NUMERICAL MODELING FOR SEDIMENT-PASS-THROUGH RESERVOIRS

Sediment accumulation in reservoirs on the North Fork Feather River wi ll soon affect hydroelectric power generation. For sediment control, l ow-level outlets through the dams have been considered to allow Sedime nt-Pass-Through (SPT) the reservoirs. The objective of SPT is to maint ain sediment balance through the reservoirs with no net erosion or dep osition over an extended operating cycle. The velocity required for be d sediment to pass through a reservoir will be achieved by reservoir l evel drawdown during large floods. A numerical modeling study, using F LUVIAL-12, was made to evaluate the feasibility and effectiveness of S PT for the system. The study developed the following features: (1) rat ing curves that specify the reservoir drawdown in relation to the chan ging discharge; and (2) reservoir operation rules that specify the ope rational procedure and settings for control gates. Simulated results a re presented to demonstrate that mass balance for the river/reservoir system can be achieved, without adverse siltation in the river channel to affect fish spawning. This approach for reservoir sediment control should be useful for similar problems.