Buggy water spells healthy Roaring Fork
The Aspen Times
Aspen, CO Colorado
BASALT – Judging from the bugs that live underwater in the Roaring Fork River and its tributaries, the river was in good shape a year ago, when a bountiful winter snowpack gave a boost to water flows that lasted well into the summer and fall.
Next month, the Roaring Fork Conservancy will again lead an effort to net aquatic insects in the Roaring Fork and adjacent creeks, tallying up the number and variety of squiggly bugs hiding in the rocks and sediment. The end result will be a comparison of extremes – between last year’s high water and the unusually low flows produced by this year’s drought.
“Here we have, in back-to-back years, the extreme ends of the spectrum,” said Chad Rudow, water quality coordinator for the Basalt-based conservancy and leader of the insect collection. “It’s a unique opportunity to collect data at the same sites in vastly different years.”
Last year, the conservancy and the state Water Quality Control Division teamed up to sample macroinvertebrates – aquatic insects that are large enough to be seen without a microscope – at 20 sites in the Roaring Fork watershed between Aspen and Glenwood Springs.
Rudow led a corps of volunteers in the collection work. The state agency, part of the Colorado Department of Public Health and Environment, handled the laboratory work, tallying the number and variety of insect species gathered at each sampling site. That work is the focus of a recently released report – A Review of Aquatic Life and Stream Health in the Roaring Fork Watershed – which concludes the river as a whole and its tributaries meet or exceed state standards for stream health, though some sampling locales, including two in Aspen, produced subpar results.
This year, Rudow said, the conservancy has decided a second year of study is worthwhile and will undertake the project without the state agency’s involvement. A laboratory will be contracted to assess the results of what is collected, and the city of Aspen and Snowmass Water and Sanitation District will join as financial partners for a more in-depth look at look at their respective areas of particular interest. Aspen will help fund greater sampling of the stretch of the Roaring Fork through town; the water and sanitation district will help finance a closer look at Brush Creek, a tributary that runs through Snowmass Village and empties into the Roaring Fork.
In addition, most of the other sites throughout the watershed will be resampled this fall, Rudow said.
Of the sites sampled last year, two were deemed “impaired” compared to state standards and past results – the Roaring Fork at the Slaughterhouse bridge on the downstream edge of Aspen, and Cattle Creek where it flows beneath Highway 82 between Carbondale and Glenwood Springs. In addition, results of sampling on the Roaring Fork below the Mill Street bridge in Aspen landed in a “gray area” – not impaired, but not healthy, either, according to the report.
“We’re really going to try to pinpoint what’s going on there,” Rudow said.
While the exact cause of less-than-prime results at the two spots in Aspen hasn’t been defined, it’s likely that human-induced impacts play a role, and that low flows exacerbate the situation, Rudow theorized. Water diversions reduce the Roaring Fork’s flows through Aspen significantly in the summer months. The river gets a boost where Maroon Creek empties into it below town, he said.
Rudow also made note of the sampling results on Thompson Creek south of Carbondale. The creek flows into the Crystal River, which is a tributary to the Roaring Fork.
“Thompson Creek ended up being one of the highest scorers of all the streams in the study,” he said. “It’s just one more thing that shows how clear and healthy the water coming out of that area is.”
Thompson Divide, in which several branches of Thompson Creek originate, is something of a battle ground between gas-development interests and those who want the area made off-limits to resource exploration and extraction.
While the creek sometimes dries up near its confluence with the Crystal as a result of water diversions, the sampling site is farther up the Thompson, below the point where water from North, Middle and South Thompson creeks converges into one stream, Rudow said.
The collection of macroinvertebrates involves use of a mesh net of a defined size, and kicking up a square meter of river bottom to set the bugs loose in the water’s flow so they can be captured in the netting.
“It’s pretty interesting to see the number of bugs you collect in a square meter of river bottom,” Rudow said. “It’s literally on the order of hundreds.”
The aquatic insects are an ideal indicator of stream health because the aquatic stage of their life is lengthy – a year or more, their mobility is limited and they’re sensitive to water quality, he explained. Insect species typical to the Roaring Fork – stoneflies, caddis and mayflies – are all sensitive to pollution, according to Rudow. Strong populations of those insects are a good indicator of a healthy river.
Those insects are well known to anglers, but their presence is important to more than just trout and trout fishermen, Rudow said. The insect population translates to a healthy food chain – from trout to herons, osprey and eagles, for example.
Go to http://www.roaringfork.org to view the results of last year’s macroinvertebrate study (click on Publications and look for 2011 Roaring Fork Watershed Macroinvertebrate Study under the Research Studies section).
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