four components respectively. The maximum value of US$ 977 million per year has been found for the scenario 5 which gives equal priority weight to all the four sectors. The developed model can be applied to other two reservoirs (in series) for optimization of rule curves. [ABSTRACT FROM AUTHOR]

Construction of river diversion barrages produces a shallow reservoir, called the pond, which is used more often for flow balancing between the inflows of the river and the outflows of the off-taking canal. However, deposition of sediment in the pond due to the relatively low velocities reduces the pond capacity. The current study investigates the effectiveness of gate operation and variations of other parameters in flushing out these sediment mounds, or shoals, from the barrage pond. Data from laboratory experiments on a scaled model of a prototype barrage is used to train and test different Artificial Neural Network (ANN) models of the system. The models map the relationship between flushing efficiency of a sediment shoal from the upstream of a barrage, and the parameters river discharge, barrage pond depth and area of gate opening, position of the sediment shoal with respect to the barrage. The ANN models are then used to study the effect of different parameters on the sediment flushing efficiency. Apart from river discharge and net area of gate opening, upstream pond depth is also found to have a significant effect on flushing efficiency, with a general trend of decrease in efficiency with increase in pond depth becoming apparent. Efficacy of different gate opening pattern is also tested, with the 'inverted arch' gate opening pattern proving to be the most efficient when compared with 'arch' and 'uniform' gate opening. [ABSTRACT FROM AUTHOR]

This paper presents a multi-objective optimization model for the coordinated regulation of flow and sediment in cascade reservoirs. The model was developed to address two contradicting issues: sediment trapping and flow regulation. The benefits of flood control, hydropower generation and navigation, and sedimentation in cascade reservoirs were considered as the target functions; then the corresponding submodels for reservoir operation and sediment computation were established. The model was implemented by reducing it to a single objective nonlinear model using the constraint method. Non-inferior solutions were obtained by solving the model with catfish effect particle swarm optimization algorithm. The model was applied to the cascade system of Xiluodu and Xiangjiaba reservoirs in the lower Jinsha River in the flood recession period. Under the safety of flood control and navigation, a non-inferior set for impounding time, power generation, and siltation-loss rate of capacity was obtained and optimal solutions with different weights were derived. The results demonstrate that the model is a useful tool in coordinated operations of cascade reservoirs. [ABSTRACT FROM AUTHOR]

Reservoirs are the key infrastructure for the socio-economic development of a country. The reservoirs are proven to be a remedial solution of highly erratic spatial and temporal availability of water. The growth in population and consequent developmental activities within a catchment area has shown to aggravate the problem of sedimentation which comprised of erosion, sediment transport and its deposition in these reservoirs. Among all above mentioned, reservoir sediment deposition is most important as it reduces its useful life and impairs the purposes of these vast water resource. The sediment yield has been considered as comprehensive index for assessing sustainability of such resources. The present study investigates the suitability of Pacific Southwest Inter-Agency Committee (PSIAC) model in determining the sediment yield rate for a drainage basin considering nine basin factors in geographical information system (GIS) environment. For the analysis, a large river basin at the foothill of Himalayas in India has been considered as case study. It was realized that the GIS approach made large basin characteristic sampling very easy and efficient for this hilly basin. A regression equation between specific sediment yield and effective model factors was established based on geomorphic features for this basin. It was observed that most of the basin area is falling under moderate to high sediment yielding potential zone, leading to high sediment yield. [ABSTRACT FROM AUTHOR]

Communal water storage reservoirs (embungs) that serve many villages in West Timor, Indonesia, during the prolonged annual dry season are plagued with sedimentation problems. Sedimentation progressively reduces water storage capacity, and consequently the benefits that community can derive from embungs. This paper investigates four alternative strategies for managing the sedimentation of a typical village embung: (1) current management (a 'no management' situation), (2) soil conservation in the embung catchment, (3) periodic sediment removal and (4) a combination of soil conservation and sediment removal. Without periodic sediment removal, an embung has a finite life dependent on the rate of sedimentation. The results indicate that periodic cleaning is worthwhile. Strategy (4) gives the highest net present value followed by strategy (3). The study shows that the current 'no management' strategy is the worst strategy. Sensitivity analyses were conducted to investigate how robust the ranking is to alternative discount rates and to assumed effectiveness of soil conservation measures in reducing sedimentation. [ABSTRACT FROM AUTHOR]

Assessment of soil erosion, sediment transport and deposition of sediment in the reservoirs, irrigation and hydropower systems are considered essential for the land and water management. The magnitude of sediment transported by rivers has become a serious concern for the water resources planning. In the present study, an assessment of sediment yield has been made for the Satluj River, which flows through the western Himalayan region. Two approaches have been used for the assessment of sediment yield (i) relationship between suspended sediment load and discharge and (ii) empirical relationship. The first approach was used for Satluj Basin up to Suni (52 983 km²), Kasol (53 768 km²) and also for the intermediate basin between Kasol and Suni (785 km²). The sediment-discharge relationship was developed using daily data for a period of three years (1991-1993) for different basins and was applied for each basin for the years 1994 and 1996 for estimation of sediment yield. The second approach, which gives annual sediment yield, has been used for a small intermediate basin only because of data availability constraints. For estimation of the sediment yield using the empirical relationship, various geographical parameters such as land use, topographical etc. were generated using Geographic Information System (GIS) technique. The annual sediment yield for the intermediate basin was estimated for three years and compared with observed values. The trend of difference between computed and observed sediment yield suggested an effect of physical features of mountainous basins. The available empirical relationship was, therefore, revised by incorporating a basin parameter in the equation. This basin parameter represented an integrated effect of slope and spatial distribution of rainfall in the mountainous basin. Using the revised empirical relationship, the sediment yield was estimated for two independent years and a good correlation was found between computed and observed sediment yield. [ABSTRACT FROM AUTHOR]

The useful life of Tarbela reservoir, on the River Indus, is threatened by a sediment delta which is approaching the dam's intake tunnels; these lead to a hydroelectric power station and are used for irrigation releases. This article describes the simulated system, involvingTarbela Dam, with Ghazi Barotha hydropower scheme downstream, and the planned construction of Basha Dam upstream. This study formed an innovative approach which enabled the relationship between demands and supply in the basin to be studied, under a range of development and operating scenarios, and to different time horizons. A computer software package, 'Hydro', was used to perform system simulation modeling of Tarbela Dam and the Upper Indus Basin, Pakistan. The results enabled estimation of the economic benefits of several potential future operating strategies for Tarbela to be tested and compared. Employing the results of associated sediment modeling, projected storage/elevation curves were used to predict the irrigation and power benefits available to Pakistan over the coming sixty years. It was subsequently demonstrated that the most beneficial remedial measures are an underwater dike or dam to protect the intakes, and low-level flushing facilities. [ABSTRACT FROM AUTHOR]

A unique integrated modelling system has been developed and applied for environmental assessment studies in connection with the Gabcikovohydropower scheme along the Danube. The modelling system integrates model codes for describing the reservoir (2D flow, eutrophication, sediment transport), the river and river branches (1D flow including effects of hydraulic control structures, water quality, sediment transport), the ground water (3D flow, solute transport, geochemistry), agricultural aspects (crop yield, irrigation, nitrogen leaching) and flood plain conditions (dynamics of inundation pattern, ground water andsoil moisture conditions, and water quality). The uniqueness of the established modelling system is the integration between the individual model codes, each of which provides complex descriptions of the various processes. The validation tests have generally been carried out for the individual models, whereas only a few tests on the integratedmodel were possible. Based on discussion and examples, it is concluded that the results from the integrated model can be assumed less uncertain than outputs from the individual model components. In an example, the impacts of the Gabcikovo scheme on the ecologically unique wetlands created by the river branch system downstream of the new reservoir have been simulated. In this case, the impacts of alternative water management scenarios on ecologically important factors such as flood frequency and duration, depth of flooding, depth to ground water table, capillary rise, flow velocities, sedimentation and water quality in the river system have been explicitly calculated. [ABSTRACT FROM AUTHOR]