Estimating Soil Erosion to Highlight Potential Areas for Conservation Priority in Rukarara Catchment, South-western Rwanda

Abstract

Soil erosion is one of the major environmental problems in tropical ecosystems; however, the lack of information on the amount of eroded soils in  Rwandan mountainous watersheds hinders effective decision-making toward sustainable soil management. This study aimed at predicting soil erosion in  the Rukarara River watershed, one of the mountainous watersheds in Rwanda, and identifying potential areas of high erosion risk using the revised  universal soil loss equation (RUSLE) implemented in a GIS environment. The annual soil loss was estimated by computing and performing a spatial  overlay analysis of relevant layers including rainfall erosivity (R), soil erodability (K), slope length and steepness (LS), cover management (C), and  conservation practice (P) factors. The results indicate that the annual soil erosion varies from 54 to 134 t ha⁻¹ year⁻¹ (95% confidence interval) with a  mean of 39.96 t ha⁻¹ year⁻¹. The study area is generally characterized by very low and low soil erosion classes and the mean erosion correlated with literature results in the tropics. Agricultural lands are the hotspots of soil erosion with a mean of soil loss of 61.29 t ha⁻¹ year⁻¹. The produced maps and  soil loss estimates can facilitate informed decision-making toward sustainable soil management in mountainous areas of Rwanda, especially in the  Rukarara River watershed.