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In the literature, optimization of reservoir operation has been mostly carried out to achieve certain objectives including water and/or energy supply, flood control, and environmental preservation. These objectives can be less important for the reservoirs with high sedimentation. Sefid-Rud Reservoir in Iran has been facing extreme sedimentation rates in the past. A major challenge in operation of this reservoir has been to create a tradeoff between sediment removal and water supply to downstream users. The lack of modeling tools for balancing sediment removal with water supply objectives has been the main driving force behind this study. In this paper, a new approach is proposed for monthly reservoir operation optimization of Sefid-Rud Reservoir considering water supply and sediment removal objectives concurrently. The model minimizes the total deficit in supplying demands and maximizes the total volume of sediments removed from the reservoir. The sediment outflow is determined debased on Tsinghua university flushing equation. A new evolutionary algorithm “Imperialist Competitive Algorithm (ICA)” is used to solve the resulted nonlinear optimization model. Five scenarios were assessed for depending on the relative weights assigned to each of objectives of sediment removal and water supply. Based on the results obtained, the feasibility of increasing efficiency of flushing operation while supplying downstream water demands was illustrated. Moreover, the significance of the improved system’s operation with higher long-term reliability of supplying downstream water demands and sediment removal, compared to historical operation, was investigated.

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In this research simulation model of sedimentation in dam reservoirs in the arid and semi-arid basins (Water Availability in Semi-Arid environments-SEDiments) was developed. Rainfall-runoff, erosion-sedimentation processes and sediment transfer in the river's catchment, can be simulated by WASA-SED. In this research a new module was added to the WASA-SED model. This module was developed by Fortran programming and will about a decision supporting system for reservoir desilting that supported by engineering relationships that allow the quantification of basic parameters. The model helps to evaluate the technical and economic feasibility of implementing the life cycle management approach. Validation of the model has been made using prototype data (Barasona dam in Spain). The computer simulations agree well with the prototype measurements and show that the model is a promising tool for feasibility study and economic evaluation of alternative strategies for reservoirs desilting. The results from the economic optimization routine identify the preferred sediment management technique for sustainable use of the water resource infrastructure.

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Dam reservoirs are cosnidered as impronatnt hydraulic structures in water resources management and flood control. Therefore, reservoir operation and method of water release has sepcial importance. In this study, a new alorithm is used for reservoirs operation. This alorithm is a combination of  Harmony Algorithm and Particle Swarm Optimization (PSO) algorithm, and supports these two algorithms such that it solves the problem of lack of balance between exploration and exploitation. This hybrid method  improves the harmony method so that the trap probability in local optimum is decreased. Moreover, the hramony method hepls to correct the responses which don’t fall in feasible space of the solution in PSO method. The hybrid method was used for Mahabad and Karun 4 dam reservoirs, aiming at reducing the shortages and/or enhancing hydropower generation. Results showed that the hybird method has closer resposes to global optimum, as compared to the other two methods. In additon, simulated results of water release, storage, and genrated power in Mahabad and Karun 4 reservoirs match very well to nonlinear-programing results obtained by using Lingo software.  

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Entry of density current into dams' reservoirs leads to reduce the useful life of the dam and reduce or even eliminate the volume of water regulation and the loss of profits from flood control and power generation. One of the methods for controlling density current is the creation of barriers before the main reservoir of the dam. In this study, the effect of three bed slopes and arrangement of permeable barriers with six different types of layout on front height, forward velocity and Densitometric Froude number of high concentrations has been investigated. Experiments were performed in a channel of 10 meters in length and in three slopes of zero, one and two percent with similar convergent arrangement, similar divergent, parallel, z-shaped, Zigzags and checkered at two concentrations of 40 and 80 g / l, respectively. According to the results, the arrangement of similar convergent, checkered, similar divergent, zigzag, parallel and Z-shaped had the most effect on the hydraulic flow characteristics of the density current. The effect of different arrangement of the barriers on the hydraulic characteristics of the density current in a bed without sloping is more than the sloping bed, and also the effect of the arrangement of barriers in the critical current range is greatly reduced. The slightest effect of the obstacles on the bed without sloping is due to the similar convergent arrangement, which has reduced the Densitometric Froude number by 65%, and the effect of this arrangement on the sloping bed (the slop is 2%) has reached to 19% .The least effect of the arrangement is related to the barriers of the z-shaped arrangement. In this arrangement, the decrease in the Densitometric Froude number in the bed without sloping has been 50%, and this value with an increase in the bed slope (by 2%) has reached to 16%.

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Sediment desilting of dam reservoirs is done by different methods such as hydrosuction. In order to precisely design of hydrosuction systems resulting in higher efficiency and avoiding water loss of the reservoir, it is necessary to experimentally study the process of sediment desilting. The main parameters which influence on the efficiency of such systems include: the suction pipe diameter, the angle of suction pipe relative to the bed surface, and the effective head (head difference between reservoir water level and system outlet). To study the impact of those parameters on outflow density, a physical model of reservoir has been designed, constructed and investigated. Experiments have been conducted on each parameter at three levels and three replications for each run. Results show that the outflow gets denser by increasing amount of these parameters. For example by increasing effective head from 50 cm to 65 cm and then 80 cm, the outflow density increases 9.4% and 20.9%, respectively.

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In this study, reservoir water level effects on nonlinear dynamic response of concrete gravity dams are investigated. For this purpose, the nonlinear behavior of the dam concrete is captured using the concrete damage plasticity (CDP) on the non associated flow rule assumption. Water in the reservoir is represented by the Lagrangian (displacement-based) fluid finite elements. The program ABAQUS is applied for nonlinear dynamic analysis of dam-foundation-reservoir systems and employed in the response calculations. Nonlinear dynamic analysis of Shafarood concrete gravity dam subjected to three far-fault and three near-fault earthquake groundmotions are performed for three different water levels. The crest displacements, the failure element distribution in dam body and damaged Index in different conditions are presented. The results obtained from nonlinear analyses for different water levels are compared with each other. It is apparent that the reservoir water level significantly affected the dynamic response of gravity dam but under near-fault ground motions reservoir has a mitigation effecton nonlinear dynamic response of dam.

 

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The present study investigate the effects of mechanical properties of the rock layers in the foundation of concrete gravity dam on the seismic response of gravity dam–reservoir –foundation systems. The mutual effects of different domains are considered in the present research. As a case study the biggest section of Shafarud dam in the north of Iran is modeled two dimensionally using ABAQUS software and its response to the may 1940 El–Centro California earthquake is considered.Four different ratio of elasticity modulus of foundation to the elasticity modulus of concrete of dam body are applied in the analysis obtained results show a significant effect of the foundation material properties on the crest displacement of dam and stress distribution in the dam bodywhich highlight the importance of detailed survey in order to identify the features of the site before construction.

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Morning Glory Spillways are an important type of flood evacuation systems. According to the specific hydraulic and structural conditions, the evaluation of the seismic behavior of these kinds of spillways could be more precise with considering the interaction of the solid-water-foundation system. In this research, a three dimensional modeling of the morning glory spillway was conducted, considering the reservoir, foundation and overflow tunnel system interactions. The analysis was performed with finite element method using ANSYS.16 software, in order to evaluate the effects of system components interaction on dynamic responses of spillway. ​To determine the effect of shaft geometry on the responses, Tabas earthquake accelerations in three directions applied on seven models with four different values for elevation and four different values of shaft diameter. Also displacements of spillway crest and principal stresses of the node connecting knee into the tunnel were extracted. Frequency Analysis shows that, the increase of the shaft height reduces the system frequencies, but the shaft diameter is not an effective parameter on the frequency of the system. Also the increase of the vertical shaft height, led to the maximum values of the vertical displacement of spillway crest and increase of principal stresses of the knee.

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The stability of a gravity dam on a jointed rock foundation might be endangered by weak joints that may be present in the fracture network of the bed rock. A review of the literature shows that there are few studies of the effect of a weak joint in the foundation rock on the stability of dams. This research uses the finite difference numerical modelling software ABAQUS to model a gravity dam, the foundation rock, and the influence of a weak joint (using interfaces), that exist in the bottom of dam with different direction, on the stability of the dam. To do this, a conceptual model has been developed and one representative joint of a discrete fracture network with seven different dip angle was examined. Thses different varying dip angles were studied in order to investigate the critical configuration that has the most significant effect on the dam’s stability.As a case study, Pine Flate dam, is modeled with the ABAQUS software as a two-dimensional and Nonlinear dynamic analysis is done by implicit method with applying vertical and horizontal components of the El-Centro earthquake. The obtained results show that existness of joint in the foundation significantly affected the dynamic responcse of dam.

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Aim of this study is to estimate the optimized volume of reservoir in un-gaged basins and extract the estimation pattern of reservoir capacity for other regions. For this purpose, Ziarat was divided to 9 sub-basins using ArcGIS and the physiographical parameters was determined for each of them. for modelling of volume variation, demand before and after rain and also product before and after spill, were considered as different of Possible scenarios. Time history for amount of volume, was obtained as an equation according to other variables. The optimized volume calculated by mentioned equation as objective function and constrains.i.e. cost, demand and spill for each sub-basin. These volumes vary from 700 to 5000Mm3 and significant relation between volume and curve number index was observed. To extract a relation for prediction of reservoir optimized volume in un-gaged regions, regional parameters and optimized volume was considered and 6 equations was prepared by dimensional analysis and different functions. in this equations, 12 rainfall of 24-h probable maximum event were used for 4 consecutive years (2012-2015). Finally, using R-square and standard deviation error, the more optimized equation was presented. 

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Generally, the design of dams and other hydraulic structures is carried out based on deterministic approaches. However, there are many uncertainties in the estimation of different effective parameters in hydraulic structures design. The inherent uncertainties in these parameters necessitate reliability analysis to ensure the structure stability. In this study, after investigating various uncertainties in design, the height and overtopping failure of Namrood dam as a case study was calculated based on reliability analysis. For this purpose, the Monte Carlo Simulation Technique that is a well-known method for reliability analysis, was used. Results showed that to get 100% safety from design flood, the height of Namrood dam should be considered as 78.7 m. However, in this case the probability of overtopping failure due to control flood was 64%. Moreover, similar analysis was carried out to investigate the effect of spillway type on overtopping probability of failure. Results showed that by increasing the spillway crest length, the probability of failure in the case of Morning glory spillway increased more rapidly than ogee spillway.

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The optimization algorithm of African vultures (AVOA) has been used to solve the problems of optimal operation of two four- reservoir and ten- reservoir systems in order to maximize the release for the production of hydroelectric energy. then the performance of the aforementioned algorithm with three optimization algorithms of Harris's hawks (HHO), Whale (WOA) and Gray wolves (GWO) were compared using Friedman test for 10 runs, 300 search agents and 4000 iterations. The results showed that in the four- reservoir system, AVOA and GWO were ranked first and second with the optimal values of 296.67 and 283.65, respectively. In the next rank, HHO and WOA were placed with the same Friedman rank equal to 3.33 and the average values of the objective function equal to 264.92 and 254.3, respectively. In the ten- reservoir system, AVOA with the average objective function values of 1059.42 ranked first, followed by GWO, WOA, and HHO with optimal values of 1051.54, 1031.89, and 963.6, respectively. Therefore, AVOA was able to estimate 96.27% and 88.7% of the global optimum of the objective functions of the four- reservoir and ten- reservoir systems, which are equal to 308/292 and 1192/414, respectively.