Estimating soil erosion risk and evaluating erosion control measures for soil conservation planning at Koga Watershed, Ethiopian Highlands

Abstract. Soil erosion is one of the major factor affecting sustainability of agricultural production in Ethiopia. This research applied recently validated RUSLE soil erosion model based on 6 to 14 years data for the Ethiopian highlands to estimate soil erosion and to evaluate soil conservation strategies in the Koga watershed. In this study, the average annual soil loss rate determined is 30.2 t ha−1 yr−1. The lowest soil loss is estimated about 12.1 t ha−1 yr−1 around the outlet of the Koga river which is greater than the minimum tolerable soil loss (2 t ha−1 yr−1). The highest soil loss is estimated from the steep slopes of upper watershed which is 456.2 t ha−1 yr−1 by far higher than the maximum tolerable soil loss (18 t ha−1 yr−1). Using ordinary least square regression, existing land use aggravates soil erosion with 92 % overall coefficient of determination (R2). The topographic factor also influences soil loss with 89 % R2 value. Based on the evaluation of technical standards of soil conservation measures, 35.56 % of the existing soil conservation practices fit with the recommended national standard which has less contribution to tackle soil erosion. Therefore, to sustain agricultural practices, appropriate and standardized soil conservation structures on different erosion prone land uses and landforms should be implemented in Koga watershed.