VAIL – The phrase “climate change” did not appear on the agenda of a recent three-day meeting of the Colorado Water Congress, but the topic was often front and center at the conference, as it increasingly is at water meetings around the state and the region.

Amy Haas, the new executive director of the Upper Colorado River Commission, told the Water Congress audience of about 300 water managers, irrigators, engineers and lawyers that “hydrology is changing more rapidly than we once thought” and that “it is primarily due to climate change.”

And, Haas said, attitudes among water managers about climate change are changing too.

“I feel that water managers are not only talking about climate change, they are talking about it frequently,” she said. “This is the new reality that we have to contend with. And I’m encouraged to hear the discussion, openly, in all sorts of water management forums.”

Haas also recognized Brad Udall, who was also at Water Congress, in her remarks.

A senior climate researcher and scientist at Colorado State University, Udall continues to get the attention of water managers with studies that tie rising temperatures to declining river levels.

Udall recently published a paper, along with Mu Xiao and Dennis Lettermaier, on the declining flows of the Colorado River.

The paper found that flows in the upper Colorado River basin declined by 16.5 percent from 1916 to 2014, while annual precipitation increased only slightly, by 1.4 percent.

By conducting experiments with a model that uses temperature and precipitation as inputs, the researchers found that “53% of the decreasing runoff trend is associated with unprecedented basin-wide warming, which has reduced snowpack and increased plant water use,” Udall explained. “The remaining 47% of the trend is associated mostly with reduced winter precipitation in four highly productive sub-basins, all located in Colorado.”

Udall is also using “aridification” at water meetings to describe what’s happening in the Colorado River basin, and he’s offered up a succinct summary of his research on climate change, on a t-shirt, that says “it’s warming, it’s us, expert agree, it’s bad, (and) we can fix it.”

Andy Mueller, the general manager of the Colorado River District, also makes no bones about climate change.

He told the Water Congress audience that the River District is “planning for a future with less water, and it being a permanent situation.”

And on Sept. 14, at a River District seminar in Grand Junction, Mueller told an audience of over 250 water managers, users and stakeholders that science shows that “climate change is going to reduce the natural flow into Lake Powell by 20 percent by 2035 and by the end of the century, 35 percent.”

Mueller added, “We’ve got to recognize that we have a supply problem in the upper basin.”

Jim Lochhead, CEO/Manager of Denver Water, center, on a tour of a forest in one of the watersheds that provide water to Denver, in September 2017. Mike King, Denver Water Credit: Denver Water

Past not relevant

Jim Lochhead, the CEO and manager of Denver Water, said during his remarks at the Colorado Water Congress meeting that the impact of climate change goes even beyond supply issues.

“A warming climate is something we’ve built into our scenario planning process, but it’s not just a water supply concern,” Lochhead said, also citing wildfires and the resulting runoff into reservoirs and rivers, and the increased cost for water treatment from “warmer water” and “emerging contaminates.”

He also said Denver Water no longer thinks that the past is a reliable guide to the future, citing the “over-assumptions of water supply” in interstate compacts like the 1922 Colorado River Compact, the state’s water rights system which is based on “past hydrology,” and state and federal regulations that are based on “past water temperatures and water quality parameters.”

“Those are all geared to the past and not to the future,” Lochhead said.

Denver Water has also “abandoned linear water-supply planning,” where, as he put it, “you look at the past hydrology, look at past population trends, and project those out into the future, look at a water supply gap, and then go out and find water to meet that gap.”

“That no longer can meet the challenges that we face today,” Lochhead said.

And Lochhead said that “firm yield,” the capacity of a given water supply system to meet demands in a dry spell, and the Holy Grail for water providers, was now an outmoded concept.

“We don’t use that term any more, actually, because we know that no yield is firm,” he said.

And if that wasn’t riveting enough for water managers to hear, Lochhead also said that “as we look at the warming climate some of the scenarios in our scenario planning are actually pretty scary, and they will be coming at us more and more quickly.”

Brent Gardner-Smith, the founder of Aspen Journalism, and who served as AJ’s executive director until August 2021 and as editor from 2011-2020, is the news director at Aspen Public Radio. He's also been...