A study has found that despite record rainfall in Los Angeles in 2023, the region’s groundwater supply remained depleted. The researchers used a network of sensitive seismometers to monitor water levels and developed a new “Seismic Drought Index” to quantify water deficits.
The data showed that shallow aquifers were filled to nearly capacity after the series of storms, but deeper aquifers regained only about 25% of the groundwater they had lost since 2006. The study’s lead author, Shujuan Mao, warned that a single epic storm season is not enough to restore the depletion accumulated over recent droughts.
The new method allows for high-resolution groundwater measurements via decades of seismic vibrations, which were previously considered “noise” by seismologists. This technology can assess entire basins at once and provides data on groundwater recharge.
Mao hopes that this method can enable water managers to divert more water as needed and refill underground reservoirs, which could hold up to 17 times the volume of California’s surface basins. Groundwater is responsible for between 40% and 60% of the state’s freshwater supply, making accurate assessments critical. However, some areas may have already collapsed due to prolonged droughts and overuse, highlighting the need for continued monitoring and conservation efforts.
Source: https://thehill.com/policy/energy-environment/5143151-los-angeles-groundwater-depletion-study