Co-created citizen science to understand the quality of harvested rainwater and influential predictors for current and future irrigation use

Abstract:

As climate change exacerbates water scarcity, rainwater harvesting for household gardening becomes an increasingly common practice. However, the quality of harvested rainwater is not well studied, and the human health risks associated with its use are unknown. Additionally, there is currently no federal U.S. standard to assess harvested rainwater. Project Harvest is a co-created citizen science project studying the quality of harvested rainwater, primarily used for garden irrigation, in four environmental justice communities in Arizona. Rooftop harvested rainwater samples were collected by trained participants seasonally over the course of three years (2017- 2020). Several samples, out of 581, exceeded the United States Department of Agriculture agricultural irrigation standard for aluminum (0.34), cadmium (0.68%), chromium (0.17%), copper (5.85%), manganese (2.93%), nickel (0.34%), and zinc (4.30%), indicating that rooftop harvested rainwater may not be safe for consistent garden irrigation. Furthermore, linear mixed-models indicate that community, season, and rainwater harvesting infrastructure (e.g., roof material, cistern type) significantly influence the concentrations of metal(loid)s in harvested rainwater. This study contributes a robust citizen science dataset, which provides an opportunity to study local scientific questions to inform community use of natural resources and influence the creation of local, state, and federal rainwater quality standards or individual and collective actions to protect this resource.