67. Large Hydropower Plants and Reservoir Sedimentation

Hydropower is a renewable, economic, non-polluting and environmentally benign source of energy. Hydropower stations have inherent ability for instantaneous starting, stopping, load variations etc. and help in improving reliability of power system. Storage reservoirs are in integral part of the large hydropower projects which play an important role in the future development of water resources in a country. But these storages are subject to silting, sedimentation in reservoirs being a matter of vital concern to all Water Resources Development projects. Sediment deposition in reservoirs not only occurs in the dead storage but also encroaches into live storage capacity which impairs the intended benefits from the reservoir. Sediment deposition in reservoirs causes loss of water storage capacity, sediment entrainment in hydropower equipment, blockage of gates and intake, impairment of navigability, loss of flood control benefits downstream, increased flooding upstream due to stream bed aggradations in the deltaic region, etc. This paper highlights the importance of hydropower plants and the extent of the damage caused by the sediment entering through the intake into the machines, importance of the sediment control into the reservoirs, Sediment transport mechanism within the reservoirs, the various possible methods available for assessing/predicting the sediment load entering into the reservoir for predicting the useful life of the reservoir. A comparison between the analysis of hydrographic data using mathematical procedure (Empirical Area Reduction Method) for prediction of sediment deposition and that using mathematical model has also been highlighted.