The Napa River is one of the largest Central Coast Range rivers draining 426 sq. miles on its 50 mile journey from Mt. St. Helena to the San Pablo Bay. The last 17 miles of this journey, from the Trancas Steet bridge in Napa to Vallejo, are an estuary system: twice daily, high tides carry salty water up the river from the San Pablo Bay, and twice daily, as the tides retreat, the river level drops, exposing mudflats where wading birds can hunt for food. In summer, the salinity at Trancas may be 10%, in winter, it is freshwater.

Riparian Habitat

The Napa River and its 47 tributaries serve as a linear wilderness running through the heart of an intensely farmed and partially urbanized valley. At one time, a dense canopy of riparian habitat dominated by cottonwoods and willows lined the river’s upper reaches. For the most part, the gallery forest bordering the riparian zone is gone and the remaining vegetation exists only in the channel. FONR is working to restore the riparian habitat.

What is the Napa River Watershed?

A watershed is a drainage basin, or an area of land where precipitation collects into a common area: think of a funnel. In our case, all the surface water from rain and streams that falls on the Napa Valley and its hillsides empties into the Napa River. We call this area the Napa River Watershed, and this is why we say "the River begins at the ridgetops." The Napa River empties into the San Pablo Bay, which is part of the San Francisco Bay Watershed. The short YouTube video clip below from "Caring for our Watersheds" explains watersheds nicely.

The Napa County Watershed Information Center and Conservancy is a repository for information about our Napa River watershed. Visit the WICC here.

Health of the River

In Napa, government and community united to develop and implement a unique, innovative, scientifically based approach based on “Living River” objectives to alleviate flooding and simultaneously  improve the health of the river, build a river community and revitalize the waterfront. Learn more about this framework here: Napa River Living River Objectives. 

Challenges to river health include:

• Pollution is caused by the run-off of fertilizers. During summer, algae bloom decreases the oxygen available to aquatic life

• Water diversion from the streams that feed the river decreases the fresh water flow, affecting fish habitat

• Stream bank erosion and removal of plant life due to development causes sedimentation

• 70- to 200-thousand tons of sediments enter the Napa Valley watershed every year due to roads, development and hillside vineyards

• Sediment deposits in the stream and river channels are harmful to anadromous fish, (salmon, trout and lamprey) by reducing habitat diversity, filling in gravel used as spawning beds, and decreasing the food supply for fish