Source water protection: How well do traditional water quality indicators correlate with pathogen occurrence?

The relationship between traditional water quality variables and pathogen occurrence in sources water is unclear. Through funding from the National Agri-Environmental Standards Initiative (NAESI), under Canada's Agricultural Policy Framework, four agricultural watersheds in Canada were surveyed for pathogens, bacterial water quality indicators, and a suite of physico-chemical water quality indicators to better understand these relationships. Water samples were collected bi-weekly during the spring, summer and fall seasons at 27 sites across all 4 watersheds and tested for these parameters. Statistical analyses, such as descriptive and univariate statistics, probability analysis and regression (multiple linear/logistic regression) were used to ascertain the relationship between water quality parameters and pathogen occurrence in the context of existing standards of source water quality. Overall, there was lack of spatiotemporal consistency or robustness in the correlative relationships between pathogen and traditional water quality indicators. Statistical approaches involving probability analyses provided some important insights about occurrence of pathogens in relation to general water quality in watersheds. The data suggest that each watershed is unique with respect to the spatiotemporal occurrence of pathogens, features which are important for understanding applications and approaches for quantitative microbial risk assessment. 2009 © American Water Works Association WQTC Conference Proceedings. All Rights Reserved.