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Tarbela vital for

food autarky

LAHORE: Tarbela, world's largest earth and rock-filled dam with 85-year life is key factor in self-sufficiency in food and accelerating the pace of economic development.

Wapda sources told APP here on Sunday that Tarbela completed in 1974 under Indus Basin Settlement Plan, had greatly enhanced the agriculture and industrial potential in the country which is now a major support to the economy.

Sedimentation to the extent of 2.521 million acre feet (maf) in Tarbela reservoir since its operation has reduced the gross reservoir capacity from 11.620 maf to 7.3 maf at present.

Billions of units of electricity generated at Tarbela Power Station have reduced the gap between the supply and demand and also save a huge amount of foreign exchange required.

During the year 1997-98, 8.66 maf water was released from the storage which worth Rs 7,794 millions at the rate of Rs 900 per acre foot while the value of 15,108 million mkwh power generated amounts to Rs 453,240 million at 30 paisa per kwh. A total of about Rs 113 billion have been recorded in terms of direct benefits from water releases and power generation during the last 24 years of its operation.

Wapda sources again categorically announced that there would be no water shortage at all for irrigation purpose as Tarbela and Mangla dams despite low monsoon and winter rains in the country, would continue to meet the requirement of current Rabi crop. "Water flow can be diverted through fifth tunnel in case power house received excessive sediment".

Sources said that despite failure of the monsoon and low winter rains this year, 4.1 maf (million acre feet) water in excess of inflow into Tarbela was released from Tarbela Reservoir during the October 99 to February 2000 to meet the requirement of Rabi crop. Following this, 2.1 million acre additional land was benefited for Rabi.

Sources further said that now Wapda was releasing 47,000 cusecs water as per IRSA's indent causing the reservoir to deplete 3 feet daily. After discussion with IRSA (Indus Review System Authority) and provincial secretaries, Irrigation, it has been agreed to reduce releases from Tarbela to 35,000 cfs and to compensate this reduction from Mangla by increasing its outflows from 25,000 cfs to 30,000 cfs.

About the water reservoirs condition at Tarbela and Mangala, sources said the reservoir at Tarbela was filled, however, the water level in Mangla was 13-feet below the target because of scarcity of monsoon and winter rains in its catchment areas.

Sources said initially Tarbela Dam project was designed to have a useful life of 55 years, however, measurement of actual deposition in the reservoir during the last 25 years of its operation indicate that sediment influx had been on the lower side and it was anticipated that with careful operation in future, its storage life could be enhanced to some 85 years. The live storage capacity of reservoir had reduced from (original) 9.68 maf (million acre feet) to 7.3 maf at present.

Sources said that with the yearly cycle of reservoir operation, the delta formation was continuously re-worked and moved down stream coming closer to the dam. On an average rate, the pivot point of delta has been advancing at half-a-mile per year and the pivot point is nine miles upstream dam site at present. The yearly hydrographic surveys reveals that about 200 feet deep sediment deposits have accumulated up to 30 miles upstream the dam.

Sources said that Wapda while meeting the water requirements for Rabi crop, would also fully ensure safety of the structure of the project which he added was paramount.ÑAPP