Scientists found parts of the Sacramento Valley subsided as much as a foot per year during the 2020–2022 drought, primarily because of intensified groundwater pumping. By 2021, some compaction stopped reversing, indicating permanent loss of aquifer storage roughly equal to San Francisco's annual water use. Experts recommend recharge when surface water is available and demand-management strategies to reduce reliance on pumping.
Study: Sacramento Valley Subsided Up to a Foot Per Year During 2020–2022 Drought; Some Aquifer Damage May Be Permanent
Photo Credit: iStock
Scientists say parts of California's Sacramento Valley sank faster than expected during the 2020–2022 drought, and some subsurface damage appears irreversible — reducing the aquifer's ability to store water when dry conditions return.
Key Findings
A new study combining high-resolution satellite observations with groundwater records from 2016–2022 found that intensified pumping during the recent drought caused subsidence in sections of the valley of nearly one foot per year. By 2021, researchers observed compaction in some areas that no longer rebounded, indicating permanent loss of storage capacity.
"There is still water, but it's a big loss," said study co-author Kristel Chanard, who estimated the lost storage is roughly equal to San Francisco's annual water use.
What Caused the Drop
Researchers identified heavy groundwater pumping as the primary driver. In 2022, Sacramento River water suppliers received about 0%–18% of expected surface-water deliveries, far below the 75% deliveries that contracts call for in critically dry years — a shortfall that pushed more users to rely on wells.
Why It Matters
Groundwater is a vital safety net in California when rivers, reservoirs and snowpack fail to provide enough water. The Northern California Water Association estimates groundwater supplies nearly 30% of the Sacramento Valley's water overall, and an even larger share during droughts. When subsurface layers compact permanently, they reduce the aquifer's storage capacity and leave the region with less flexibility in future droughts.
Responses And Solutions
Scientists and water managers recommend two main actions to limit further damage: actively recharging groundwater when surplus surface water is available, and managing demand to reduce dependence on pumping. One commonly used approach is in-lieu recharge, where extra surface water is delivered to users so they do not need to pump groundwater.
Local officials say work is already underway. Jordon Navarrot, deputy manager at Reclamation District No. 108 (serving parts of Yolo and Colusa counties), said districts are working with growers to shift some land onto surface-water service and to coordinate recharge and extraction so subsidence is minimized.
Outlook
Chanard warned that climate projections make continued pressure on water supplies likely, increasing the importance of measuring and managing changes in aquifer storage. David Guy, president of the Northern California Water Association, called the study a "warning sign" for regional officials and urged action to prevent further subsidence.
Help us improve.
