Assessing the impact of rainwater harvesting infrastructure and gardening trends on microbial indicator organism presence in harvested rainwater and garden soils

Aim: To assess the microbial water quality of harvested rainwater infrastructure used to supplement household water uses for homegrown produce. Methods and Results: Using a co-created community science methodology, between 2017 and 2020, a total of 587 harvested rainwater samples and 147 garden soil samples irrigated with harvested rainwater were collected from four Arizona communities and analyzed for coliform, Escherichia coli, and/or Salmonella. Participants also completed a home description survey regarding their home and surrounding area, water harvesting infrastructure, and gardening habits. Conclusion: Chi-Square tests revealed that the quality of harvested rainwater is affected by proximity to a waste disposal or incineration facility, animal presence, cistern treatment, and cistern age (P < 0.05), while soil samples were associated with community (P < 0.05). Coliform and E. coli concentrations in both sample types were greater in the monsoon season. Significance and impact of the study There is an increased interest in harvesting rainwater in the southwestern United States, but a few studies have looked at rainwater harvesting infrastructure, and water safety to inform gardening practices. This study sheds light on the presence and absence of fecal indicator bacteria in harvested rainwater.