One-Dimensional Simulation of Sediment Flushing through Reservoirs

ABSTRACT: Control of sedimentation in reservoirs of dams is considered to be one of the most important issues in exploitation of dams and increasing the useful life of them. Reservoirs act as traps for sediments and prevent transport of sediment to the river. The deposited sediments will decrease the capacity of the reservoirs so that they cannot be in use any more. Various methods are discussed in this study to remove a part of the deposited sediments, but Flushing is the method, which has been used extensively in many projects all over the world due to the fact that the flow energy is utilized and there is no need to employ an additional source of energy. In this study a one-dimensional model with uniform flow is developed in which continuity equation of the sediment is solved by the finite difference method using the Crank-Nicolson method while having the initial profile of the sediment. The developed model is capable to compute the variation of the reservoir bed profile with time. Also, the accumulated flushed sediment volume and reservoir water volume are calculated at different time steps. The FORTRAN language used for programming of the model was based on the results obtained from physical models employed by several investigators. And comparison was done with HEC-6 Model. The verification of the model was done using data from the natural reservoir of Dashidaira dam in Japan. The results were compared with the actual measurements. A good agreement was observed between them but comparing the results of the model with HEC-6 model indicates the advantage of this model and the weakness of HEC-6 model in prediction of the eroded bed profile.