San Luis province has an important hydrographic network, which, together with dams and reservoirs, provides this vital resource for human consumption, irrigation and tourism.
Due to the rainfall variations throughout the year, a change occurs in the regime of each river or stream in the province. With Summer being the period of greatest flow, and Winter the period of lower flow.
The water courses are concentrated in the centre-north of the province, where San Luis mountain range is located. In the south of the province, the presence of rivers and streams is subject to local runoff during the rainy season.
The drainage network can be divided into watersheds, which would be the area surrounding a main river and its tributaries. In San Luis there are several river basins, including the Basins of Conlara, North Plains, South Plains, Vilance, Desagüadero, Bebedero, Salado and Quinto.