Résumé
In addition to a general decline in rainfall in the Sahel since 1970, which has affected river flows, land use changes also are affecting runoff generation and ultimately, river flows. The hydrological behavior of the Nakambe River (Burkina Faso) and land use changes from 1955-98 are reviewed to assess impacts on water-holding capacity (WHC) of the soil. Two monthly hydrological models using different rainfall, potential evapotranspiration, and WHC data sets were compared. From 1965-95, natural vegetation in the river basin declined from 43% to 13% of the total basin area, while the total cultivated area increased from 53% to 76% and the area in bare soil nearly tripled from 4% to 11%. WHC reduction was estimated to be from 33% to 62%, depending on the model used. River flow simulations appear to be better when time-varying values of soil WHC are used. The possible influence of other factors, such as surface runoff processes and groundwater trends, on Nakambe River hydrology also is considered.