LA Times – 02/13/2025 | The rainstorms that drenched Southern California two years ago weren’t enough to replenish deep underground aquifers that had been depleted by pumping over the last two decades, a new study has found.

Stanford University scientists analyzed how the historic 2023 storms affected groundwater levels across Los Angeles and Orange counties. They found that while shallow aquifers rebounded, deeper aquifers more than 150 feet underground regained only about 25% of the water they had lost to pumping since 2006.

“The rain that comes down in a big burst, a lot of that recharges the shallow aquifers, but it doesn’t necessarily percolate into the deep ones,” said William Ellsworth, a seismologist and geophysics emeritus professor at Stanford who co-wrote the study. “It’s a reminder to everyone that the damage of these long-term droughts has not been replenished.”