General Description

The Delta Division provides for the transport of water through the central portion of the great Central Valley, including the Sacramento-San Joaquin 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.  This system provided full and supplemental water, as well as temporary water service, for a total of about 380,000 acres of farmland in 1992.

The Sacramento-San Joaquin Delta's continual salinity intrusion from San Francisco Bay through Suisun Bay caused problems, especially for the towns of Antioch and Pittsburg, which depended on the nearby water for agriculture and industrial uses. Periods of high salinity made the water useless for these purposes. Unless water flowed past Antioch at a minimum rate of 3,300 cubic feet per second against the high tide, salt water entered Suisun Bay and the Delta, lowering the water quality. Between 1919 and 1924, salt water in Suisun Bay fostered the growth of teredo, a woodboring, salt water worm, whose increased population destroyed $25 million of the bay's wharves and pilings. In 1924, the water reached its lowest recorded stream flow, and the salt water content at Pittsburg reached 65 percent. Both Pittsburg and Antioch had used water from Suisun Bay for crops and industry, but in 1926, high salinity forced them to stop.

An idea for a dam to block salt water gained momentum in the 1920s. Delta residents rejected the idea because they believed it would raise water levels in Suisun Bay. On July 2, 1920, Antioch filed a lawsuit against upstream irrigators to stop the diversion of excess water which slowed the stream flow. Sacramento Valley water users pushed for a salt water barrier in hopes of ending the litigation against them by the Delta interests. The head of the Sacramento Valley Water Development Association worked especially hard to promote construction of the barrier. The U.S. Army Corps of Engineers (Corps) proposed a salt water barrier with a moveable crest and multiple locks between Suisun Bay and the junction of the Sacramento and San Joaquin Rivers. The Corps wanted to create a reservoir, raising the water five to ten feet, but the prospect worried area residents. In a report about the salt water barrier, Reclamation engineer Walker R. Young predicted it would prove an expensive proposition and hinder navigation. Young estimated the water level of Suisun Bay could not be safely raised high enough for operation of a barrier with the existing (1926) Delta levees. In 1924, Major U.S. Grant III, COE's Second District Engineer, argued water storage should be the first priority, and the barrier could prove more expensive than the benefits would justify. The barrier went down in defeat for numerous reasons, including the belief that the proposed Kennett (Shasta) Dam would sufficiently help curb the salinity problem. 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.

The Water Exchange Contract was a water supply agreement with San Joaquin Valley irrigators to exchange northern water for natural flows of the San Joaquin River diverted at Friant Dam. The contract came about to assure lower San Joaquin farmers that they would not lose irrigation water due to construction of Friant.

In 1944, Reclamation officials realized the salinity problem in the Delta was more pronounced than they previously thought. The Region Two Director believed Shasta Dam could not entirely control the salinity problem, precluding use of the Delta as a reservoir as planned at one time. One possible alternative to alleviate the salinity problem was to build a closed conduit through or around the  Delta to carry Sacramento River water directly to the other side without letting it mix with Delta water. The proposed closed conduit foreshadowed later plans for the Peripheral Canal.

In the course of Delta Division development, though not built, the Peripheral Canal became one of the most controversial elements of Division planning. Reclamation proposed the Peripheral Canal to the Interagency Delta Committee (IDC) in early 1963 as an alternative water transfer system. By early 1965, the proposed canal had almost universal acceptance in the Delta region. California wanted Reclamation to design and construct the Peripheral Canal, and then the State would assume control of the feature. Reclamation did not want State control of the canal, but did not have the authority to build it. California's Department of Water Resources (DWR), on the other hand, did have the authority to construct the canal.

Changing attitudes in the United States, toward the environment and a myriad of other issues, soon infected perceptions of the Peripheral Canal. Contra Costa County opposed the canal because residents viewed it as another way to transport fresh water out of their locale and into southern California. About the same time, questions arose about the environmental impact of the Peripheral Canal on fish populations in the Delta and the Central Valley. Environmentalists believed the canal's outlets would draw fish to them. They also believed the nitrogen rich water from agricultural drainage could foster algae growth, stagnating waters and suffocating the fish.

The Department of Water Resources "proposed an amalgam of joint state-federal programs and facilities," including the forty-two mile Peripheral Canal, in 1977. DWR contended the canal would circumvent the Delta channels and carry water more efficiently from the Sacramento River to the pumping plants of the CVP and the State Water Project. The canal could release fresh water into the Delta at certain points along its reaches to support irrigation, to benefit fish and wildlife, and to combat salt water intrusion. Supporters, including the Metropolitan Water District of southern California and various agri-businesses, argued the canal would help end the reverse flows caused by the south Delta pumps.

The powerful pumping plants in the Delta Division had a major and often detrimental effect on stream flow in the Delta and the San Joaquin River Basin. During periods of low water flow and high quantities of exports, the Delta pumps actually reversed the flow of the San Joaquin River, taking it back upstream. Through the Delta's transport system, water normally travelling to the west, toward San Pablo Bay, instead moves back toward the east and south. The "reverse flows" disorient migratory fish, often luring them to the pumps, and draw salty ocean water into the San Joaquin River and other waterways.

Opponents continued arguing against further exports of water to southern California and against the environmental impact of the canal. A referendum on the entire project went before California voters as Proposition 9 in 1982. Proposition 9 failed because of cost (an estimated $3.1 billion) and environmental concerns. Other alternatives surfaced after the defeat of Proposition 9, but none went forward.

All divisions of the Central Valley Project and the features of the State Water Project supply water to the Central Valley, and they all contribute to environmental problems. One high profile problem which grew out of the CVP was the declining population of Chinook salmon in the Sacramento River. Most attention focused on the winter-run Chinook salmon, listed as threatened species by the Federal Government and endangered species by California. The estimated population of the winter-run Chinook in 1969 reached 117,000. In 1991, only 191 adults returned to the Sacramento River to spawn.

Factors linked to the decline of the Chinook population include predation by two species introduced into the Delta, Striped bass and Colorado River squawfish, lack of water flow in the rivers because of upstream dams, and disorientation and destruction by the Delta Division pumping plants. The Striped bass population also experienced large declines. Another species facing declines and possible extinction is the three inch long Delta smelt. A fish found only in the Sacramento-San Joaquin Delta, the smelt faces destruction by the same forces as the Chinook salmon. The California Fish and Game Commission rejected the smelt for a State listing as a threatened or endangered species, but in March 1993, the Fish and Wildlife Service listed the smelt as a threatened species under the Federal Endangered Species Act.

Delta Cross Channel

On January 12, 1945, Reclamation announced the final location for the Delta Cross Channel. The route follows the plan chosen by California's State Engineer. The Delta Cross Channel is a controlled diversion channel between the Sacramento River and Snodgrass Slough. Water is diverted from the river into the slough through a short  excavated channel near Walnut Grove . The channel has a bottom width of 210 feet and a capacity of 3,500 cubic feet per second. Fresh water is drawn from the Sacramento to the Mokelumne to combat salt water intrusion in the Delta and to dilute local pollution. The water then flows through natural channels for about 50 miles to the vicinity of the Tracy Pumping Plant. The diversion provides an adequate supply of water to the intakes of the Contra Costa and the Delta-Mendota Canals, and improves the irrigation supplies in the Sacramento-San Joaquin Delta. Reclamation believed the Delta Cross Channel and the training works in the San Joaquin River were necessary to prevent the highly polluted low water flows of the San Joaquin from getting into the Tracy Pumping Plant. The intrusion could raise salinity in the adjoining waters above the standards set in the Water Exchange Contract for low water flow. Reclamation closes the control gates of the Delta Cross Channel during high water to prevent flood stages in the San Joaquin section of the Delta.  After the flood danger passes, Reclamation opens the gates to allow Sacramento River water through to the Tracy Pumping Plant.

Contra Costa Canal

Reclamation started work on the Contra Costa Canal on October 19, 1937, and work was completed in 1948. The canal originates at Rock Slough, about 4 miles southeast of Oakley, California, where it intercepts natural flow in the Sacramento-San Joaquin Delta. Water for irrigation and municipal and industrial use is lifted 127 feet by a series of four pumping plants. The 47.7 mile-long canal terminates in Martinez Reservoir. The initial diversion capacity is 350 cubic feet per second, which gradually decreases to 22 cubic feet per second at the terminus. Two short canals, Clayton and Ygnacio, are integrated into the Contra Costa Canal system. Reclamation started work started on Contra Costa Pumping Plants 1 through 4 on March 14, 1939 completed work on March 7, 1940.

Reclamation completed work on the Contra Costa Canal headworks, Dutch Slough Dam bridge, a bridge at Station 1+98, and a bridge at Rock Slough by September 15, 1940. Reclamation started test pumping at Pumping Plant One during the summer of 1940, in preparation for using operational portions of the Contra Costa Canal in the fall.  Reclamation turned the first water into the sea level section of the canal on August 9, 1940.

The hardness of Pittsburg's well water supply increased from 150 parts per million (ppm) in 1929, to about 800 ppm in 1940. The decreasing water quality convinced Pittsburg residents to contract with Reclamation for water deliveries from the canal. Pittsburg built a water treatment plant in 1939 to accommodate expected delivery. Pittsburg received its first water delivery from Contra Costa Canal on August 18, 1940. On that date, the Contra Costa Canal stretched twenty miles, reaching four miles past the city. Reclamation continued earthwork, canal lining, and structures into 1942, when it halted work because of World War II. The work remaining after World War II consisted of ten miles of canal, two re-lift canals, and pumping plants. Reclamation finished work on the last section of the Contra Costa Canal on September 29, 1947.

Tracy Pumping Plant

Reclamation awarded the first contract related to construction of the Tracy Pumping Plant and appurtenant facilities on June 23, 1947. Reclamation completed the plant in 1951.  It consists of an inlet channel, pumping plant, and discharge pipes. Water in the delta is lifted 197 feet into the Delta-Mendota Canal. Each of the six pumps at Tracy is powered by a 22,500 horsepower motor and is capable of pumping 767 cubic feet per second. Power to run the huge pumps is supplied by Central Valley Project powerplants. The water is pumped through three 15-foot-diameter discharge pipes and carried about 1 mile up to the Delta-Mendota Canal. The intake canal includes the Tracy Fish Screen, which was built to intercept downstream migrant fish so they may be returned to the main channel to resume their journey to the ocean.

Delta-Mendota Canal

The Delta-Mendota Canal, completed in 1951, carries water southeasterly from the Tracy Pumping Plant along the west side of the San Joaquin Valley for irrigation supply, for use in the San Luis Unit, and to replace San Joaquin River water stored at Friant Dam and used in the Friant-Kern and Madera systems. The canal is about 117 miles long and terminates at the Mendota Pool, about 30 miles west of Fresno. The initial diversion capacity is 4,600 cubic feet per second, which is gradually decreased to 3,211 cubic feet per second at the terminus.

Contra Loma Dam

Reclamation awarded the contract for construction of Contra Loma Dam on March 17, 1966. The dedication ceremony for the dam was held on November 3, 1967, and construcation was completed on November 24, 1967.

Contra Loma Dam is an offstream storage facility for the Contra Costa Canal. The facility includes two dikes. The dam is a zoned earthfill structure 107 feet high with a crest length of 1,050 feet. The top width of the dam is 30 feet and the maximum base width is 630 feet. Contra Loma Dam has a total volume of 641,000 cubic yards. Contra Loma Reservoir has a capacity of 2,100 acre-feet. The emergency spillway on the right is an uncontrolled ogee crest with a concrete chute and stilling basin. The spillway has a capacity of 600 cubic feet per second. The dam and reservoir sit at the southern end of the city of Antioch. The pumping plant pumps water from the Contra Costa Canal into the reservoir for storage; the releases are by gravity.

Recreation

For specific recreation opportunities, click on the name below:

Contra Loma Reservoir

Development

Because settlers moved into the Central Valley long before Reclamation started construction of the CVP, 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 and employ greater numbers of workers, especially during World War II. Contra Costa County grew from a population of 31,674 in 1910, to 100,450 in 1940. The county's population exploded to 298,984 by 1950. Merced County had a population of 46,988 in 1940, and Stanislaus had 74,866 inhabitants, which grew to an estimated 81,000 by 1942. As with the rest of California, the counties in the Delta Division reached population numbers rarely found in the counties of other western states. By 1990, Alameda County had a population of 1,279,182, and Sacramento was the second largest county with 1,041,219. Contra Costa County reached a population of 803,732, and Fresno had 667,490. Stanislaus County came in next to last with 370,522 inhabitants, and Merced County had 178,403. Delta Division facilities served 3,914 farms in 1992, with a population of 10,686.

Authorization

President Franklin D. Roosevelt authorized the Central Valley Project on December 2, 1935. Originally the Project contained three Divisions; Friant, Kennett (Shasta), and Contra Costa (Delta). The Rivers and Harbors Act of 1937, re-authorized the CVP's initial divisions. The act prioritized improvement of navigation, regulation, and flood control of the Sacramento and San Joaquin Rivers, with irrigation and domestic uses secondary. On July 1, 1937, Reclamation changed the name of the Contra Costa Division to the Delta Division. The Division included the Contra Costa Canal and the San Joaquin Pumping System.

Benefits

The facilities of the Delta Division provide irrigation water for many acres of farm land in the Central Valley. Most of the land lies outside the Delta. The Contra Costa and Delta-Mendota Canals served over 300,000 people in 1966. Only about 18,000 people in the Delta received irrigation water from the Central Valley Project in 1977. Over 190,000 received water for municipal and other uses during the same year. One priority of Delta residents is assuring a supply of fresh water for a variety of uses. Salinity control contributed to some discord between Reclamation and Delta water users. Reclamation encountered problems in negotiating repayment contracts with the water users because irrigation expenses for other Central Valley water users became salinity control costs for Delta water users. Reclamation did reach a repayment agreement with the Sacramento River and Delta Water Association and the Delta Water Users Association in November 1965. World War II created more problems for agriculture on the Delta than just halting construction of Delta Division facilities. The removal of Japanese and Japanese-Americans from the west coast and the Central Valley caused a shortage of farm workers at harvest time, but the importation of farm workers from Mexico alleviated the problem.

The Delta Division supports a large agricultural industry even with the problems it faces with salinity intrusion. Farmers in the Division grow a large number of crops on many acres of land (see Table. III). Much of the acreage lies south of the geographic Delta.

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