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Napa County Resource Conservation District |
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Napa County Resource Conservation District |
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A watershed is defined as the land over which water flows on its way to join a larger body of water. The Napa River watershed covers an area of approximately 426 square miles and is contained by the ridge tops of the mountains to the north, west, and east. The watershed is an example of the northwest-southeast trending topography typical of the California Coastal Range. It provides many different habitats for fish and wildlife, including chaparral, riparian, freshwater, brackish and salt water marsh, vernal pool, oak and pine woodland, and grassland communities.
The Napa River runs through the center of the watershed on the valley floor as it drains numerous tributaries along a 55 mile run from high in the headwaters of Mt. St. Helena in the Mayacamas Mountain Range, to the San Pablo Bay. The Napa River winds through varied landscapes of forested mountain slopes, vineyards, urban areas, open pasture, industrial zones, grasslands, and marshes.
The Napa River Watershed supports a great diversity of fish and wildlife, including several rare or threatened species. These include aquatic organisms such as fish, frogs, salamanders, snakes, turtles, crayfish, aquatic insects, and fresh water shrimp. Fish species include steelhead/rainbow trout, Chinook salmon, green sunfish, smallmouth bass, white catfish, brown bullhead, Sacramento pikeminnow, Sacramento splittail, threespine stickleback, mosquito fish, California roach, sculpin, Sacramento sucker, and Pacific lamprey. Two streams in the Napa River watershed are known to have populations of the federally endangered California freshwater shrimp.
Terrestrial wildlife is abundant throughout the watershed, and the river along with its tributaries are important to many birds that feed and nest in the riparian zone along the water's edge. Bird species dependent on the river include mallard, green-winged teals, mergansers, wood ducks, herons, egrets, kingfishers, rails, and grebes. The federally listed Northern spotted owl can be found in tributary canyons on the west side of the watershed in forested regions. Riparian habitat is used by mink, muskrat, raccoon, deer, gray fox, bobcat, mountain lions, wild turkey, wood rats, snakes, and salamanders.
Historically, large runs of steelhead trout, Chinook salmon, and coho salmon made their way up the Napa River to spawn. Coho salmon are no longer found in the Napa River, and the steelhead population has been greatly reduced. The National Marine Fisheries Service (now called NOAA Fisheries) listed steelhead as a threatened species in Napa County in August 1997. Adult steelhead are still observed spawning in many of the riverīs tributaries each year, and juvenile steelhead can be seen in the summer months. Despite reduced populations, the Napa River watershed is still considered one of the most significant anadromous fish streams within San Francisco Bay, with the exception of the Delta.
In the Napa Valley, most streams have been altered since 1800, either directly, indirectly, or both. Development of the Napa Valley has been markedly accelerated in the last 40 years, compared to the previous 100 years.
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