Soil erosion is a major environmental in most high lands of Ethiopia. The Ribb watershed which is found in the Upper Abbay Basin, is among the most affected areas by runoff, sediment transport and land degradation. Hence, this study aimed to estimate runoff and the mean annual sediment yield of Ribb watershed and to identify and prioritize erosion prone sub watersheds for conservation planning. Ribb watershed was delineated and divided into 47 sub watersheds using SWAT model. Model calibration and validation was done at Ribb gauging station (near Addis Zemen) using SWAT-CUP with acceptable performance evaluation result. The whole watershed contributes mean annual surface runoff, flow and sediment yield were calculated as 321.8mm, 26.89m 3 /s and 41.62ton/ha/yr respectively to downstream flood plain and lake Tana. The upper Ribb watershed which contributes to Ribb irrigation dam had simulated surface runoff, flow and sediment yield of 273mm, 13.16m /s and 49.1ton/ha/yr respectively. Overall, 47 sub watersheds elevens are very sever and produced 61.32% of the total annual sediment yields, demanding early involvement in the planning and implementation of soil conservation measures. 3