Source: The Library Of Congress Country Studies
There are 146 named rivers on Mahe, Praslin, La Digue and Silhouette.
The granitic islands have many small, steep watercourses, but most of them have only ephemeral flows. Groundwater resources are limited and often contains traces of salt. The wetlands have recently become an attraction for eco-tourism. The total dam capacity is 0.970 million m3. The Rochon Dam, which collects its waters from the Rochon River, has a storage capacity of 0.050 million m3. Surplus water is forwarded to the La Gogue Dam, which has a storage capacity of 0.920 million m3.
About 1.0 million m3/year of desalinated water is produced for potable use to compensate for the shortage that occurs during the dry period. There are four desalination plants, two on Mahe Island, one on Praslin Island and one on La Digue Island.
Most of the agricultural, domestic and industrial waters come from small streams or rivers from the hillsides, depending on monsoons and the rainfall pattern. The abstraction of surface water amounts to around 11.2 million m3/year (2003) and of groundwater to 0.3 million m3/year (2003.) The principal groundwater abstraction is on la Digue Island for domestic and agricultural consumption.