The impact of suspended sediment load on reservoir siltation and energy production: A case study of the Indus River and its tributaries

Suspended sediments load estimation in the Indus River and its important tributaries in Khyber Pakhtunkhwa, Pakistan is presented to determine siltation in major reservoirs in the area and to create a strategy to minimize and/or control this risk for the enhancement of hydel energy production, irrigation, and other domestic purposes. The study area is part of an orogenically active region along the northwestern collision zone of Indian-Eurasian plates. During spring and summer suspended sediment load is highest, but least in winter. Sediment load of all rivers studied is directly proportional to the melting of glaciers and/or high rainfall during spring and summer. Glacier melt, rainfall, lithology of rocks (shale, slate, phyllite, mudstone, and siltstone), discharge, and other anthropogenic factors caused the high suspended load in rivers. Mostly the fine sediments settle during winter due to flow velocity of rivers reducing appreciably and residence time of water increasing in reservoirs. The high sediment influx deposition in major reservoirs like the Terbella and Warsak, etc. reduces their storage capacity as well as power generation capacity. So it is proposed that life span of these reservoirs can be lengthened by the construction of small check dams (silt control dams) on upstream, dam cleaning tactics, effective watershed management, extensive afforestation on the steep mountain slopes upstream of the lake, and the use of runoff rivers for electricity generation using steep gradient and fast flow velocity.