The Dranse is a river located in Haute Savoie, near Thonon les bains, it flows into the Lac Léman (Lake Geneva).
It is composed of 3 rivers coming from the Haut Chablais. They join nearly at the same point: the Dranse of Morzine coming from Morzine; the Dranse of Abondance coming from Abondance valley (Chatel); and the last one, the Brevon or Dranse of Bellevaux coming from Bellevaux.
The Dranse of Abondance is considered as the main part of the river, so as a consequence, the others are tributaries.
It flows into Lake Geneva in the Dranse delta in Thonon les Bains.
The river is rain and snowfall, it means that it is fed by the thaw as well as rain.
We can find dams on the Dranse of Abondance and Morzine. They are both regulated by the hydroelectric plant of Bioge. They permit to maintain the adequate level of water during the whole summer for white water activities.
The river is classified as grade II – III on the classic part and IV – V on the part of « ex-infranchissables ».
Levels of water vary according to seasons and weather. In springtime, levels are often higher than 20-30 cumecs a seconde. During summer, it is around 12 cumecs . And sometimes, after the rain, this level can rapidly reach or exceed 100 cumecs .
The Dranse is a pearl for white water activities thanks to its variety in terms of difficulty and levels of water.
More information on wikipédia
Technical information on Eaux-vives.org