Net Groundwater Recharge in California Occurs Primarily During Above‐Average Snowpack Years

Abstract In a new application of GRACE and GRACE‐FO satellite observations, we estimate basin‐scale net groundwater recharge rates for the combined Sacramento, San Joaquin, and Tulare basins encompassing California's Central Valley aquifer. Net recharge is calculated as the temporal derivative of groundwater storage anomalies and compared with precipitation and snow water equivalent over a fixed study area. Net positive recharge is rare, occurring in only six water years since 2004, and is consistently associated with years of above‐average Sierra Nevada snowpack. Across the observational record, net positive recharge is observed only in years when snow water equivalent exceeds approximately 21 km 3 (17 MAF; ∼121% of the 20‐year mean value), with the largest recharge event coinciding with the exceptionally wet winter of water year 2023. These results suggest that above‐average snowpack conditions, rather than rainfall alone, are an important enabling condition for basin‐scale groundwater recharge under a warming climate.