Lac du Chambon, Reservoir in Isère, France

Lac du Chambon is a reservoir on the Romanche in Isère, held back by the Chambon dam at 1,040 m elevation. It fills the valley floor between Le Bourg-d'Oisans and the Lautaret pass, its opaque turquoise water edged by pale stony shoreline below forested slopes. The dam, the highest in Europe when completed, stands at the downstream end.

The Chambon dam was built by Campenon-Bernard between 1929 and 1935 on the Romanche, and when filling began on 24 April 1935 it submerged the villages of Chambon, Dauphin and Parizet along with the old Oisans road. At the time it was the highest dam in Europe. A chapel near the reservoir commemorates the roughly thirty workers who died during construction, and President Albert Lebrun inaugurated the dam.

The lake takes its name from the village of Chambon, submerged with Dauphin and Parizet when filling began on 24 April 1935. When the reservoir is emptied for dredging, the old valley road and the ruins of the drowned hamlets reappear on the lakebed. A chapel near the reservoir commemorates the roughly thirty workers who died building the dam.

The lake lies along the D1091 between Le Bourg-d'Oisans and the Col du Lautaret, upstream of Le Freney-d'Oisans and downstream of La Grave. The D1091 runs beside the water, and the reservoir is drawn down for maintenance, exposing the old valley road and the ruins of the drowned hamlets. The Ferrand torrent is diverted through a penstock that passes under Mizoën and discharges straight into the lake; this flow stops during full drawdowns.

Beneath the water lies an old road that once connected the sunken villages. This pathway becomes visible during maintenance operations and offers a window into the landscape that existed before the dam.