Analysis of water quality and trophic status of reservoirs in Chuzhou City, China

Reservoir is a vital tool for human utilization of water resources, and the deterioration of its water quality can seriously threaten the water cycle and sustainable urban development. However, there are relatively few studies in academia that analyse and evaluate the water quality of multiple reservoirs at the same time. To address this knowledge deficit, we collected 108 water samples from three different reservoirs in Chuzhou City for 36 months (from 2019 to 2021), explored the drivers of changes in water quality parameters over time and the extent of eutrophication. Our results indicated that the water quality of the reservoirs was deteriorating during the study period, among which Huanglishu Reservoir and Shahe Reservoir reached mild eutrophic status, and both had higher eutrophication levels than Chengxi Reservoir. Secchi depth, total nitrogen and total phosphorus were the principal factors inducing eutrophication. The biassed utilization of reservoir functions was the major contributor to the discrepancy in the degree of eutrophication. Furthermore, Pearson correlation analysis revealed that there are significant correlations between many water quality parameters. Cluster analysis grouped the 12 months of each year into three clusters (stable water level period, rainy season high flow period and winter low flow period). Based on this, analysis of variance showed that most water quality parameters varied considerably between the clusters. Collectively, this study identified the actual water quality conditions of three reservoirs in Chuzhou City and provided guidance for local water quality management and environmental protection.