ISLAMABAD – The water storage capacity of Tarbela Dam has been reducedby40.58 percent owing to silting in the reservoir as a per HydrographicSurvey 2017, Advisor to Prime Minister Dr BabarAwan told Senate on Tuesday.

Answering the question of Senator Samina Saeed, he said as per results ofHydro graphic Survey 2017 of Tarbela reservoir, since operation the liveand gross storage capacities of Tarbela reservoir have reduced by 37.524%and 40.58% respectively.

He said, the best possible arrangement will be to provide an upstreamstorage tocatch the sediment before entering the Tarbela reservoir. There is noprovisionfor raising of Tarbela Dam.

Inflow of sediment is a natural phenomenon and cannot beprevented.However,the Govt. of Pakistan has taken steps for construction ofDiamer Basha Dam which will help to reduce the inflow of silt into TarbelaDam Wapda had conducted sedimentation studies in the years 1987, 1991,1997, 1998, 1999, 2007, 2013 and 2014 for evaluation of possibilities ofde-silting Tarbela reservoir.

Quoting studies he said, sediment flushing is uneconomical, technicallyrisky, impacts on the existing infrastructure will be overwhelmingresulting into increased variation in bed profile of downstream riversystem will impact on barrage operations with increased sediment enteringthe canals.

Additionally, it will accompany the loss of electricity generation atTarbela and Ghazi Barotha besides the loss of water storage for theirrigation purpose. Hence the de-silting is neither technically feasiblenor economically favourable.

Babar Awan said the relevant departments would be directed to arrange adetailed briefingto upper House of the Parliament on overall situation of dams.