High stream temps prompt closures of Fraser, Colorado Rivers for first time in two decades

A dry winter and an early summer has left trout struggling in warmer water across the state.
Courtesy of Breckenridge Outfitters

Colorado’s cold water fisheries are experiencing something close to a crisis this summer as anemic stream flows and consistently high temperatures threaten the survival of trout and other sport fish across the High Country.

The situation in the rivers and streams of Colorado’s Rocky Mountain region has gotten so bad this summer that Colorado Parks and Wildlife has begun voluntarily closing rivers and streams to fishing, for the first time in at least two decades.

“We are experiencing one of the hottest, driest years in decades and with that we are experiencing stream temperatures that are too hot for the survival of trout,” said Kirk Klancke, president of the Colorado River Headwaters chapter of Trout Unlimited.

Parks and wildlife officials announced July 27 that they would be closing down a pair of rivers in Grand County, with the Fraser River now closed from 2 p.m. to midnight, from County Road 8 to the confluence of the Fraser and Colorado Rivers west of Granby, and the Colorado River closed to fishing during those same hours, from Windy Gap Reservoir downstream to the confluence point of the Colorado and Williams Fork River near Parshall.

Klancke explained the simple science behind the problem that trout and other fish that live in the high Rockies are cold water fish. They have evolved to survive through both the frigid winter months and the relatively mild summers experienced in the mountains. The fish, however, rely on dissolved oxygen in the water to breathe and the warmer water becomes, the less dissolved oxygen there is available.

“At stream temperatures above 65 degrees, enough dissolved oxygen can escape into the atmosphere to stress trout,” Klancke stated. “At temperatures of 74 degrees, trout can die.”

Afternoon stream temperatures on the Fraser River are reaching 74 degrees and up to 72.5 degrees on the tributary streams that pour into the Fraser, according to Klancke. Both Colorado Parks and Wildlife and the Headwaters Chapter of Trout Unlimited were already recommending that anglers halt fishing operations in the afternoon before the state announced local river fishing closures.

Jon Ewert, aquatic biologist for Colorado Parks and Wildlife in Grand County, closely monitors river conditions on the Fraser River and the upper Colorado. Ewert said 2018 represents one of the worst years, in terms of stream temperatures and water flows, that he has seen during his 12 years in Grand County.

“It is really a pretty poor year,” he said. “The only other year this compares to is the summer of 2012. But in 2012 we had good consistent monsoons. The cloud cover helps a lot, but we haven’t had much actual measurable rainfall.”

Ewert said concerns about the lack of summer monsoon rains helped prompt the decision to institute voluntary closures of the Fraser and Colorado Rivers in Grand County. This year marks the first year that parks and wildlife has instituted voluntary river closures in nearly two decades.

“We were really close in 2012, but the monsoons came around,” Ewert said. “We have to go back to the 2001-02 drought, the last multi-year drought, when we did a big spate of these.”

Stream flow levels recorded on the Fraser River near Tabernash and on the Colorado River near Windy Gap place this year in the bottom 25 percentile of all years for which data has been recorded, according to Ewert. Officials measured stream temperatures on July 14 as high as 75 degrees in the Fraser River at Kaibab Park in Granby.

“Trout are seriously stressed at 75 degrees,” Ewert said. “If you catch one at that temperature chances are very good that fish will die, whether it swims off or not.”

Recent calls for water downstream on the Colorado River has prompted the release of water from Williams Fork Reservoir, Wolford Mountain Reservoir and Green Mountain Reservoir, Ewert indicated, shifting the dynamic in stream temperatures and helping to cool portions of the Colorado River near Kremmling and at points further downstream. Though the reservoirs that are currently helping cool the Colorado River in western Grand County play no part in stream temperatures further upstream. The Colorado River receives some help from releases of water from the Three Lakes region, but the Fraser River has no such repository from where cooling flows can be released. Water diverted out of the Fraser River, instead, is largely transported directly under the Continental Divide from the streams and creeks that crisscross the valley.

Denver Water, the entity that oversees diversions out of the Fraser River, is aware of the ongoing concern about stream temperatures, explaining that there is a program of selective diversion in place to address such issues.

“When we have temperature issues affecting fish, we try to use flexibility in the reservoir collection system to try and alleviate the problem to the extent we can,” said Dave Bennett, director of water resource strategy for Denver Water. “We try to get water to streams to help alleviate high temperatures. We have limited flexibility this year, but we are bypassing some additional water to the Fraser and I hope it is helping.”

In the process, developed through the Learning By Doing adaptive management group, stream flows that would have otherwise been diverted to the Front Range are instead bypassed and sent downstream into the Fraser River. In the same fashion, the water releases from local reservoirs help cool temperatures in the Colorado River. The process employed by Denver Water is meant to lower stream temperatures in the Fraser River and its tributary creeks.

Once Denver Water completes the Gross Reservoir expansion project, according to Bennett, 1,000 acre feet of water will become available for the process in the future.

“In the meantime, we are voluntarily working with Learning By Doing to use the system flexibility to the extent we have it,” he said.

Despite a potential effect on their business, local anglers support the decision to implement river closures.

Andrew Herst, a fly-fishing guide at Devil’s Thumb Ranch Resort & Spa in Tabernash, said he believes the decision to institute voluntary closures of the Fraser and Colorado Rivers was a prudent decision.

“I think that is probably the best way to go about it,” Herst said of the voluntary closures. “At the end of the day it is still public water and it should be used within limitations. But as far as the fish go, any time you catch them and fight them in water over 65 degrees it is unhealthy for them.”

Herst and other guides at Devil’s Thumb carry thermometers on them while guiding, and fishing trips are called off any time the water reaches 65 degrees. Devil’s Thumb is pushing clients to start their fishing trips earlier in the day to overcome the issue.

Herst, who has been with Devil’s Thumb for the past three years, said stream temperatures have historically been an issue of concern for himself and other guides in late July through August.

The stream temperature issue isn’t only in Grand County. At the same time of Grand County’s closures, Colorado Parks and Wildlife also announced plans to close segments of the north and south fork of the White River. These recent closures followed another round of closures that were announced in mid-July. Parks and wildlife closed the section of the Colorado River running from State Bridge to Rifle along with segments of the Eagle, Crystal and Roaring Fork Rivers.

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