Sediment sluicing in mountain reservoirs

Reservoir sedimentation generally follows a similar pattern. Material carried as bed load is deposited close to the reservoir entrance, material transported in suspension settles down uniformly all over the reservoir. In mountain reservoirs, it usually is the deposition of coarse material that causes problems. Removal of the gravel deposits at the reservoir entrance by means of flushing can be a suitable remedy to solve the problem, particularly when it is combined with water level drawdown. Sluicing of coarse sediment through the reservoir can also be supported by creating a defined channel at the bottom of the reservoir. Analytical treatment of reservoir sedimentation and sediment sluicing is difficult due to the many parameters involved and due to the uncertainties concerning the evaluation of reliable data. A simplified method to estimate the efficiency of sediment sluicing is presented. Its practical application is demonstrated by means of an example.