The Dranse () is a French river in the department of Haute-Savoie, that empties into Lake Geneva between Thonon-les-Bains and Évian-les-Bains. The name "Dranse" comes from the former Drantia, based on the hydronym dur-, dora and the suffix -antia. Geography The Dranse is formed from the combination of three mountain rivers originating from the peaks of the upper Chablais Alps, which converge upstream from the delta: To the east, the Dranse d'Abondance irrigates the Val d'Abondance and passes through the communes of Abondance and Châtel; To the south, the Dranse de Morzine passes through Morzine, Saint-Jean-d'Aulps and the Gorges du Pont-du-Diable; To the west, the Brevon, also called the Dranse de Bellevaux, originates from Roc d'Enfer and passes through Lac de Vallon and the villages of Bellevaux, Vailly and Reyvroz. The Dranse d'Abondance is considered the higher-ordered stream of the Dranse. The Dranse de Morzine is consequently considered its tributary, according to Sandre, the French National Service for Water Data and Common Repositories Management. The Dranse empties into Lake Geneva and forms a delta, which is integrated into the Delta de la Dranse National Nature Reserve, situated to the east of the commune of Thonon-les-Bains, which although small at an area of , offers an incomparable botanic diversity. The river is long. Whitewater kayakers and commercial rafting companies frequently run this river. Hydrology The Dranse is a high-volume river, as are all the rivers which originate in the Alpine mountain ranges. Its discharge was observed for a period of 97 years (1906–2003) in Reyvroz, a locality in the department of Haute-Savoie situated on the southern bank of Lake Geneva at the same elevation as its outlet. The drainage basin for the river is in its totality , which is not quite three times the surface area of the city of Paris. The annual average discharge of the river at Reyvroz is per second. The Dranse is a typical seasonal river regime, with depends slightly on a small rain component. It exhibits sharply delineated seasonal fluctuations in discharge, which is characteristic of Alpine waterbodies. High flows occur in the springtime and are attributed to snowmelt. These accompany average monthly discharges of around per second from April to June (the maximum being reached in May). At the end of June, discharge rates sharply drop while the volume moves downstream. From the end of July to the end of February discharge is continuous,