Hydrological modeling of nutrient transport and mitigation strategies for non-point source pollution in the Bailin...

The Bailin River, a key tributary of the Yangtze River, faces significant water quality challenges due to agricultural non-point source (NPS) pollution exacerbated by industrial discharge and urban runoff. This study employs the Soil and Water Assessment Tool (SWAT) to analyze the temporal and spatial dynamics of runoff as well as total nitrogen (TN) and total phosphorus (TP) loads in the Bailin River basin from 2020 to 2023. A critical source area analysis was performed to identify regions disproportionately contributing to pollutant loads. Through various simulations, including different Best Management Practices (BMPs) scenarios, the study explores their effectiveness in reducing nutrient loads. The findings reveal that nutrient losses are significantly concentrated during the flood season, with TN and TP losses accounting for 58.61 % and 58.92 % of annual totals, respectively. Specific BMP scenarios, combining optimized fertilization, vegetation buffer strips, and grass ditches, demonstrated substantial pollutant reduction, with the best combinations exceeding 58 % reductions for both TN and TP. The study emphasizes the necessity of targeted interventions in critical source areas to optimize management strategies and achieve better water quality outcomes. Continuous monitoring and adaptive management practices will be crucial to addressing ongoing challenges of non-point source pollution in this basin. Ultimately, this research contributes to a deeper understanding of NPS pollution in mountainous watersheds and highlights effective management pathways for improved ecological health and water quality.