Posted Aug 25, 2011, 12:10 pm
Arizona’s water future will depend more on how we manage the dwindling resource than on how much we have, says the lead author of a report from Arizona State University.
The state’s age-old struggle among agriculture, mines and cities is likely to heat up in coming decades as global warming saps an estimated 15 percent of our water supply and growth further stresses our metro areas.
“It grows every year and it‘s still a ways off, but there is an impending need to sort out those competing uses,” said Grady Gammage, Jr. of the Morrison Institute for Public Policy.
'Do you want growth, or do you want a lifestyle?'
The institute’s report - Watering the Sun Corridor - takes a look at the Tucson-Phoenix water situation in light of some new research and new ways to measure demand.
The intricate and sometimes delicate system - both physical and political - by which we get our water will be tested as the Arizona’s population centers continue to grow into an economically (but probably not physically) linked “megapolitan area” stretching from Tucson to the Phoenix valley.
The state will continue to shift from agriculture to urban use, the report said.
About half of the water in the Tucson-Phoenix corridor goes to crops. In Maricopa County, it’s just less than half, and in Pima County it’s about a third. But in Pinal County, where groundwater pumping has depleted some portions of the aquifer and caused the ground to sink 10 feet or more, it’s 96 percent.
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Native American tribes - most notably the Gila River Indian Community - have said they plan to use much of their share of Colorado River water to expand farming.
“There are going to be pressures to put more of that water to urban uses,” Gammage said.
The Morrison Institute questions the wisdom of stripping away funding and staff at the state Department of Water Resources at a time when the importance of water planning is rising.
The state has long served as an example for water planners across the nation. The 1980 Groundwater Management Act, which created the Active Management Areas to guide the flow of water across political boundaries, has served to soften the political head-butting that is a hallmark of Western water negotiation.
The Department of Water Resources was created to manage the use of our limited and shrinking supply. But since 2008, the state has cut more than 70 percent of the department’s budget. The department’s staff shrunk from almost 300 to fewer than 100.
“Shrinking ADWR and potentially jeopardizing our history of careful water management do not seem the best way to celebrate Arizona’s centennial,” the report said.
The report teases out a few details of water use that other demand estimates have traditionally not examined, Gammage said.
The traditional measure of demand for a community is expressed in gallons per capita per day, or GPCD. But those figures do not include significant urban uses, including factories, dairies (which use a lot of water), golf courses using wells, mines, gravel pits and quarries.
“It understates the demand,” Grammage said.
The corridor uses a combined 3 million acre-feet of water each year - a number the report warns is not sustainable. A combined water “budget” of 2.2 million acre-feet would be a sustainable average use, based on supply and population projections, the report said.
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The report asserts that ultimately, assuming that commercial agriculture is replaced by urban growth and a freeze on such uses as golf courses, mines and other non-residential urban uses, the Tucson-Phoenix corridor will have enough water to support about 8 million people. Other estimates have concluded the region could support 10-15 million.
The report does not examine how the water would be distributed among the players in the three counties of the Sun Corridor - it recognizes only that the Sun Corridor will be an inextricably linked economic unit.
In the end, residents of Arizona’s population centers will have to collectively decide whether they want to continue along the current water-use path, which would eventually stifle growth, or continue to grow and stave off water use.
“Do you want growth, or do you want a lifestyle?” Gammage asked.
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