By Brent Gardner-Smith, Aspen Journalism
ASPEN – For the second time in two years the native flows to the upper Roaring Fork River have been restored as the Twin Lakes Reservoir and Canal Co. has had to curtail its diversions and close the Twin Lakes Tunnel, which since June 6 had been moving 600-plus cubic feet per second of water under the Continental Divide.
After the tunnel was closed Thursday afternoon and the upper Roaring Fork River had regained the natural flow of its two biggest tributaries – Lost Man and Lincoln creeks – the river bounded down the slick granite in the Grottos area and erupted in a frenzy of churning whitewater.
The Grottos on June 13, and on June 16
Twin Lakes Reservoir and Canal Co. began diverting the headwaters of the Roaring Fork in earnest this year in late May. It ramped up diversions through the Twin Lakes Tunnel to above 600 cfs on June 6 and kept them in the 610 cfs to 620 cfs range until Tuesday, June 14, when the diversions in the tunnel were reduced by about half.
By Wednesday, flows in the tunnel were around 250 cfs and were turned down to a trickle of 4 cfs by Thursday afternoon.
Twin Lakes Reservoir and Canal Co. first reduced the flow of water to the tunnel on Tuesday by letting the natural flow of Lost Man Creek run into the Roaring Fork River again, instead of diverting it to the entrance to the Twin Lakes Tunnel, which begins at Grizzly Reservoir.
The flows of Lost Man Creek added about 250 cfs into the main stem of the upper Fork as it ran past Lost Man campground.
Then on Thursday afternoon, Twin Lakes Reservoir and Canal Co. took the next step and closed the tunnel. That sent another 200 cfs or so down lower Lincoln Creek, which runs into the Fork just above the Grottos.
Just after 5:30 p.m. on Thursday, Lincoln Creek quickly went from a clear and docile stream that could be easily walked across to a turbid river flowing strong enough to lift a man off his feet.
Lincoln Creek, before and after
The 4-mile long Twin Lakes Tunnel is now expected to remain closed for two to three weeks and the recent hot weather may keep the water rising in the Fork as the last of the high elevation snowpack comes off.
On Friday, a cold and swiftly moving Roaring Fork had risen above its banks in portions of the North Star Nature Preserve, flooding some areas but not to the extent of the high water in June 2015.
Last year on June 18 the Fork reached a peak flow of 1,680 cfs, as recorded by the gauge “Roaring Fork River Near Aspen, CO,” located at Stillwater Drive just east of Aspen proper.
Yesterday at 4:30 p.m., as the tunnel was closed, the Fork at Stillwater was flowing at 597 cfs.
But by midnight, with the strong flow from Lincoln Creek added, the Fork had climbed to 817 cfs.
It then hit a high of 927 cfs at 7:45 a.m. on Friday morning, before falling back to 857 cfs by 2:30 p.m. Friday.
By midday Friday, the swelling river was licking the porch of a small cabin on the banks of the Fork in the Stillwater section, but unlike last year, it had not yet flooded the inside of the cabin and a nearby art studio.
The river, however, had risen high enough to flood portions of the North Star Nature Preserve and other land along the river. So far, the high water had not produced flooding in scale with the dramatic size of last year’s “Lake North Star.”
Turn Tunnel Off
The Twin Lakes Tunnel is the key component of the Independence Pass Transmountain Diversion System, which was constructed in the 1930s and is owned and operated by Twin Lakes Reservoir and Canal Co.
Notably, the company does not own and operate Twin Lakes Reservoir, as it sold the reservoir on the east side of Independence Pass to the Bureau of Reclamation and the reservoir is now managed as part of the Fry-Ark project.
The Twin Lakes Reservoir and Canal Co., did, however, retain the right to store 54,452 acre-feet in Twin Lakes Reservoir, which can hold a total of 147,500 acre-feet, or about a third again more than Ruedi Reservoir.
But under its water rights, after Twin Lakes Reservoir and Canal Co. reaches its storage allotment in Twin Lakes Reservoir as it did this week, it has to stop diverting if the Colorado Canal can still divert 756 cfs directly from the lower Arkansas River.
It’s rare that two of the constraints in the water rights held by Twin Lakes Reservoir and Canal Co. overlap and it has to stop diverting West Slope water, but it happened last year and again this year.
And both times were a reflection of the high levels of water in the lower Arkansas River basin.
If flows in the lower Arkansas drop, then the Colorado Canal will likely be called out by a senior diverter and Twin Lakes Reservoir and Canal Co. can again divert water from the headwaters of the upper Roaring Fork and send it directly to the canal.
The Colorado Canal is near Ordway, CO, where Twin Lakes Reservoir and Canal Co. is based. Most of the shares in the company are owned by Front Range cities, which receive the majority of the water normally diverted from the upper Roaring Fork.
Tunnel Diversion Graphics
Grottos, Broad View
Grottos, Middle Indicator Rock
Grottos, Lower Indicator Rock
Lincoln Creek, log indicator