Assessment of soil erosion and sedimentation dynamics in the Rift Valley Lakes Basin, Ethiopia

Abstract

Soil erosion and sedimentation are global issues threatening livelihoods and development, including in the Ethiopian Rift Valley Lakes Basin (RVLB). Despite several studies conducted at the watershed and subbasin levels in the basin, there is a lack of an organized review. This review synthesizes findings from 32 studies (2008–2023) to assess soil erosion and sedimentation rates, causes, and impacts in the RVLB. Key findings indicate that land use changes, such as converting vegetation and woodlands into cultivation and settlements, are the primary drivers of soil loss, with additional factors including steep slopes, poor conservation practices, and high rainfall. The mean annual soil loss rate in the basin is 28.44 t/ha/year, surpassing the national average of 16.5 t/ha/year and the RVLB average of 15.8 t/ha/year. Methodologies mainly rely on the Universal Soil Loss Equation and its revised version, Revised Universal Soil Loss Equation, alongside tools such as Soil and Water Assessment Tool, Integrated Valuation of Ecosystem Services and Tradeoffs—Sediment Delivery Ratio, object-based image analysis, and field measurements. The impacts include severe effects on crop production, hydrological efficiency, and lake sedimentation. Research gaps highlight methodological inconsistencies, limited studies on direct economic impacts, underrepresented gully erosion dynamics, and a lack of high-resolution data. Future research should focus on integrating high-resolution datasets, employing advanced geographic information system and machine learning techniques, and conducting socioeconomic impact studies. Addressing these areas is crucial for developing sustainable soil and water conservation strategies in the RVLB.