Evaluation of Spatial-Temporal Variation of Soil Loss and Best Conservation Measures in an East Africa Catchment

Soil conservation (SC) is essential to maintain the reservoir service life and increase the yield since soil erosion is a major global concern that adversely affects not only the storage capacity but also the land fertility. This study evaluates the spatio-temporal variation of soil erosion using the popular SWAT model and identifies the best SC practice for Tekeze watershed located in the Northern part of Ethiopia. To accomplish this, four soil conservation management scenarios involving baseline, terracing, contouring, and grassed waterway scenarios are selected for soil loss evaluation. The SWAT model was calibrated and validated with R-2 values of 0.7 and 0.9 and NSE values of 0.8 and 0.7, respectively, indicating satisfactory model performance. Five sub-basins of the catchment were found to be more susceptible to erosion with an average annual soil loss of 25.15 tons/ha/yr. Employment of the proposed SC measures in the sub-watershed erosion was reduced by 35.18%, 27.11%, and 18.76%, respectively, which is significant when compared with the baseline scenario. Since the investment cost of execution of an SC measure in a large watershed is very high, priority areas are also identified for cost savings as well as improved work efficiency.