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Official: Phoenix could survive future CAP shortage

Official: Phoenix could survive future CAP shortage

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Will Phoenix run out of water if the Central Arizona Project has a few dry years?

Emphatically not, says the head of a Phoenix-area water users group in a recent blog post. At least not in the short term.

Recently, reports have circulated from CAP officials -- based on federal Bureau of Reclamation projections -- that Lake Mead has a 17 to 29 chance of falling below 1,000 feet between 2016 and 2026.

The lake is now at 1,083 feet, 8 feet above the level in which a small-scale shortage could hit the CAP, affecting mainly non-Indian farmers and users of unallocated, "excess" CAP water. That's not likely to happen in the immediate future, because 2014 has been a decent year on the Colorado. This year's spring-summer runoff into Lake Powell -- which feeds Mead -- is expected to hit 106 percent of average.

But if the drought resumes and the lake drops below 1,000 feet, the chances increase that water cuts would affect Tucson and Phoenix. Las Vegas then also would be unable to go deep enough in the lake to get access to its Colorado River supplies. Hoover Dam's power output would be slashed.

CAP and other Colorado River Basin states' water officials hope to avert these possibilities by conserving more water, finding new supplies and/or persuading federal officials not to let that happen.

In any event, Kathleen Ferris, director of the Arizona Municipal Water Users Association, wrote on her blog that the Phoenix area has other supplies to fall back on at least for some time, should CAP deliveries be curtailed. The association calls itself "a non-profit corporation governed by a board of directors composed of mayors and council members representing its ten member cities and towns."

Here's an excerpt:

"Over the last two decades, the AMWUA cities have collectively stored almost 1.7 million acre-feet of unused surface water and treated wastewater underground as a savings account for use in emergencies – like the one we might be facing from Lake Mead shortages. This stored water would meet our cities’ needs for over two years, but it would never be used up that quickly.

"That’s because Colorado River water delivered through the Central Arizona Project makes up only about 37 percent of the AMWUA cities’ water supplies, while Salt and Verde River water (51 percent), treated wastewater (5 percent), and groundwater (7 percent) make up the rest. Add to this the fact that for over 30 years, we’ve stretched every drop of water by making conservation part of our lives and our culture. The AMWUA cities supplies are so robust that the state Department of Water Resources has determined we have enough water for 100 years for existing and planned growth.

"That doesn’t mean we can be lackadaisical about Lake Mead. It is in every basin state’s best interest to keep the lake’s water levels higher. Potential solutions include paying farmers to fallow land and non-urban users to conserve more water. Arizona and its water users will contribute our share to decrease the risk of shortages so our Colorado River water will be there when we need it."

Tucson Water officials made similar comments two weeks ago. The city has 44,000 acre feet of CAP water stored underground today, expects to have another 300,000 stored by 2020 and has access to 177,000 acre-feet of CAP stored in the Tucson area. Together, that's more than 5 years of city water supplies, at Tucson's current rates of use, if future CAP deliveries were to be cut off.

I asked Ferris about the prospects of drought also reducing Salt and Verde river supplies. She replied that those rivers' reservoirs are about 52 percent full, whereas Lake Mead is about 40 percent full. She said that depending on how long the drought lasts and on the impacts of climate change, "I might start worrying about the Salt and Verde."

But what she's trying to say right now is that the Phoenix area still has a variety of water sources besides the Colorado, so the loss of one supply won't mean apocalypse.

Also, "the AMWUA cities don't compete with other basin states for the Salt and Verde," unlike the seven Western states competing for the rights to use the Colorado River water, she said.

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