Beyond the 'Big Ditch': CAP holds Water Leadership Forum

Published in July 2008 issue of Tucson Green Magazine.

On May 14, the Central Arizona Project (CAP) held a Water Leadership Forum at the Four Points Sheraton Hotel, inviting the public to learn about the history and future of Arizona's most valuable resource. In the face of eight years of drought, climate change, and a potential water shortage, the forum explored ways to meet the water needs of Arizona's exploding population.

During the early 1900s, the seven states of the Colorado River Basin--Arizona, California, Nevada, New Mexico, Wyoming, Colorado, and Utah--competed for access to Colorado River water. Out of this debate came the Colorado River Compact of 1922, which divided the states into the upper and lower basins, each allotted 7.5 million acre-feet per year. (One acre-foot equals 325,851 gallons, the amount used annually by an average family).

Legal and political disputes, particularly between Arizona and California, caused Arizona to be the last state to approve the Compact, which it did in 1944. In 1968, President Lyndon B. Johnson signed the Colorado River Basin Project Act authorizing construction of CAP, and three years later, the Central Arizona Water Conservation District (CAWCD) was established to manage CAP and reimburse the federal government for construction costs.

From Lake Havasu to south of Tucson, CAP's canal system stretches 336 miles to distribute 1.5 million acre-feet of water per year to Maricopa, Pinal, and Pima Counties. CAP is "more than just a 'big ditch,'" said CAWCD General Manager Sid Wilson. It includes 14 pumping plants, a hydroelectric pump/generating plant at New Waddell Dam, 39 radial gate structures to control water flow, more than 40 turnouts to deliver water to treatment plants, and the Lake Pleasant reservoir. In order to lift water more than 2,900 vertical feet, the system requires significant energy--over 2.5 billion kilowatt-hours per year, which comes from the Navajo Generating Station, Hoover Dam and New Waddell Dam.

Coping with a potential shortage, which could begin as early as 2011, is a key concern for CAP. In a shortage, a priority system governs allocation. According to the Colorado River Basin Project Act, Arizona's allotted 2.8 million acre-feet is subordinate to other states in the basin. Within Arizona, there is another system of priorities. Municipal and Industrial (M&I)--including the City of Tucson--and Native American use will take precedence over non-Native American agriculture and excess water users such as the Arizona Water Bank and the Central Arizona Groundwater Replenishment District.

The availability of water for downstream users is determined by the water elevation (above sea level) in Lake Mead, which is currently around 1108 feet. 1075 feet is considered the first level of shortage, but has no impact on water delivery. At 1025 or lower, water bank replenishment and agriculture would begin to face reductions. A recent study by Tim Barnett and David Pierce at Scripps Institution of Oceanography, UC San Diego, forecasted a 50% chance that Lake Mead will go "dry" by 2021. CAP spokesman Bob Barrett called the study "flawed," not taking into account river augmentation efforts and shortage reduction plans.

In the event of a shortage, CAP is exploring a number of coping strategies, including replacing non-native salt cedars (tamarisks) with native cottonwoods, which absorb less water; desalinization and possible re-operation of the Yuma desalting plant, which has been dry for over a decade; imported surface water; groundwater development, and cloud seeding to increase Colorado snow packs. The Arizona Water Banking Authority was established in 1996 to develop long-term storage in underground recharge projects for times of shortage.

The forum also addressed conservation. The Lower Colorado River Multi-Species Conservation Program of 2005 balances existing and projected Colorado River water usage with conservation of threatened species and habitat restoration. The 50-year program conserves existing habitat, creates new habitats (8,132 acres), and protects six endangered and threatened species, including the Yuma clapper rail, the southwestern willow flycatcher, the desert tortoise, the bonytail, the humpback chub, and the razorback sucker. CAP has agreed to cover $52 million of the project's total $626 million costs over 50 years.

To learn more about CAP visit online at www.cap-az.com or call its Phoenix office at (623) 869-2333