Lac du Vieux Émosson

46°3′45″N 6°53′21″E / 46.06250°N 6.88917°E / 46.06250; 6.88917Catchment area4.6 km² (1.8 sq mi)Basin countriesSwitzerlandMax. length1.5 km (0.93 mi)Surface area0.55 km² (0.21 sq mi)Max. depth42 m (138 ft)Water volume13.8 million cubic metres (11,200 acre⋅ft)Surface elevation2,205 m (7,234 ft)

Lac du Vieux Émosson is a reservoir in Valais, Switzerland, in the municipality of Finhaut at an elevation of 2205 m. The lake drains into the reservoir Lac d'Émosson, 300 m below.

In September 2014, an increase of the dam by 21.5 meters was completed. The capacity of the lake was thus doubled to 25 million m³. The larger capacity is used for the Nant de Drance pumped storage plant, for which Lac du Vieux Emosson forms the upper basin and Emosson reservoir the lower basin.^[1] The storage power plant went into operation on July 1, 2022, after 14 years of construction. The construction of the plant cost the equivalent of 2 billion euros. The installed capacity is 900 MW, and 20 GWh can be stored.^[2]

The arch dam Vieux Émosson was completed in 1955. Efforts to raise the dam 20 m (66 ft) began in 2013. The lake forms the upper reservoir for the 900 MW Nant de Drance Hydropower Plant which began operations in 2022.^[3]

See also

• List of lakes of Switzerland
• List of mountain lakes of Switzerland

References