Estimating RESCON model parameters for efficient sediment flushing in a dam reservoir

Abstract

In this study, we developed a parameter estimation method of a reservoir conservation model that was developed by the World Bank for efficient sediment flushing operation in dam reservoirs. The parameters for sediment flushing operation are flushing discharge, duration, frequency, and necessary reservoir drawdown. The parameter estimation method was applied to Shahpur Dam in Pakistan, in which sediment balance ratio and long-term capacity ratio were used as indicators of flushing efficiency. For efficient flushing of Shahpur Dam, we recommended that bottom outlets at the dam be retrofitted to achieve a flushing discharge of 7.5m(3)/s. The reservoir water elevation should be drawn to a minimum level of 430m, and the flushing operation should be performed annually over a 15-day span. Flushing using these parameters would result in 100% sediment balance, with 69% of original dam capacity recovered in the long term. We also assessed constraints on dam site for successful flushing. The drawdown ratio was 0.72, sediment balance ratio at full drawdown was 1.58, flushing width ratio was 0.88, and top width ratio was 1.23. For every increment of 0.5m(3)/s in flushing discharge, the amount of sediment flushed increased by 0.020-0.025million tonnes. This method can provide guidelines for implementation of sediment flushing operations for reservoir sediment management.