Combining RUSLE and vegetation health index model to unravel the relations between soil erosion and agricultural drought

Recurrent droughts, intensified by rising global temperatures, erratic rainfall patterns, and soil erosion, lead to crop failures, water scarcity, and food insecurity across most parts of Ethiopia. However, it has not yet been evaluated using appropriate data and methods. To address these research gaps for actionable policy development input on the integrating drought conditions and soil erosion problem, in Awash River Basin, Ethiopia, this study developed a Google Earth Engine (GEE) based Revised Universal Soil Loss Equation (RUSLE) and Vegetation Health Index (VHI) modeling approach to assess soil erosion and drought event spatiotemporal occurrence and their relation for 23 years (2001–2023). To do this, the VHI was derived by integrating the Vegetation Condition Index (VCI) and the Temperature Condition Index (TCI), both of which were computed using the Normalized Difference Vegetation Index (NDVI) from the MOD13A2 product and Land Surface Temperature (LST) from the MOD11A2 product, respectively. This integration was used to characterize the spatiotemporal dynamics of agricultural drought conditions. The GEE RUSLE approach was applied to estimate the qualitative and quantitative soil loss from the river basin. Pearson's correlation was used to examine the relationship between soil erosion and drought conditions. The results of these approaches revealed that the Awash River Basin experienced recurrent mild-to-extreme spatial and mild-to-severe temporal droughts during the study period. Spatially, the upper and middle parts of the river Basin experienced extreme drought (VHI ~ = 3%). Temporally, the months May (2002, 2009, and 2022), March (2008 and 20,216), and April (2015 and 2021) were characterized by severe drought in the area. The maximum, minimum, and mean soil erosion rates were determined to be 150, 5.0, and 25.67 $$t/ha/yr,$$ respectively. This amount of soil loss was intensified by rainfall, slope length, and steepness in the highland areas of the river basin and by soil texture, nature, and lower vegetation cover in the lowland area of the basin. Across the river basin, the interrelation between soil erosion and drought conditions showed spatial variation ranging from −0.2 to 0.4, with an overall mean weak positive correlation (r = 0.20). As a recommendation, policymakers and basin master plan developers should consider soil and water conservation and vegetation preservation as key activities in the upper and lower parts of the river basin, respectively.