Lake of Émosson, Reservoir in Valais, Switzerland

Lake of Émosson is a reservoir in the Valais canton, held back by a 180 m high arch dam completed in 1974. It lies at 1,930 m between the peaks Le Cheval Blanc, Pic de Tenneverge, Mont Ruan, Tour Sallière and Fontanabran, covers 3.27 km² and holds 227 million m³. When the water is low, the old Barberine dam emerges above the surface.

The first dam, Barberine, was built in 1925. The current 180 m arch dam was built between 1967 and 1974 by Motor-Columbus, creating a reservoir of 227 million m³ that flooded the old dam and the Alp Emosson. A 1963 treaty with France allowed the border to be shifted so the dam sits entirely on Swiss soil, while France gained usage rights. The reservoir was fully impounded on 10 September 1975.

The dam is reached by road or by a three-stage mountain transport chain from Le Châtelard: the Funiculaire du Châtelard, the steepest two-cabin funicular in the world at 87 percent, then a 600 mm panoramic train, then the Minifunic up to the lake. A 450 m zipline runs across the dam face. The old Barberine dam appears when water is low in spring.