The Public Trust Doctrine in Napa County:
Tragedy of the Commons?Agriculture and residents in Napa County rely on groundwater for irrigation, hydration, and winery operations. As the limited water resources in Napa County decrease due to climate change and over-pumping, we face the consequences of harming the public trust. Consequently, everyone is impacted. This issue becomes apparent in projects presented to the Planning Commission. As Supervisor Manfree stated in the September 29, 2025, BOS meeting, “our county government must find the balance of protecting private property rights while not harming the public trust. We must consider the commons, which the Public Trust Doctrine addresses.”
A key part of considering a project before the Planning, Building, and Environmental Services in Napa County is assessing water resources to evaluate not only whether there is enough water for the project but also to understand how the project could impact nearby streams and wells. This analysis is where controversy often lies. Appeals often question the veracity of Water Availability Analyses or the fact of missing Water System Feasibility Reports (Bonny’s Vineyard, May, 2025, as appealed by Water Audit California). In some cases, it appears the water analyses prepared by the applicant is overly optimistic. Is our County doing enough to safeguard this crucial resource?
Inspired by the over-pumping of groundwater in the state, California enacted the Sustainable Groundwater Management Act (SGMA) in 2014, establishing a new framework for managing groundwater resources at the local level through local agencies. Since the Napa watershed was considered to be under stress, the state required Napa County to form a Groundwater Sustainability Agency (GSA). Recent reports from the GSA indicate that groundwater in the Napa County sub-basin has been over-drafted.
The public trust did not protect groundwater until 2018, when the Courts decided that if groundwater is connected to a navigable source, it is considered part of the Public Trust. Read more here.
In California, waters in our streams and rivers are part of the Public Trust. Those who divert water from streams (owned by the public) for use in irrigation or for domestic use must apply for water rights. An irrigation pond requires state licensing, yearly fees, and reporting. The waters belong to the state, not the user, and use of these waters cannot hurt the public trust.
Forty-five states in the United States have a public trust doctrine. The concept dates back to ancient Roman law, where it protected public access to certain resources, especially navigable waters. It was later codified in the Magna Carta to safeguard the public’s use of land from the king, who owned the land. In California, the doctrine was established when the state was admitted to the Union in 1850. The public trust relates to the commons and the greater good, but there is significant variation among states regarding what this includes, including air, groundwater, and wildlife.
