A new study published in Science reveals that California’s aquifers, which serve over 10 million residents of Los Angeles and Orange counties, remain depleted despite a year of extreme precipitation. Researchers used seismic data to estimate water levels in the region’s aquifers, finding that even deep aquifers regained only about 25% of the groundwater they had lost since 2006.
The study analyzed the impact of historic atmospheric river storms in 2023, which dumped over 140% of California’s 20th-century average annual precipitation in just three months. However, this was not enough to replenish deeper aquifers, which took longer to recover. Lead author Shujuan Mao said that a single epic storm season is not enough to restore groundwater depletion accumulated over recent droughts.
Mao and her team developed a new “Seismic Drought Index” for quantifying water deficits at different depths. The index values largely reinforce what water managers already know – recharging deep aquifers can take many years. The study found that the seismic method can measure entire basins at once, across different depths down to 800 meters, and over a period of decades.
“This new technology is potentially game-changing for groundwater management,” said Gregory Beroza, a professor in Earth Science. “It moves us to a possible future where we can measure groundwater recharge – how much there is and where it’s going – much as we do with stream gauges for surface water.”
Source: https://www.jsg.utexas.edu/news/2025/02/new-method-for-measuring-groundwater-shows-californias-aquifers-remain-depleted