Report predicts warmer Colorado with decreased streamflow by 2050

Colorado can expect to continue getting warmer in coming decades, which means it likely will get drier too, a new report says.

The drying trend could come despite a possible increase in mid-winter precipitation, and could hit southwestern Colorado the hardest.

The report was released by the Western Water Assessment, a program of the University of Colorado at Boulder, and by the Colorado Water Conservation Board. It updates a report released in 2008 and takes into account numerous climate models.

In a conference call with reporters this week, lead study author Jeff Lukas of the Western Water Assessment said Colorado’s climate already has warmed about 2 degrees Fahrenheit over the last three decades. Various models suggest the state could warm anywhere from 2.5 to 6.5 degrees by 2050.

A 2-degree increase would make Denver’s climate more like Pueblo’s, while a 6-degree rise would make it like that of Albuquerque, N.M., he said.

The precipitation outlook isn’t so clear. Climate models for the western United States suggest climate change will result in a drying Southwest and increased moisture to the north. That split could occur right in the middle of Colorado, although models suggest an overall increase in mid-winter precipitation in the state.

However, it’s expected that statewide streamflows could nevertheless decrease by 2050, especially in southwest Colorado. Any increase in snowpack is expected to be offset by warmer spring and summer temperatures that pull more water from plants, lengthen growing seasons and cause snowpack to melt earlier. The latter also has been accelerated by dust storms that cause debris-darkened snowpack to absorb rather than reflect sunlight.

“So we have this uncertainty in future precipitation but then the more certain effects with warming,” Lukas said.

The report suggests a continuing increase in heat waves, wildfires and droughts, all of which already have become more common over the last 30 years.

Lukas said one reassuring finding from the study is that it predicts a similar range of Colorado climate futures as had been previously predicted. Some global climate-change outlooks have suggested warming will be more accelerated than once was thought.

James Eklund, director of the Colorado Water Conservation Board, said climate modeling is being considered as the state continues work on projects including crafting of a statewide water plan.

“We need to, as we say, hope for the best and plan for the worst,” he said.

He noted that snowpack that melts out over time serves as a form of water storage. If Colorado is to receive more mid-winter snow that melts off sooner, that points to a need to consider storage projects to capture that snowmelt for use, he said.


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