Abstract

Intermittent water supply (IWS), where piped water 6 is not continuously available, can compromise water security and 7 quality. Extreme rainfall may exacerbate these risks by enabling 8 microbial contaminants to enter distribution systems. We assessed 9 the association between household piped water intermittency and 10 Escherichia coli concentrations in drinking water samples sourced 11 from piped systems (n = 1098) and whether extreme rainfall events 12 (>90th percentile) modified this relationship. Participants included 13 234 households from six Ecuadorian communities in the ECoMiD 14 birth cohort. We measured intermittency as days/week, hours/day, 15 and hours/week without water supply. Households in IWS 16 communities had significantly more contaminated water samples 17 than those in the city, which had a nearly continuous water supply 18 (CWS) (OR: 10.4 [95% CI: 5.9−18.4]). Extreme rainfall modified the association between IWS and water contamination (p for 19 interaction = 0.014): each additional day without water was associated with 42% higher odds of contamination when an extreme 20 rainfall event occurred within 4 days prior to sampling (1.42 [1.09−1.84]). Effect modification was also observed for rainfall lag 21 windows of 3−7 days but not for other intermittency definitions. These findings suggest that more frequent water service 22 interruptions per week may exacerbate household vulnerability to extreme weather events, reinforcing the need for a resilient, well23 maintained water infrastructure.

KEYWORDS: water intermittency, water quality, Escherichia coli, water insecurity, piped water