Abstract:
Land degradation especially soil erosion has already been treated as one of the most serious Problems all around the world that is threatening human existence and survival, with its impacts far felt environmentally, economically and socially. Establishing the impacts of soil erosion requires thorough studies to determine the erosion rates and map out erosion risk areas, and that is being aided by field studies as well as geospatial analysis. However, the best proven way of arresting the erosion effects is by adopting sustainable soil and water conservation measures. This research centered on establishing a detailed understanding of the erosion and sedimentation processes in the watershed, to evaluate a watershed scale effectiveness of the conservation and, to identify optimal BMP types and sites that may be used in the future to further reduce sedimentation of the Namalu sub watershed. In this study ArcGIS 10.4 was used to prepare thematic maps and develop RUSLE model. SWAT was used to develop the model and evaluate the pre- and postmanagement practices of the sub watershed. SWAT output viewer and Microsoft excel were used to analyze the results. The results show that there was an increase in annual sediment yield from 2001 to 2010 that is 10.3394/ha in 2001 and 18.7527t/ha in 2010, With a cumulative sediment yield of706.7667 t/ha. The highest sediment yield was observed in 2007 with 605.25 t/ha. Furthermore, implementation of contouring and terracing resulted in a 75.92% and 74.6% sediment yield reduction with the overall sediment yield reduction of 68.4%. Furthermore, filter strips averagely reduced sediment yield by 82.28% with the highest reduction of 96.246% achieved with a 6 m wide filter strip. Generally, implementation of these conservation measures yields some good results, however, further studies on the cost effectiveness of these conservation practices are highly recommended.
Keywords: RUSLE model, SWAT model, water erosion and sustainable conservation measures
