Untangling the Links Between Microbial Activity and Water Quality Dynamics in a Drinking Water Reservoir via Multivariate Analyses

Conventional physicochemical parameter-based monitoring fails to provide real-time early warning of microbial risks in drinking water sources, highlighting the critical necessity to unravel the inherent associations between microbial activity and water quality dynamics. This study integrated a domestically developed microbial enzymatic analyzer with multivariate analyses to assess real-time microbial activity in a complex reservoir. Measurements of microbial indicators and physicochemical parameters were conducted at eight sites during dry and wet seasons, plus six months of continuous monitoring at a polluted tributary site. Key findings: (1) Water quality showed clear spatiotemporal variation, worse in the wet season than the dry season, with tributaries more polluted than mainstream, and downstream better than upstream; (2) Microbial activity exhibited spatial heterogeneity, with a significant positive correlation between E. coli and Enterococcus (EC); (3) Microbial activity responded to key water quality indicators, and both E. coli and EC correlated positively with NH3-N. EC also correlated positively with TP. In summary, this study reveals a mechanism-based link between microbial activity and key water quality parameters, providing a theoretical foundation for a microbial-response-centered early warning model. This marks a shift from conventional reactive monitoring to proactive risk management for drinking water safety, offering a new paradigm with ecological indication and practical value.