Arizona faces potential water supply shortage from Colorado River by 2011

In a 1970s television commercial, heartburn relief was spelled R-O-L-A-I-D-S. In drought-plagued Arizona on the verge of a 14th consecutive year of moisture deprivation, relief is spelled R-U-N-O-F-F from rain and spring snowmelt in the Rocky Mountains into the mighty Colorado River.

If runoff fails to achieve near normal levels in the Colorado River watershed over the next few years, a shortage could be called on the river for the lower basin states (Arizona, California and Nevada) by 2011. Arizona would take 96 percent of the water loss, Nevada four percent, and none for California. About a third of Arizona’s water needs are supplied by the Colorado River.

“The good news is there are tremendous amounts of storage on the Colorado River in Lake Meade and Lake Powell with each about 50 percent full,” said Tom Carr, assistant director with the Arizona Department of Water Resources (ADWR).

“The bad news is if we don’t get great improvement in water supplies to near normal runoff, we have a good chance of a shortage declaration by 2011.” Reduced runoff into the Colorado River has occurred annually since 2000.

Lake Meade is located on the Arizona-Nevada border east of Las Vegas. Lake Powell is bordered by three states — Arizona, New Mexico, and Utah.

A shortage would be long-term, five to 10 years depending on hydrology, Carr said. U.S. Department of Interior Secretary Dirk Kempthorne would declare a shortage. The Colorado River is operated by the Bureau of Reclamation’s regional office in Boulder City, Colo.

Carr explained the impending water shortage’s potential impact on Arizona irrigation districts and agriculture in a presentation to farmers at the 2007 Maricopa Agricultural Center Field Day in Maricopa, Ariz. in early October.

“We’re trying to help people understand the possibility of a shortage and to start looking for other water sources,” Carr said. “People don’t need to overreact — they need to look ahead and plan for it,” Carr said.

More than half of Arizona’s Colorado River draw is delivered to Central Arizona through the Central Arizona Project (CAP). The river is tapped at Lake Havasu, Ariz., where 336 miles of concrete canals slither like a rattlesnake across the low desert into the Phoenix area and then south beyond Tucson. The CAP delivers more than half of the annual water supply to the four million-plus residents in Maricopa, Pima, and Pinal counties.

For Central Arizona agriculture, the CAP provides irrigation water to about 300,000 acres of farmland. According to Carr, the CAP has dibs on about 1.6 million acre-feet (a-f) from the Colorado River annually, of which 400,000 is set aside in the agricultural pool for contractors, and some water is delivered under Arizona water banking activities.

“If farmers and irrigation districts don’t have a full water supply (from a shortage), they need to determine the amount of needed replacement capacity (wells) and the related costs,” Carr said. “They need to make the financial investment to ensure adequate water supplies.”

Yuma County, Ariz. farmers don’t need to break a sweat over the water shortage issue. The five water districts in the Yuma area have higher priority than the CAP. Yuma County borders the Colorado River.

“Yuma won’t be shorted under any foreseeable projection we have,” Carr said. “According to the ‘Law of the River’, CAP water would have to dry up completely before Yuma river water supply was affected.”

Yuma’s five water districts include the Yuma County Water Users’ Association, the Wellton Mohawk Irrigation and Drainage District (IDD), the North and South Gila Irrigation Districts, and the Yuma Mesa IDD, Carr said.

The “Law of the River” is a compilation of federal laws and U.S. Supreme Court decisions. The 1968 Colorado River Basin Project Act, which authorized the CAP, also mandated junior river rights to the CAP compared to those with pre-1968 water rights. The same law dealt senior lower basin state priority to California over Arizona and Nevada.

Carr has 30-plus years in resource planning and water rights management. At ADWR, he’s in charge of water rights adjudication, primarily negotiations on the Colorado River Compact and river operations.

The compact is a 1922 agreement among the seven states in the Colorado River basin. The upper basin state makeup includes Colorado, New Mexico, Utah, and Wyoming. Shortages there can be called anytime.

A lower basin shortage call would be a history-setting first. Shortage guidelines are expected from Kempthorne by the end of the year.

Among the secretary’s option are the components of a basin state-developed plan for the continued operation of Lake Meade and Lake Powell. If a shortage is called, reductions would be based on Lake Meade water levels.

If Meade’s level dips below 1,075 feet but remains above 1,050, deliveries to the lower basin would be cut by 333,000 a-f, including 320,000 a-f less for Ariz.; between 1,050 and 1,025 — a 417,000 a-f reduction (400,000 for Ariz.), and below 1,025 feet — 500,000 a-f (480,000 for Ariz.). At 1,025 feet, Kempthorne and basin state representatives would discuss additional reductions.

Due to statutory priority, California would not lose a single water drop under a shortage. The Golden State enjoys pre-1968 rights for their Colorado River allocation.

Current law affords maximum Colorado River water apportionments to the lower basin states as follows: California - 4.4 million a-f, Arizona - 2.8 million a-f, and Nevada - 300,000 a-f. A 1944 U.S.-Mexico treaty earmarks 1.5 million a-f to Mexico. One AF equals 325,851.42 U.S.gallons.

“When I say the CAP would be shorted, the shortage actually falls first on our water banking activities through the Arizona Water Banking Authority,” Carr said. The authority recharges water for long-term municipal and industrial shortages.

Under an Arizona shortage, the first cut would be shared between two cities, Bullhead City and Lake Havasu City on the Colorado River (10 percent), and the CAP (90 percent). The next cuts within the CAP would be the Arizona Water Bank (including recharge conducted by the Central Arizona Water Replenishment District), followed by long-term contracts within the same district, and third, contracts for excess water apportionment to the agricultural pool. The bottom line impact of water cuts for farmers in Central Arizona – reduced water to irrigation districts participating with the Arizona Water Bank. In addition, a reduction in hydropower available from Hoover Dam during the shortage period would likely occur, Carr said.

“Individual farmers and irrigation districts should examine backup water supplies from groundwater to replace CAP losses by the district,” Carr said. “For Central Arizona farmers, it would be a moderate shortage of water that would impact the number of acres farmed without adequate backup water supplies.”

Irrigation districts have been actively planning for a potential shortage for several years, Carr said. His advise to the districts - assess the ability to deliver water to customers and the actions necessary to build capacity for backup supplies.

“There are many hard questions facing us (ADWR),” Carr said. “We’re working to establish a system of regulations in case a shortage occurs. The next thing is how do those affected, irrigation districts and producers, adapt in the future.”

email: [email protected]

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.