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Central Arizona Project

About CAP

The Southwest United States is an arid region, with little rainfall and few water sources. Water is therefore a prized resource around which population bases have grown. The Colorado River has been eyed as a water provider by surrounding states for as long as people have settled here. California and Arizona have fought over the rights of its use for most of this century. In Arizona, it was originally proposed as a source for irrigation of agricultural lands in Yuma and western Maricopa counties in 1918 by an Arizona Engineering Commission; this proposal was extended by George Maxwell in 1922 to include Pinal and all of Maricopa County.

Some basic facts about the CAP are:

• it is a 336 mile long series of aqueducts carrying Colorado River water from Lake Havasu in western Arizona to the Phoenix and Tucson valleys in central and southern Arizona (see map); it includes a number of dams, pumping stations and pipelines to enable the flow of water along the system

• its purpose is to transport 1.5 million acre-feet of Colorado River water to supplement the groundwater aquifers for use in irrigation, industry, municipalities and private homes; its initial function was to benefit the agriculture industry specifically, but due to the high population growth is used now to augment other water uses, as well as recharge groundwater systems

• bills proposing the CAP were originally introduced into the Senate and the House beginning in 1947, but it was not authorized until 1968 under the Colorado River Basin Project Act

• construction did not begin until 1973 at Lake Havasu and was not fully functional until 1993 when the Tucson aqueduct was completed; the whole project came in at a total cost to the Federal Government of over $4 billion

• the Colorado River Water Conservation District was set up in 1972 to oversee the CAP and facilitate repayment by Arizona to the Federal Government of $1.2 billion, amended to $2.3 billion in 1988; meanwhile funding is authorized annually by Congress through Energy and Water Appropriations Acts

• the CAP has proved to be a controversial undertaking, with many issues arising from its construction, beginning with opposition to the dams and aqueducts; more recent issues include repayment of construction costs to the Federal government, using the entire allotment provided by legislation, supply of CAP water to households in the Tucson area, recharging groundwater supplies and/or the Rillito river, charges to customers, and demands by Nevada for a bigger share to be taken from Arizona's allotment