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STANFORD, Calif. — Could a large chunk of the Pacific Coast disappear in the near future? Imagine the ground beneath your feet slowly but steadily sinking — so dramatically that canals crack, wells break, and entire landscapes transform. This isn’t a disaster movie; it’s the stark reality unfolding in California’s San Joaquin Valley. A new study documents how the earth is literally collapsing under the weight of our water demands.
A groundbreaking report by Stanford University researchers reveals a startling trend: the valley’s land is sinking at a rate of nearly an inch per year, a phenomenon scientists call “subsidence” that threatens one of the world’s most critical agricultural regions.
“There are two astonishing things about the subsidence in the valley,” says Rosemary Knight, the study’s senior author, in a university release. “First, is the magnitude of what occurred prior to 1970. And second, is that it is happening again today.”
The problem isn’t new. Between 1925 and 1970, aggressive groundwater pumping caused more than 4,000 square miles — an area half the size of New Jersey — to sink dramatically. Some locations dropped a staggering 30 feet. Now, history appears to be repeating itself.
Think of underground aquifers like a natural sponge. When water is continuously extracted without replenishment, the sediments compress, permanently altering the landscape. It’s similar to squeezing a wet sponge until it can no longer hold its original shape.
According to the report in the journal Communications Earth and Environment, the consequences could be dire. Multimillion-dollar infrastructure repairs are now required for critical water canals. Local wells and irrigation systems are being damaged, further complicating water supply in a region that feeds much of the country.
“How much was last year’s flooding worsened by subsidence? How much are farmers spending to re-level their land? A lot of the costs of subsidence aren’t well known,” highlights Matthew Lees, the study’s lead author.
The researchers used cutting-edge satellite technology called interferometric synthetic aperture radar (InSAR) to track these elevation changes. By beaming radar signals from orbit and analyzing their reflections, they could measure ground movement with remarkable precision.
Their solution? A strategy called flood-managed aquifer recharge (flood-MAR). This approach involves strategically diverting excess surface water — from precipitation and snowmelt — to locations where it can seep down and replenish underground water reserves.
Knight is cautiously optimistic. The study suggests the valley needs about 220 billion gallons of water annually to prevent further subsidence — an amount remarkably close to the region’s average surface water surplus.
“We should be targeting the places where subsidence will cause the greatest social and economic costs,” Knight explains.
This means prioritizing areas near critical infrastructure and small community wells. As California continues to grapple with climate change and water scarcity, this research offers a crucial roadmap. It’s a stark reminder that our relationship with water is complex, and the ground beneath our feet is far more dynamic than we imagine.
Paper Summary
Methodology
The researchers studied land subsidence in California’s San Joaquin Valley, focusing on the years 2006 to 2022. To measure how much the land sank, they used data from satellites equipped with a technology called InSAR, which can track ground movement over time. They also filled gaps in the satellite data by using information from local GPS stations and other monitoring tools, like leveling surveys and extensometers. This data was carefully analyzed and cross-validated to ensure accuracy, enabling the team to estimate the total volume of subsidence across the valley during different time periods.
Key Results
The study found that between 2006 and 2022, the San Joaquin Valley experienced significant land sinking, totaling 14 cubic kilometers — about the same amount as a similar sinking event that took 24 years in the mid-20th century. The sinking was especially severe during drought years when farmers relied heavily on groundwater for irrigation. Two key areas, near El Nido and Corcoran, showed the most dramatic sinking. This subsidence caused serious damage to infrastructure like aqueducts, wells, and even the proposed high-speed rail route.
Study Limitations
There was a lack of consistent satellite data for a few years (2011–2015), so the team had to estimate the sinking during that period using less detailed information. Additionally, the study’s focus on large-scale trends means some of the findings might not apply to smaller, local areas. The methods also relied on assumptions about how subsidence patterns remained consistent over time, which could introduce some uncertainty.
Discussion & Takeaways
The findings emphasize the need for better groundwater management to prevent further land sinking. The researchers suggest focusing on reducing water extraction from deep aquifers where most of the subsidence occurs. They also recommend improving recharge efforts to refill these aquifers. This study provides a warning that subsidence will continue to threaten agriculture, infrastructure, and communities unless more sustainable water-use practices are adopted.
Funding & Disclosures
The research was supported by Stanford University, the University of Manchester, and the California Department of Water Resources. Researchers also received a grant from the Gordon and Betty Moore Foundation. There are no reported conflicts of interest from the authors, ensuring that the findings are unbiased and purely based on the data and analysis conducted.
