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San Francisco Bay Delta

About the Watershed

Map of the San Francisco Bay Watershed
The five main areas of the San Francisco Bay Delta Watershed (click image for a larger version)
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The San Francisco Bay Delta watershed covers more than 75,000 square miles and includes the largest estuary on the west coasts of North and South America. It also contains the only inland delta in the world.

The watershed extends nearly 500 miles from the Cascade Range in the north to the Tehachapi Mountains in the south, and is bounded by the Sierra Mountain Range to the east and the Coast Range to the west. Nearly half of the surface water in California starts as rain or snow that falls within the watershed and flows downstream to the Pacific Ocean through the Golden Gate Strait.

In addition, the watershed provides a primary source of drinking water for 25 million Californians, irrigation for 7000 square miles of agriculture, and includes important economic resources such as California's water supply infrastructure, ports, deepwater shipping channels, major highway and railroad corridors, and energy lines. In the Delta specifically, declining water quality and increasing demand for limited water resources are the subject of intense review and planning to protect this valuable resource for the future.

The watershed includes a diversity of fresh water, brackish water, and salt water aquatic habitats. Several endangered and threatened aquatic species are found here including delta smelt, steelhead, spring run Chinook salmon, winter run Chinook salmon, and others. Two-thirds of California's salmon pass through these waters, and at least half of the state's Pacific Flyway migratory water birds rely on the region's wetlands.

EPA Uses a Watershed Approach to Protect Water Quality

Castle Crags and the Sacramento River
Castle Crags and the Sacramento River

EPA addresses water pollution from the watershed approach, a comprehensive framework for addressing water resource challenges. The effects of pollution and stressors (such as dams, water diversions and invasive species) in one part of an aquatic system can negatively impact other parts of the system. Restoring water quality is most effective when pollution sources, stressors and solutions are identified for the entire watershed.

The watershed approach facilitates participation from interested stakeholders, optimizes use of environmental laws, and fosters local stewardship necessary to generate and sustain water quality improvements.

Water quality problems are more completely characterized when a diverse group of stakeholders are invested in identifying sources and solutions. Science and technical information can be generated with direction from stakeholder groups and used to identify options for addressing the most pressing watershed vulnerabilities. The community investment generated by this process is important for ensuring that water quality improvements persist over time.

Major Areas of the Watershed

The San Francisco Bay Delta Watershed consists of several major waterways, including the Sacramento and San Joaquin Rivers and their tributaries. Where these two large rivers meet near Sacramento, a great inland Delta is formed where the river waters collect before passing through the Carquinez Strait into San Francisco Bay.

Besides major rivers and the Delta, the watershed also includes Suisun Bay, San Pablo Bay, San Francisco Bay and the Golden Gate Strait where the entire watershed drains into the Pacific Ocean.

  • San Francisco Bay
  • The Sacramento-San Joaquin River Delta
  • The Sacramento River Watershed
  • The San Joaquin River Watershed
  • The Tulare Lake Basin Watershed

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