Any skier in Aspen can tell you it was a below-average year for snowfall. Though the books are closed on the winter season, the effects of the snowpack are going to reverberate through the summer and each drop of that snowmelt will be important for keeping fish healthy. The current outlook is tepid.
The valley’s river ecology has evolved to depend on peak flows and cold water temperatures. With the spring runoff on the rise, many local organizations are looking at what’s downstream for the fish of the Roaring Fork River.
The Roaring Fork Conservancy is a nonprofit that works on behalf of its namesake watershed, which includes all water sources from high in the Elk Mountains and the Fryingpan basin that confluence with the Colorado River in Glenwood Springs. The Roaring Fork Conservancy works year-round to provide the best science possible to decision makers and the public, taking real-world water issues and interpreting them at various levels. This includes understanding snowpack and how much water goes where, getting to know the macroinvertebrates that live in our streams and working on policy issues.
“Our mission is to inspire individuals to explore, value and protect the Roaring Fork watershed,” said Roaring Fork Conservancy education and outreach coordinator Liza Mitchell. If people value the water, they are more likely to work together for its protection, she added.
“Right now, we are at 61 percent of normal — that’s the snow-water content in the snowpack,” Mitchell said.
The numbers are compared to a 30-year rolling average, from 1980-2010. “So it does not include the past eight years in that average. 2012 was a pretty dry year; in relation we are sitting just higher in terms of snowpack at this time of year,” she said.
The seasonal snowpack peaked around April 7 and has been decreasing since then. Some of that snowpack evaporates, some saturates the soil and the rest flows into streams and rivers. Most everything below 10,000 feet has melted, but there is still a high-alpine snowpack that, while well below average for May, is still to come down as the temperatures rise.
“We are starting to see stream flows increase,” Mitchell said. “They are still on the up, so it hasn’t peaked yet. That said, they are not predicted to get anywhere near average stream flow.”
Cleansing flow is critical
According to Mitchell, the local ecosystem has evolved over millennia in a manner dominated by the snowmelt cycle.
“There is a pattern of low flow all winter, while it’s snowing. [Then] it rises, it peaks, and then it drops back down to base flow.”
The ecological processes that occur during peak flow are of the utmost importance for the overall health of the rivers and surrounding environs. Peak flows can move rocks, which changes the substrate of the stream, knocking loose algae and debris from previous years. As the water pushes sediment downstream and clears up space between the rocks, the base of the food web can grow in those interstitial places. Macroinvertebrates are aquatic insects, at their juvenile or nymph stage. May flies, caddis flies and stone flies are most common in the Roaring Fork watershed.
“If you never have those peak flows, flushing flows, then those areas build up with mud and suffocate the macroinvertebrates; without macroinvertebrates you don’t have trout; without trout there is no food for eagles and ospreys,” Mitchell said. Runoff also inundates the flood plains, bringing water to the riparian vegetation, which then provides shade to keep the streams cool.
Peak flows also assist in scouring the river channel, creating a spawning habitat for trout.
“Trout like loosely packed cobbles with water flowing through — it’s good for bug habitat as well as for laying eggs,” said Kendall Bakich, aquatic biologist for Colorado Parks and Wildlife. “This is particularly an issue with recurring low-flow years, so it may not be an issue this year as long as we return to average in the future.”
Fish friendly before noon
But as the runoff peaks earlier and lower than normal, the river gets to base flow sooner and the fish begin to feel the impacts. Introduced sport fish like brown trout, rainbow trout and mountain whitefish are most at risk. Native cutthroat and brook trout live in higher elevations where the temperatures are the coldest, but as the smaller headwaters streams fall to lower flows they will face concentration, or even streams drying up entirely.
In any river, as the water drops the fish begin to lose some habitat, adding to their stress. This puts them at a competitive disadvantage for food and makes them more susceptible to disease. Habitat concentration causes weakened immune systems among stressed fish and the proximity serves to pass disease between them faster.
“At lower water flows and higher temperatures, fish become extremely stressed,” said Matt Kelsic, a fishing guide and president of the local chapter of Trout Unlimited. “There is less oxygen in the water and it makes it harder for fish to recover.
“Even if you do all the best catch and release tactics — keeping the fish wet, using barbless hooks, making sure your hands are wet before handling the fish — all those things become moot if there isn’t enough for the fish to recover,” Kelsic said.
From a commercial perspective, Kelsic said that means trying to get trips out the door early and being off the water no later than noon.
“Keep water temperature in mind, fishing earlier in the day when it’s the coolest and not again until [later]. But that may not even be feasible with [water] temperatures,” he said, suggesting anglers get thermometers to be aware of conditions.
“Sixty-five degrees is usually the trigger to start looking at asking for voluntary fishing closures,” added Bakich, of Colorado Parks and Wildlife.
Kelsic also suggested fishing higher in the watershed to find colder temperatures. “The upper valley, high mountain water and the Fryingpan are all going to be cooler,” he said.
The Fryingpan River is known as a “tailwater stream” because Ruedi is a bottom-release dam. The thermal stratification in the reservoir allows the water to stay very cold at the bottom. “So the Fryingpan may stay cooler than some of the other rivers,” Mitchell said. “This provides a buffer for the fish and we might see some fish from the Roaring Fork coming into the Fryingpan as a cold-water refuge if it gets really warm.”
Both Trout Unlimited and Roaring Fork Conservancy will be doing ongoing education for the public as the summer progresses. In past dry years, Roaring Fork Conservancy ran a program called Hotspots for Trout, an educational campaign about the negative effects of warm water on fish. This year they are considering citizen-science programs to get water thermometers into the hands of anglers, rafters or anyone who is out of the river.
“It’s a simple data point to collect, and then report that to us,” Mitchell said. “And then we can help continue to be the eyes on the river and the voice for the river. If the river is getting too hot and people are out there helping us see that, then we can elevate that voice and share that message with the public.”
As part of its ongoing research efforts, Roaring Fork Conservancy will closely monitor a strain of algae in the Fryingpan River, which is called Didymosphenia geminata or locally referred to as “rock snot.” As temperatures go up, algae and bacteria can flourish. Low water already has less oxygen and algae use up what little is left, exacerbating problems for fish and macroinvertebrates.
Roaring Fork Conservancy will also partner with Colorado Parks and Wildlife to connect with fly shops so they can help spread the word through their guides and try to concentrate the times people fish, out of the heat of the day.
Jordan Curet is a freelance writer and photographer who lives in Aspen.