Saturday, May 28, 2011

Desilting to prolong Tarbela Dam`s life.

Wapda, the Water and Power Development Authority, has decided to remove silt from the Tarbela Dam reservoir.

Official sources told that two multinational consultant companies would start studying the feasibility of the project next month. The World Bank has pledged $3 million for the study, the sources said.

Wapda conducted five such studies in the past but none was implemented for one reason or the other, an official said, adding that desilting would enhance the life of Tarbela Dam which is the biggest sources of hydel power generation in the country.

According to the official Wapda has engaged the consultant firms HR Walling Ford and Mott Macdonald Pvt Limited Pakistan for preparing a feasibility report on enhancing the dam`s life, the methodology of removing sediment, the volume of funds required should it be dredged or flushed out, and the time required for completing the project. The feasibility part of the project reportedly would be completed within 15 months.

Wapda`s annual report said sediment had been increasing in the dam because of rampant deforestation in the 65,500 square miles catchments of Indus River.

A delta that has developed three or four kilometers upstream is a lurking danger for the power house. The size of delta, according to official sources, was 50 miles long, 1 to 2 miles wide and its depth was estimated at around 200 feet.

The ever growing sediments in the reservoir have reduced the usable storage capacity to 6.77 Million-Acre Feet which was 9.68 MAF when this gigantic dam was constructed back in 1974. Tarbela Dam was built at a cost of $3 billion during 1968-1974 after inundating over 100 villages of Haripur district alone and displacing a vast population. Tarbela Dam is the biggest source of hydel power generation in the country and it contributes 3,478 megawatts of electricity from its 14 generating units. Work on the fourth extension project, commonly known as tunnel No.4, is also likely to start by the end of this year which would generate another 960 megawatts.