“Deep Aquifers in Southern California Still Depleted Despite Historic Rainstorms: Stanford Study Reveals”

A new study conducted by Stanford University scientists has revealed that the rainstorms that hit Southern California in 2023 were not enough to fully replenish deep underground aquifers that had been depleted over the past two decades due to excessive pumping. The research, published in the journal Science, focused on groundwater levels in Los Angeles and Orange counties.

While the shallow aquifers in the region saw a rebound in water levels following the storms, the deeper aquifers located more than 150 feet underground only recovered about 25% of the water lost to pumping since 2006. This indicates that the damage caused by long-term droughts has not been fully repaired.

Lead author of the study, Shujuan Mao, who is now an assistant professor at the University of Texas at Austin, stated that it will take many more wet years for the deep aquifers to fully recover from the depletion accumulated during recent droughts. The findings emphasize the need for sustained efforts to replenish groundwater in the region.

Approximately one-third of Southern California’s water supply comes from groundwater wells, with the rest being imported from various sources. The study highlights the importance of implementing strategies to conserve and manage water resources effectively.

The researchers utilized a novel approach to track groundwater levels by repurposing seismic data from California’s earthquake monitoring network. This method, known as seismic interferometry, allowed them to analyze minute vibrations underground to assess water deficits at different depths, down to 2,600 feet.

The study examined trends in several watersheds and groundwater basins, revealing variations in groundwater recharge across different areas. While some regions experienced significant increases in groundwater levels post-storms, others showed less improvement. The research also highlighted the effectiveness of managed recharge efforts, such as Orange County’s Groundwater Replenishment System, in maintaining sustainable groundwater pumping levels.

Overall, the study provides valuable insights for local water officials and policymakers to make informed decisions regarding water use and conservation. The innovative use of seismic data offers a cost-effective way to monitor changes in groundwater levels and guide future efforts to safeguard this vital resource in California.