Alps rivers such as the Danube have major tributaries flowing into them that originate in the Alps. The Rhône is second to the Nile as a freshwater source to the Mediterranean Sea; the river begins as glacial meltwater, flows into Lake Geneva, and from there to France where one of its uses is to cool nuclear power plants. The Rhine originates in a 30 square kilometre area in Switzerland and represents almost 60 percent of water exported from the country. Tributary valleys, some of which are complicated, channel water to the main valleys which can experience flooding during the snow melt
Swiss Plateau the southwest, the Swiss Plateau is confined by Lake Geneva, in the northeast, by Lake Constance and the Rhine. Geologically, the Swiss Plateau is part of a larger basin that extends beyond the border of Switzerland. At its southwestern end, in France, the plateau, in the Genevois, ends at Chambéry where Jura and Alps meet. At the other side of the Lake Constance, the plateau continues in the German and Austrian Pre-Alps. Within Switzerland, the Swiss Plateau has a length of about , and its width increases from the west to the east: In the Geneva region, it is about