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
Alps season when rapid runoff causes debris torrents and swollen rivers. The rivers form lakes, such as Lake Geneva, a crescent shaped lake crossing the Swiss border with Lausanne on the Swiss side and the town of Evian-les-Bains on the French side. In Germany, the medieval St. Bartholomew's chapel was built on the south side of the Königssee, accessible only by boat or by climbing over the abutting peaks. Additionally, the Alps have led to the creation of large lakes in Italy. For instance, the Sarca, the primary inflow of Lake Garda, originates in the Italian Alps. Scientists have been studying