2050 Napa Valley Water Resources Study

In 2003 the Napa County Flood Control and Water Conservation District authorized the preparation of the 2050 Napa Valley Water Resources Study. The study was funded and prepared cooperatively with the cities of American Canyon, Calistoga, Napa, St. Helena, Town of Yountville, Napa County, and the Napa Sanitation District.

The 2050 Water Study updates information from the 1991 Water Resources Study for the Valley floor and compares available water supplies to existing and future water demands of Napa County's municipal, rural, and agricultural water users within the Napa Valley Region. The 2050 Water Study identifies specific water supply project options to fill future water supply shortfalls. All water supply options were considered including recycled water, groundwater, local surface water, imported surface and groundwater, and water conservation.

The conclusions for municipalities indicate water supplies for normal years are adequate through the year 2050. Water supply shortages occur in the cities for multiple dry years in the year 2050 and for single dry years for all study periods through the year 2050. Single dry years were modeled using a worst-case year equivalent to the 1977 drought and multiple dry year events were modeled using the drought in the late 1980s and the drought in the 1930s.

The conclusions for agricultural and rural water supplies indicate shortages in single dry years and for multiple dry years for all study periods. Agricultural and rural water supplies for normal rainfall years may begin to show a deficit by the year 2020, and additional groundwater monitoring will be necessary to determine where and when these shortfalls will occur and to more precisely identify water supply shortages.

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. 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.

As part of the 2050 Water Resources Study, the recommended water supply alternatives from the 1991 Water Resources Study and other subsequent studies were reviewed. 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 have made modification to existing diversion structures and construction of new diversion structures infeasible in the Napa River watershed.

A fact sheet and the various Technical Memos that comprise the 2050 Study can be viewed by visiting the Library Documents linked to this page under the Related Content heading above.

Questions about the 2050 Study should be directed to the Napa County Flood and Water Conservation District Engineer at (707) 259-8600.