Phoenix, Tucson Launch 2015 Water Sharing Plan

Phoenix and Tucson have announced a plan to collaboratively store and make use of their shares of Colorado River water.

Both cities have contracts with the Central Arizona Project, the canal that diverts Colorado River water from a pumping station near Lake Havasu throughout the rest of the state. Through these contracts, each city is allotted a set amount of the water, says Wally Wilson, the Chief Hydrologist at Tucson Water.

All cities contracting with the Central Arizona Project pay the same amount of money per unit of water, Wilson says. This is done as a practical matter, but it happens to be beneficial to cities far from the pumping station up north, Wilson says, because it means there is no additional cost associated with sending and storing the water in more distant locations. And that is exactly what will happen under the plan announced last week.

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Phoenix hasn't been using its entire allotment of water, but it simply doesn't have a way to handle the excess. The city has plenty of underground storage space, but lacks the wells needed to pump the water back out in large quantities, says Kathryn Sorenson, Director of Water Services for Phoenix.

Under the new Phoenix-Tucson partnership, set to begin in January 2015, Phoenix will begin storing some of its unused Colorado River water in Tucson, which has the needed well capacity. Instead of building additional wells, Phoenix will simply have a set portion of its water order pumped to Tucson instead of to the Valley over the course of 2015. "This partnership is a smarter, kind of more efficient way to accomplish the same thing, in a manner that uses less resources," Sorenson says.

"This fits easy within existing infrastructure," says Wilson. "Nothing has to be built to do this."

Tucson will eventually pump Phoenix's water out of storage and deliver it to its own customers, Sorenson says. But Phoenix will have a sort of contractual I-O-U with Tucson, and later on, if the city should need the water back, Tucson will send it north.

The likelihood that Phoenix will cash in on that I-O-U is high, Wilson says, with current predictions estimating a water shortage from the Colorado River as soon as 2017. "Smart water resources people have always known it's a matter of when, not if," Wilson says. "This is an effort between Tucson and Phoenix to do a little bit more banking before these supplies might be reduced."

Through the program, "we can be sure to continue reliable deliveries to our customers even during times of shortage on the Colorado River," Sorenson says.

And the partnership between the cities will likely be long-lasting. Wilson says master planning for the Tucson facility was done with room for growth in mind. As a result, it has storage capacity, land space, and room for expansion that the Phoenix facility simply doesn't. Phoenix will likely be given the option to eventually invest money in expanding a portion of Tucson's facilities, which it will own and Tucson will operate, Wilson says.

Though the idea of water sharing amongst Central Arizona Project users is not new, the specific Phoenix-Tucson partnership has not been long in the works. The idea first started circling only a year ago, Sorenson says. She can't even remember who first suggested the partnership, but she's thankful that someone thought of it. "It's a fantastic idea," she says. "Sometimes we just need to think outside the box a little."

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