Water Supply

To effectively manage and ensure long-term water supplies for Napa County, local municipalities and regional agencies regularly estimate water supply and demand numbers.

Studies and water management plans are developed to compare available water supplies to existing and future water demands of the County's municipal, rural, and agricultural water users. These technical reports recommend management actions and identify specific water supply project options to fulfill any future water supply shortfalls. 


Various water supply options have been studied including recycled water, groundwater, local surface water, imported surface and groundwater, and water conservation. Projects identified to supplement water supplies for municipalities and rural agricultural areas include the further development of recycled water in the Milliken-Sarco-Tulocay area, the Carneros region, and in and around each of the cities. These and other recycled water projects are currently being taken up by the North Bay Water Reuse Program.

The preferred water supply option for the larger municipalities is to pursue dry year supplies through contracts and/or purchases from outside of Napa County to ensure the North Bay Aqueduct is kept full when cutbacks from the State Water Project occur. These dry year purchase options are being pursued by other state water contractors and opportunities exist to partner in these purchases.

Increased use of groundwater will continue in the rural areas and is being considered by municipalities and must be done carefully to ensure overdraft and depletion of this resource does not occur.

Projects including Napa River diversions, new dams, and raising the City of Napa's Lake Hennessey were found to be infeasible in today's regulatory environment. The listing of salmonid fish species, such as steelhead trout, has made the modification of existing diversion structures and construction of new diversion structures infeasible in the Napa River watershed.