Once the delta at the confluence of the Sacramento and San Joaquin rivers was an intricate mosaic of wetlands spreading over hundreds of square miles, a maze of meandering tidal sloughs teeming with fish and wildlife. Perch and minnows avoided the salmon and Steelhead that navigated the sinuous channels to their upstream spawning grounds. Salmon were so plentiful that farmers speared them out of the streams to spread on their fields as fertilizer. Enormous flocks of geese and ducks filled the sky.
That ecosystem has been manipulated so much that only a shadow of its splendor remains. It’s been drained for agriculture, navigation channels have been straightened and dredged, homes are built along the sloughs, and much of the water has been diverted. The hub of the state’s complex water delivery system, the Delta’s narrow channels surround sunken flood-prone islands enclosed by fragile levees. The decline of the Delta ecosystem is attributable to a perfect storm of environmental changes: increased diversion of fresh water, loss and modification of habitats, introduction of exotic species, and poor water quality from pesticides and other pollutants.
As a result, the abundance of small planktonic species at the bottom of the Delta’s food web has plummeted. Many indigenous fish species have either disappeared or are threatened with extinction. These include most of the historic salmon runs and resident fish like the Delta smelt, a finger-sized fish that used to be extremely abundant. The abundance index for Delta smelt in the summer of 2007 was the second lowest ever measured. The survival of the species is so precarious that in 2007 a federal judge ordered a reduction in the amount of water pumped from the Delta during critical times to protect the species until new safeguards are in place. The judge’s ruling could reduce the volume of water sent south by up to a third.
Without dams or diversions, runoff from about forty percent of the state, an average of about thirty million acre-feet of water, would flow each year into the Delta from the Sacramento and San Joaquin rivers, and then into San Francisco Bay. Now, about eleven million acre-feet of water is diverted annually before reaching the Delta, primarily for agriculture. Another six million acre-feet is sucked out near Tracy by two giant pumping facilities operated by the State Water Project and the federal Central Valley Project. These water exports provide drinking water for millions of people and irrigation for three million acres in the San Joaquin Valley and Southern California. The pumps are so strong that at certain times of the year the northern San Joaquin River actually reverses course and flows towards them.
In 2007, Governor Schwarzenegger appointed a task force to develop a sustainable vision for the Delta that addresses the multiple challenges of statewide water use, governance, population growth, public safety, public service infrastructure, long-term climate change, ecosystem threats, and seismic risk. The task force has recommended “a significant increase in conservation and water system efficiency, new facilities to move and store water, and likely reductions in the amount of water taken out of the Delta watershed.” It also recommended study and analysis of a dual conveyance system—using both through-Delta and around-the-Delta conveyance of water to Southern California. An implementation plan is due later this year. See www.deltavision.ca.gov.