Roaring Fork River flows drop in Aspen as Twin Lakes diversions resume
Roaring Fork River flows have dropped dramatically this week as the Twin Lakes tunnel, which diverts water from the upper Roaring Fork under Independence Pass, re-opened Monday after closing June 14.
At about 5:30 p.m. Monday, flows in the tunnel jumped from 1 cubic foot per second of water to 124 cfs as conditions on the lower Arkansas River allowed the Twin Lakes Reservoir and Canal Co. to begin diverting again.
But as water was again sent east to the benefit of Colorado Springs, Pueblo, Pueblo West and Aurora, flows in Lincoln Creek and the Roaring Fork dropped sharply.
Flows at 11:45 a.m. Monday in Lincoln Creek below Grizzly Reservoir, where the tunnel begins on the Western Slope, were at 187 cfs. By noon, the river below the reservoir was flowing at just 3 cfs.
Lincoln Creek is one of the bigger tributaries of the upper Roaring Fork and joins the Fork just above the Grottos area, about halfway up Independence Pass.
Farther down the valley, just above Difficult Creek at the bottom of the Pass, flows in the Fork dropped Monday from about 270 cfs to 65 cfs as the tunnel began diverting water again.
Wednesday morning, flows in the tunnel were once again reduced back to nearly zero, but it was part of routine operations, which include periodically driving through the tunnel to reach the eastern portal, and the low flows did not immediately impact local river levels.
While the Fork and its tributaries may have suffered this week due to the sudden drop of water, the river system benefited when flows in the tunnel were turned down from about 600 cfs on June 13 to only 2 cfs on June 14.
As the tunnel closed in June, Lincoln Creek and the upper Fork jumped to life as native flows were restored.
“I suppose they could handle turning the tunnel back on differently and ramp flows up or down the way it is done on the Pan,” said Rick Lofaro, the executive director of the Roaring Fork Conservancy, referring to how flows are managed in the Fryingpan River below Ruedi Reservoir. “But high flows were and always are very beneficial. Particularly in the upper Fork, which is normally flow-challenged.”
Lofaro said it was good to see the North Star area east of Aspen inundated with water again this year, as it helps with cottonwood regeneration and revitalizes wetlands.
This marked the third year in a row that good water supplies in Twin Lakes Reservoir and in the lower Arkansas River forced the Twin Lakes Tunnel to stop diverting for about two weeks due to legal and physical constraints.
Valerie MacDonald, the emergency manager for Pitkin County, said public safety officials in the county did not have to respond to any situations directly caused by the higher flows between June 14 and July 3.
And she praised the manager at the Twin Lakes Reservoir and Canal Co. for communicating with her about the timing of the diversions through the tunnel.
Aspen Journalism is collaborating with The Aspen Times on the coverage of water and rivers. More at http://www.aspenjournalism.org.
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