Tracing the source: Forest Service experiment seeks to pinpoint Hanging Lake headwaters
The fire, floods and massive debris flows of the past year in Glenwood Canyon could help answer an eons-old question: Where exactly does the underground source of water that feeds Hanging Lake begin?
The U.S. Forest Service is working with scientific consultants from the renowned Ozark Underground Laboratory out of southwest Missouri to conduct an experiment that may answer that very question once and for all.
Last week, the team placed special carbon samplers at key locations in Hanging Lake and at points where multiple springs emerge at the lake and Spouting Rock above the lake and in nearby surface streams.
Then, they traveled into the Flat Tops above Glenwood Canyon to place non-toxic fluorescent tracer dye into the water at various potential source points.
The idea is that the dye will travel through the extensive karst (caves) system that defines the geology of Glenwood Canyon and, whichever color dye or dyes come out at Hanging Lake, that’s the source.
“If you’re making land management decisions related to water, one of the first questions you always have is, ‘What is the source of that water?’” explained Tom Aley, owner of Ozark Underground Laboratory and founder of the nonprofit Tumbling Creek Cave Foundation.
In the same way surface water delineates a watershed boundary, his firm specializes in gathering that kind of information when dealing with groundwater, especially as it relates to karst systems.
When caves are present a substantial amount of surface water makes its way underground and can travel for a substantial distance before emerging into surface streams and lakes, Aley explained.
Such is the case with Hanging Lake, where that water travels through limestone deposits deep underground and eventually pools amid the steep cliffs of Glenwood Canyon at what’s become one of the most popular hiking destinations within the White River National Forest.
It’s that passage through the travertine formation and the unique vegetation in and around the lake that gives Hanging Lake its unique turquoise-green color.
Part of restoration effort
The source water project was made possible through some of the Glenwood Canyon and Hanging Lake fire and flood rehabilitation funds that came through various organizations including the White River National Forest Fund, the National Forest Foundation and the Aspen Community Foundation.
The work is being contracted through the National Forest Foundation.
“When you manage a unique, natural feature such as Hanging Lake, you want to learn as much as possible about it and the science behind it,” said Leanne Veldhuis, White River National Forest Eagle-Holy Cross District ranger.
When funding became available aimed at protecting the resource from the damage caused by the Grizzly Creek Fire and potential future flood events, the agency jumped at the opportunity, she said.
For now, the area remains closed indefinitely after mud and debris slides caused by torrential monsoonal rains over the 2020 Grizzly Creek Fire burn scar in late July and early August covered the trail in spots and wiped out bridges leading to the lake.
“Cave and karst resources in general are something that require a lot of expertise,” Veldhuis said. “Not every forest area has them, and we have many caves all over this district.”
The Forest Service has worked with groups like the Colorado Cave Survey to get a better inventory of caves and how they’re interconnected within the White River National Forest.
Hanging Lake is unique in that it’s formed as a result of those groundwater systems.
“For the same reasons Hanging Lake is so popular, because it’s such a unique, travertine resource and that it’s accessible, we think the findings of this work will be something people are interested in,” Veldhuis said of the source water study.
Aley was joined on the Hanging Lake study by his lead scientist and associate, Dave Woods.
Ozark Underground has been doing groundwater tracing for about 50 years, including work associated with hazardous materials and mining sites, on every continent except Antarctica.
“We are involved in about 40% of all professionally directed groundwater tracing in the U.S.,” Aley said. “We have delineated recharge areas for 50 significant caves or springs around the country. Many of them are habitat sites for endangered or threatened species.”
The Hanging Lake study is especially important, because it involves detecting the water source of an area that’s designated as a National Natural Landmark.
The lab itself, based in Protem, Missouri, is situated on property that has a large cave which also is a National Natural Landmark and has its own unique cave fauna, he said.
The Tumbling Creek Cave Foundation was formed to protect and highlight the unique features of the local cave system, which contains approximately 2 miles of mapped passages defined by highly decorated stalactites, stalagmites, columns, flowstone and cave coral.
Long and short of it
The Hanging Lake study involves the placement of both active and passive carbon samplers near cave openings and in springs and creeks that descend Glenwood Canyon in the vicinity where the tracer dye might come out, Aley further explained of the process.
The active samplers allow for more immediate first-hand observations, while the passive ones can be examined after the fact over several months’ time to trace dye concentrations.
Tracer dyes were introduced at different locations up above in stormwater flow drainages that could carry water into the underground systems.
That water can travel fairly rapidly through the ground to where it emerges on the surface, while some of it lingers, winding its way through and pooling inside the caves before coming out.
“If we have more rapid flow, we expect to have some answers yet this fall,” Aley said. “If it takes longer, we may not know until the snowmelt begins next spring.”
Before any results would be released, the findings would need to go through a quality assurance process as a cross-check to ensure accuracy, he said.
Aley also noted that much of the vegetation that contributed to the travertine process of dissolving the limestone formations is now gone due to the fire and won’t reestablish for some time to come.
“Fire has made a dramatic difference in the chemistry of the area, so knowing which of the surface streams is a contributor of water to Hanging Lake is the first step in trying to understand the damage that may be occurring,” he said. “That way, we know what work needs to be done to try to mitigate those damages.”
Senior Reporter/Managing Editor John Stroud can be reached at 970-384-9160 or firstname.lastname@example.org.
Editor’s note: This story has been updated to correct the name of the Colorado Cave Survey.
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