Water erosion in South-Western Niger: impacts of natural and anthropogenic factors on soil losses

摘要

This study was conducted in the extreme south-western of Niger, at the scale of the Kori Ouallam watershed. It proposes to assess the potential soil losses induced by water erosion in connection with natural constraints and anthropization. The methodology adopted involves field campaigns, laboratory analyses confronted with the tools composed of the Geographic Information System (GIS), remote sensing and the Revised Universal Soil Loss Equation (RUSLE). The use of these data reveals that the annual average of potential soil losses generated by water erosion is 1.54 t/ha/yr. On the scale of the watershed, the erosion risk varies from a very low erosion rate (0-0.5 t/ha/yr) largely observed in the North to an extremely severe erosion rate (> 5 t/ha/yr) with an increasing gradient towards the South. The correlation matrix shows that topographical factors related to slope length (L) and slope steepness (S) are the main erosive factors influencing soil loss. Soil erodibility and erosivity of rainfall are secondary factors. The gradual degradation of soils by water erosion is also amplified by inappropriate human activities, which undermines the resilience of ecosystems and communities. In a Sahelian context marked by climatic uncertainties and strong anthropization, the regional pattern of soil erosive dynamics deserves more adequate monitoring for a sustainable management of natural resources.