The Delta Division provides for the transport of water through the central portion of the great Central Valley, including the Sacramento-San Joaquin River Delta. The main features of the division are the Delta Cross Channel, Contra Costa Canal, Tracy Pumping Plant and Delta-Mendota Canal, constructed and operated by the Bureau of Reclamation.
The Delta Division is the hub around which the Central Valley Project rotates. This Division contains the facilities for transporting water from the Sacramento River to the San Joaquin Valley and to farm land in the Delta Division. The Delta Cross Channel diverts water from the Sacramento River to the Tracy Pumping Plant, the Contra Costa Pumping Plants, and the intakes of the Contra Costa and Delta-Mendota Canals, sending the much needed water south into the San Joaquin Valley.
Because settlers moved into the Central Valley long before Reclamation started construction of the Central Valley Project, the project had little effect on settlement of agricultural land in the area. The CVP's improvement of the area's industrial water supply showed the greatest effect on the Delta region, allowing industry to grow.
Salinity control, especially in the Sacramento-San Joaquin River Delta, became a major concern for northern California water users and a major component of the California State Water Project.
The Delta frequently experienced salinity intrusion, which caused problems for Antioch and Pittsburg. Unless water flowed past Antioch at a minimum of 3,300 second-feet, salt water from San Francisco Bay moved into Suisun Bay and the Delta during high tide, making the water unusable for crops and industry. Between 1919 and 1924, the salt water in Suisun Bay allowed sufficient growth of teredo, a woodboring, salt water worm, to destroy $25 million of the bay's wharves and pilings. In 1924, the water reached its lowest recorded stream flow. The maximum salt water content at Pittsburg reached 65 percent. In 1926, Pittsburg and Antioch stopped using water from Suisun Bay for crops and industry. Both communities had used the bay water since the middle of the 19th century.
The California State Water Plan called for construction of a 420 foot high dam at Kennett (Shasta Dam), on the Sacramento River, to maintain a regular flow of water to Antioch and keep the salt water intrusion out of the Delta.
In the 1930s, California state officials realized the state could not afford to implement the State Water Plan. California turned to Reclamation for assistance in constructing the planned facilities and salinity control in the Delta became one of the major goals of the Central Valley Project through the Water Exchange Contract, aimed to satisfy lower San Joaquin farmers that they would not lose irrigation water due to construction of Friant Dam.
The Delta Division is complex in its operation, and all its features do not operate in conjunction with each other. The Contra Costa Canal transports water to Contra Costa County. The Delta Cross Channel moves water from the Sacramento River through an excavated channel and natural channels to the Tracy Pumping Plant, which pumps the water into the Delta-Mendota Canal. The Delta-Mendota Canal delivers water to the west side of the San Joaquin Valley, ending at the Mendota Pool, 30 miles west of Fresno.
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The Sacramento-San Joaquin River Delta is roughly, a triangle shaped patch of land just northeast of Oakland and San Francisco. The Delta is about 50 miles long north to south with a maximum width of approximately 25 miles. Over one-half of the once marsh-filled basin lies at or below sea level.
The Delta Division of the Central Valley Project acts as the hub around which the CVP revolves. The Delta Division contains facilities that transfer water from the Sacramento River, to bolster irrigation supplies to lands formerly dependent on water from the San Joaquin River