[Comprehensive Eutrophication Evaluation and Water Environment Capacity Analysis of Yiwu Yankou Reservoir]

The accumulation of excessive nitrogen, phosphorus, and other nutrients in rivers, lakes, and reservoirs has greatly accelerated eutrophication, which has led to the frequent outbreaks of algal blooms and brought great ecological risks to the related aquatic ecosystems. Evaluations on the eutrophic status of water bodies and estimations of water environment capacity are not only crucial for comprehensive assessment of eutrophic status but also indispensable references for comprehensive management of the aquatic ecosystems. In this study, major environmental variables （chemical oxygen demand, total nitrogen, and total phosphorus） of Yankou Reservoir watershed were monitored monthly from May 2020 to March 2022 and based upon the determined results, the comprehensive eutrophic conditions and water environment capacity were evaluated and estimated. The results showed that the water quality of Yankou Reservoir and upstream rivers exhibited an obvious seasonal variation pattern and during summer, the water qualities of the surface, mesosphere, and understratum of Yankou Reservoir showed significant differences. Estimations on the water environment capacity indicated that nutrients of nitrogen and phosphorus were currently the management focus for the Yankou Reservoir watershed. Integrated evaluation of eutrophic conditions exhibited that the upstream rivers were fundamentally improved to a mesotrophic or oligotrophic state, whilst the surface water of Yankou Reservoir was down to a mild eutrophication state in spring and summer. Based on this study, future treatment and management focuses on controlling water pollution and eutrophication in Yankou Reservoir were proposed. This study provided supportive reference for scientific evaluation and protection of water qualities, control and prevention of water pollutants, and sustainable development of the aquatic environment in Yankou Reservoir.