Modelling and assessing eutrophication and antibiotic risks in a lake system under large‑scale water diversion

Abstract

Water diversion projects are widely implemented to address water scarcity, improve water quality, and restore ecological conditions in degraded aquatic systems. This study applies a process-based hydrodynamic-environmental model to investigate the dynamics of eutrophication and the representative antibiotic tetracycline in Chaohu Lake under the influence of the Yangtze–Chaohu Water Diversion Project. To explore the influence of different diversion pathways, two numerical scenarios were developed representing two alternative water diversion options: western and eastern routes. The model was validated against field data, achieving Nash–Sutcliffe efficiency values ranging from 0.34 to 0.80 and absolute relative differences between 9.31% and 18.64%, indicating satisfactory performance. Assessment results revealed that tetracycline posed high ecological risks during summer, while nutrient concentrations and eutrophication levels remained within mild to moderate ranges throughout the study period. Comparison of the two scenarios indicated that the western route more effectively reduced ecological risks, yielding annual reductions of 9.12% in total phosphorus, 13.68% in chlorophyll-a, and 11.5% in tetracycline concentrations. This study provides critical insights for optimizing the operation of water diversion projects and supports the sustainable management of aquatic ecosystems, particularly in mitigating the combined threats of eutrophication and antibiotic pollution.