The lakes of Haute-Alsace are, for many Alsatians, the symbol of unspoiled nature. Water supplying has always been a thorny issue in the east of the granite Vosges massif. This sector receives only low rainfall: this is the foehn effect. Reservoirs were therefore created in the ice circuses to accumulate water reserves during favorable seasons. The lac Noir is, in addition, connected to the lac Blanc, 344 ft (105 m) higher, by a pipe that allows the production of electricity.