Assessing the rate of soil loss and sediment Yeild from Tullu Gana Watershed in Horo Guduru Wollega Zone, Ethiopia

Abstract

The two main issues facing Ethiopia's highlands are soil erosion and sedimentation. The purpose of this study was to evaluate the rate of soil loss and sediment yields in the Tullu Gana Watershed in the northwestern region of Ethiopia over the previous three decades (1990–2021). To create Rainfall Erosivity, Soil Erodibility, Slope Length and Steepness, Cover Management, and Conservation Practices, input data sets including rainfall, soil, Digital Elevation Model, land use, and land cover were utilized. Once more, the drainage area was used to determine the sediment delivery ratio. The RUSLE model and GIS were integrated in this study. The average soil loss rate was 1.01 tons ha⁻¹ yr⁻¹ in 1990, according to the results, but it increased to 43.80 tons ha⁻¹ yr⁻¹, 45.18 tons ha⁻¹ yr^−1, and 46.43 tons ha⁻¹ yr⁻¹ in 2000, 2010 and 2021, respectively. Between 1990, 2000, and 2010 to 2021, the average sediment yield in the study area increased from 0.19 tons ha⁻¹yr⁻¹, 8.41 tons ha⁻¹yr⁻¹, and 8.67 tons ha⁻¹yr⁻¹ to 20.61 tons ha⁻¹yr⁻¹, respectively. Over the past three decades, there has been an increase in agricultural land, plantations, and settlement, according to the results of changes in land cover. Grazing land, open forests, and shrub land, on the other hand, decreased during that time. In addition, the research area was divided into six sub-watersheds, with the aim of prioritizing them for conservation planning in the future, based on the average rate of soil loss. Among the six crucial sub watersheds, Sw2, Sw4, Sw5, and Sw6 were classified as having extremely high severity, while Sw1 was classified as having low severity. In general, determining erosion-prone areas and implementing sustainable land management depend on an understanding of the quantity of soil loss and sediment yield and the mapping of its distribution. These results are intended to assist decision-makers to prepare reliable plans for managing soil erosion while taking identified priority classes and hotspot areas into account.