California Scientists Find Early Warning Sign of Irreversible Groundwater Damage
Some farming towns in California’s Central Valley have sunk by more than 11 feet in recent years because of groundwater pumping, the extraction of water from underground aquifers using wells and electric pumps for drinking, farming and industry.
While some land subsidence is temporary, excessive pumping can cause aquifers to permanently collapse, reducing storage capacity and damaging homes, roads, bridges and canals.
New research from UCLA and Caltech has outlined a way to detect when temporary land subsidence becomes permanent and irreversible.
The research, published this week in Proceedings of the National Academy of Sciences, uses satellite imagery to identify the “abrupt transition to irreversible damage.” Researchers hope this will give decision makers new tools to keep an eye on water resources.
“If you start seeing that the ground is subsiding this fast, like we’re seeing, we’re hoping this is really an early warning signal that, okay, something is wrong, we need to stop pumping groundwater right now,” said Stacy Larochelle, an assistant professor at UCLA.
Larochelle and co-authors found that parts of the Sacramento Valley, which has a centurylong history of groundwater exploitation to sustain the region’s intensive agricultural economy, underwent an abrupt and widespread change around 2021, indicating a shift to rapid, permanent subsidence.
Essentially, researchers saw if ground movement, as detected by satellites, linked up with water levels in wells, which indicated temporary sinking. If the ground didn’t bounce back when water levels did, the sink was permanent. Larochelle’s hope is that one day this monitoring can be done by satellites alone.
“We think this is the first time that we’re really able to image this transition with such high- quality data,” Larochelle said.
Roland Bürgmann, a UC Berkeley geophysicist who was not involved in the research, said the research clearly showed how permanent damage was done to the Sacramento Valley water system by overuse during the recent drought.
“This could and should have been avoided by proper monitoring and water management,” Bürgmann said. “Every water district in the world should probably be using the kind of satellite imaging data and analysis the authors relied on, so they can recognize when their valuable water storage systems are in danger of such irreversible loss of storage capacity.”
The U.S Geological Survey’s California Water Center estimates 15% of the Central Valley’s groundwater storage capacity has been permanently lost because of subsidence.