Los Reyunos Dam, Embankment dam and hydroelectric station in San Rafael, Argentina.

Los Reyunos is a stone-and-clay embankment dam on the Diamante River, 35 km from San Rafael in Mendoza Province. Its 134 m wall holds a 750-hectare reservoir, and a pumped-storage station below the water level generates 224 MW. The photograph shows white buildings with arched openings on the slope and a floating blue-roofed platform.

Built between 1973 and 1983 across the Diamante canyon, the dam is an embankment structure of compacted stone and local clay rising 134 m. Its reservoir, holding 220 hm³ at maximum level, regulates floods on the Diamante basin and feeds a 224 MW pumped-storage station generating about 305 GWh a year.

The Los Reyunos Fishing and Nautical Club on the western shore is the base for windsurfing, canoeing and sport fishing; the reservoir is stocked with Salmonidae and silverside. Private summer residences and a hotel stand beside it, and weekend houses, restaurants, campsites and cabins line the shores.

The best access is from nearby San Rafael, which serves as the main entry point. Visitors should know that the area can be hot and dry, especially during the summer months.

The power station sits below the reservoir's water level, reached by an access road that runs under the lake surface. At night, when demand drops, its turbines reverse to pump water from the smaller El Tigre compensation dam about two kilometres downstream back up into Los Reyunos, using roughly 20.2 GWh a year for the pumping.