Evaluation of Land Use Changes on Stream Discharge by SWAT Model and Remote Sensing in Agro-Forestry Basin in Nghinh Tuong Subwatershed, Northern Vietnam

The goal of this study is to use the "Soil and Water Assessment Tool (SWAT)" model and GIS to assess the influence of land-use changes on stream discharge in the Nghinh Tuong watershed (a branch of the Cau river) in Northern Vietnam. The watershed was covered by 56% forested land, 30% agricultural land, and remain for others.

For the calibration period, Stream discharge observed data from 2001 to 2010 was employed, while the validation period was from 2011 to 2020.The results revealed thattwo coefficients (NSE and PBIAS) to evaluate model performance were 0.76 and 6.54% for calibration and 0.87 and 4.74% for validation period respectively. Stream discharge is strongly influenced not only by the amount of precipitation but also by changes in land use. In comparison to the baseline scenario, agricultural land (corn, orchard, and tea) increases by 9782.67 ha (2.45%), while forest (forest-mixed) decreases by 1091.77 ha (2.75%). Furthermore, relative to the baseline period, precipitation increases 3.74 percent in the mean wet season but falls 0.5 percent in the mean dry season. Not only for the Baseline scenario, but also for Scenario 1, the SWAT model was able to successfully simulate stream discharge and sediment output for the Nghinh Tuong watershed. In brief, SWAT demonstrates its ability to simulate stream discharge at the subwatershed level. It is a useful instrument for assisting in the management of water quantity and quality in the Nghinh Tuong watershed. SWAT is a good method for resource and environmental management, according to this research.