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.

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.

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.

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.

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.

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.