Itaipú Dam (25°24'50" S, 54°35'34" W), located on the Paraná River at the Brazil/Paraguay border, is the world’s largest hydroelectric power facility. Completed in 1991, the dam is a joint effort of of the governments of Brazil and Paraguay. The Paraná River is the seventh largest river in the world and the second largest in South America. The river meanders through Brazil, the border of Paraguay, then south through Argentina until finally entering the ocean at the Rio de la Plata (Silver River) estuary in Uruguay. Severe droughts in the region initially motivated the construction of the dam, as both governments wanted to ensure sufficient water supplies for their people. Itaipú is an indigenous word meaning “singing stones;” it was the name of an isle near the site of the dam.
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In 1966, the Ministers of Foreign Affairs of both Brazil and Paraguay signed the “Act of Iguaçu.” A study was carried out under this Act that assessed the potential hydraulic resources of the Paraná River, which is jointly occupied by the two countries. In 1967, the Brazilian-Paraguayan Joint Technical Commission was established to carry out the study and the development of the Paraná River. The construction of the dam began in 1975 and was not completed until 1991.
The main structure, a hollow, concrete gravity dam, has a powerhouse capable of generating 14,000 megawatts (MW) of electricity (12,600 MW in the original construction plus 1,400 MW added in 2006). The main powerhouse has 18 Francis turbines each with a rated power of 715 MW. The spillway is located on the right bank, and it has 14 segmented sluice-gates with a total discharge rate of 62,200 cubic meters per second. Itaipú provides 25 percent of Brazil's energy supply and 78 percent of neighboring Paraguay's energy supply.
The Itaipú Reservoir is 170 km long with an area of 1.35 km2 and has a volume at maximum normal level of 29 x 109m3. Approximatey 4 million people were resettled during the construction of Itaipú.
During its construction, workers shifted the course of the seventh largest river in the world by removing 50 million tons of earth and rock to dig a 1.3-mile bypass. The main dam, as high as a 65-story building, is composed of hollow concrete segments, while the flanking wings are earth- and rock-filled. The volume of iron and steel utilized in the dam structure would be enough to build 380 Eiffel Towers, and the volume of concrete used in Itaipú represents 15 times the volume utilized to build the Channel Tunnel between France and England. Itaipú is one of the Seven Wonders of the Modern World, according to a worldwide survey conducted by the American Society of Civil Engineers.