One of the side effects of climate change and retreating glaciers is the formation of glacial lakes. These have been growing in the Alps and are causing concern. If the dam holding the lake bursts, the sudden release of water can flood habitations lower down the mountain. Such floods have been the cause of numerous catastrophes in the past. In 1892 the lake of the glacier de Tête Rousse burst emptying some 200,000 m3 of melt-water killing some 200 people in St-Gervais.
A new monitoring station, a first in France has been put into service on the lac de Rochemelon in the Vanoise. This glacial lake covers an area of 5 hectares and is up to 25 meters deep. It is situated at 3218 meters altitude. Monitoring uses two pressure sensors located at 10 and 17 meters depth. If there is a significant change in water level an alert is given by radio to the French Electricity Company’s (EDF) site on the dam at Mont Cenis. Just installing the device was a difficult and dangerous operation. A hole had to be cut through three layers of ice totaling 80cm to enable divers to position the sensors. The installation has cost some 50,000 euros. The lake was partially drained in the autumn because the glacier that retains the lake is melting.
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