Water balance simulation for resource evaluation at the catchment scale: application to the Nema (Sudano-Sahelian zone, Senegal)

Abstract

The Nema is a river in western Senegal where only a minority of inhabitants has access to drinking water. Rainfall has been decreasing in this region since the 1960s. It is crucial to understand how this change affects groundwater recharge. The objective of this research is to determine the current proportions of ground- water recharge, runoff, subsurface runoff and evapotranspiration using a simulation approach. The Nash criterion and water balance error were used to evaluate the quality of the simulations. The following results were obtained: the Nash criterion was 0.73 for calibration (0.73 for validation), and the water balance error was −0.35% and 0.005%, respectively, for the hydrological years 1995/96 and 1997/98. Evapotranspiration and groundwater recharge are the main processes involved.