The Seychelles, an archipelago of 115 islands, occupies a total land area of 455 Km2 and consists of 41 inner islands of granitic nature, out of which Mahé, Praslin and La Digue offer significant population numbers for hydrological purposes.
Details on Rivers and Streams:
The most abundant freshwater sources found on the granitic inner islands of Mahé, Praslin and La Digue are the numerous rivers and streams. Many of these are temporary with very few perennials. Given the steep topography of the islands the rivers and streams are swift flowing, chocked sources, with streams riddled by boulders.
The soil type of Seychelles (low retentive stratum) allows for only 2% recharge of the groundwater aquifers even with a very high average annual rainfall of over 2362 mm/yr and thus our rivers and stream run dry during the months of April to early September thereby adding to the nation’s water stress.
In total 38 catchments are gauged periodically by P.U.C on Mahé, with 11 on Praslin and 8 on La Digue. The biggest contributing catchment to hydrology on Mahé is Mare Cochons (area of over 5.42 km2).
Ongoing Management and Restoration projects
The EEWS has the mandate to clean and restore river flow ecosystems and this is achieved by a dedicated outsourcing program. The Government of Seychelles has financed an annual budget of over SR3 million, geared to cleaning, de-silting, and restoring major river ways and channels thereby reducing the flood risk vulnerability of embankment housing, downstream habitats while allowing for a thriving bio-diversity within.
Factors affecting Seychelles waterways health
With increased population and need for land, the exploitation of upper catchment areas for development has seen the diversions, abrupt termination and in some cases pollution of river sources. Moreover, the ongoing waste management issues associated with a Small Island Developing States further encroaches onto waterways thereby adding to loss of bio-diversity.
The increased illegal reclamation of marshes and wetlands, results in reduced flow to sea, and increased inundation of low lying terrain during high precipitation events. Finally being open to sea from all corners, the saline intrusion into fresh water resources remain largely unchartered yet relatively dangerous situation for the Seychelles.