SOIL LOSS ESTIMATION BY USING GIS AND RUSLE APPROACHES IN SOUTH ETHIOPIA, NORTHERN-BILATE (BOYO LAKE AREA) WATERSHED

Abstract

Soil erosion in Ethiopia exacerbates land degradation, desertification, the decline in productivity, and drought and affects farmers' livelihoods. Therefore, this study aimed to estimate annual soil loss in southern Ethiopia, North-Bilate watershed. For this purpose, the land-based ETM image was divided into seven classes using Erda's Imagine 10.5. Soil, topography, and precipitation data were also obtained from various sources and analyzed in Arc GIS 10.8. Accordingly, five factors (soil erosivity, erodibility, topography, cover management, and support practice) were calculated in ArcGIS 10.8 using the RUSLE model to estimate annual soil loss. As a result, 537035.13 ha (96.1%) and 16521.21 ha (3.1%) of the watershed showed very little and little water erosion, respectively. As can be seen, about 99% of the watershed area had a lower (0.64.73 t/ha/year) risk of soil erosion, while the remaining 1% of the watershed area had a moderate to extreme soil erosion state; which remove a large amount (64.73 1500 t/ha/year) of a clay soil from the riverbanks and muddy areas, mainly from upstream of the Bilate River (the largest in the watershed); due to the maximum slope length and steepness and the rapid flow of water. In conclusion, areas with higher rainfall intensity, active human intervention, lots of sandy soil content, sloppy topography, and thinner soil depth are collectively degraded and prone to erosion. Therefore, such vulnerable areas should mitigate their risk by using organized soil and water conservation techniques to conserve the watershed's total land resources. Physical measures such as terracing and dams should be implemented. In addition, to preserve and increase the biodiversity of the study area, the planting of various types of native vegetation and plantation tree species should be carried out with a viable afforestation and reforestation program.