The Xiaowan Dam () is an

arch dam An arch dam is a concrete dam that is curved upstream in plan. The arch dam is designed so that the force of the water against it, known as hydrostatic pressure, presses against the arch, causing the arch to straighten slightly and strengthen ...

on the Lancang (Mekong) River in

Nanjian County Nanjian Yi Autonomous County () is a county in the Dali Bai Autonomous Prefecture located in the west central part of Yunnan province, China. Administrative divisions Nanjian Yi Autonomous County has 5 towns and 3 townships. ;5 towns ;3 townsh ...

Yunnan Province Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...

, southwest China. The primary purpose of the dam is

hydroelectric Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...

power generation and it supports a 4,200 MW power station. Constructed between 2002 and 2010 by

Huaneng Power International Huaneng Power International, Inc. (HPI), commonly known as Huaneng Power, is a Chinese electric power company. It was established in 1994 by the China Huaneng Group, one of the five largest power producers in China. It engages in the development, ...

at a cost of ¥32 billion (nearly

US$ The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...

3.9 billion), it is the world's second highest arch dam at . It is also third highest among dams of all types behind Jinping-I and Nurek and the third largest hydroelectric power station in China.

Background

The feasibility study for the dam was completed in 1992, with it as part of the Lancang River Project. In 1995 the report was reviewed and approved by the Chinese government. Three years later in 1998, a consortium to fund and construct the dam was organized. In 1999, preliminary construction (roads, bridges, river diversion) began. Official construction on the dam started on 1 January 2002. The river was diverted by November 2003 and concrete pouring began in 2005. The river diversion was closed and the reservoir began to impound in November 2007. The first generator was commissioned in September 2009 and the dam was complete in March 2010. The last of the six generators went operational on 22 August 2010. The creation of the dam's reservoir submerged of land and displaced 32,737 people.

Specifications

The Xiaowan Dam is a tall and long double-curvature arch dam. Its crest is wide while the base sits at in width. The dam's crest is at an elevation of while the normal reservoir level is slightly lower at . The dam's reservoir has a normal storage capacity of ; of that capacity, is active (or "useful") storage. The dam traps water from a

catchment area In human geography, a catchment area is the area from which a location, such as a city, service or institution, attracts a population that uses its services and economic opportunities. Catchment areas may be defined based on from where people are ...

covering . The surface of the reservoir at normal level covers . Helping to control floods, the dam has two spillways, 5 gates near the crest and a tunnel on the left bank. The gates can discharge up to while the tunnel has a maximum discharge of . In the middle portion of the dam, there are six orifice openings that can discharge . In addition, the dam can release additional water and sediment with two bottom outlets. All of the dam's outlets including the power station give it a maximum flood discharge of . On the right bank of the dam is the power station intake which receives water into six diameter

penstock A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydro turbines and sewerage systems. The term is inherited from the earlier technology of mill ponds and watermills. H ...

s which each feed a 700 MW

Francis turbine The Francis turbine is a type of water turbine. It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today, and can achieve over 95% efficiency. The proces ...

-turbine in the

underground power station An underground power station is a type of hydroelectric power station constructed by excavating the major components (e.g. machine hall, penstocks, and tailrace) from rock, rather than the more common surface-based construction methods. One or mor ...

. The drop in elevation from the intake to the turbine affords a maximum

hydraulic head Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum., 410 pages. See pp. 43–44., 650 pages. See p. 22. It is usually measured as a liquid surface elevation, expressed in units of length, ...

of . Once discharged by the turbine, the water is sent down one of two diameter tailrace tunnels towards the river.

References

{{Dams on Mekong River Basin Hydroelectric power stations in Yunnan Dams in the Mekong River Basin Dams in China Arch dams Dams completed in 2010 Underground power stations 2010 establishments in China Energy infrastructure completed in 2010 Buildings and structures in Dali Bai Autonomous Prefecture Buildings and structures in Lincang

Background

Specifications

See also

References