Clearing silt of the dam was technically feasible but WAPDA’s obstinate attitude did the damage: Fazlullah Quresh.
Can silt be flushed out of Tarbella Dam which continues depleting its reservoir capacity over the last many years? This question led us to a project which its supporters claim was not only a practical one but also could save billions of rupees that Pakistan plans to spend on construction of Bhasha Dam.
Former Secretary Planning Fazlullah Qureshi told Engineering Review that Tarbella Dam could be cleared off the sit which was reducing the storage capacity of the reservoir. Back in the 1990s, the international experts had offered to clear Tarbella Dam of accumulating silt which slips down to the pond from Korakoram range upstream of the Indus River.
Tarbella Dam which was built after Pakistan and India signed Indus Basin Treaty had a design water storage capacity of 9.5 million acre-feet that has now reduced to 6.3 million acre-feet because the silt has accumulated into a mammoth island spread over many miles.
Now Pakistan government and the Chief Justice of the Supreme Court of Pakistan (SCP) are super active to build a replacement dam—Diamer Bhasha Dam costing over US$13 billion. It is a concrete-filled gravity dam which would store 8.5 million acre-feet, produce 4500 megawatts of energy and also extend the life of Tarbela Dam located downstream by 35 years.
Mr. Qureshi who also supports the construction of Bhasha Dam said they had invited international experts for clearing the silt off the dam and they presented a practical plan which cost little less than US$1 billion.
As per the plan, a wall was supposed to be erected in front of the silt delta on the right abutment where the water is released for power generation so that the flows do not affect the turbines.
On the left side where irrigation supplies flow downstream of the dam, an extra tunnel was to be created in addition to tunnel six. With the passage of time, the silt was expected to be softened and thus to be passing downstream through both tunnels (Tunnel 6 and 7). It was a continuous process which at least would have maintained the storage capacity of the dam.
The report of the international experts was referred to the Indus River System Authority (IRSA). The then Chairman IRSA Fateh Azam and Sindh member A.R Memon approved the plan. But WAPDA refused to give its nod as it would put an end the prospects of the construction of Kalabag Dam because the releasing silt which was supposed to be cleared of Tarbella Dam was to accumulate in the gorge downstream at the project silt of Kalabag Dam. (By Engineering Review Research Desk).
