Napa River’s Low Surface Flow Levels May Affect Napa Wineries & Vintners

Napa County’s agricultural water users rely on both groundwater and surface water flow to provide frost protection and irrigation. Similar to other areas of the state, it is anticipated that Napa vineyard owners will rely on groundwater resources to make up any shortfalls in surface water availability.

Many vintners rely on the surface flows from the Napa River for frost protection, which is a court-adjudicated river. Each party holding water diversion rights under the 1976 court decree is allotted a certain amount of water from the river during a court-defined “frost season” (March 15-May 15). According to the decree, water right holders must cease all diversions from the river when flow levels drop to 10 cubic feet per second (cfs) or less. Napa has a watermaster, appointed by the State Water Resources Control Board, who oversees all diversion activity from the Napa River.

DP&F has collected data from the California Dept of Water Resources (CDWR) and discovered that the Napa River has never dropped below 10 cfs since CDWR began to collect the data in 1993; however it was very close in 1994, 2004, and, most notably, in 2013. (To review the Napa River’s cfs history since 1993, click here.) Due to the low precipitation we have experienced to date and a forecast calling for more sunny days, it is possible that river flows will not meet the 10 cfs level after March 15, requiring the Napa River Watermaster to stop all diversions. Consequently, property owners may have to rely more heavily on groundwater for frost protection and other water needs, to the extent it is a viable option.

For more information, please contact Tom Adams at [email protected] or Jeff Dodd at [email protected].