Central Arizona Project

Central Arizona Project. The Central Arizona Project is a 336-mile system of aqueducts, tunnels, pumping plants, and pipelines designed to bring Colorado River water to central and southern Arizona. Constructed by the United States Bureau of Reclamation, it is the largest and most expensive aqueduct system ever built in the United States. Its primary purpose is to supply water for agriculture, municipal use, and tribal communities in Maricopa, Pinal, and Pima counties, fundamentally altering the state's water resources and development.

History

The project's origins lie in early 20th-century efforts by Arizona politicians to secure a reliable water supply from the Colorado River, culminating in the landmark Colorado River Compact of 1922. Decades of legal and political battles followed, most notably Arizona v. California, a Supreme Court case decided in 1963 that affirmed Arizona's water allocation. This victory paved the way for federal authorization under the Colorado River Basin Project Act, signed by President Lyndon B. Johnson in 1968. The legislation authorized the United States Bureau of Reclamation to construct the system, fulfilling a long-held goal for lawmakers like Senator Carl Hayden and Representative Morris Udall.

Design and construction

The system begins at the Mark Wilmer Pumping Plant on Lake Havasu, which lifts water 824 feet in the initial stage. The water then flows through the Granite Reef Aqueduct and across the desert, requiring a total lift of over 2,900 feet through a series of pumping plants, including the New Waddell Dam and the Hieroglyphic Mountains. Key engineering features include the Salt-Gila Aqueduct, the Tucson Aqueduct, and the Hassayampa siphon. Major construction, managed by the United States Bureau of Reclamation, began in 1973 and faced challenges like tunneling through the Superstition Mountains. The final segment reached Tucson in 1993.

Operations and water management

Operations are managed by the Central Arizona Water Conservation District. Water is delivered to a diverse set of users, including cities like Phoenix and Tucson, agricultural districts in Pinal County, and Native American tribes such as the Gila River Indian Community and the Tohono O'odham Nation. A sophisticated system of recharge projects and groundwater storage, like the Tonopah Desert Recharge Project, helps manage the allocation. The water supply is governed by the Arizona Department of Water Resources and is subject to the priorities established by the Colorado River Compact and subsequent agreements like the Drought Contingency Plan.

Environmental and economic impact

The project enabled massive population growth and economic development in the Phoenix metropolitan area and Tucson, supporting industries from semiconductor manufacturing to real estate development. Agriculturally, it initially sustained large-scale farming in Pinal County, though urban demands have since reduced this allocation. Environmental impacts include the creation of artificial waterways and riparian areas, but also the consumption of significant energy for pumping and contributions to groundwater depletion in some areas. It has also supported ecological restoration, such as projects along the Santa Cruz River.

Legal and political issues

The system operates within a complex legal framework defined by the Law of the River, including the Boulder Canyon Project Act and the Arizona Groundwater Management Act. Ongoing disputes involve the allocation of dwindling Colorado River supplies among the Lower Colorado River Basin states, particularly during prolonged drought. Recent agreements like the Colorado River Drought Contingency Plan and negotiations with entities like the Imperial Irrigation District and the Southern Nevada Water Authority are critical. The project's future is intertwined with interstate negotiations, tribal water settlements like the Gila River Indian Community agreement, and federal legislation from Congress.

Category:Canals in Arizona Category:United States Bureau of Reclamation Category:Colorado River