The Bakhtiari Dam is a planned arch dam

Arch dam

An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes...

 on the Bakhtiari River

Bakhtiari River

The Bakhtiari River is a river in Iran and a tributary of the Dez River in southwestern Iran. Before forming the Dez, the Bakhtiari has a confluence with the Sezar River....

 within the Zagros Mountains

Zagros Mountains

The Zagros Mountains are the largest mountain range in Iran and Iraq. With a total length of 1,500 km , from northwestern Iran, and roughly correlating with Iran's western border, the Zagros range spans the whole length of the western and southwestern Iranian plateau and ends at the Strait of...

 in Lorestan Province

Lorestan Province

Lorestan Province is a historic territory and province of western Iran, amidst the Zagros Mountains. The population of Lorestan was estimated at 1,716,527 people in 2006.Lorestan covers an area of 28,392 km²...

, Iran

Iran

Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

. At a planned height of 315 metres (1,033.5 ft), it will be the world's tallest dam once completed and withhold the largest reservoir in Iran. 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

Dez Dam

The Dez Dam is a large hydroelectric dam built in Iran in 1963 by an Italian consortium.The dam is on the Dez River in the Northwestern province of Khuzestan, the closest city being Andimeshk. It is high, making it one of the highest in the world, and has a reservoir capacity of...

 50 km (31 mi) 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 of 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

Sinohydro Corporation

Sinohydro Corporation is a Chinese state-owned hydropower engineering and construction company. It is the world's largest hydroelectric company...

 who is also working with Farab Co. of Iran. The contract is worth $2 billion and is being funded with direct investment from China. Sinohydro signed the 118 month contract on March 15, 2011 and will be working with Iran's Farab.

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 (3,776 ft) and 1180 m (3,871 ft) 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

Roller-compacted concrete

Roller-compacted concrete or rolled concrete is a special blend of concrete that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of fly ash for Portland cement. RCC is a mix of cement/fly ash, water, sand, aggregate...

 cofferdam

Cofferdam

A cofferdam is a temporary enclosure built within, or in pairs across, a body of water and constructed to allow the enclosed area to be pumped out, creating a dry work environment for the major work to proceed...

s will be constructed. The upstream cofferdam will be 51 m (167 ft) high and the downstream 25 m (82 ft). Material to construct the dam including aggregate

Construction Aggregate

Construction aggregate, or simply "aggregate", is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined material in the world...

 will come from the actual excavation of the dam site along with three quarries in the area.

Design

The Bakhtiari will be a 315 m (1,033 ft) tall and 434 m (1,424 ft) long variable-radius arch dam. It will be 10 m (33 ft) wide at its crest and 30 m (98 ft) wide at its base while being composed of 3100000 cubic metre of concrete. The dam's reservoir

Reservoir

A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

 will have a normal capacity of 4845000000 cubic metre and an active or "useful" capacity of 3070000000 cubic metre. At a normal elevation of 830 m (2,723 ft) above sea level, the reservoir will have a surface area of 58.7 km² (23 sq mi), maximum width of 1 km (0.621372736649807 mi) and length of 59 km (37 mi). Its catchment area

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 will be 6288 km² (2,428 sq mi).

The dam will contain two spillway

Spillway

A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...

s. The main service spillway will be an 11 m (36 ft) 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

Underground power station

An underground power station is a type of hydroelectric power station constructed by excavating the major components from rock, rather than the more common surface-based construction methods....

 at the left abutment. It will be 161 m (528 ft) long, 64 m (210 ft) high and 24 m (79 ft) wide; containing 6 x 250 MW vertical Francis turbine

Francis turbine

The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts....

-generators. Before reaching the power station, water will be transferred by six 51 m (167 ft) long penstock

Penstock

A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills....

s. Feeding water to the penstocks is a 504 m (1,654 ft) long headrace tunnel with a three gate intake structure.