정연지 Jeong Yeonji , 박상준 Bak Sangjoon , 이봉국 Bong-kuk Lee , 임경재 Lim Kyoung Jae , 한정호 Han Jeongho

DOI:10.15681/KSWE.2025.41.2.91 Vol.41(No.2) 91-101, 2025

This study aimed to quantify total nitrogen (T-N) pollutant loads in the Kyoungan Stream watershed by distinguishing among point sources, direct non-point sources, and base non-point sources. Continuous daily streamflow and water quality datasets were generated using the Soil and Water Assessment Tool (SWAT), which was calibrated against observed streamflow and T-N data. Subsequently, the WAPLE4 program was used to separate total streamflow into direct runoff and baseflow and to estimate pollutant loads. Over the study period (2017-2022), the average annual T-N load in the watershed was approximately 4,032 tons, of which direct non-point sources, base non-point sources, and point sources accounted for 68.4%, 25.4%, and 6.2%, respectively. Subwatershed-scale analyses revealed that subwatersheds with higher proportions of urban areas were associated with larger contributions of direct non-point source loads, whereas subwatersheds with abundant agricultural and forested areas showed a higher proportion of base non-point pollution. These findings highlight the critical influence of urban land use on runoff-driven T-N loads and underscore the need for targeted pollution mitigation strategies based on specific pollutant generation characteristics of each control area. Future research should incorporate evolving land use patterns and other environmental factors affecting pollutant behavior to improve long-term pollutant load predictions and guide sustainable watershed management.

Base non-point source pollution, Direct non-point source pollution, Non-point source pollution, SWAT, T-N pollutant load, WAPLE4