4. Lake restoration on an ecosystem scale: Lac du Bourget (Savoie)

4.1 The lake and its degradation

Lac du Bourget is a peri-alpine lake, formed during the last ice age and geologically linked to the Jura massif. With a surface area of 44 km ² (watershed of 588 km ² ) and a maximum depth of 147 m, it has a water retention time of around 7 to 10 years. Since 1982, it has been connected to the Rhône via the Savières canal, enabling water to be exchanged in both directions and regulating the lake level. Like many Alpine lakes, since the early 1950s Lac du Bourget has been the victim of degradation linked to a number of successive or concomitant causes: significant human development, with an increase in urban and peri-urban areas (over 200,000 inhabitants today),...