Study finds California farmland is sinking shockingly fast

Farmland across the Sacramento Valley sank rapidly as water was drained from underground aquifers during the historic 2020 drought, a new study found, a sign that the Central Valley’s water problems could be spreading north.

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Satellite observations over the Sacramento Valley detected “irreversible deformation” from 2020 to 2022 due to increased groundwater pumping, according to research published in the Proceedings of the National Academy of Sciences on Monday. The study found that land did not rebound following the extreme drought years. The rapid and extensive land subsidence in the region pointed to a loss of storage capacity in the aquifer system, which researchers said poses “a serious threat to California’s water resources and infrastructure.” 

The Sacramento Valley is the northernmost section of California’s Central Valley, which has been an agricultural powerhouse for over a century. However, aquifer depletion now threatens the industry. The San Joaquin Valley in the region’s southern portion by as much as 30 feet, which has forced farms to shutter under decreasing water supplies.

Letitia Grenier, the director of the PPIC Water Policy Center, which was not affiliated with the study, called the research a “wakeup call” for water management in the region in an email to SFGATE.

“This is the first time that permanent damage to the aquifer has been documented in the Sacramento Valley—when the land surface sank due to groundwater pumping and did not rebound,” Grenier said. 

Stacy Larochelle, a co-author of the report and an assistant professor of geophysics at UCLA, said in an email to SFGATE that the study found an uneven ground loss across the study area, with the largest loss at around 2.7 feet. Just 50 miles north of Sacramento in Colusa County, permanent subsidence reached approximately 2 feet from January 2021 to October 2022. 

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Aquifers are underground water reserves that provide massive amounts of water that can be quickly extracted by farmers and other industries. Grenier said the permanent loss of ground is particularly troubling because it means there is now less capacity to store water for future use. 

“As climate change moves forward and droughts become more intense, this study is a reminder that even regions with relatively more water, like the Sacramento Valley, will need to focus on better groundwater management in order to avoid damaging their aquifers,” Grenier said.

Grenier said other impacts of land subsidence can cause roads and canals to break, which can lead to costly fixes.

“The significance is that we are seeing a practice go from reversible effects to irreversible effects,” Grenier said. “And that is a big difference. Since climate projections tell us that future droughts will be very intense, like 2021 and 2022, we know that we need to learn from this experience.” 

While the “overexploitation” of groundwater during the drought years created permanent damage, the study’s authors said they were hopeful the recent resurgence in California’s rainy season could prevent further harm to the aquifer system.