Résumé
The hydrological studies undertaken during the last twenty years have shown that the hydrological variability observed since the year 1970 on the Sahelian river basins is due to the combined effect on landcover of climate changes and human activities. Runoff coefficients have increased, inducing more important flows than in the earlier years despite a reduction in rainfall. These modifications to the rainfall-runoff relationship require new approaches that make it possible to take into account both the climatic variability and the human dimension in hydrological modelling of these basins. A method is presented and preliminary results are analysed and discussed.