Reservoir releases for Colorado River endangered fish coming after peak flows
The Colorado River east of Grand Junction in DeBeque Canyon is forecast to hit its annual peak Saturday, in a quick climb to 21,000 cubic feet of water per second before dropping over the next week as cooler weather arrives.
The operators of five upstream reservoirs have been closely watching this season’s large, and late, spring-runoff pattern, and they are now starting a coordinated release of water designed to improve habitat for endangered fish in a 15-mile stretch of the river below Palisade.
The reservoir releases, which collectively will add about 1,300 cfs of water to the river, are being timed to reach Palisade on Monday or Tuesday, after this weekend’s peak flows have subsided.
The goal of this year’s coordinated release of water is to extend the high flows, not add to the peak flow, as it is in most years, said Don Anderson, a hydrologist with U.S. Fish and Wildlife, who said care is being taken not to increase the risk of flooding this weekend.
The releases from Ruedi, Homestake, Wolford, Williams Fork and Green Mountain reservoirs are designed to benefit four ancient species of fish.
The well-timed higher water will send spawning cues to Colorado pikeminnows, large powerful fish that swim upstream to spawn in the gravel beds of what’s known as “the 15-mile reach.”
Higher water will give the recent offspring of razorback suckers a chance to find refuge in calm side channels.
Higher, faster water will scour fine silt from gravel beds, flush away dry-year vegetation growth and help the river absorb nutrients from wet floodplains.
And the high water also will benefit populations of humpback chubb downstream of Grand Junction — at Blackrocks, in Westwater canyon and near Moab — and may also help the struggling bonytail chubb.
As part of this year’s effort, the outflow from Ruedi Reservoir into the lower Fryingpan Reservoir will climb from 354 cfs to 654 cfs, before stepping back down Wednesday.
The flow from Rocky Fork Creek, which runs into the Fryingpan below Ruedi Dam, added 75 cfs to the river Friday, which means the Fryingpan could be 700 cfs or above by Wednesday.
Tim Miller, a hydrologist at the Bureau of Reclamation, said a flow of about 700 cfs is consistent with most of the other 10 years since 1997 that Ruedi has participated in what is called the Coordinated Reservoir Operations (CROS) program.
Miller’s operational goals with this year’s CROS program include keeping outflow from the reservoir below inflow, so he can fill the 102,000 acre-foot reservoir in early July, while keeping flows in the lower Fryingpan below 850 cfs.
Operators at other participating reservoirs are juggling similar goals.
Releases from Homestake Reservoir, which is on Homestake Creek in the Eagle River basin and is managed by Aurora and Colorado Springs, are going to climb in a similar timeframe as Ruedi’s, moving from 6 cfs to 100 cfs Monday and then stepping back down to 6 cfs by week’s end.
Releases from Green Mountain Reservoir, which is on the Blue River north of Silverthorne and managed by Reclamation, are slated to rise from 800 cfs to 1,400 cfs and then drop back down.
Releases from Williams Fork Reservoir, which is on a tributary of the Colorado east of Kremmling and managed by Denver Water, will increase from 350 cfs to 650 cfs and then drop.
And Wolford Reservoir, on Muddy Creek north of Kremmling and managed by the Colorado River District, is currently spilling about 400 cfs of water due to high inflows.
During a series of conference calls over the past several weeks, reservoir managers have described this year’s snowpack as “bashful” and “tentative” due to colder temperatures in May and June. And while the snow is still deep in the Colorado River’s headwaters, more cool weather is in the forecast.
And every water manager sounds glad there is at least water this year to run after last year’s deep drought, and most now expect their reservoirs to fill, which gives them flexibility this week to release water for the fish and for the river.
This year’s high flow — 21,000 cfs, forecast for Saturday — was the opposite of last year, when the Colorado peaked, as measured at the Cameo gauge, on May 19 at about 6,800 cfs.
Aspen Journalism covers water and rivers in collaboration with The Aspen Times. More at http://www.aspenjournalism.org.
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