The Tarbela Dam and Reservoir, Pakistan – January 30th, 2009
The Tarbela Dam is a large dam, completed in 1974, on the Indus River in Pakistan. It is located about 50 kilometers northwest of Islamabad, in the Tarbela Valley.
The Tarbela Reservoir, created by the dam, is easily spotted in the center of the image; the dam is located at the southernmost extremity of the reservoir.
With a height of 485 ft (148 m) above the river bed and a reservoir size of 95 square miles (250 km2), it is the largest earth filled dam in the world.
The dam was designed to store water from the Indus River for irrigation and flood control by maintaining the flow of the Indus during seasonal fluctuations, and for the generation of hydro-electric power. It is a major source of Pakistan’s total hydroelectric capacity.
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.
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. Some such sediments are visible in the upper part of the reservoir and throughout the Indus River.
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. 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.