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< Sept-Oct 2007
	Features
Hotter, Drier Demand for water in the desert is increasing, but the resource is projected to decline Mike Kord

Whether or not you believe the International Panel on Climate Change’s assessment that human activity is the main cause of global warming, it’s hard to deny that projected temperature increases in the southwestern United States would cause nearly perpetual drought.

The IPCC announced in February that if carbon dioxide concentrations in the atmosphere reach twice their pre-industrial levels, the global climate will likely rise 3.5 to 8 degrees. The panel also specified that the Colorado River Basin could see a 3.6-degree temperature rise.

Some residents of Flagstaff, Arizona, who saw the temperature drop to a record low of -15 on January 14, might have welcomed a temperature increase about then. In the not-too-distant future, however, record lows could be a coveted—and decidedly rare—discomfort.

For those who live in the southwest, the five-year period between 1999 and 2004 could be considered a trial run at life in a drier, hotter future. During this stretch, the Upper Colorado Basin experienced five straight years of below-average flows. 2002 was its lowest year ever, dropping to 25 percent of the average annual flow.

Get used to it, would be the message from a 2006 study compiled by Martin Hoerling and Jon Eischeild—both from NOAA’s Earth Systems Research Lab in Boulder, Colorado—who published their findings in Southwest Hydrology, a non-peer-reviewed trade magazine for hydrologists.

Using a climate model that projected an average temperature increase of 2.5 degrees between 2006-2030 and a 5-degree increase between 2035-2060, Hoerling and Eischeild suggest that a “near perpetual state of drought will materialize in the coming decades as a consequence of increasing temperature.”

With these temperature increases and no changes in precipitation, the authors posit that the river’s flow over the next 25 years would average 10 MAF (Million Acre Feet), about the same as in the 1999-2004 drought, but significantly down from its annual average of roughly 15 MAF.

And those would be the good years.

The 2035-2060 period would see an average streamflow of only 7 MAF. When asked if it’s possible that the Rocky Mountains could receive more snowfall with warmer temperatures, Andrea Ray, a research scientist at the NOAA Earth Systems Research Lab, said probably not.

“The research we’re compiling is coming down on the side of less precipitation.”

Droughts have always been a natural part of the climatological cycle. Recent National Research Council studies used the history of tree rings to determine southwestern climate patterns over the last 500 years and confirmed this. But a combination of higher temperatures and lower precipitation would make the foreseeable future even worse than the recent drought.

There would be an earlier spring, a later fall, and greater emphasis on reservoirs to store water. That could mean more dams (see “Imperfect Solution,” page 35).

Many dams have already been built along the river, including Glen Canyon Dam, which forms Lake Powell on the Utah-Arizona stateline. In non-drought years, most of the water is diverted for agricultural and municipal water use. Nearly 90 percent of that is for irrigation usage.

The Colorado is also home to diverse ecological habitats and provides hundreds of miles of recreational use through some of the West’s most captivating landscapes, including the Grand Canyon. Further complicating the matter is that multiple years of warmer weather results in drier soil, which will absorb runoff before it reaches the riverbed.

From its 9,000-foot-high headwaters in northern Colorado’s Rocky Mountain National Park, the Colorado River drains a 242,900 square-mile area on its way to the Gulf of California, where it dissolves in the Sonoran Desert before reaching saltwater.

Twenty-five million Americans in seven western states—Colorado, Wyoming, Utah, New Mexico, Arizona, Nevada, and California—rely on the river as their primary water source. Rising temperatures, manmade or natural, coupled with reduced runoff, would severely decrease their supply.

For paddlers, the 1,450-mile-long Colorado is arguably the most important river in the United States, especially the 277-mile stretch from Lees Ferry to Grand Wash Cliffs, as the river carves through the Grand Canyon. Five million people visit the national park each year.

Nearly 25,000 recreational users run some section of the canyon each year. Lower flows have affected the river-running experience.

“What lower water means for us is that it moves slower through the canyon,” says Rob Elliott, owner of Arizona Raft Adventures, one of 16 commercial outfitters in the Grand. “We have a harder time making our itinerary, so we’ve increased the lengths of our trips. Rapids were bigger in the ’80s and ’90s than today or what they will be in the future.”

According to the Outdoor Industry Foundation’s Fall 2006 Active Outdoor Recreation Economy report, the Mountain States contribute $61.5 billion annually, which results in $8.9 billion in state and federal taxes. However, “the interesting thing is that recreation is really important economically, and yet it doesn’t really have a right to water,” says Ray.

As streamflow decreases, demands for water are nearly certain to increase. Arizona’s population, for instance, has grown from 3.6 million in 1990 to an estimated 6.1 million in 2006. Colorado grew by 30 percent in the 1990s.

The Colorado River Compact was an agreement signed by the seven above-mentioned states in 1922 to govern the allocation of the river’s water based on an average flow of 16.4 MAF.

“I’m immensely concerned with climate change,” Elliott says, “but not for river-running. We’re not going to run out of water for one single reason.”

That reason: The lower-basin states of Arizona, Nevada, and California will demand that water stored in the upper-basin states be released. If projections of rising temperatures and less precipitation materialize, however, the competition for rights to drinking water and irrigation will imperil the agreement.

As Utah State University earth resources professor Jack Schmidt told the Salt Lake Tribune, “How do we [Utah] compete against states like Arizona and California that are ecomonic powerhouses? ... They’re going to have to renegotiate the whole [contract].”