Long-term groundwater pumping in Napa Valley remains at unsustainable levels, according to a recent county report.

Groundwater pumping totaled about 16,580 acre-feet in the 2025 water year — from October 2024 through September 2025 — according to the annual groundwater report, surpassing the 15,000 acre-feet the county considers sustainable for the Napa Valley subbasin and representing about 40% of total water use.

Precipitation during the same period was 21.59 inches, a normal “below average” amount, according to the county report.

The county’s average annual pumping over the past seven water years is 17,700 acre-feet, beyond the 15,000 acre-feet and considered an “undesirable result” under the county’s state-approved groundwater sustainability plan, an effort to reduce groundwater use by 10%. Though the county has come close to the 15,000 acre-feet number in recent individual water years, it surpassed that threshold during the past six years, with a total of 19,050 acre-feet used in 2022 and 22,510 acre-feet in 2021.

Natural resources manager Jamison Crosby said at a Napa County Board of Supervisors meeting May 19, the county is working on several efforts to improve groundwater sustainability. That includes an update this year to the county’s Water Availability Analysis, which will address groundwater use in proposed projects. For existing projects, Crosby said, the county is developing “a menu of incentives” that will give groundwater users a reason to preserve water.

Such efforts include “distribution uniformity testing” — which Crosby described as testing “an irrigation system to determine if the amount of water it’s applying is the same it was designed to apply” — through the Napa County Resource Conservation District at no cost to grapegrowers.

Crosby also said the agency is working on a certification pilot program connected to use of conservation measures, and is exploring possible economic incentives to encourage grapegrowers to delay replanting vines they’ve removed, allowing for increased groundwater recharge.

“We’re in that phase of GSP implementation where we’re stressing voluntary participation,” Crosby said.

Supervisor Joelle Gallagher said at the meeting the county needs information from the wine industry about what incentive programs make sense.

Board chair Amber Manfree said at the meeting she thinks the county’s efforts to improve groundwater monitoring and reporting, while not complete, have led to the solid ground needed to lead the county into a more sustainable groundwater use situation.

“Now that we have more data we see that it’s very clear we actually have things of concern, not extreme concern, but not no concern,” Manfree said.

You can reach Staff Writer Edward Booth at 707-521-5281 or edward.booth@pressdemocrat.com.