Artificial flood support on Senegal river : a challenge to protect natural resources in the valley

Formed on the upper basin by the annual monsoon, the flood of Senegal River inundates a vast floodplain on its lower course, called "the valley". This one, several hundred kilometres long, can be regarded as an inland delta. This annual flooding, which offers ecosystem services and promotes traditional activities, must be maintained despite the presence on the Bafing of the Manantali reservoir dam, which controls since 1987 half of the river flows through the valley. In addition to its other objectives (energy production, low water support for irrigation and navigation, mitigation of too high floods), this dam therefore achieves a flood support, designed to maintain adequate flood in the valley. Here we present a decision support system dedicated to flood support that aims to: 1) define a flood hydrograph goal for Senegal river, according to a target area of recession crops; 2) define the optimal date for flood support, in order to penalize the least possible energy production at the dam; 3) calculate the discharges to release of the dam to support the flood, according to the real-time hydrological situation known. We finally analyse the respective impacts of natural climate hazard and of Manantali dam on the river's flood observed