Application of SWAT model for estimate the effect of Land Use to Streamflow at Mae Thang subwatershed, Phrae Province

The transformation of forest land into agricultural areas is one of the factors affecting soil hydrology. The soil plays an important role in water retention. When the soil is degraded, it directly affects the streamflow. Therefore, this study focused on the effect of land use on streamflow using the SWAT model, which is a hydrological model for estimating streamflow in the agent area of agricultural watershed, in Mae Thang subwatershed, Phrae Province. This study simulates 2 scenarios: 1) determining the watershed class area 2 as the forest area with no other changes, and 2) changing both watershed class areas 2 and 3 as forest areas and perennials, respectively. When compared to the existing land use condition, the results showed that the streamflow from both simulations tends to drop during the wet period and increase during the dry period. This is because there are more perennial and forested areas, which leads to more plant transpiration. In contrast, it aids in reducing surface flow, which promotes soil infiltration, soil water storage, and stream flow during the dry season.