Pakistan is an agricultural country that depends on rain to get water for irrigation. Pakistan has around 150 dams spread across all the provinces. These dams not only help in electricity generation and for supplying water but they also provide perfect recreational spots for the local people.
The Indus River basin extends from the Himalaya Mountains that form to the alluvial plains of Sindh near the Arabian Sea coastline. Tarbela Dam is part of the Indus Basin Project, which resulted from a water treaty signed in 1960 between India and Pakistan. This treaty guaranteed Pakistan water supplies independent of upstream control by India. Designed primarily for water storage rather than power generation, the dam was completed in 1977.
Tarbela Dam is one of the world’s largest earth and rock filled Dam and greatest water resources development project in Pakistan. Dam is located on the river Indus at a distance of 130 KM (50 Miles) to the North West of Islamabad, in district Sawabi, KPK. The World Bank accepted Tarbela Dam Project as a part of the Settlement (Replacement) plan under Indus water treaty in 1965. WAPDA has entrusted with its execution on behalf of the Government of Pakistan.
Turquoise waters of the Indus River (to the south of the dam) reflect the high proportion of silt and clay suspended in waters released by the spillways. 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.
The Tarbela Dam Project involved the construction of an earth and rock-fill dam on the River Indus and a power plant. Maximum height of the main embankment from the lowest foundation point is 470ft and length is 9,000ft at its crest. The dam required 138 million cubic yards of fill. The main embankment is flanked by two auxiliary embankments on the left bank. The maximum height of one of the auxiliary embankments is 345ft, while that of the other is 220ft. The lengths at crest are 2,340ft and 960ft respectively. The two auxiliary embankments carry two spillways, the service spillway and the auxiliary spillway. The service spillway is fitted with seven gates and has a discharge capacity of 650,000cusec. The auxiliary spillway with its nine gates can discharge 850,000cusec. The valley wall on the right bank, at the upstream end, was cut through to build a group of four tunnels. Three of these tunnels were intended for hydro-power generation, while the fourth tunnel is used for irrigation releases. The Tarbela hydro power plant is constructed on the right side of the main embankment. It is installed with 14 power generating units and the water is fed from outlet tunnels one, two and three. The plant has a total installed capacity of 3,478MW.
The primary purpose of the Tarbela Dam Project was to regulate the flows of the Indus River for irrigation use. Other objectives were to achieve substantial generation of hydroelectric power and flood control by conserving snow melt and monsoon flows of the Indus River.
by: Abeer Arshad
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