Some property owners above Napa Valley’s 72-square-mile groundwater subbasin will see a new fee on their property tax bills in December.
As part of the Napa Valley Subbasin Groundwater Sustainability Plan, Napa County mailed informational postcards this past week to subbasin property owners and groundwater users, encouraging them to review information about the groundwater fee that will range anywhere from $38 to $129 per acre per year.
County officials expect to raise $2.17 million per year from a total of 2,600 subbasin residents, according to the county’s natural resources manager Jamison Crosby.
The Napa Valley Subbasin is a defined underground area where groundwater is stored and moves through layers of soil and rock. It functions as a natural reservoir within a larger watershed, supplying water for homes, farms, businesses and local ecosystems above it, according to the county.
Under California’s Sustainable Groundwater Management Act — a state law requiring local agencies to sustainably manage groundwater — the fee will fund water monitoring, reporting, planning and compliance, but not the actual use of the groundwater, the county said.
In December 2025, the fee was adopted by the Napa County Groundwater Sustainability Agency, the governing body created to oversee the subbasin’s groundwater in the wake of the state law, for the upcoming 2026-27 fiscal year.
Since 2019, $500,000 in annual Napa County General Fund contributions and additional state grants have been used for groundwater sustainability efforts. However, the county said a local funding source was added because outside funds do not cover ongoing operational costs. The fee amount is also subject to change based on groundwater conditions.
Fees waived for low-income property owners
To help alleviate financial burden for residents, Napa County is offering fee waivers for households whose income does not exceed 80% of the area median income. Individuals interested in a waiver can contact the county by July 10.
Additionally, the fee applies to three specific categories in the Napa Valley Subbasin: agricultural groundwater users, self-supplied groundwater users primarily with domestic wells, and public water systems that pump groundwater. The groundwater sustainability fee doesn’t generally apply to properties served by municipal water systems in the cities of Napa, St. Helena, Calistoga or the town of Yountville.
“Property owners who believe their well is located outside the Napa Valley Subbasin, or who identify inaccuracies in the information associated with their property, should contact Napa County by July 10, 2026, so records can be reviewed and updated if necessary,” the county notice said.
Napa County said it will continue additional outreach before billing begins this December, including postcards with frequently asked questions and upcoming virtual community meetings where residents can ask questions and learn more about the fee.
The webinars are being held Wednesday from 3 p.m. to 4:30 p.m. and July 1 from 5:30 p.m. to 7:00 p.m. Residents can also email questions or phone (707) 253-4471.