–Water storage capacity of Tarbela dam has dropped by 40.58% since it began operating
ISLAMABAD: The water storage capacity of Tarbela Dam has been reduced by 40.58 per cent owing to sitting in the reservoir as a per Hydrographic Survey 2017, the adviser to Prime Minister Dr Babar Awan told Senate on Tuesday.
Answering the question of Senator Samina Saeed, he said as per results of Hydrographic Survey 2017 of Tarbela reservoir, since operation the live and gross storage capacities of Tarbela reservoir have reduced by 37.524 per cent and 40.58 per cent respectively.
He said, the best possible arrangement will be to provide an upstream storage to catch the sediment before entering the Tarbela reservoir. There is no provision for raising of Tarbela Dam.
Inflow of sediment is a natural phenomenon and cannot be prevented. However, the Govt. of Pakistan has taken steps for construction of Diamer Basha Dam which will help to reduce the inflow of silt into Tarbela Dam 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 he said, sediment flushing is uneconomical, technically risky, impacts on the existing infrastructure will be overwhelming resulting into increased variation in bed profile of downstream river system will impact on barrage operations with increased sediment entering the canals.
Additionally, it will 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 is neither technically feasible nor economically favourable.
Babar Awan said the relevant departments would be directed to arrange a detailed briefing to upper House of the Parliament on the overall situation of dams.