Land degradation is a series problem in Ethiopia highlands, particular in abbay basin reflected in the form of soil erosion and soil fertility decline from time to time. Beshilo catchment is one of the Abbay basin tributary, which covers 5,700 km2; this shows that the problem of the catchment is significant effect in Abbay basin development. In this study the impact of Land use/ Land cover change on annual outflow contribution of Beshilo Catchment is evaluated, distributed physically based hydrological model known as soil and water assessment tool (SWAT) model was used this study. Changes were analyzed and characterized impacts on surface runoff were evaluated. The model was calibrated and validated over the gauged upper reaches of catchments of Gummara River. The model was calibrated for the period from 1999-2008 and validated for the period from 2009-2014. The performance of the model was evaluated on the basis of performance rating criteria, coefficient of determination, Nash & Sutcliff efficiency. The overall performance of the models gives good result. For this study the land use land cover change scenario, were developed using its change. From the land cover change analysis results it was found that there has been a substantial decline of forest lands, shrub lands, grass lands and expansion of agricultural land. The SWAT modeling shows the result indicated that the mean annual surface flow were increase by 7.4 % with 2004 LULC and increased by 6.8 % with 2013 LULC from 1996 LULC.
Keywords: Stream flow analysis Arc SWAT-model –SWAT-CUP