Crossed by the Durance and ten major tributaries, the Alpes-de-Haute-Provence department has eleven large watersheds whose flows vary according to the nature of the rivers and their hydroelectric developments. If those of the Durance, Verdon and Ubaye are regularly supplied, the balance of the others (Bléone, Asse, Largue, Lauzon, Jabron, Sasse, Vançon, Calavon) is more precarious and even in deficit in the summer season.