Assessment of River Ecosystem Health Based on Wastewater Treatment Plants and Land Use in the Geum River Basin

This study evaluated the impacts of point source pollution originating from wastewater treatment plants (WTs) and non-point source pollution associated with agricultural and urban areas on fish-based ecological health in the Geum River Basin. Comprehensive analyses were conducted, including chemical assessments for eutrophication (in terms of TN and TP), organic pollution (BOD and COD), algal biomass (Chlorophyll a), fish-based ecological health assessments (FAI), and fish guild analyses using the statistical approaches of regression for chemical variables as independent variables and FAI as dependent variable and non-metric multidimensional scaling (NMDS) analyses (for ordination of sampling sites according to pollution sources). Chemical analysis indicated that the upstream sites, as a pristine area, were classified as an “excellent∼good” condition (rank: Ⅰa∼Ⅰb) for the key chemical criteria, whereas urban and agricultural sites were classified as a fair (rank: Ⅲ), and the WTs as poor (rank: Ⅴ), reflecting severe chemical degradation. The ecological health, based on the FAI model values, were “excellent” at the upstream sites, “good” in urban areas, and the “fair” at the agricultural and the WTs sites, indicating a moderate ecological impairment. The model values of FAI declined with increasing concentrations of TN and TP, accompanied by higher relative abundances of tolerant and omnivorous species. The NMDS analysis revealed that the pristine upstream sites were associated with high sensitive and carnivorous species, whereas the WTs and non-point source sites (agricultural and urban) were characterized by tolerant and omnivorous species. Overall, these findings demonstrate that sensitive species dominate in the upstream areas with low pollution, while tolerant and omnivorous species prevail in degraded habitats. The pronounced influence of WTs underscores the necessity for integrated management of both point and non-point pollution sources. This study provides essential insights for land use based river basin planning and offers a scientific basis for future river management and ecological restoration efforts.