Hot, dry future in the forecast
Climate models show long-range reduction in West Slope water supply
Western Colorado’s future looks to be hot and dry, according to climate research at the University of Colorado, promoting calls for preparations.
Global climate models suggest the likelihood of longer periods of warmth combined with a confluence of change in the way precipitation falls west of the Rockies, growth in the demand for water and a general reduction of the supply of water, according to Jeff Lukas, senior research associate at Western Water Assessment at the University of Colorado in Boulder.
“We’re basically going to be pushing the climate to the south,” meaning that Grand Junction summers are growing more like those in Phoenix, Ariz., while Cody, Wyo., is looking like Grand Junction once did.
The upshot, Lukas said at a Colorado Mesa University Water Center seminar, is that spring runoff is shrinking.
As a practical matter, it might take decades to measure the degree of the effect of climate change on the water supply of western Colorado, but most scenarios painted by global climate models point to reduced runoff, Lukas said.
The implications of less water aren’t lost on water managers.
“The only solution to drought is to store water in the good years, so we need to build reservoirs and we need to store water,” Ute Water Conservancy District General Manager Larry Clever said.
The best sites for dams, however, have been taken, Clever said, leaving only those that pose physical and permitting challenges.
More dams, however, aren’t necessarily the best answer, said Chris Treese, spokesman for the Colorado River Water Conservation District.
In some cases, for instance, Colorado water law can prohibit storage because of limitations on the times in which runoff can be captured for certain reservoirs, Treese said.
“Just saying we need more storage doesn’t do much good if all you end up with is a bigger hole,” Treese said.
The likely future of storage is that of smaller projects tailored to meet specific needs, Treese said.
The amount of water available to be captured, however, is shrinking, Lukas said.
By 2050, climate changes are likely to reduce the average amount of water available to be captured, now some 10 million acre feet, to 9 million acre feet, Lukas said.
That’s because there is likely to be a million-acre-foot increase in the amount of water lost to the atmosphere and plant life as temperatures rise.
Global climate models see the average temperature of Colorado rising 4 degrees Fahrenheit by 2050 and 6 degrees Fahrenheit by 2080, he said.
Most of the increase in the temperatures is likely to be felt during the summer, Lukas said. That will mean earlier springs and later falls, increasing by 20 percent by 2040 the amount of water that will be needed by crops.
Though climate change is continuing, Lukas said, drought years such as 2002 and 2012 are attributable to global warming.
Tree-ring studies show a 60-year period of drought in Colorado in the 1100s, he said citing an instance of greater drought extremes.
“We don’t have to invoke climate change to explain what happened in 2002,” Lukas said.