The real backbone of Provence, the Durance crosses the current South Region over 200 miles (323 km) from the Alps to the Crau plain and irrigates the regional economy by supplying 75% of the region's water needs. Divided into three parts (the Upper, Middle, and Lower Durance), it runs through two departments (the Hautes-Alpes and the Alpes-de-Haute-Provence), serves as a geographical limit for the Vaucluse and the Bouches-du-Rhône and makes a brief foray into the Var. The Durance also supplies Marseille with water thanks to the construction of the Marseille Canal in the 19th century.