Beyond Dissolved Oxygen: Integrated Assessment of Multistage Vortex Aeration Effects on Urban Reservoir Water Quality

Aeration is widely used to increase the oxygen concentration in urban reservoirs, but its broader effect on nutrients, organic matter, and integrated water quality status remains uncertain. This study evaluated the response of the Jangrim reservoir, Busan, South Korea, to a multistage vortex aerator (MVA) using monthly monitoring data from the Water Environment Information System by the Ministry of Environment from 2020 to 2025. The dataset was divided into pre-MVA and post-MVA periods, and water quality changes were assessed using descriptive statistics, box plots, percentage change, time-series regression, Pearson’s correlation analysis, principal component analysis, and three water quality indices: CCME-WQI, RT-WQI, and NSF-WQI. After MVA installation, dissolved oxygen increased from 8.7 mg/L, corresponding to a 72.4% increase. TN and TP decreased by 41.2% and 59.6%, respectively. In contrast, organic matter indicators showed mixed responses: BOD decreased by 18.8%, whereas COD and TOC increased by 4.6% and 13.2%, respectively. WQI scores improved after MVA operation, but CCME-WQI remained in the Poor class. PCA showed that urban pond system water quality was controlled by oxygen-related, nutrient, and organic–particulate factors. Overall, MVA improved oxygen conditions and partially reduced nutrient pressure, but aeration alone was insufficient for full urban pond system restoration.