Management strategies for reducing soil degradation through modeling in a GIS environment in northern Ethiopia catchment

Abstract

Soil degradation by erosion is the most serious threat to food security in Ethiopia. Thus, effective management strategies (scenarios) that reduce soil degradation are crucial. However, the application of models such as Soil and Water Assessment Tool (SWAT) that simulate the impact of different scenarios on soil degradation by erosion in Ethiopia condition is limited. This study is aimed to evaluate the effectiveness of different scenarios in reducing runoff, sediment and soil nutrients losses using the SWAT model for the Mai-Negus catchment, northern Ethiopia. The highest erosion in terms of runoff, sediment yield, total nitrogen (TN) and phosphorus (TP) losses was simulated by the baseline scenario at the catchment outlet as 168 mm, 42,000 t year−1, 22,400 and 1,360 kg year−1, respectively. In contrast, the lowest runoff, sediment yield, TN and TP losses were simulated by the scenario that integrated land-use redesign and conservation measures (scenario 6c) at catchmen level as 50 mm, 9,215 t year−1, 6,284 and 341 kg year−1, respectively. These indicate that reduction of sediment, TP, TN and runoff losses by 78, 75, 72 and 70%, respectively, can be achieved by scenario 6c compared to the baseline scenario. Thus, scenario 6c appears relatively more effective as potential management strategy in reducing soil degradation than the other scenarios. This study demonstrates that SWAT model is powerful to select the most technically effective management strategies in reducing soil degradation in a catchment. However, further research is required related to the cost-benefits of such management strategies.