General Description

The Central Arizona Project is a multipurpose water resource development and management project that delivers Colorado River water, either directly or by exchange, into central and southern Arizona.  The project was designed to provide water to nearly one million acres of Indian and non-Indian irrigated agricultural land areas in Maricopa, Pinal, and Pima Counties, as well as municipal water for several Arizona communities, including the metropolitan areas of Phoenix and Tucson.  Authorization also was included for development of facilities to deliver water to Catron, Hidalgo, and Grant Counties in New Mexico, but these facilities have not been constructed because of cost considerations, a lack of demand for the water, lack of repayment capability by the users, and environmental constraints. In addition to its water supply benefits, the project also provides substantial benefits from power generation, flood control, outdoor recreation, fish and wildlife conservation, and sediment control. The project was subdivided, for administration and construction purposes, into the Granite Reef, Orme, Salt-Gila, Gila River, Tucson, Indian Distribution, and Colorado River (?) divisions.  During project construction, the Orme Division was re-formulated and renamed the Regulatory Storage Division.  Upon completion, the Granite Reef Division was re-named the Hayden-Rhodes Aqueduct, and the Salt-Gila Division was renamed the Fannin-McFarland Aqueduct. 

The CAP was authorized by the Colorado River Basin Project Act of 1968.  This Act provided for the Secretary of the Interior to enter into an agreement with non-Federal interests, whereby the Federal Government acquired the right to 24.3 percent of the power produced at the non-Federal Navajo Generating Station, Navajo Project. The agreement also includes the delivery of power and energy over the transmission facilities to delivery points within the Central Arizona Project service area.

Construction of the project began in 1973 with the award of a contract for the Havasu Intake Channel Dike and excavation for the Havasu Pumping Plant (now Mark Wilmer Pumping Plant) on the shores of Lake Havasu. Construction of the other project features followed.  The backbone aqueduct system, which runs about 336 miles from Lake Havasu to a terminus southwest of Tucson, was declared substantially complete in 1993.  The new and modified dams constructed as part of the project were declared substantially complete in 1994.  All of the non-Indian agricultural water distribution systems were completed in the late 1980´s, as were most of the municipal water delivery systems.  Several Indian distribution systems remain to be built; it is estimated that full development of these systems could require another 10 to 20 years.

Plan

The CAP consists of a system of pumping plants and aqueducts that convey Colorado River water from the Bill Williams River arm of Lake Havasu to the project service area. When authorized, the plan included the construction of a two dams and reservoirs on the Gila River to provide conservation storage, flood and sediment control, and recreation opportunities, and Orme Dam at the junction of the Salt and Verde Rivers to provide flood protection and water conservation.  None of these facilities have been built.  The proposed Gila River structures, although still authorized, were not constructed because of cost considerations, a lack of demand for the water, lack or repayment capability by the users, and environmental constraints.  Following concerns about the social and environmental impacts of Orme Dam, a new plan - Plan 6 - was developed to fulfill the authorized functions of this facility.

Unit descriptions and facilities

New Waddell Dam

New Waddell Dam was constructed to provide water conservation. The dam is located on the Agua Fria River about 35 miles above the Gila River Confluence. The dam has a crest elevation of 1,728 feet and a Crest length of 4,900 feet.

Camp Dyer Diversion

Camp Dyer Diversion Dam is a concrete and masonry dam located on the Agua Fria River about 35 miles northwest of Phoenix, Arizona. The dam was originally constructed in 1926 and modified in 1992. The dam has a structrual height of 79 feet and a crest length of 872 feet.

Havasu Intake Channel Dike and Hayden-Rhodes Aquduct

An intake channel and high-lift Mark Wilmer Pumping Plant, located on the south side of the Bill Williams River arm of Lake Havasu, diverts and lifts Colorado River water approximately 824 feet from the lake to the inlet portal of the Buckskin Mountains Tunnel. The water is discharged at the outlet portal of the tunnel into the open channel of the Hayden-Rhodes Aqueduct, and conveyed to the Phoenix metropolitan area.  The Hayden-Rhodes Aqueduct consists of about 173.9 miles of concrete-lined open channel, seven major inverted siphons with a total length of about 7.4 miles, three tunnels totaling 8.2 miles, and 0.6 mile through three pumping plants.  The aqueduct has a maximum capacity of 3,000 cubic feet per second. Relift pumping stations are located at Bouse Hills, Little Harquahala Mountains, and near the Hassayampa River. The total pump lift from the Colorado River to the Phoenix service area is about 1,200 feet.

Fannin-McFarland Aqueduct

The Fannin-McFarland Aqueduct begins at the terminus of the Hayden-Rhodes Aqueduct just east of Phoenix and south of the Salt River.  This aqueduct consists of the Salt-Gila Pumping Plant and about 57.5 miles of open, concrete-lined channel and one major inverted siphon with a length of 0.6 miles.  The aqueduct´s initial capacity is 2,750 cubic feet per second; at the end of this aqueduct, the capacity has dropped to 2,250 cfs because of water deliveries along the way. The Salt-Gila Pumping Plant lifts the water 86 feet from the Hayden-Rhodes Aqueduct to the Fannin-McFarland Aqueduct.

Tucson Aqueduct

The Tucson Aqueduct begins at the terminus of the Fannin-McFarland Aqueduct, and ends 87 miles later southwest of Tucson.  This aqueduct -  which includes nine pumping plants, one major inverted siphon and two major pipeline sections - has an initial capacity of 2,250 cfs, which is reduced to 200 cfs at its terminus.

Indian Distribution System Division

In 1983, the Secretary of the Interior allocated 12 Arizona Indian Tribes 309,818 acre-feet of Colorado River water from the Central Arizona Project for irrigation purposes.  Since then, the completion of several water settlement acts has increased the amount of water available for Federal purposes to meet Tribal needs to a current total of 453,224 acre feet.  Currently, the only tribes with completed distribution systems are the Ak-Chin and Salt River Pima-Maricopa Indian Communities.  Construction of the Gila River Indian Tribe distribution system was begun in 1998; completion is anticipated after 2012.  The individual allocation, by Tribe, is:   (list tribes and current allocations - using 453,224 acre feet as total).

Buttes Dam and Reservoir--Gila River Division

Buttes Dam was investigated for construction on the Gila River about 4 miles upstream of the existing Ashurst-Hayden Diversion Dam, northeast of Coolidge, AZ.  The objective of this investigation was to develop additional CAP water through conservation of Gila River flows, to provide flood and sediment control, and to provide outdoor recreation and fish and wildlife benefits.  Although Buttes Dam is an authorized part of the project, it has not been constructed and remains in deferred status.

Hooker Dam and Reservoir -- Gila River Division

Hooker Dam and other alternatives were the focus of the Upper Gila Water Supply Study.  The objective of the study was to look at alternatives for developing an annual water supply of 18,000 acre-feet for a portion of western New Mexico, and for providing flood protection along the Gila River in eastern Arizona.  Although Hooker Dam is an authorized part of the project, it has not been constructed and remains in deferred status.

Charleston Dam

Charleston Dam was authorized for construction on the San Pedro River southeast of Tucson to provide water conservation and flood control.  A Presidential review of the project in 1977 recommended elimination of this feature from the project, and no further work or investigation was performed.  

Power Sources

The Colorado River Basin Project Act allowed the federal government to participate in the non-federal Navajo Project. The Navajo Generating Station, near Page, Arizona, provides the power for pumping water along the CAP aqueduct. The Southern and Western Transmission Systems, features of the Navajo Project, transmit this power to Westwing Substation near Phoenix and McCullough Substation near Boulder City, Nevada.

The Navajo Generating Station was constructed by the Salt River Project Agricultural Improvement and Power District of Arizona. The Southern Transmission System, completed in 1974 by the Arizona Public Service Co., consists of two 500-kV transmission lines to the Phoenix area. The Western Transmission System consists of one 500-kV transmission line to the McCullough Switchyard near Boulder City, Nevada. This line was constructed by the City of Los Angeles Department of Water and Power, and was placed in service on October 27, 1974. Other participants in the Navajo Project are the Nevada Power Co., the Tucson Gas and Electric Co., and the Bureau of Reclamation. Reclamation´s share of the plant´s annual output is 24.3 percent, or 546,750 kilowatts per year.

Construction of the Navajo Generating Station began in April 1970. The third, and last, generating unit was completed and placed in operation on April 30, 1976. Until energy was required for the CAP or other purposes authorized by Public Law 90-537, Reclamation's share of the interim energy produced was sold to other participants in the station and to the Southern California Edison Co.

Transmission System

A transmission system also constructed as part of the project to supply power to the pumping plants and check structures along the aqueduct.  The portion serving the Hayden-Rhodes Aqueduct has a total length of about 309 miles, of which 250 miles comprise the 230-kV line interconnecting the delivery portion of the transmission system. The radial transmission lines to the pumping plants consist of about 51 miles of 115-kV lines and 8 miles of 230-kV lines.

The 230-kV transmission line begins at the McCullough Switching Station in Clark County, Nevada, and interconnects the Davis Switchyard, the Parker Switchyard, and the Liberty Substation in Arizona. The Harcuvar substation was constructed in Yuma County, eight miles north of Wenden, Arizona, and a new tap station, the Hassayampa Tap, was constructed in Maricopa County, twelve miles north of Buckeye, Arizona. Approximately 59 circuit miles of radial transmission lines were constructed to supply power to Mark Wilmer, Bouse Hills, Little Harquahala, and Hassayampa Pumping Plants.

Power is delivered to the Fannin-McFarlan Aqueduct utilizing existing transmission lines and the transmission lines constructed for the Hayden-Rhodes Aqueduct. A new tap station was constructed in Maricopa County, Arizona, (NEAR?) on the existing Mesa-Coolidge 230-kV line, and about 6 miles of 69-kV line was constructed to feed the Salt-Gila Pumping Plant.

Power is also delivered to Tucson Aqueduct facilities using existing and constructed transmission lines for the Hayden-Rhodes Aqueduct. About 40 miles of existing transmission lines were reconstructed and additional capacity was added to the Coolidge Substation to supply the Tucson Aqueduct pumping plants. About 25 miles of new 115-kV transmission lines were constructed to supply power to pumping plants near Picacho Mountain.

Development

Since prehistoric times, communities have irrigated the lands along the Gila and Salt Rivers by diversion of streamflow into systems of ditches, with temporary brush and rock dams.  In the late 1800's, the Pima Indians farmed possibly as much as 35,000 acres along the Gila River within the present Gila River Indian Reservation. In the 1860's, settlers began to redevelop and extend abandoned farmland along the Salt River in the vicinity of Phoenix. These early enterprises were severely handicapped by raging spring floods and low waterflows during the later stages of the growing season.

The Salt River system was almost totally controlled by a series of dams constructed between 1911 and 1946 on the Salt and Verde Rivers. The Bureau of Indian Affairs completed Coolidge Dam on the Gila River in 1928. With the increased control and regulated supply of available water, agriculture expanded and prospered along the desert plains adjoining the streams.

In the Salt River Valley, application of irrigation water led to a rise in the water table and eventually to drainage problems. By 1918, waterlogging threatened the productivity of the irrigated area. A system of shallow wells was established to draw down the water level, and the pumpage was used for new agricultural expansion. Conditions were ideal for ground water development because of the highly permeable alluvial aquifers, a shallow water table, and good quality water. Pumping soon exceeded recharge and eventually led to a decline in water levels below the original levels.

The 1930's through 1950's brought low-cost hydropower, improved well drilling equipment, and high capacity pumps. As a consequence, the pumping rate was further increased, and ground water irrigation spread from the vicinity of the rivers throughout the central Arizona desert basins. The rate of pumping eventually far exceeded the rate of recharge, water levels dropped rapidly, and in some areas, increased pump lifts, poor water quality, and farm crop controls forced farmland out of production .

The mild winters of central and southern Arizona, the development of efficient air conditioning, and the growth of air transportation all contributed to the post-World War II expansion of urban population, particularly in the Phoenix and Tucson metropolitan areas.

As agricultural lands were taken over by urban growth, the surface and ground water supplies shifted to municipal and industrial users at approximately the same delivery requirement per acre. In areas where urban projects expanded onto raw desert areas, municipal and industrial uses contributed to the increasing overdraft of ground water supplies.

Investigations

Formal investigations for the Central Arizona Project were started in 1944 by the Phoenix Development Office. The Central Arizona Project report was published as House Document No. 136, 81st Congress, 1st session, and was recommended for authorization in 1949.

During the 1950's, investigations for the project were halted while the Supreme Court heard the issue of lower Colorado River water rights in the case of Arizona v. California. In 1961, when it appeared  a Supreme Court decision favorable to Arizona might be imminent, the Phoenix Development Office reopened investigations, using funds provided by the States of Arizona and New Mexico.

The resulting report, dated January 1962, documented the major changes that had taken place since the initial report. Continuous investigations through authorization provided data for reports on this project in 1964, 1967, and 1968.

Authorization

The Central Arizona Project was authorized for construction under the Colorado River Basin Project Act, Public Law 90-531 (82 Stat. 885), approved September 30, 1968. In March 1977, a Presidential Review of water projects was initiated. A statement on the water projects was released April 18, 1977, recommending modification of the Central Arizona Project by the elimination of Orme, Hooker, and Charleston Dams and making federal funding contingent upon further study of ground water supplies and institution of ground water regulation and management by the State of Arizona. Since Public Law 90-537 qualified the authorizing language for Orme and Hooker Dams with the phrase "or suitable alternatives," other plans were formulated in an effort to determine suitable alternatives for those features.  The Central Arizona Water Control Study was initiated in 1978 to study alternatives to Orme Dam, to replace its authorized functions of regulatory storage and flood control on the Salt and Verde Rivers.  At the same time, Reclamation was evaluating the existing dams on these rivers under the Safety of Dams Act.  Because both studies were looking at modifying the existing dams, they were combined for plan formulation purposes.  In November 1981, the Secretary of the Interior identified a proposed action (Plan 6).  This plan included New Waddell Dam on the Agua Fria River (which was subsequently constructed) for regulatory storage purposes, and Cliff Dam on the Verde River, New or Modified Roosevelt Dam on the Salt River, and Modified Stewart Mountain Dam on the Salt River for flood control and dam safety purposes.  Cliff Dam was later deleted from the Plan, but Roosevelt Dam and Stewart Mountain Dam were modified as identified by the Plan.

Construction

Initial construction of the Central Arizona Project began in 1973.  The backbone aqueduct was declared substantially complete in 1993, and the Plan 6 features were declared substantially complete in 1994.  Non-Indian agricultural distribution systems and municipal water delivery systems have also been completed.  Only two of the planned Indian distribution systems have been completed; it is estimated that full development of these systems could require another 10 to 20 years.

Benefits

Project water is delivered to 314,820 acres of lands owned by non-Indian farmers with a past history of irrigation, and to those tribal farmers who irrigate all of their presently developed acreage.

Municipal and Industrial

Over 1.8 million people in several municipalities in the Phoenix metropolitan area receive Colorado River water from the CAP.  The delivery system for Tucson is also complete, but CAP water is being used only for groundwater recharge at  present.

Recreation

The Central Arizona Project has created substantial recreational opportunities.  Reclamation has helped replace existing facilities and develop new facilities at the enlarged Lake Roosevelt behind Modified Roosevelt Dam, and at the enlarged Lake Pleasant behind New Waddell Dam.  Additional recreational facilities have been developed and are being planned for the lands along the CAP aqueduct, including golf courses, picnic areas, hiking trails, polo fields, and equestrian paths, and for other activities like hot-air balloon, auto and boat shows, and horse and dog exhibitions.

For specific information about any of these recreation sites, click on the name below.

Lake Pleasant
Westworld

Fish and Wildlife

The project has also provided some fish and wildlife benefits for the area, and has greatly enhanced the sport fishery at Lake Pleasant.

Flood Control

Although central Arizona usually suffers from water shortages, periodical and destructive floods do occur. Extensive flood control benefits are included in the project through modification of Roosevelt and Stewart Mountain Dams, as well as that provided by the dikes along the aqueduct.  The project has 50,000 acre-feet of capacity assigned to flood control.  Between 1950-1999, dikes along the aqueduct have provided $14,100,000 in accumulated flood control benefits, while New Waddell Dam has provided $6,174,000 in accumulated flood control benefits.

Reduction of Groundwater Overdraft

By providing an annual average of over 1.4 million acre-feet of Colorado River water to Arizona through the CAP, the project is helping reduce the State´s ground water overdraft and related land subsidence.

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