Potential soil loss estimation for conservation planning, upper Blue Nile Basin, Ethiopia

Abstract Soil loss is a continuous ecological problem. The loss of top fertile soil by erosion creates severe limitations to sustainable agricultural land use, which lead to reduced soil productivity and food insecurity. Soil loss is not affect only agriculture but also causes streams, lakes, dams, and reservoir sedimentation. Efforts should be focused to decrease risks of high erosion rates. This requires erosion prone area identification for urgent conservation plan. Techniques to know the spatial variability of erosion severity is essential for improving landuse management. The Revised Universal Soil Loss Equation (RUSLE) model with ArcGIS and Multi Criteria Evaluation (MCE) technique were used to estimate the annual soil loss rate and to identify high erosion risk areas in Gilegel beles watershed with a size of 770 km2, to prioritize area for conservation planning. land use land cover, soil map, digital elevation model (30m resolution), and twenty five years rainfall data at nine rain gage stations across the watershed were used to estimate soil loss in RUSLE model. The result showed that annual soil loss of the watershed ranges from 0 to 511.2ton/ha/yr with average of 28.68 ton /ha/ yr. Spatially 10.4% and 13.2% of the watershed was extremely sever and high soil erosion respectively. However, the remaining 46.4% and 30.03% of the area lies within low to moderate level. Our study revealed the most extensive soil loss rates were estimated in steep slopes, bare lands, crop land and biological degraded areas were aggravated soil loss problem. Finally, the combined models were effective for soil erosion estimation in small watersheds, so the outcome verified that integrated land management practices have needed to apply effective soil erosion control techniques like agroforestry, grass strips reduce runoff velocity and allow for infiltration, provide sediment trapping, erosion control blankets, dust control and percolation ditches for erosion prone areas and managing the inter catchment can be the best solution.