Water for lawns, showers, fountains and farms will become increasingly scarce in the West, according to a dire new assessment of the Colorado River Basin, which stretches from Wyoming to California.
A new report from the National Research Council describes growing pressure from three trends: fast population growth, global warming and a 2,000- year history of recurrent droughts worse than what has been seen in the last 100 years.
“This should be a wake-up call,” said Connie Woodhouse, a climate researcher with the University of Arizona at Tucson and one of the report’s 13 authors.
“Water is a precious commodity in the semi-arid West,” Woodhouse said. “It’s not a given. And it’s going to become even more precious in the future.”
Seven states share Colorado River water, said Ernest Smerdon, a retired engineering professor at the University of Arizona and chairman of the National Research Council panel.
Colorado, Wyoming, Utah, Arizona, New Mexico, Nevada and California divvy up water according to complicated rules laid out in the 1922 Colorado River Compact, Smerdon said.
“The years leading up to that agreement, those were unusually wet years,” Smerdon said.
Back then, the Colorado River was flowing at about 16.4 million acre-feet annually at a key measuring spot in Lees Ferry, Ariz.
Droughts more common
The longer-term average, calculated from 80 years of river- gauge data and thousands of years of tree-ring data – is probably about 10 percent less, Smerdon said.
Tree-ring data also show that decades-long droughts are more common than researchers once thought in the 240,000 square miles of land that feed the Colorado River, Woodhouse said.
“We’re seeing records of drought that are longer and more severe than anything we’ve seen” in the last century, Woodhouse said.
It’s also warming in the West, and that will almost certainly drop the Colorado River’s flow further, the report said.
The region has heated up more than 2 degrees since 1895. It will continue to warm as people pump greenhouse gases into the atmosphere, according to 18 computer models used in a recent United Nations climate report, Smerdon said.
That makes snow melt earlier, when reservoir managers aren’t always prepared to “catch” water, and it means more water is lost by evaporation and plants pulling water through their roots and releasing it into the air.
“I think a reasonably savvy person would have to say you’re going to see less water in that river,” said Brad Udall, director of Western Water Assessment at the University of Colorado at Boulder, who was not a member of the report committee. “The real question is how much less. Is it 5 percent less, or is it 40 percent less, and by when?”
More people, less water
Four of the Colorado River Basin states are growing faster than all others, Smerdon said.
Nevada, Arizona, Colorado and Utah all grew 29 percent or more from 1990 to 2000, he said.
“Costly, controversial and unavoidable trade-off choices will result” as the region’s water is put under greater pressure, Smerdon predicted.
States and municipalities will need to take actions such as requiring greater water conservation by residents, limiting growth or other regulations, he said.
“But our charge was not to tell municipalities or states what they should do,” Smerdon said. “We present the science to them.”
Rod Kuharich, director of the Colorado Water Conservation Board, said he was aware of the National Research Council study, though he hadn’t yet read it.
Western Colorado and at least 1 million Front Range residents rely on water from the Colorado River Basin, Kuharich said.
“A significant portion of the state’s population, and the economy, depend on it,” Kuharich said.
The Los Angeles Times contributed to this report.
Staff writer Katy Human can be reached at 303-954-1910 or khuman@denverpost.com.
