Sedimentation in Mangla Reservoir – Effects on Power Generation System and Mitigation Measures

Mangla reservoir is the second biggest reservoir in Pakistan. It was constructed in 1967 as multipurpose dam project with priority for irrigation. It has a live storage of 5.34 MA which is used to transfer water from high flow season to low flow season. It has a power house with installed capacity of 1000 MW. Since its operation in 1967 it has lost about 20% of live storage. The pivot point of sediment delta has moved to about 4 miles away from the dam. The river intakes are in close proximity of the dam on left side of the main embankment. Sedimentation studies of Mangla Dam Raising Project revealed that after about 25 years pivot point of delta would reach the power intakes. To stop the rate of advancement of delta towarqs the dam operational rules of reservoir have been studied. Increasing the Dead Storage Level (DSL) from the existing value of 1040 ft asl to 1100 ft asl delayed the time of reaching the delta by 10 years, however the intakes remain under threat. To address the said challenge of sediment ingress into the power intakes certain measuresl strategies are required to be studied and implemented. This paper studies the like threat of sediment ingress into the power intakes by studying vertical concentration of sediment in the water column in front of the power intakes at the point of quasi equilibrium state of the reservoir. On the basis of the computed vertical concentrations, placement as well as type of the intakes would be suggested.