Soil Loss Estimation and Sub-Watersheds Prioritization for Management Using GIS-Based RUSLE Technique in Halaba-Bilate Watershed, Ethiopia

Background and Objective: Soil erosion is a global problem that causes land degradation. Soil loss risk had posed a serious threat to farmer’s livelihood of Halaba Bilate Watershed. This study was carried out with the main objective of examining soil loss risk and assessing soil loss vulnerability by the RUSLE model using GIS for soil conservation in Halaba Bilate Watershed. Materials and Methods: Data on rainfall, soil, digital elevation model and satellite imageries were acquired and processed to develop RUSLE factors. The rainfall erosivity, soil erodibility, slope length and steepness, vegetation covers and conservation practice factors were used as input for model. The factors were processed and combined on Arc GIS 10.8. The annual soil loss rate was estimated using RUSLE. The watershed was divided into five subclasses based on the drainage of the area. Hotspot areas were identified and prioritized based on the mean annual soil loss value of each sub-watershed. Results: Annually about 1,536,907.46 tons of soil were lost from 13120.17 ha with an average rate of 16.5 t/ha/year. About 20.67% of watershed was categorized under severe to very severe with respect to the annual soil loss. The sub watersheds (3, 4, 2, 1 and 5) ranked 1st to 5th, respectively based on mean annual soil loss rate for planning intervention. The 3rd Sub watershed (Swsh3) had highest average annual soil loss value poor vegetation cover, poor management, degraded lands and inappropriate farming practices in steep slope areas of watershed. Conclusion: It can be concluded that the watershed is exposed to soil loss. The entire parts of watershed especially the fields covered by cultivated land, grasslands and bare lands require intervention. Therefore, Swsh3 should attain the first priority level during SWC planning and intervention based on the availability of budget, labor, time, skill and capacity of project.