How Fast, How Deep, and How Much? — Seismic Sensing of Groundwater Recharge from the 2023 Atmospheric-River Storms

In early 2023, California was struck by intense storms from a series of atmospheric rivers, inflicting extensive damage and hardship on Californians. These storms have also alleviated California's historical drought, rapidly refilling surface reservoirs; however, it remains unclear how much water California's depleted underground reservoirs have absorbed. Understanding these aspects is crucial for assessing the state's total water deficit and guiding sustainable water management.

Here we apply advanced seismic interferometry techniques to assess the natural recharge of aquifers in Greater Los Angeles from 2003 through the 2023 storms. The derived seismic hydrographs reveal that the expression of groundwater drought is distinct from that of surface-water drought: While surface-water storage nearly fully recovered in the epic wet season of 2023, less than 25% of the groundwater lost over the previous two decades was replenished. On a decadal scale, we find significant depletion with slight storm-related replenishment in aquifers below 50 m depth. Furthermore, seismic imaging across the study area shows prominent groundwater restoration in San Gabriel Valley, highlighting the role of mountain recharge for aquifer replenishment.

This study showcases the promise of seismic sensing for providing new insights into groundwater hydrology at different depths. Our findings emphasize the need to monitor deep aquifers for a more complete assessment of water resources, which is crucial for facilitating data-informed amidst extreme weather patterns.