Ariz. would bear brunt of water restrictions

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.titles {font-family: Myriad, Arial, Helvetica, sans-serif; font-size: 18px; font-style: normal; line-height: normal; font-weight: bold; color: #3399FF;}Of all the states that divided the waters of the Colorado River in 1922, Arizona may have cut the best deal — at least it seemed so at the time.
But 85 years later, because of the state’s explosive growth, the ongoing drought and the state’s junior rights to its allocated water, the deal might not be so good after all.
Under the 1922 Colorado River Compact, the Lower Basin states of Arizona, California and Nevada were jointly entitled to 7.5 million acre feet of “mainstem flow” from the Colorado River. Of this, California was allocated 4.4 million acre feet, Arizona 2.8 million and Nevada 300,000 acre feet.

Cities of the River
Week 1 Colorado River
Week 2 Colorado River Compact
Week 3 Las Vegas
This Week Phoenix
Week 5 Los Angeles
Week 6 Colorado Springs
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For years, California used more than its share of Colorado River water appropriated through the 1922 Colorado River Compact, but the rights to surplus water the state was granted for discontinuing the overuse might be rights to water that never will exist.

This disproportionate allocation has meant that while both heavily populated California and booming Nevada have lived for years with the looming prospect of water shortages, much of Arizona has enjoyed an apparently limitless supply of water.
But those days are almost certainly coming to an end, driven by drought, competing demands for the river’s water, and by Arizona’s precarious claims to the water that it currently uses.
Piped in
The Phoenix metropolitan area draws more than 60 percent of its water from the Colorado River, via the canals and pipelines of the Central Arizona Project, which went online in 1984. Groundwater supplies another 5 percent and the remainder comes from the Salt River Project, which collects water from the Verde River and Salt River watersheds in Arizona.
The impacts of a continuing drought in the Colorado River Basin, especially if overlaid by regional climate change, are particularly severe for the Phoenix area. Drought mitigation strategies such as agricultural land fallowing and more extensive exploitation of groundwater resources might be sufficient for the short run, but such steps will not solve the long-term problems that an extended drought will pose.
Thirty-five percent of Phoenix’s water comes from the Salt River Project. But since the Salt River/Verde River watersheds are low altitude sources that are particularly susceptible to a drier climate, the project’s effective yield is likely to be sharply reduced during coming years. According to Dr. Robert Balling, a climate scientist from Arizona State University in Tempe, scientists have an 85 percent confidence level that increasing temperatures will reduce surface water in the Salt River and Verde River systems.

Editor’s Note

This is the fourth of a six-part series exploring the critical importance of the Colorado River to the growth, development, and continuing prosperity of Colorado Springs, Las Vegas, Los Angeles and Phoenix.

The river’s waters are already over-allocated, and there is little prospect that average yearly flows will increase. There is a real possibility that what we now consider drought will become the norm and that the cities will enter into a new era of reduced water availability and enforced conservation.

How will the cities meet these new challenges? Who will gain, and who will lose? Will the historic model of growth-driven prosperity continue? Are businesses, politicians, water managers, developers and government officials creating sustainable blueprints for the future, or are they simply continuing with business as usual and hoping for the best?

During such conditions, the project’s annual yield could shrink by 30 percent, or 300,000 acre feet.
Such shrinkage would, climate scientists stress, almost certainly be accompanied by extreme drought conditions in the Colorado River Basin. In that event, the U.S. secretary of the interior would declare a “severe drought,” which would require all seven of the states that draw water from the Colorado River to cut back.
Junior rights
That would be particularly ominous for Phoenix, since the CAP’s water rights in the Colorado are junior to all other Lower Basin users. Arizona, and Phoenix, might suffer draconian supply cuts, as the Phoenix Water Department acknowledges on its Web site.
“…under the current law of the river, the Colorado’s flow is divided by compact between Upper Basin and Lower Basin states. Arizona is entitled to 2.8 million acre-feet of Colorado River water. However, about 1.7 million acre-feet of this allocation has junior standing on the system. What that means is that a shortage in the lower basin allocation dictates that Arizona is cut back first. California and Nevada (4.4 million acre feet and 300,000 acre feet respectively) will be affected only after Arizona loses its entire 1.7 million acre-feet of ‘junior’ status water (more than half of the state’s total allocation).”
These figures, disturbing as they might be, do not reflect Mexico’s rights to 1.5 million acre-feet of the river’s flow, which, under a 1944 U.S.-Mexican treaty, might be superior to those of the states.
In mid-August, the United States and Mexico announced that they will open talks about how the two nations share the Colorado River and what happens if the river’s flow runs short.
The negotiations are expected to focus on the current drought, the potential effects of climate change, the river’s damaged delta and potential American investment in desalination.
The seven signatory states to the 1922 compact want Mexico to be included in a proposed drought mitigation plan that would spread future shortages among all users. Under the plan, which was agreed upon by the states earlier this year, and is expected to be ratified by the federal government this fall, Arizona would probably lose the most water during a severe drought.
If Mexico declines to join the drought plan, citing the 1944 treaty, Arizona’s losses could be even more dramatic.