Reservoir Sedimentation

Abstract

All the reservoirs, big or small, created by constructing a dam across a river are subjected to silting to some extent. This results in reduction of storage capacity affecting the useful life of the reservoir. The problem in India is more severe in the reservoirs which are located in Himalayas where rivers carry more sediment with water as compared to the reservoirs on southern rivers. The two basic parameters of reservoir sedimentation problems are the rate of silting and the pattern of deposition. The deposition of coarser sediment occurs in the upper reaches of reservoir whereas finer sediment reaches the dam and influences the design of outlet works. The weighted average rate of loss of gross storage in Indian reservoirs is 0.44 percent per year. In some reservoirs of run-of-river type schemes, the silting was observed at a very fast rate and these got silted upto the spillway crest in 2 to 7 years such as Maneri Stage-I, Ichari, and Pandoh dams. Nizamsagar and Dhukwan reservoirs have practically lost all its useful capacity. The world over many reservoirs have lost practically all the useful storage. Hence, there is a need to plan and implement the sediment control measures in all the reservoir projects. In this chapter three aspects of reservoir sedimentation i.e. rate of sediment, deposition pattern and sediment control measures are briefly discussed. For more details readers may refer (Asthana, Ref. [2].