The San Joaquin Valley in California has experienced unprecedented levels of land subsidence over the past two decades, primarily due to excessive groundwater extraction. A study conducted by the Stanford Doerr School of Sustainability and published in Communications Earth & Environment reveals that between 2006 and 2022, the valley’s land surface sank at an average rate of nearly one inch (2.5 centimeters) per year.
“This is the first comprehensive effort to quantify the full extent of subsidence in the valley over the last 20 years,” said Rosemary Knight, the study’s lead author and a professor of geophysics at Stanford. “Our findings provide a broader perspective to help address and mitigate this alarming rate of subsidence.”
The rapid and uneven sinking has caused significant damage to infrastructure, requiring costly repairs to canals and aqueducts. It has also harmed local wells and irrigation systems, intensifying water supply challenges in one of the world’s most agriculturally productive regions.
Subsidence occurs when water is extracted from underground reservoirs called aquifers, which store water in sediment layers made up of sand, gravel, and clay. When these water-filled pores are drained, the sediments compress—sometimes permanently—reducing the aquifer’s capacity to store water in the future and causing the ground to sink.
