Salinity variability in the Senegal River Estuary (West Africa).
Résumé
Due to its location, the Senegal River Estuary, SRE (West Africa), has a strategic importance for large populations through its roles for biodiversity, agriculture, fisheries and drinking water supply. Separated from the ocean by a sandy bar, named Langue de Barbarie, the SRE communicates with the Atlantic Ocean by a mouth of about 1 km wide. It is a channeled water body of about 50 km long and 0.6 to 2 km wide. It is connected to several wetland areas and tributaries but as a response to drastic decrease of annual rainfalls and large inter-annual flow variations, major infrastructure developments have been built and have considerably transformed an unmanned system into a largely regulated one. Then, a hydroelectric dam operated in 2002 at Diama controls the freshwater flow. In addition, a major change occurred in October 2003, when a breach was made in the Langue de Barbarie located in the south of Saint-Louis Island, in order to prevent the flooding of Saint-Louis City. This temporary solution turned out to be irreversible: the shallow river mouth, located 30 km south to the breach, has been progressively closed with sediments and the widening and deepening breach became the unique river mouth. This subsequent change produced deep modification of the estuarine functioning. It is therefore important for both scientists and public authorities to gain access to a tool allowing anticipating various changes. To achieve this goal, the present work is dedicated to the salinity distribution and variability in this complex ecosystem . This study combines modeling using 3D model and field measurements. It has been performed in the frame of the DelSen project, which aimed at studying the response of the SRE to natural and anthropogenic forcing.