A fine line remains between snowmaking, healthy creek
August 9, 2002
The state has drawn a line on the bank in Snowmass Creek. Go below that line and fish eggs may be stranded.
Stay above that line and the snowmaking system at the Snowmass Ski Area can easily go through two million gallons of water in a night.
The snowmaking crews in the control building near Coney Glade are used to pumping water to their snow guns while also keeping an eye on the amount of water in Snowmass Creek.
“They are watching it and anticipating having less water to work with because you can’t just instantly turn the system on and off,” said Mike Kaplan, senior vice president of mountain operations for the Aspen Skiing Co. “We keep an eye on it to make sure we don’t run more snowmaking guns than we have water for.”
And the Skico has had to back off the system’s capacity when it got close to the state’s minimum stream-flow line.
Snowmaking crews could not operate to full capacity last season “less then 10 but more than two” times, Kaplan said. “We had cold temps but we couldn’t pull our capacity because they were bumping into minimum stream flows.”
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Dan Merriman, chief of stream and lake protection for the Colorado Water Conservation Board, said it is important that snowmaking operators understand their margin for error.
“We don’t want a train wreck,” Merriman said. “We try and get the train slowed down just as the tracks end. If you are pumping at full capacity and wait until you hit the line, by the time you get the equipment turned off, you are way past the line. We just don’t want to be there.”
The minimums on Snowmass Creek have not been violated from snowmaking, Merriman said.
With rivers and streams around the state at near-record-low levels, most ski areas are concerned about how much water will be available for snowmaking. Merriman plans to call a meeting before this winter to make sure ski areas know their limits.
The Skico is well aware of its limits and expects to bump into them again this winter.
“We anticipate not being able to pull water from Water and San up to our full capacity,” Kaplan said.
The Skico is digging out a 5 million-gallon storage pond this summer below the base of the Sheer Bliss lift in Snowmass. The new buffering pond will allow the Skico to set aside water for a cold night of snowmaking without having to draw water directly from the creek.
“When it is warm and there is enough water, we will be filling the pond, so that when it is cold and there isn’t water, we can still make snow,” Kaplan said.
That state likes that concept.
“Buffering works well,” said Merriman. “It allows them to take less water out of the stream over a 24-hour period.”
Under the state’s decree for Snowmass Creek, the Skico is bound to stay above a negotiated minimum stream flow that varies between 7 and 12 cubic feet per second.
The minimums are set by biologists who determine at what low point fish will have trouble laying and hatching eggs.
Exactly where the bottom line is in any given year depends on whether it is a wet or dry year. Each October, the stream is monitored for five days and a regime from very wet to very dry is selected.
Snowmass Creek is now running at around 34 cfs. If it is below 19 cfs this October, it will be declared to be in the most restrictive regime.
Whatever regime is selected, snowmaking crews will watch the stair-step, week-by-week change in the state’s minimum water levels for Snowmass Creek.
And they’ll do so with increasing intensity during the first three weeks of December, when a “perfect snowstorm” of snowmaking can occur.
The coldest temperatures of the snowmaking season typically come right as the ski area hopes to make the most snow – just before Christmas – which is also when the most restrictive state minimums kick in.
Technically, the Aspen Skiing Co. cannot go below the minimum stream flow because it is just a customer of the Water and Sanitation District. It is up to the district to stop pumping water for snowmaking when the stream flow gets to the state’s line.
The district pumps water up the hill from the diversion dam on the creek, at a spot just downstream from the base of the Campground chairlift on the far western side of the ski area.
The water is directed to the district’s control plant and sent to the Skico’s snowmaking pump station, which sends it around the ski area.
Dean Wieser, the water plant supervisor for Water and Sanitation, said his crews are adept at monitoring the stream level and tailoring the district’s withdrawals.
“We get a pretty good feel for it,” Wieser said. “The creek doesn’t fluctuate very much.”
During an intense cold snap, however, ice dams can form on the creek and the flow can drop quickly.
“That actually makes it pretty tricky to keep on an eye on the creek,” said George Wear, who monitors the stream for the Colorado Division of Water Resources. “Everyone has to monitor it pretty closely, even on an hourly basis.”
[Brent Gardner-Smith’s e-mail address is email@example.com]