Identification of sediment sources in a small grazed Sahelian catchment, Burkina Faso

The Sahelian region of Burkina Faso is currently facing serious problems of natural resource degradation, especially soil erosion, due to the aggressive climate and anthropogenic impacts. This study aimed to quantify total soil losses at the outlet of a catchment and to estimate the contribution of different sediment sources. To do this, surface water flow and associated particulate material transport were monitored for three years (1998-2000) in a small grazed catchment (1.4 ha). About 64% of the catchment is covered by permeable sandy aeolian deposits (DRY soil surface type), which support most of the vegetation, and about 34% is covered by impermeable bare soils (ERO soil surface type). To establish the contribution of the two surface soil types to the sediment load observed at the catchment outlet, several different techniques were used. These included the particle-size distribution of the sediment, clay mineralogy (kaolinite/quartz ratio) and physically-based modelling. The results indicated that the ERO surface type appeared to be the main source of sediment within the catchment.