Thousands of domestic and public supply wells face failure despite groundwater sustainability reform in California’s Central Valley

Declining groundwater levels are causing wells to run dry, increasing water and food insecurity, and often acutely impacting marginalized communities across the world. Despite the ubiquitousness and severity of impacts, groundwater research has focused on piecemeal policy instruments or quantified groundwater depletion. How sustainability definitions shape the fate of sustainability reforms and their outcomes is unexplored. Here, we examine one of the world’s large-scale sustainability reforms, the California Sustainable Groundwater Management Act (SGMA), and estimate the impact of sustainability criteria on well failure. We show that proposed sustainability measures accommodate business as usual groundwater level decline, impacting over 10,000 drinking water wells, and 14,000-120,000 domestic well users who could lose access to their source of drinking water. These findings highlight the necessity of carefully and critically engaging in the evaluation of sustainability definitions and their operationalization to prevent detrimental impacts, like threats to household and municipal water supply.