The Central Arizona Project delivers Colorado River water 336 miles uphill — from Lake Havasu near Parker to Phoenix to 20 miles south of Tucson in a concrete-lined canal. The CAP supplies about 1.5 million acre feet of water annually to central and southern Arizona for agricultural, municipal, and industrial uses in Maricopa, Pima, and Pinal counties.

About 400,000 acre feet of the total (27 percent) is for agricultural use including irrigation in the tri-county area, says CAP spokesman Robert Barrett. He says future deliveries for agriculture will decline in the future; in part due to the 2008 Arizona Water (Indian Tribe) Settlement. 

Central Arizona farmers produce a wide variety of crops with irrigation including alfalfa, wheat, barley, cotton, melons, citrus, and others; plus water for livestock operations.

CAP is the primary water supply to more than 300,000 acres of farmland and is available as a supplemental supply to many more acres.

CAP-supplied irrigation water users have the lowest water priority on the Colorado River. If available water is reduced, CAP farmers would be shorted first.

Colorado River-supplied districts in Arizona’s Yuma County and California’s Imperial and Riverside counties which border the river are the most secure with more senior water rights on the river. Schorr says this does not guarantee existing water supplies will continue in the future.

“Colorado River-supplied districts in Yuma, Imperial, and Riverside counties are not free of worry,” Schorr said. “If the drought persists and there is a forced reallocation, this will have some effect on these river counties as well.”

Arizona shares the Colorado River lower basin annual allocation of 7.5 million acre feet (AF) with California (4.4 million AF) and Nevada (300,000 AF). Arizona receives 2.8 million AF. One acre foot equals 325,851 gallons; enough water to supply an average size family for one year.

In 2010, the water level at Lake Mead on the Colorado River in northwest Arizona dropped to 1,190 feet. If the Arizona drought persists and the level falls below 1,075 feet, a shortage could be declared on the Colorado River. At that point allocations for all states could be reduced.

If this occurs, Schorr says CAP districts would suffer the most due to the lower priority.

After the year 2030, CAP long-term excess water contracts will expire. It is possible that Colorado River water deliveries could be scaled down to central Arizona irrigation districts. At this point, districts could lease Indian-owned water allocations, invest in new wells, acquire wells via lease, or purchase water from other area farmers to maintain the use of existing water delivery infrastructure.

“Farms without good on‐farm wells may be marginally productive if the irrigation district is not able to furnish enough water,” Schorr said. “If groundwater pumping increases significantly, a water-table recession would be likely.”