The Delta


Just a few miles south of Sacramento, two of California’s major rivers converge to form one of the most important features of California’s water system – the Sacramento-San Joaquin River Delta. More than 25 million Californians and millions of acres of farmland rely on the Delta for all or part of their water supply, and countless species depend on it for their habitat.


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. It is a popular destination for boaters and other recreationists, and home to more than 750 distinct species of plants and wildlife. Salmon, striped bass and other key species such as Delta smelt depend on the Delta and its many marshes and waterways for their food and habitat.

Since about two-thirds of the islands and tracts are below sea level, the Delta relies on a maze of levees to protect land and key infrastructure from floods and daily high tides. In all, there are more than 1,100 miles of levees in the Delta, including many built more than a century ago to protect farmland. Were it not for these levees, the Delta would be a 740,000-acre brackish inland sea.

Today, the Delta’s aging and increasingly fragile levee system is being asked to protect much more than farmland. Three state highways, a railroad, natural gas and electric transmission facilities, and aqueducts serving water to parts of the Bay Area also are depend on Delta levees. In addition, more 400,000 people live in Delta towns and communities, some of which rank among the fastest growing areas in California.

The Delta is also the single most important link in California’s water supply system. Two of the state’s biggest water projects – the State Water Project (SWP) and the federal Central Valley Project (CVP) – depend on Delta waterways to convey water from Northern California rivers to 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.

Key Issues

For all its importance, the Delta faces many challenges. It is in an ecological collapse that threatens key fish species as well as water supply reliability for much of the state. By any measure, it has seen significant declines in water quality and ecosystem health in recent decades, and faces tremendous pressures in its dual role as water conveyance system and important habitat for critical species.

Regulatory restrictions to protect salmon and Delta smelt have significantly reduced on water deliveries through the Delta at key times. The reductions have exacerbated the effects of recent dry years, creating shortages for urban as well as agricultural water users in some parts of the state.

Bay-Delta Conservation Plan

The Bay Delta Conservation Plan is a planning and environmental permitting process to restore habitat for Delta fisheries in a way that reliably delivers water supplies to 25 million Californians. Federal and state agencies, environmental organizations, fishery agencies, water agencies, and other organizations are working together to develop the Plan.

Launched in 2006, the BDCP is currently focused on the following:

  • Identifying conservation strategies to improve the overall ecological health of the Delta
  • Identifying ecologically friendly ways to move fresh water through and/or around the Delta
  • Addressing toxic pollutants, invasive species, and impairments to water quality
  • Providing a framework and funding to implement the plan over time

The BDCP is being developed under the Federal Endangered Species Act (ESA) and the California Natural Community Conservation Planning Act (NCCPA) and will undergo extensive environmental analysis that will include opportunities for public review and comment. As the BDCP evaluates alternatives necessary to restore the Delta ecosystem while providing water supply reliability, state and federal agencies are developing a joint Environmental Impact Report/Statement (EIR/S) to determine the environmental impacts of the BDCP. The draft EIR/EIS is expected to be ready for public review and comment by November 2010.

To learn more, visit the BDCP's website.

Latest News about Delta

The State Water Resources Control Board Thursday issued revisions to its Feb. 3 Temporary Urgency Change Order covering state and federal... read»
A new report by the Legislative Analyst’s Office describes problems facing the Sacramento-San Joaquin Delta and identifies several... read»
This morning the U.S. Supreme Court decided it would not hear the appeal of several water agencies and Central Valley farmers who had asked... read»
A federal appeals court on Monday upheld a 2009 biological opinion that called for reductions in the amount of water pumped from the... read»
SACRAMENTO - Timothy Quinn, executive director of the statewide Association of California Water Agencies (ACWA), issued the following... read»

Latest Posts about Delta

The ongoing State Board and Regional Board water quality proceedings and their potential impact on water supply will be revealed at this... read more»
SACRAMENTO, Calif. – Leaders from six federal agencies, in partnership with the State of California, will host a meeting in... read more»