In 2020, a historic drought struck California’s Central Valley, where one-quarter of the food produced in the United States is grown, causing farmers to pump vast amounts of water from wells to keep their crops alive. All that pumping reduced the water pressure within the porous sediments storing that water deep underground. As a result, those sediments compacted over the next 2 years—causing land surfaces in the northern part of the Central Valley, known as the Sacramento Valley, to sink by more than half a meter.
This kind of subsidence is typically reversible, or “elastic.” Rainfall seeps into the ground and refills the empty sediment pores, causing the surface to rebound. But in 2021, the aquifer compacted so quickly and extensively
that it likely permanently lost its capacity to store water, researchers report today in the
Proceedings of the National Academy of Sciences.