The Delta
The Delta consists of approximately 57 reclaimed islands and tracts, surrounded by 1,100 miles of levees that border 700 miles of waterways. The southwestern side of the Delta lies at the foothills of the California Coast Ranges, while to the northwest sit the lower Montezuma Hills. Most of the Delta lies within Contra Costa, Sacramento, San Joaquin, Solano and Yolo Counties. The total human population of the Delta was 515,264 as of 2000.
Altogether, the Delta covers 1,153 square miles, with 841 square miles, or nearly 73 percent, devoted to agriculture. About 100 square miles of the Delta area is urban and 117 sq miles are undeveloped land. The rivers, streams, sloughs and waterways of the Delta total about 95 square miles of surface, although this fluctuates greatly with seasons and tides.
The main source rivers include the Sacramento River from the north, the San Joaquin from the southeast, and the Calaveras and Mokelumne Rivers from the east. The Calaveras and Mokelumne are both tributaries of the San Joaquin River. The Sacramento and San Joaquin Rivers join at the western end of the Delta near Pittsburg, at the head of Suisun Bay, although they are linked upstream by the Georgiana Slough, which was first used by steamboats in the 19th century as a shortcut between Sacramento and Stockton. The southwestern part of the Delta is also transected by the Middle River and Old River, former channels of the San Joaquin. These rivers transport more than 30 million acre feet (8.9 cu miles) of water through the Delta each year – about 50 percent of all California's runoff.