Ilay and drinking water

The Petit Maclu and the Ilay lake provide 10 municipalities with drinking water, including Frasnois. 67,000 cubic meters are used up every year. The lakes on the Frasnois plateau are natural. The icebergs that covered the Jura 20,000 years ago have “planed” the earth and created the necessary depressions for the lakes to form. The limestone and moraine deposits from the movement of icebergs are watertight and are able to retain the water. To best preserve the quality of the water, a prefectural order bans the use of thermal engines.