Tarbela Dam

Tarbela Dam (Urdu: تربیلا بند ) is a large dam on the Indus River in Pakistan. It is located about 50 kilometers northwest of Islamabad, and a height of convert|485|ft|m|abbr=on above the river bed and a reservoir size of convert|95|sqmi|km2 makes it the largest earth filled dam in the world. The dam was completed in 1974 and was designed to store water from the Indus River for irrigation and flood control, and for the generation of hydro-electric power.

History

The Tarbela Dam is a major source of Pakistan's total hydroelectric capacity. It is part of the Indus Basin Project which resulted from a water treaty [http://www.waterinfo.net.pk/pdf/iwt.pdf treaty detail] signed in 1960 between India and Pakistan guaranteeing Pakistan water supplies independent of upstream control by India. The project was funded by the World Bank. Construction began in 1968, and continued until completion in 1976. The dam has a volume of 138,600,000 cubic yards (106,000,000 m³). With a reservoir capacity of 11,098,000 acre-feet (13.69 km³), the dam is approximately 143 m high and 8,997 feet (2,743 m) wide at its crest. It helps to maintain the flow of the Indus during seasonal fluctuations. [Structurae|id=s0003769
title=Tarbela Dam. Retrieved on 2007-07-09.]

A new, smaller hydro-electric power project has been developed downstream known as the Ghazi Barotha Hydel Power Project. It is solely for generating electricity and has a water channel with the highest flow in the world.

While the dam has fulfilled its purpose in storing water for agricultural use in Pakistan, there have been environmental consequences to the Indus river delta. Reduction of seasonal flooding and reduced water flows to the delta have decreased mangrove stands and the abundance of some fish species.

Tarbela is a beautiful valley surrounded by mountains. It is divided in different colonies like Sobra City, Right Bank Colony, Sanobar Colony and Mehran Colony. Many of the residents are employees of the Water And Power Development Authority (WAPDA) of Pakistan.

Life span

Because the source of the Indus River is the monsoonal rainfall over the Himalayas, the river carries huge amounts of sediment. The annual suspended sediment load is about 430 million tonnes per year. This means that, over time, the reservoir will fill with sand and will overflow, causing a huge flood as the river is released. The useful efficiency of the dam and reservoir are estimated to be somewhere around fifty years, since the dam's completion in 1976, meaning that the reservoir will be full of sediment within 20 years.

Sedimentation however, has been much lower than predicted due to the Tarbela Reservoir and it is now estimated that the useful life-span of the dam will be 85 years [Lorrai, C and Pasche, N. 'Tarbela Dam-Case Study' Swiss Federal Institute of Technology Zurich: April 2007]

Notes