ISLAMABAD – Silting has caused over 40 per cent loss to water storage capacity of Tarbela dam so far. “As per Hydrographic Survey 2017, water storage capacity of Tarbela Dam has been reduced by over 40 per cent due to silting in the reservoir”, official sources told APP here Wednesday. They said since operation, the live and gross storage capacities of Tarbela reservoir had reduced by 37.524 per cent and 40.58 per cent respectively. They said inflow of sediment was a natural phenomenon and could not be prevented. However, construction of Diamer Bhasha dam would help reduce the inflow of silt into Tarbela dam and it would also enhance the life of Tarbela dam up to 35 years, they said. They said Wapda had conducted sedimentation studies in the years 1987, 1991, 1997, 1998, 1999, 2007, 2013 and 2014 for evaluation of possibilities of de-silting Tarbela reservoir.
Quoting studies they said, sediment flushing was uneconomical, technically risky, impacts on the existing infrastructure would be overwhelming resulting into increased variation in bed profile of downstream river system would impact on barrage operations with increased sediment entering the canals.
Additionally, it would accompany the loss of electricity generation at Tarbela and Ghazi Barotha besides the loss of water storage for the irrigation purpose. Hence the de-silting was neither technically feasible nor economically favourable, they concluded.