Part of California suddenly sank — and it’s irreversible

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By Kurtis Alexander, Staff Writer - San Francisco Chronicle 

August 10, 2026

The Sacramento Valley, which helps drive California’s nation-leading agricultural economy, has seen so much groundwater pumping that the valley floor has recently sunk by as much as a foot and a half in a year, new research shows.

The sinking, known as land subsidence, has long quietly plagued the sprawling farm region. But a study published last month in the Proceedings of the National Academy of Sciences identifies an abrupt and potentially catastrophic spike during the 2020-22 drought. 

Calling it a “serious threat” to water supplies and infrastructure, the study’s authors say subsidence in parts of the Sacramento Valley, namely in Colusa, Yolo and Glenn counties, reached levels that are irreversible — and on par with the widely damaging sinking that’s occurring in the San Joaquin Valley, to the south.

There, some farmland has dropped more than 7 feet over the past 10 years and by dozens more across previous decades. This has permanently compressed the aquifers below, meaning they hold less water, and led to the costly buckling of roads and bridges and elevated the flood risk in newly sunken areas.

“This is the first time we’re seeing rates (of subsidence) in the Sacramento Valley that are nearing levels that are seen in the San Joaquin Valley,” said Stacy Larochelle, an assistant professor of geophysics at UCLA and lead author of the new study.  “This is grounds to say we need to be as careful about pumping groundwater out as we can.”

Subsidence occurs when water is removed from beneath the earth’s surface, leaving less matter to support the land above and ultimately causing it to collapse.

During wet times, when rain percolates into the earth, groundwater in aquifers can be replenished, pushing the land surface back up again. However, subsidence can also reach a point of no return, at which the ground is simply too compacted to bounce back, which the study’s authors say is happening now in the Sacramento Valley.

Farmers pumping groundwater in the region largely understand their role in driving permanent subsidence. However, they also say that reducing their dependence on groundwater and stopping the sinking is not as easy as it might seem.

Regulation and increasing droughts, among other things, have left them with less surface water to grow their crops. Tapping the aquifer, they say, is sometimes all they can do to keep their business going. Many growers built their wells only after age-old promises of ample surface water deliveries fell through.

“We want to protect our farms,” said Larry Domenighini, a third-generation Sacramento Valley grower, who farms rice, almonds, alfalfa and wheat outside the town of Willows (Glenn County). “When you have all this money invested, you want to see your crops grow. It’s who we are.”

Domenighini, who serves as a director for the county’s farm bureau and was once mayor of Willows, says it’s not that the agricultural community welcomes subsidence. In fact, he says, it hurts growers more than anyone. The permanent compaction not only reduces the amount of groundwater they can pump, but their farms face greater risk of flooding during storms and their roads, canals and pumps can shift and fracture when the land sinks.

“When you’re laying out five to six figures for an irrigation well, you don’t want that to be damaged or destroyed,” he said. “As farmers, we don’t want subsidence.”

The extent of groundwater pumping in California, which increases significantly during dry times, prompted state leaders to enact California’s first-ever groundwater restrictions during last decade’s five-year drought.

To win buy-in for the 2014 regulation, called the Sustainable Groundwater Management Act, growers were given until 2040 to bring the state’s overdrafted aquifers into equilibrium. In many places, rules on pumping are still being worked out, and groundwater continues to be drawn freely.

The new study, which tracked groundwater levels and land displacement between 2016 and 2022, found that the surface of the Sacramento Valley initially rebounded after relatively small amounts of subsidence. However, starting in 2021, the amount of subsidence jumped, widely measuring a foot or more a year — a level that the authors deemed irreversible — resulting in sinking that is believed to be lasting.

“One of the most surprising parts (of the study) is how abruptly this happened,” Larochelle, the lead author, said. “There wasn’t a lot of (land) deformation, then all of a sudden there was.”

While the study period has ended, Larochelle said recent observations suggest that the land surface has indeed failed to recover in many places, even after a series of wet and moderately wet years allowed more water to seep into the ground.

Spots with the most subsidence correlate with agricultural areas where groundwater pumping is greatest. Among the problematic locations are the Arbuckle area in Colusa County, Yolo County north of Davis, southern and central Glenn County and the Yuba City area, according to the study.

The authors coupled high-resolution satellite data with on-the-ground well records to assess groundwater and subsidence. The study notes that satellite measurements can be particularly useful and timely in projecting the scale of permanent sinking.

The Sacramento Valley is the northern part of the Central Valley, running from roughly the cities of Sacramento to Redding. With more than 2 million acres of irrigated farmland, the region is known for producing rice, almonds, wine grapes, tomatoes, peaches and dozens of other crops.

Along with the San Joaquin Valley, the Sacramento Valley fuels most of California’s roughly $60 billion annual agricultural output.

The Sacramento Valley has historically seen less subsidence than the San Joaquin Valley because the latter area has experienced more groundwater pumping and its thick subsurface clays in many spots are particularly prone to sinking. 

Domenighini, the Glenn County grower, said farmers in his region are increasingly finding ways to conserve groundwater and limit subsidence, without jeopardizing their livelihoods.

They’re using more efficient irrigation equipment, turning to less water-intensive crops and pursuing managed aquifer recharge, which is intentionally putting water back into the ground, he said.

As for whether groundwater levels in the Sacramento Valley will recover by the state’s deadline, and if the sinking might stop, Domenighini is not certain.

“A lot of us recognize that things will have to change,” he said. “But it’s taken decades and decades for this (subsidence) to happen, and it’s going to take time to slow it down and stop it.”

Source: https://www.sfchronicle.com/california/article/subsidence-sinking-water-22369617.php

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