Data-driven approaches to advance California’s Human Right to Water Law: Characterizing inequities in drinking water quality among domestic well communities and public drinking water systems

Abstract

In 2012, California became the first state to recognize the Human Right to Water. However, roughly 10% of California’s public drinking water systems are currently out of compliance with federal and state drinking water quality standards, and an estimated 6 million Californians are served by systems that have been in violation at some point since 2012. A disproportionate number of water quality violations occur in smaller drinking water systems that serve rural, low income communities color, where a lack of resources make it challenging to treat contaminated water and meet regulatory standards. Additionally, significant data gaps exist regarding the location and water quality of unregulated water sources, such as private domestic wells.The UC Berkeley Water Equity Science Shop sought to characterize demographic differences in water quality for communities reliant upon domestic wells and community water systems. We integrated data from the Department of Water Resources; Tracking California’s Drinking Water Systems Geographic Reporting Tool; and the US Census to identify the location of likely domestic well communities across California. Using water quality data from CalEnviroscreen 3.0 and the Groundwater Risk Index Tool, and demographic data from the American Community Survey, we estimate sociodemographic differences in water quality using multivariate analysis.Results indicate that over 1.3 million Californians rely on private wells for drinking water. We estimate 49,000 and 102,000 people live in domestic well areas where drinking water is likely to exceed regulatory standards for nitrates and arsenic, respectively. Average contaminant concentrations of arsenic and nitrate are over 1.5 times higher in areas served by domestic wells than in community water systems. Multivariate statistical models indicate that area-level measures of race/ethnicity and poverty are associated with increases in drinking water contaminant concentrations in domestic well areas.