The swellings of the affluents of the Limay and Neuquén Rivers and of the Black River (Río Negro) became catastrophic floods for the population and for the productive areas of the High and Medium Valleys prior to the construction of El Chocón Complex –Cerros Colorados. Floods like those in the years 1945 and 1951 and others previous to these periods caused serious damage, not only the overflow in urban and rural areas but also the uncontainable erosion of harvested areas.

In the year 1967, the state administration created the company Hidroelectrica Norpatagónica S.A. (HIDRONOR S.A) with the purpose of developing the exploitation of hydraulic energy in the Limay and Neuquén Rivers.

By the end of the year 1968, HIDRONOR S.A. started the first work stations, camps and access. The construction of El Chocón Complex began. Due to the dimensions and power installed of the work, the complex would become a fundamental piece for the energy system of the country.

December 1972 was the start-up date for the first turbine of El Chocón Plant. The construction works finished in the year 1977 with the Qualification of the sixth generator. With a view to optimize the use of the hydraulic resource, the construction of the compensator Dike Arroyito began in the year 1976. It is located dowstream from El Chocón. This work achieved its aim of attenuating the flow of water by discharges made through the openings in the spillway until the year 1982. The first turbogroup started operating in July 1983 and the third and last turbogroup was qualified in March 1984.

The company was granted in concession as from 11th August 1993 for a 30 years’ effective term to consortium HIDROINVEST S.A, a holding partership with a 59% controlling interest.

With the filling of the reservoir of the dam of El Chocón, important floods reported in the years 1977, 1980, 1982, 1984, 1993, 2001 and 2002 were atenuated by means of the artificial reservoir without causing any serious damage downstream.
Since the end of 1990, the dam in Piedra del Aguila, upstream El Chocón, has contributed with additional capacity for the atenuation of overflow.

The extended droughts recorded in the years 1988, 1989 and 1990 tested the holding capacity of the reservoir of the dam of El Chocón, which purpose is to satisfy human consumption and irrigation in periods of shortage. Even in periods of serious drought, particularly in the years 1998 and 1999, El Chocón was able to comply with the consumptive use then with a record 43% lower than the historic record of minimal flow.