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

Across the world, declining groundwater levels cause wells to run dry, increase water and food insecurity, and often acutely impact groundwater-dependent communities. Despite the ubiquity and severity of these impacts, groundwater research has primarily focused on economic policy instruments for sustainable management or the quantification of groundwater depletion, rather than assessing the impacts of management decisions. In particular, how definitions of groundwater sustainability shape the fate of resource users remains unexplored. Here, we examine one of the world's largest-scale environmental sustainability reforms, the California Sustainable Groundwater Management Act (SGMA), and estimate the impact of sustainability definitions proposed in groundwater sustainability plans (GSPs) on well failure. We show that locally-proposed sustainability criteria are consistent with business as usual groundwater level decline, and if reached, could impact over 9000 domestic wells and around 1000 public supply wells. These findings highlight the necessity of careful and critical evaluation of locally-developed sustainability definitions and their implementation to prevent detrimental impacts, such as threats to household and municipal water supply. [ABSTRACT FROM AUTHOR]