Résumé
This study deals with the issue of using GCMs data to assess the impact of climate change on runoff in western Africa. It requires evaluation of the reliability Of four GCMs (HadCM3, ECHAN14, NCAR-PCM, CSIRO-MK2) regarding the rainfall they provide, and then assessment of the impacts of climate change on the discharge of four main rivers (Senegal, Gambia, Sassandra, Chari). First, GCM rainfalls were compared to observed ones. It appears that the data generated by the GCMs cannot be used as direct input to hydrological models to evaluate the impacts as they are not realistic enough. For this reason, two climatic scenarios were developed from the results provided by HadCM3-A2. These two scenarios were used as input to the hydrological model GR2M. The results demonstrate that expected runoff variations remain strongly linked to rainfall and so to the quality of the GCMs outputs used.