# Meteorological Influence on Drinking Water Quality: Microbial Variability in Groundwater Wells and Piped Distribution Networks from Western Romania

## TL;DR

This study shows how weather affects drinking water quality in Romania, with groundwater wells being more vulnerable to contamination than piped networks.

## Contribution

The study quantifies meteorological influences on microbial contamination in temperate continental climates.

## Key findings

- Groundwater wells are more prone to coliform and E. coli contamination, especially in summer.
- Precipitation causes short-term contamination spikes in wells with a 2-day lag.
- Piped networks show delayed and weaker responses to weather changes.

## Abstract

Climate variability plays a crucial role in shaping drinking water quality, yet the quantitative links between meteorological factors and microbiological contamination remain underexplored in temperate continental climates. A secondary data analysis was conducted on 15,394 microbiological water quality test results collected between 2015 and 2024, including heterotrophic plate counts (22 °C and 37 °C), coliform bacteria, and Escherichia coli, and their associations with local meteorological conditions across groundwater wells and piped distribution networks were examined. A clear distinction emerged: groundwater wells showed higher vulnerability to primary microbial contamination (coliforms and E. coli), whereas distribution networks exhibited higher odds of heterotrophic plate count exceedances, indicating greater susceptibility to post-treatment microbial regrowth. In groundwater wells, temperature showed strong positive associations with all microbial indicators (p < 0.001), with pronounced summer peaks in coliforms and E. coli, while precipitation triggered short-term contamination spikes characterized by a 2-day lag. In contrast, piped networks exhibited weaker and more delayed meteorological responses. These results highlight the need for a shift from climate-responsive to climate-pre-emptive water quality monitoring by incorporating meteorological forecasts, especially for non-chlorinated groundwater sources.