California and Nevada want to claim up to 29 billion gallons of water stashed away in Arizona's aquifers, but officials aren't sure they can honor the request, even though the other two states already own the water.
In recent weeks, both the Metropolitan Water District of Southern California and the Southern Nevada Water Authority have asked to withdraw water they previously deposited in Arizona's interstate water bank. The two agencies are scrambling to replace water lost when the U.S. Interior Department limited their access to the Colorado River.
To cover what both states seek, Arizona would have to ask farmers in Pinal County to switch from water delivered by the Central Arizona Project canal to water drawn from wells. That process can take months, depending on the condition of the wells and may not produce enough water this year to satisfy the withdrawal demands.
Both Nevada and California are trying to draw on water "deposited" in a pilot banking program about seven years ago. Nevada wants 10,000 acre-feet, about 3.3 billion gallons, from the 50,000 acre-feet it banked. California wants all the water it banked, about 26 billion gallons.
The way the bank works, the other two states would take the amount of water they sought directly from the Colorado River. Arizona would then reduce what it takes from the river by the same amount and instead use groundwater.
The states already own the water, which was originally part of their river allocation, and have paid Arizona to store it, a payment that would cover the withdrawal as well.
At issue, said Larry Dozier, deputy general manager of the Central Arizona Project, isn't whether the states are entitled to the water but whether Arizona can deliver it all at once on such short notice.
"We told Nevada it's highly likely we could accomplish the water they asked for," Dozier said. "We told California it's highly unlikely we could accomplish the full amount they want, but maybe some of it."
Since the 1992-93 pilot project, Nevada has negotiated an interstate banking agreement with Arizona's Water Banking Authority, while California has not. Bank General Manager Tim Henley said that means California would need such a pact before Arizona can release any water.
Any agreement would have to protect Arizona, Henley said, "so we don't have to give them the (full amount) if we don't have it."
He said the state Department of Water Resources warned California during the pilot project that without an agreement, there was no guarantee the water would be available on demand later. At the time, federal rules didn't cover interstate deals.
California's need for more water intensified in January after a water transfer with an Imperial Valley agricultural district collapsed. Without that transfer, the Interior Department refused to allow California to continue using more than its share of the Colorado River.
Officials from the Metropolitan Water District, which serves Los Angeles and San Diego, initially said the lost river water wouldn't affect supplies. But in a letter to the CAP, Chief Executive Ronald Gastelum cited the botched transfer as the culprit behind the district's needs.
The Southern Nevada Water Authority, which serves Las Vegas, approached Arizona about withdrawing banked water as one of several options to cover the lost river allocation, spokesman Vince Alberta said.
"Nothing's definite yet, but we want to open all doors," he said. "Before we would withdraw any water, our first priority would be conservation."
Arizona first devised its water bank as a way to use the state's full share of the Colorado River and keep the unused portions from flowing downstream to California. Banking water for other states was an offshoot of that plan, meant to help restore some of Arizona's depleted aquifers.
Since 1996, Arizona has stored about 500 billion gallons of its own river allotment. That water can be withdrawn and used within the state under bank guidelines.