The El Chocón Dam is the fourth of the five dams on the Limay River in the northwestern Argentine Patagonia (the Comahue region), at 381 m above mean sea level. El Chocón Cerros Colorados is on the Limay River at about 80 km upstream of its confluence with the Neuquén River. El Chocón Cerros Colorados is used to regulate the flow of the Limay River, for irrigation, and for the generation of hydroelectricity. Its power station is the largest hydroelectric power plant in Patagonia, with a capacity of 1260 MW. It was built by the state-owned company Hidronor (Hidroeléctrica Norpatagónica). It started operating in 1973 and achieved full capacity in 1978. In the period 1974–1995, it produced an annual average of 2,700 GWh. In 1993 it was privatized, with an exploitation concession granted to Hidroeléctrica El Chocón S. A. While the formal name of the project is Embalse Ezequiel Ramos Mexía, in common use it ended up acquiring the name of the settlement that served as the construction's base of operations, Villa El Chocón (a small town, population 957, as of 2001). El Chocón is part of a larger engineering scheme that also includes the Cerros Colorados Complex, on the Neuquén River. The Hydroelectric Complex which holds El Chocón and Arroyito Hydroelectric Power Plants, is located in the region known as Comahue, which is formed by the Argentine provinces of Río Negro and Neuquén and the southern area of the Buenos Aires and La Pampa provinces.

Technical details

The dam is made of earth, with a concrete spillway. About 13000000 m3 of materials were used. It measures 2500 m in length. Its maximum height over the river bed is 87 m. The reservoir has a maximum area of 860 km2, a mean depth of 24.7 m (maximum 60 m), and a maximum volume of 206000000000 m3. It is used for sailing, sport fishing and other forms of recreation by locals and tourists. The power plant has six vertical Francis turbines, with a nominal power of 210 MW each, which rotate at 88 rpm. The apparent powers are 200 MVA for each generator and 180 MVA for each transformer. Material: Hidroeléctrica El Chocón S.A.