LAUSR

Hydropower projects are nowadays developed on rivers carrying heavy sediment load as run-of-theriver projects. The projects are designed to sustain reservoir life by sediment management. The sediment management is achieved by drawdown flushing or sluicing. The efficiency of sediment management technique depends on several natural, technical and operational parameters of the project. Simulation with numerical and physical models is essential for optimizing the design and operation of such projects. In this paper, reservoir flushing studies carried out by 1D/2D numerical model simulations for the Dri Limb, Etalin hydroelectric project, Arunachal Pradesh is presented. The long term simulations for reservoir sedimentation were carried out using MIKE 11 and simulations for reservoir flushing were carried out using MIKE 21C. 1D simulation indicated that the sediment deposition reaches the dam at the end of about 45 years. 2D simulations were carried out for two alternative sedimentation profiles and five flushing discharges. Results indicated that the reservoir bed levels stabilize after about 36 hours. About 40% of the deposited sediment can be removed with the flushing discharge of 1000 m3/s. Annual flushing for 36 hours when the discharge exceeds 1000 m3/s is found to be effective in managing the reservoir sediment deposition.