The Ice Age created one river, and we’re creating another

The Colorado and other headwater rivers were formed roughly 10,000 years ago, when the glaciers of the last Ice Age melted. The riverbeds are broad, as necessary to carry large volumes of water.

by Allen Best

And sometimes they do. But those years have become ever more scarce in the last 75 years, the result of the canals and dams built to detain the spring flows and, in an extraordinary feat of plumbing described by historian David Lavender as a “massive violation of geography,” flush the water to the drier Eastern Slope of the Rocky Mountains.

Now, the task is underway to reconstruct the Colorado River and its tributaries and manage remaining water in ways that reflect the new realities. The goal is to restore ecological functions lost or imperiled by reduced water flows even as the two primary water-diverting agencies—Denver Water and Northern Colorado Water Conservancy District—propose to skim more water off spring runoff.

“We’re in a very difficult situation,” says Ken Kehmeier, a senior aquatic biologist with the Colorado Division of Wildlife.

Kehmeier explains that the various diversion projects through the decades have left the Colorado River from Windy Gap most of the 27 miles to Kremmling substantially modified. With reduced flows, sediments have filled in between the river cobbles, the spaces between rocks, called interstitials. These interstitials provide habitat for a native species of fish, the mottled sculpin, and also willowflies. A sampling at 18 locations last September found just one sculpin, despite a relative abundance in the Fraser River.

Although others, including Ken Neubecker, of the Western Rivers Institute, have described the Colorado River as a river system on the brink of collapse, Kehmeier won’t go that far. “I just don’t have the data to say that,” he explains. “I can say that there are components of the system that have precipitously dropped (their functionality).”

What Kehmeier’s agency has recommended  to do in collaboration with the two Front Range water agencies is “reset the clock,” as he puts it. The river channel is too wide, and must be narrowed. A more narrow channel will yield increased velocities of water, better moving the sediment and delivering habitat for the sculpin and willowflies. Also, there will be improved “pool ratios,” and cooler water. The shallow water now heats up to the threshold of killing trout in late summer.

The recommendation—this is separate from the global settlement between Denver and the Western Slope—would provide about $3.5 million in cash for rechannelization and another $3.5 to $4 million in in-kind contributions, such as bulldozing work. The agreement also provides for water in the various reservoirs to be allotted specifically to the needs of improved ecological function.

But the agreements doesn’t provide nearly enough money to reconfigure the river all the way from Granby to Kremmling. Part of the problem, says Kehmeier, is provisions that preclude spending public funds on improvements to private land or land to which there is no public access. Various agencies and non-profits may collaborate to extend the improvements in coming years, he hopes, and some private landowners have already begun work on their own. Without work throughout, he says, untouched river segments will become bottlenecks.

“It is my best guess as a biologist that, once we have rebuilt that river, we will see the sculpin come back,” Kehmeier says.

At the end of the day, more water will be removed from the Colorado River to the Eastern Slope, and Kehmeier admits that’s not something he particularly likes.

“I would love to be able to say I don’t like that, that they need to give me more water. But from a legal standpoint, they won’t let me do that.”

It’s a matter of water rights and law, he says. “Water rights will trump us every time in this state, and so we have to look at the next best step, and that’s why we negotiated this enhancement package.”

The Colorado Wildlife Commission is expected to make a decision at its June meeting in Grand Junction. Theo Stein, spokesman for the Colorado Division of Wildlife, explains that the commission’s recommendation will be delivered to the Colorado Water Conservation Board and Gov. John Hickenlooper, who will in turn inform federal agencies overseen with review of these two water projects, the Moffat Tunnel and Windy Gap firming projects. The federal agencies could incorporate the proposed agreement into their findings, or perhaps call for broader measures yet.

To see the proposed enhancement and mitigation packages, go to the Colorado Division of Wildlife website at

Allen Best