The Sacramento-San Joaquin Delta has a vital and highly complex role in the California ecosystem. Covering nearly 1100 square miles, the Delta is composed of a delicate latticework of streams, marshes and estuaries that act as a reservoir and a natural water filtration system. Water from the Delta system supplies drinking water for much of California and some of the most productive farm land in the nation.
The U.S. Army Corps of Engineers shares responsibility in this complex issue with a host of local, state and other Federal stakeholders.
The Delta is formed by the confluence of the state’s two largest rivers: the Sacramento flowing south from its headwaters near Mt. Shasta and the San Joaquin flowing north from its origins high in the southern Sierra Nevada.
Joining the Sacramento and the San Joaquin are the Mokelumne and the Cosumnes rivers, that comprise the Delta’s watershed, draining nearly 50 percent of the state’s runoff. Through a maze of 57 man-made leveed islands and tracks, these waters of the Delta flow westward.
Pumping stations move a portion of this water throughout the state: the State Water Project, the federal Central Valley Project, Contra Costa Canal, North Bay Aqueduct, City of Vallejo diversion and the Western Delta Industry diversion. The remainder of Delta water flows to farms and communities within the Delta, and then out to sea through a series of bays.