Modeling the impacts of alternative soil conservation practices for an agricultural watershed with the SWAT model

Abstract

Soil erosion is a major environmental problem worldwide. The effects of this problem are serious and require effective soil conservation to protect our land and water. The main aim of this study was to target the critical subwatersheds of an agricultural watershed and recommend effective soil conservation treatments to minimize sediment yield using a physical process based scale model, Soil and Water Assessment Tool (SWAT). The Lam-Sonthi watershed (357 km2) in central Thailand was selected for this study. The SWAT model was calibrated and validated using monitored time-series data (streamflow and sediment load) of the watershed from 1997 to 2002. The critical sub-watersheds were identified on the basis of average annual sediment yield. The study revealed that for the evaluation period the SWAT model satisfactorily predicts monthly streamflow and sediment load which was indicated by statistical means. The SWAT model identified approximately 40% of the entire watershed as serious soil erosion areas. Several soil conservation treatments were simulated for these critical areas, and the results revealed that the combination of reforestation and mulching was the most effective treatment in reducing sediment yields in the study watershed. This treatment was recommended to the watershed stakeholders.