Bolorchimeg Turkhuu2024-11-142024-11-142022-05-16https://gmitlibrary.net/handle/123456789/152The Tuul river basin is a unique region in that it covers only 3.2% of Mongolian territory, but 48% of Mongolian total population lives in Ulaanbaatar. Also, 66.5% of the Mongolian total GDP was produced within this river basin in 2020. Land-use changes due to the expansion of urbanization can pose a threat to downstream ecosystems of the Tuul river, particularly soil and water quality, leading to an increase in surface runoff and nutrient loads. The main purpose of this study is to evaluate the impacts of land-use and land cover changes in discharge and water quality in the upper part of the Tuul river basin between 2010 and 2019. Land use/land cover changes, digital elevation model, soil, and meteorological data were used as an input data for the Soil and Water Assessment Tool (SWAT) to simulate streamflow and water quality. The model’s performance was determined by statistical parameters including Nash-Sutcliffe efficiency coefficient (NSE), correlation coefficient (r), and percentage bias (PBIAS). Furthermore, prediction uncertainty was measured using the p-factor and r-factor. The values of NSE (0.56 and 0.66) and r (0.77 and 0.82) for calibration and validation periods at a daily time scale showed that the SWAT model could be used to simulate the discharge. The results of calibrated model showed the increase in surface runoff, and loads of nitrate and phosphorus due to rapid urbanization in the Tuul river basin. The outcomes of the study can be useful in understanding water management strategies and making more appropriate land management decisions and practices.enThesis