The private well water climate impact index: Characterization of community-level climate-related hazards and vulnerability in the continental United States.

Background: Private wells use groundwater as their source and their drinking water quality is unregulated in the United States at the federal level. Due to the lack of water quality regulations, those reliant on private wells have the responsibility of ensuring that the water is safe to drink. Where extreme weather is projected to increase with climate change, contamination due to climate-related hazards adds further layers of complexity for those relying on private wells. We sought to characterize community-level climate-related hazards and vulnerability for persons dependent on private wells in the continental United States (CONUS). Additional objectives of this work were to quantify the burden to private well water communities by climate region and demographic group.

Methods: Grounded in the latest climate change framework and private well water literature, we created the Private Well Water Climate Impact Index (PWWCII). We searched the literature and identified nationally consistent, publicly available, sub-county data to build Overall, Drought, Flood, and Wildfire PWWCIIs at the national and state scales. We adapted the technical construction of this relative index from the California Communities Environmental Health Screening Tool (CalEnviroScreen 4.0).

Results: The distribution of climate-related impact census tracts varied across CONUS by nationally-normed PWWCII type. Compared to the Southeast where the majority of the 2010 estimated U.S. private well water population lived, the estimated persons dependent upon private well water living in the West had an increased odds of living in higher impact census tracts for the Overall, Drought, and Wildfire PWWCIIs across CONUS. Compared to non-Hispanic White persons, non-Hispanic American Indian and Alaska Native (AI/AN) persons had an increased odds of living in higher impact census tracts for all four PWWCII types across CONUS.

Conclusions: The PWWCII fills a gap as it provides a baseline understanding of potential climate-related impacts to communities reliant on private well water across CONUS.