Runoff evolution according to land use change in a small Sahelian catchment

Abstract

Abstract Land use changes have been significant these last decades in West Africa, particularly in the Sahel region; in this area, climatic and demographic factors have led to a rise in cropped areas in recent decades causing strong changes in the water cycle and in river regimes. This study compares the rainfall-runoff relationships for two periods (1991-1994 and 2004-2011) in two small and similar neighbouring Sahelian catchments (approx 0.1 km² each). This allows highlighting the different hydrological consequences of land use/land cover change, particularly the fallow shortening as well as the consequent degradation of topsoil. The main land surface change is a 75% increase in crusted soil area. Runoff increased by more than 20% on average between the two periods while flood durations decreased by 50% on average. However runoff values remained largely constant in the lower part of the northern basin due to a strong increase in in-channel infiltration.Abstract Land use changes have been significant these last decades in West Africa, particularly in the Sahel region; in this area, climatic and demographic factors have led to a rise in cropped areas in recent decades causing strong changes in the water cycle and in river regimes. This study compares the rainfall-runoff relationships for two periods (1991-1994 and 2004-2011) in two small and similar neighbouring Sahelian catchments (approx 0.1 km² each). This allows highlighting the different hydrological consequences of land use/land cover change, particularly the fallow shortening as well as the consequent degradation of topsoil. The main land surface change is a 75% increase in crusted soil area. Runoff increased by more than 20% on average between the two periods while flood durations decreased by 50% on average. However runoff values remained largely constant in the lower part of the northern basin due to a strong increase in in-channel infiltration.