From Aspen Journalism (Brent Gardner-Smith):
Those who keep an eye on the lower Fryingpan River, below Ruedi Reservoir, may have noticed that the river’s flow increased this week in three distinct steps.
On Monday, the river was flowing steadily at just about 200 cubic feet per second.
On Tuesday, it stepped up to 250 cfs, and on Thursday, it took another 50 cfs jump, to 300 cfs.
And on Friday, the river jumped another 25 cfs, heading into the weekend flowing at about 325 cfs. (See USGS gage).
The increases in flow were directed by Tim Miller, a U.S. Bureau of Reclamation hydrologist who manages water levels in Ruedi and also manages water releases from the reservoir, which is about 14 miles above Basalt.
The water from the reservoir was being released through the dam’s outlet structures, as well as through the hydropower plant at the base the dam, into an area that’s popular with anglers, and large fish, and nicknamed the “Toilet Bowl,” due to its swirling waters.
Miller’s goal is to fill the reservoir by July 4, while avoiding overfilling the reservoir, which would cause water to flow over the dam’s spillway, which does not have a flow-controlling gate, as some spillways do.
Miller is now balancing some factors beyond his control: the deep snowpack above Ruedi, lingering cold temperatures and varying flow levels in the transmountain diversions tunnels in the upper Fryingpan Basin.
On Friday, Ruedi was 64.6 percent full and holding 66,116 acre-feet of water, according to Reclamation. When full, the reservoir holds 102,373 acre-feet.
But, given the deep snowpack above Ruedi, Miller said “it’s very possible” the reservoir could spill, something that, to his knowledge, has only happened a few times since the reservoir and dam were completed in 1968.
The Ivanhoe snow-telemetry, or SnoTel, site above Ruedi, in the Ivanhoe Creek subbasin, is at 10,400 feet. The site shows there was still 54 inches of snow at that elevation Friday. That’s up from 42 inches a week ago but still below the March 14 peak of 90 inches.
“It just really depends on the weather,” Miller said of future releases into and out of Ruedi.
Peak runoff in the upper Colorado River basin within Colorado is now expected to arrive late, between June 15 and June 25, as more cool weather is in the forecast.
Not for flood control
Victor Lee, also a hydrologist with the Bureau of Reclamation, made a presentation on Ruedi and Green Mountain reservoirs Monday at the Colorado River Basin roundtable in Glenwood Springs.
He said he expected, because of the snowpack, to see above-average releases out of Ruedi as the reservoir fills and to see above-average diversions through the Boustead Tunnel, which sends water collected by the Fryingpan Arkansas Project diversion system under the Continental Divide to Turquoise Lake, near Leadville.
Since 1972, the Fry-Ark Project has diverted an average of 54,000 acre-feet a year through the Boustead Tunnel, but it’s expected to divert 84,000 acre-feet this year, according to Lee.
On Friday, the tunnel was sending east a relatively modest 38 cfs of water, but it had been sending about 300 cfs on May 17.
Lee also sounded a cautionary note about the rare prospect of Ruedi filling, spilling and sending at least 600 cfs of water down the lower Fryingpan.
“I have to stress that Ruedi is not a flood-control project, and if we get filled, there are no gates on the spillway to stop water from going,” Lee said. “And so, if we’re full, and we fill before peak runoff, there is always that chance that we would have excess flows beyond 600 cfs.”
Aspen Journalism covers rivers and water in collaboration with The Aspen Times. The Times published a version of this story on Saturday, May 25, 2019.