Lac du Vieux Émosson, reservoir
Lac du Vieux Émosson is a reservoir in Valais near Finhaut, created by damming the Émosson River. The water fills a basin about one and a half kilometers long and is used to generate electricity.
The first dam at Lac du Vieux Émosson was built in 1955 by the Swiss Federal Railways (SBB). In September 2014, work to raise the arch dam by 21.5 metres was completed, doubling the reservoir's volume to 25 million m³. The enlarged lake serves as the upper basin of the 900 MW Nant de Drance pumped storage plant, which began operating on 1 July 2022 after 14 years of construction.
The reservoir's name comes from the older Émosson reservoir and the valley below, not from a river. Since 2022 its water has served the Nant de Drance pumped storage plant, which moves water between this upper basin at 2,205 m and the lower Lac d'Émosson 300 m below. The dam crest is a starting point for the path to the Col des Corbeaux.
The lake is easily reached by car, bus, or train from nearby Finhaut. Good footwear and weather protection are important since mountain weather can change quickly.
On 23 August 1976, well-preserved archosaur footprints were found at 2,400 m on the path to the Col des Corbeaux. The animals lived about 250 million years ago, and the tracks can be seen in summer after the snow melts.
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