The lake lies on the course of the Rhône. The river has its source at the Rhône Glacier near the Grimsel Pass to the east of the lake and flows down through the canton of Valais, entering the lake between Villeneuve and Le Bouveret, before flowing slowly towards its egress at Geneva. Other tributaries are La Dranse, L'Aubonne, La Morges, La Venoge, La Vuachère, and La Veveyse.