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Seeking the source
Study to determine origin of sediment in Lightner Creek
Herald Staff Writer
Photo by JERRY McBRIDE/Herald photos
Meghan Maloney, with the San Juan Citizens Alliance, and Buck Skillen, with the local chapter of Trout Unlimited, examined water quality last week at the confluence of Lightner Creek – to the right – and the Animas River.
Click image to enlarge
JERRY McBRIDE/Herald photos
Fall colors highlight the banks of Lightner Creek where it flows toward the Animas River.
JERRY McBRIDE/Herald photos
Fall colors highlight the banks of Lightner Creek where it flows toward the Animas River.
Jerry McBride/Herald
A shelf of Mancos shale, starting on right side of photo and going diagonally up and to the left, has been formed at the confluence of Lightner Creek and the Animas River over the years. The layer of shale is created from rock particles washed down Lightner Creek.
A coalition of public agencies has acquired funding for a three-phase hydrological study to answer questions that have stumped observers for years: Where does the sediment that Lightner Creek periodically dumps into the Animas River come from, and why?
Field work on the study, begun this week, could be done by the end of the year and lead to answers to an environmental problem seen as a potential source of harm to renowned fishing waters.
"Sediment comes and goes, but no one knows whether it's natural or human-induced," Meghan Maloney, river campaign director at the San Juan Citizens Alliance, said recently. "The reason for concern is that Lightner Creek runs into the Animas at the head of a trout fishery that the Colorado Division of Wildlife gives its highest rating - gold medal."
Buck Skillen, a board member of Trout Unlimited and a water-quality monitor for River Watch, a Colorado Division of Wildlife program, has called attention to the inconsistent clarity of Lightner Creek for five years, Maloney said. This summer enough people were listening to form a task force, with Maloney assigned to coordinate efforts.
"It's to Buck's credit that he kept the issue on our radar," Maloney said.
The task force includes Trout Unlimited, Animas Riverkeepers, San Juan Citizens Alliance, U.S. Forest Service, U.S. Bureau of Land Management, Division of Wildlife, city of Durango, La Plata County and Mountain Studies Institute.
The periodic chalky-colored water at the Animas/Lightner Creek confluence is enough of a mystery to concern Skillen.
"Turbidity has been a concern of mine," Skillen said. "In the summer of 2008, it was particularly bad, and in February this year it was as dirty as I've seen it."
When he ran 60 cubic centimeters of water (the equivalent of two shot glasses or a medical syringe), through a filter in February it became clogged by the time 45 cc had passed through, Skillen said.
Three organizations put up funding for a study - Trout Unlimited $1,000, the Colorado Water Conservation Board $5,000 and the Southwestern Water Conservation District $2,600 - to hire Mark Oliver of Basin Hydrology. Oliver started his field work this week.
"I started at the mouth where Lightner Creek runs into the Animas and I'm working my way upstream," Oliver said. "I'm looking at the channel and flood plain for sediment sources that could come from bank erosion or land-use modification.
"The Tech Center watershed and Perins Canyon seem likely sources of silt," Oliver said. "But my study will confirm whether the deposition is coming from there."
At certain points, Oliver will do sieve analysis - measuring the size of sediment particles. Along with a cross-section analysis of the channel - width, depth and slope - he can determine the movement of sediment.
"I'll focus on sediment sources and the mechanics of how sediment gets to the mouth," Oliver said. "Then I'll try to determine if the sediment is natural or caused by people - for example, the landfill above the Tech Center."
Oliver expects to have a draft of his report ready by year's end.
"The next step will be to decide on potential remediation and organize a neighborhood-watch type surveillance among private land owners," Maloney said. "They would be alert to what is happening and report what they see."
The third phase would be the implementation of remedies, Maloney said. She said the lower reaches of Lightner Creek would be the focus of the work.
The study could establish a baseline for long-term monitoring of Lightner Creek, Maloney said. "Ten years from now we could have a paper trail."
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