Napa River Watershed

US Geological Survey (USGS)  - Stretching 50 miles from Mt. St. Helena to San Francisco Bay, the Napa River and its 47 tributaries form a linear wilderness running through the heart of an intensely farmed and partially urbanized valley. The Napa River Watershed also serves as a valuable water resource for a local population of over 120,000 people. The watershed encompasses 450 square miles in Napa County, California.

The Napa River Watershed historically supported a dense riparian forest, significant wetland habitat and spawning areas for fish such as salmon and steelhead. The pressures of urbanization, agriculture and grazing have degraded the watershed’s habitats and drastically increased the rates of erosion and sedimentation. Since 1800, an estimated 6,500 acres of historical valley floor wetlands have been drain or filled, 19,700 acres of the watershed are now under hardened pavement or rooftops and another 26,000 acres have been developed to intensive cultivated agriculture. At the same time, much of the river system has been altered by straightening channels, hardening banks, changing the flow, and constructing levees. These alterations have made the natural drainage system insufficient to prevent extensive flooding in the area. Since 1862, more than 27 major floods have plagued the Napa Valley, resulting in significant loss of life and damage to property. The 1995 flood damaged 227 businesses and residences at a cost of over $100 million.

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