This is the largest reservoir in Brazil in terms of surface area, situated in the north of the State of Bahia. The dam was built in the hydrologic basin of the River Sao Francisco at a distance of 748 km from its source and 1,912 km from its estuary on the Atlantic coast. The power generation was started on 31 November 1979.

It covers an area of 4,225 km2 with mean depth of 8.6 m and a maximum depth of 30 m. At the maximum elevation of 392.5 m above sea level, the reservoir accumulates 34.1x1.0E+9 m3 of water with a regulated discharge rate of 1,060 m3 sec 1.

The geological formation of the region consists of very ancient rocks of the Brazilian shield, igneous or highly metamorphosed and dating back to the Precambrian era. The soils are predominantly latosol, quartz sand and lithosol. The climate is semi-arid, characterized by very high evaporation rate. Mean annual rainfall ranges between 400 mm and 800 mm and mean annual temperature of 26 27deg C is affected by the water body of the reservoir. The prevailing vegetation consists of caranauba (a type of palm tree), hypoxerophilous and hyperxerophilous shrubs of medium height, and low shrubs. When the water level becomes low, wet areas around the reservoir are cultivated (Q).