Erosion Source Area Identification Using Rusle and Multi-criteria Decision Analysis, Acase of Andassa Watershed, Upper Blue Nile Basin

Abstract Soil erosion reduces the productive capacity of the land, which leads to global food insecurity, decline landscape beauty, decrease quality of water, loss of aquatic lives in water bodies, and Catchments. Generally, Soil erosion problems disturbs the whole ecological process. The results of the study show that mean annual soil loss of Andassa watershed was about 68 t ha1 year-1. From soil erosion factors, Topographic wetness index followed by land use land cover have been found to have significant effect on soil erosion in the watershed. The combined result of MCE and RUSLE result showed that 21.17% of Andassa watershed was highly sensitive, 23.17% moderately sensitive, 46.78% slightly sensitive, 8.31% currently not sensitive and 0.04% were constraint to soil erosion. Based on these results, the watershed has significantly at high to moderate risk of soil erosion (44.34%) from the hole watershed. Thus, the Upper part of the watershed is under high class of soil erosion source and needs immediate attention in terms of management as well as planning perspective and it should be managed for conservation and environmental protection activities. From the overall combined map of Multicriteria decision analysis (MCDA) and revised universal soil lose map showing the areas of increased risk erosion represented by highly sensitive (S1), moderately sensitive(S2), less sensitive(S3), and non-sensitive(S4) areas so the governmental or non-governmental organizations or any concerned organization should refer this important severity map of soil erosion for watershed management and priority of the watershed.