California's Water: Facts on the Sacramento-San Joaquin River Delta

Delta Facts

• Fed by runoff from the Sierra Nevada and the southern Cascades, two of California’s most important rivers converge south of Sacramento to form the largest estuary on the West Coast. The Sacramento-San Joaquin River Delta supports more than 130 species of fish and is a key recreation site and transportation corridor. It is also a little-known but vital link in California’s water delivery system.

• Covering more than 700 square miles, the Delta is a patchwork of nearly 60 islands and tracts surrounded by natural and man-made channels and sloughs. Since about two-thirds of the islands and tracts are below sea level, the Delta relies on a fragile system of levees to protect farmland, communities and key infrastructure.

  Here are some key points about the Delta and its importance to California:

  • The Delta receives runoff from over 40% of California’s land area. Major rivers that drain the Central Valley, including the Sacramento, San Joaquin, Calaveras, Cosumnes and Mokelumne, eventually meet and flow through the Delta on their way to the Pacific Ocean.
    
  • The Delta supports more than 80% of the state’s commercial salmon fisheries as well as 750 distinct species of plants and wildlife.
    
  • It is a key source of water for 23 million Californians and more than 7 million acres of farmland.
    
  • The Delta includes more than 730,000 acres of farmland and wildlife habitat. About two-thirds of Delta islands and tracts are below sea level.
    
  • The Delta relies on more than 1,100 miles of levees – many of which were built more than a century ago – to keep islands and tracts dry and protect other key infrastructure from floods and high tides.
    
  • Delta levees protect more than 520,000 acres of farmland and three state highways, a railroad, natural gas and electric transmission facilities, and aqueducts serving water to parts of the Bay Area.
    
  • Delta levees also help safeguard the lives and personal property of more than 400,000 people living in Delta towns and cities. Some Delta towns are among the fastest growing areas in the state.
    
  • Two of the state’s biggest water projects – the State Water Project and the federal Central Valley Project – rely on the Delta to convey water from Northern California rivers to project pumping facilities in the southern Delta. Delta levees play a critical role in preventing salty water from San Francisco Bay from intruding into critical parts of the Delta and contaminating the fresh water that supplies communities and farms.
    
  • Most Delta levees are maintained by local agencies such as reclamation and levee districts.