NUMERICAL MODEL APPLICATIONS FOR SEDIMENTATION AND FLUSHING BEHAVIOUR OF STORAGE RESERVOIR -CASE STUDY

摘要

The construction of dams across the river in regulating river flows can provide specific purposes like flood control, water supply, recreation, and navigation paybacks. Following the construction of the dam the predicament manifests itself by depositing sediments within the reservoir pools. As a process, the incoming silt-laden water when it comes in contact with a quiescent pool of backwater, the flow velocity gets reduced and results in release of most of its suspended sediments down to the reservoir bed. However, its distribution pattern across and along the reservoir bed depends on a number of factors, among these, gradient of the valley, length of backwater, nature of spillway, exposure of depleted material, particle size of the suspended material, and capacity inflow ratio are the governing ones. But, the reservoir operation has an important control over these factors (S.N. Ghosh, 1997). The outgoing water from the dam is very clear as compared with the incoming turbid and has high sediment transporting potential. Thus, the redistribution of sediment load can reduce the storage capacity significantly and causes the downstream reach to be starved of sediment particles; these possibly alters the river profile in general and deteriorate the project economic life in particular.