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 , 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 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 construction contract was awarded to China's Sinohydro Corporation. The contract is worth $2 billion and was to be funded with direct investment from China. 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, and in length will be constructed at the dam's left abutment. They will have discharge capacities of and respectively. To divert the water, two roller-compacted concrete cofferdams will be constructed. The upstream cofferdam will be high and the downstream . 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 tall and long variable-radius arch dam. It will be wide at its crest and  wide at its base while being composed of of concrete. The dam's reservoir will have a normal capacity of and an active or "useful" capacity of . At a normal elevation of above sea level, the reservoir will have a surface area of , maximum width of and length of . Its catchment area will be . The dam will contain two spillways. The main service spillway will be an diameter tunnel in the right abutment with two flood gates. The discharge capacity of this spillway will be . The second spillway will be two radial gates on the dam's orifice with a  discharge capacity of . The dam's powerhouse will be located underground at the left abutment. It will be long, high and wide; containing 6 x 250 MW vertical Francis turbine-generators. Before reaching the power station, water will be transferred by six long penstocks. Feeding water to the penstocks is a long headrace tunnel with a three gate intake structure.