The waters are dammed by the Barrage de Serre-Ponçon, a 123 m high earth core dam. The lake is 20 km long and has a maximum width of 3 km, in area it is around 2,800 hectares and holds 1.2 milliard m³ of water.
The lake was created to control water flow, disastrous floods have caused severe damage and loss of live in 1843 and 1856. First proposed in 1895 construction started in 1955 and was completed by 1961, around 3 million m3 of material was moved. As well as water control, sixteen hydroelectric plants use the water and the lake provides irrigation to 150,000 hectares of land.