Researchers predict enough water for Tucson
Published on Monday, July 24, 2006
but not always available in right places
By Philip S. Moore, Inside Tucson Business
Tucson has enough water to meet its needs, now and into the distant future, but only if everyone learns to work together toward a common goal.
That was the conclusion of the Water Resources Availability report, presented on July 17 by the University of Arizona’s Water Resources Center. Sponsored by the Southern Leadership Council, Tucson Association of Realtors, Southern Arizona Home Builders Association, Metropolitan Tucson and Marana chambers of commerce, and the Tucson Regional Water Council, the report looked at water supply and demand, now and for the next 25 years, and made predictions about whether they will continue to match.
“This report is recognition of the region’s need to look at its water resources,” said Sharon Megdal, director of the research center and the report’s principal author. Since 1980, when Arizona adopted the Groundwater Management Act, she said the Tucson area has been taking its consumption seriously.
This is especially true under to the area’s Assured Water Supply rules. Either used directly or pumped back down wells to replenish the aquifer, the rules demand that new municipal growth be accompanied by sufficient non-groundwater-based water resources, based on rainfall runoff, reclaimed water or allocation from the Central Arizona Project’s canals from the Colorado River.
However, the rules don’t assure that the aquifers drained by wells are the ones replenished, and new housing subdivision contracts with the Central Arizona Groundwater Replenishment District are stretching the availability of CAP water to meet that obligation, Megdal said.
“There’s a huge and growing replenishment obligation. That means there’s a need for additional water supplies,” she said. “Tucson Water has acknowledged that additional water supply will be required after 2050,” but the need will come a lot sooner in a lot of specific areas without a regional plan, Megdal noted.
She said, “The bottom line is that we have supplies sufficient to serve the community for some years to come.” What the Tucson area doesn’t have is a strategy for getting the water from where it’s available to where it will be needed.
That leads to the question, “can water acquisition be done in a regional way?”
She said, “This area has had an interesting history of regional cooperation and a lack of regional cooperation.” Because of that, the collaboration the metropolitan area already has will need to be expanded.
Meeting the estimated 247,100 acre-feet of municipal demand by 2025 will not be possible through the groundwater replenishment district’s allocation alone. Local demand will exceed the available CAP allocation by 37,700 acre-feet. What’s going to be needed is more use of reclaimed water. The volume needed is nearly four times the current volume of 9,811 acre feet, Megdal warned, “but there doesn’t seem to be a mechanism for getting public support for it.”
Calling it “the big wild card,” she said reclaimed water consumption will become a critical factor for the future.
So will the reliability of the assumptions made today. “This scenario depends on the accuracy of the population projections by the Pima Association of Government,” Megdal said, “and it depend on estimates of per capita consumption. It’s 175 gallons per person, per day, now. Will we do better later? The projection is 165 gallons, but an optimistic forecast could put that as low as 150 gallons. That’s the difference between 2.1 million and 2.3 million gallons saved,” compared to the total population’s consumption at the current rate.
If anything isn’t right in the projections and assumptions, “we won’t get to safe yield by 2025. So, there are going to have be decisions made about what to do, and business is going to need to get involved to have a voice in that.”
E-mail comments for publication to editor@azbiz.com. Contact Philip S. Moore at pmoore@azbiz.com or at (520) 295-4238.
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