Estimation of Sediment Yield and Evaluation of Management Options in the Watershed Using SWAT Model

Abstract

Land degradation and sedimentation are global issues stemming from inappropriate land management practices within watersheds, primarily due to soil erosion. The primary aim of this investigation was to estimate sediment yield, pinpoint erosion-prone areas, and determine effective strategies for reducing erosion and sediment yield within the Mormora watershed utilizing the SWAT model. The performance of the SWAT model was assessed through calibration and validation procedures employing the Sequential Uncertainty Fitting 2 (SUFI-2) algorithm within the SWAT Calibration and Uncertainty Procedures (SWAT-CUP). Calibration was conducted for the period 1993 to 2006, while validation was carried out for 2007 to 2013, focusing on streamflow and sediment yields at gauging station. Various metrics including R2, NSE, RSR, and PBIAS were used to assess model performance. All model performance metrics indicated high accuracy. The average annual sediment yield at the outlet of the watershed was 1.19 million t/year with a spatial average of 8.54 t/ha/year. About 47.33% of the watershed was critical areas demanding implementation of soil conservation strategy. The effectiveness of five watershed management scenarios was compared to existing baseline conditions for their effectiveness in sediment yield reduction. The results indicate soil erosion decreased by 28.3% to 55.9% by applying filter strips, 61.7% to 68.4% by grassed waterways, 71.38% by terracing, 62.64% by contouring, and 46.3% by applying stone/soil bunds. Ultimately, terracing emerged as the most effective strategy for mitigating soil erosion within the study area. Consequently, the research outcomes and the developed methodology serve as a valuable resource for decision-makers, experts, and researchers involved in sustainable watershed management.