Mountain Reservoirs for Snowmaking: a Guideline for Design, Construction, Monitoring and Rehabilitation

reservoirs are hydraulic structures in ski resorts in the mountains, used to store water in general for snowmaking. There are more than one hundred of them in France, most of them less than 10 years of age. Despite their modest volumes (5,000 to 400,000 m3) and dam heights of between 5 and 20m, these structures do induce potentially high risks for people and property situated downstream from them. They are located at altitudes between 1,200 and 2,700m, and often face difficult topographical, geological and geotechnical conditions, mountain-specific hazards, a very limited period for construction in the year, considerable pressure from ice and intense cold, the difficulty of surveillance in winter, etc. A survey conducted on about 70 of these mountain reservoirs provided considerable information, particularly on the behaviour and pathologies of these small dams at high altitudes. These reservoirs are generally entirely sealed by geomembranes (85% of cases). This feedback on experience served as a basis for writing a set of guidelines on studying, designing, constructing, monitoring and rehabilitating these mountain reservoirs [4]. This guideline has been supported by the French ministry of environment and it has been prepared by a working group lead by the Cemagref and with the contribution of EDF and ISL. The article presents, through the guideline Mountain reservoirs, a summary of the feedback on the behaviour and pathology of mountain reservoirs. It gives a general description of the guideline [4], and emphasis on the main key themes: environmental impacts, risks specific to the mountain, design of embankments and drainage system, monitoring and operation, and those aspects of the underlying layer, drainage and cover layer of the GSS that appear to be essential for the system to behave correctly.