Bakhtiari Dam

The Bakhtiari Dam is an arch dam currently under construction on the Bakhtiari River within the Zagros Mountains on the border of Lorestan and Khuzestan Provinces, Iran. At a planned height of 325 m, it will be the world's tallest dam once completed and withhold the second largest reservoir in Iran after the Karkheh reservoir. The main purpose of the dam is hydroelectric power production and it will support a 1,500 MW power station. By trapping sediment, the dam is also expected to extend the life of the Dez Dam 50 km downstream.

Background
Preliminary studies for the dam began in 1996 and were carried out by Mahab Qods Consulting Engineers. The studies were carried out over a period of 33 months and in March 2000, the results were given to Iran Water & Power Resources Development Co (IWPCO). In May 2005, IWPCO awarded consultation services for the project to Moshanir Consulting Engineers, Dezab Consulting Engineers, Econo-Electrowatt/Boyri and Stucky Pars Consulting Engineers. On April 30, 2007 the $2 billion construction contract, to be funded with direct investment from China, was awarded to China's Sinohydro Corporation. Sinohydro signed the 118-month contract on March 15, 2011 and was expected to be working with Iran's Farab. But the Iranian government rejected Sinohydro's bid in late May 2012 and handed the project over to Khatam-al-Anbiya (KAA), which is controlled by the Iranian Revolutionary Guard Corps. The KAA commander announced on 19 December 2012 that construction of the dam had begun with access roads leading to the project site. On 25 March 2013, Iranian President Mahmood Ahmadinejad attended a groundbreaking ceremony for the dam, initiating its construction.

Construction
During construction, a total of six bridges will be built to support workers, vehicles and equipment in addition to various access roads. To divert the river, two tunnels, 1151 m and 1180 m in length will be constructed at the dam's left abutment. They will have discharge capacities of 2090 m3/s and 1680 m3/s respectively. To divert the water, two roller-compacted concrete cofferdams will be constructed. The upstream cofferdam will be 51 m high and the downstream 25 m. Material to construct the dam including aggregate will come from the actual excavation of the dam site along with three quarries in the area.

Design
The Bakhtiari will be a 325 m tall and 434 m long variable-radius arch dam. It will be 10 m wide at its crest and 30 m wide at its base while being composed of 3100000 m3 of concrete. The dam's reservoir will have a normal capacity of 4845000000 m3 and an active or "useful" capacity of 3070000000 m3. At a normal elevation of 830 m above sea level, the reservoir will have a surface area of 58.7 km2, maximum width of 1 km and length of 59 km. Its catchment area will be 6288 km2.

The dam will contain two spillways. The main service spillway will be an 11 m diameter tunnel in the right abutment with two flood gates. The discharge capacity of this spillway will be 5830 m3/s. The second spillway will be two radial gates on the dam's orifice with a discharge capacity of 1510 m3/s. The dam's powerhouse will be located underground at the left abutment. It will be 161 m long, 64 m high and 24 m wide; containing 6 x 250 MW vertical Francis turbine-generators. Before reaching the power station, water will be transferred by six 51 m long penstocks. Feeding water to the penstocks is a 504 m long headrace tunnel with a three gate intake structure.