The lake lies on
Jurassic rock crushed into north to south ridges by the
Alpine orogeny. It is therefore long and narrow, though rather sinuous in plan. It is about 30 kilometres long though only 21 km in a straight line. It lies in the valley of the Ain, impounded by the dam at
Cernon. The old village of Vouglans was displaced by its construction in 1968 by
Électricité de France (EDF). Some buildings of the
Carthusian monastery of Vaucluse were also moved to make way for the rising waters and to save them from demolition. The lake is arranged for tourism with view-points scattered through the woods which cover the hillsides along its shores and places set up for bathing and boating. The annual mean flow of water at the dam is 40.80 cubic metres per second. ==Statistics==