Simulating Reservoir Management under the Threat of Sedimentation: The Case of Tarbela Dam on the River Indus

The useful life of Tarbela reservoir, on the River Indus, is threatened by a sediment delta which is approaching the dam'sintake tunnels; these lead to a hydroelectric power station and are used for irrigation releases. This article describes thesimulated system, involving Tarbela Dam, with Ghazi Barotha hydropower scheme downstream, and the planned construction of Basha Dam upstream. This study formed an innovative approachwhich enabled the relationship between demands and supply in the basin to be studied, under a range of development and operating scenarios, and to different time horizons. A computer software package, 'Hydro', was used to perform systemsimulation modelling of Tarbela Dam and the Upper Indus Basin,Pakistan. The results enabled estimation of the economic benefits of several potential future operating strategies forTarbela to be tested and compared. Employing the results of associated sediment modelling, projected storage/elevation curves were used to predict the irrigation and power benefitsavailable to Pakistan over the coming sixty years. It wassubsequently demonstrated that the most beneficial remedial measures are an underwater dike or dam to protect the intakes,and low-level flushing facilities.