Impact of reservoir operation on sediment deposition

Every year, reservoir sedimentation causes an estimated 1% reduction in the total capacity of reservoirs. When sediment deposits approach the dam, further issues related to sediment passing through the turbines, blocking of the outlets and dam safety arise. One of the possible ways to tackle these problems is by management of the sediment in the reservoir itself through a selected operation strategy. A long-term reservoir sedimentation model, Ressass, is used to explore the impact of reservoir operation on sediment deposition. This paper explores the influence of different water level management strategies that result from water supply and hydropower demands. The results show that preserving the live storage may increase the rate of approach of sediment deposits towards the dam. The findings may support reservoir managers when facing these sometimes opposite objectives. To illustrate the analysis, different theoretical strategies are applied to a case study of Tarbela, the largest dam and reservoir on the River Indus in Pakistan.