Tarbela Hydroelectric Dam
Tarbela Dam on the Indus River in Pakistan is the second largest dam in the world by structural volume. It is located in Haripur District, Khyber Pakhtunkhwa, about 50 kilometres (31 mi) northwest of Islamabad. The dam is 485 feet (148 m) high above the riverbed. The dam forms the Tarbela Reservoir, with a surface area of approximately 250-square-kilometre (97 sq mi). The dam was completed in 1974 and was designed to store water from the Indus River for irrigation, flood control, and the generation of hydroelectric power.

The project is located at a narrow spot in the Indus River valley, at Tarbela in Haripur, shortly located at the point from where the District Swabi starts. Here the river formerly split around a large island close to the left bank. The main dam wall, built of earth and rock fill, stretches 2,743 metres (8,999 ft) from the island to river right, standing 148 metres (486 ft) high. A pair of concrete auxiliary dams spans the river from the island to river left. The spillways, located on the auxiliary dams, in turn consist of two parts. The main spillway has a discharge capacity of 18,406 cubic metres per second (650,000 cu ft/s) and the auxiliary spillway, 24,070 cubic metres per second (850,000 cu ft/s). The outlet works are a group of four tunnels that have been cut through the valley wall at river right, for uses of hydropower generation and flow control. These tunnels were originally used to divert the Indus River while the dam was being constructed. The fifth river outlet is situated on the left side of the dam and was completed in April 1976.

A hydroelectric power plant on the right side of the main dam houses 14 generators fed with water from outlet tunnels 1, 2, and 3. There are four 175 MW generators on tunnel 1, six 175 MW generators on tunnel 2, and four 432 MW generators on tunnel 3, for a total generating capacity of 3,478 MW. Tarbela Reservoir is 80.5 kilometres (50.0 mi) long, with a surface area of 250 square kilometres (97 sq mi). The reservoir holds 11,600,000 acre feet (1.43×1010 m3) of water, with a live storage of 9,700,000 acre feet (1.196×1010 m3). The catchment area upriver of the Tarbela Dam is spread over 168,000 square kilometres (65,000 sq mi) of land largely supplemented by snow and glacier melt from the southern slopes of the Himalayas. There are two main Indus River tributaries upstream of the Tarbela Dam. These are the Shyok River, joining near Skardu, and the Siran River near Tarbela.

The Tarbela Dam is the third largest in terms of dam volume in the world.

Tarbela Dam
Official name Tarbela Dam
Locale Tarbela, Pakistan
Construction began 1968
Opening date 1974
Construction cost USD 1,497 Million
Dam and spillways
Height 143.26 metres (470 ft) from river level
Length 2,743.2 metres (9,000 ft)
Impounds Indus River
Creates Tarbela reservoir
Capacity 13.69 cubic kilometres (3.28 cu mi)
Catchment area 168,000 km2
Surface area 250 km2
Power station
Turbines 10 x 175 MW, 4 x 432 MW
Installed capacity 3478 MW
Maximum capacity 4200 MW