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Low creek flow spawns warm-water worries

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By Stephen Knapp

For Bear Creek’s finned-and-freckled set, midsummer is surely the cruelest season. By late July, the inevitable double-whammy of sunny weather and dwindling snowpack conspire to make local trout accommodations a trifle stifling.

When rushing down the canyon at its typical average volume of 60 to 70 cubic feet per second, greater depth and generous contributions from chilly tributaries help Bear Creek keep its cool. Just about now, however, the ever-shallow watercourse slows and thins, allowing the sun to heat it like a 40-watt light bulb warms an Easy-Bake Oven. It’s a predictable yearly cycle that, for cold-blooded browns and rainbows, usually amounts to more sweat than threat.

“Stream temperatures generally go up every summer,” explains Gerry Schulte, general manager of the Evergreen Metropolitan District. “Right now we’re at about 20 cfs, and a minimum of 10 cfs is considered necessary to maintain a healthy fishery. And Bear Creek is a cold-water fishery, so at an MWAT (maximum weekly average temperature) above 20 degrees Celsius (68 degrees Fahrenheit), the fish start to get really stressed. We get an MWAT close to 20 degrees just about every year, and right now we’re at about 19.”

Not surprising, given the prevailing extra-hot and ultra-dry conditions. Still, if history is any guide, relief should start pouring down any day now.

“August is generally our rainiest month, and those afternoon showers help cool stream temperatures,” Schulte says. “If it was early July and we were at 19 degrees, I’d say it could be a crisis. Since we’re into August, temperatures will probably start going down soon.”

As it happens, the trout riding out the hot season in greatest comfort are those with an Upper Bear Creek address. That’s because the Evergreen Lake dam holds back a 40-acre solar sponge with an average depth of 15 feet.

“There’s an incredible heat-sink effect,” explains Hugh Gardner, an Idledale resident and dedicated member of Friends of Bear Creek. “The water picks up a massive amount of heat in the reservoir, and some more heat is added during the treatment process. Cool water flowing in from above the Lake House can heat up by 5 degrees (Celsius) or more by the time it’s discharged downstream.”

Fortunately, the folks at Evergreen Metro have a proven strategy for beating the heat.

“The water on the lake’s surface is 19 degrees, but deeper underneath it’s 15 degrees,” says Schulte. “We take 15-degree water from lower down and blend it into the stream below the dam. It helps moderate stream temperature.”

Of course, tweaking the creek that way only works when there’s a creek to tweak. When the stream folded up its tent completely in late summer, 2002, no art or device of man could have saved the trout from their waterless doom. But, even assuming that this year’s flow follows less extreme historical patterns, there’s still plenty that Mr. and Mrs. Evergreen can do on behalf of their aquatic neighbors.

“If we all agree we want a healthy creek in the future, there’s something all of us can do, starting with simply conserving water,” Gardner says. “Low flows encourage algae blooms that suck oxygen out of the water and basically suffocate the fish. And driveways and construction sites can be modified so that sediment doesn’t wash into the creek every time it rains.

“Property owners could plant vegetation along the banks to create habitat, and highway crews can be careful to not push road sand right off the road and into the stream.”

Alongside the things people could do for Bear Creek is another list, just as important, of things they should not.

“For one thing, they could not cut down willows to make hot dog sticks,” Gardner says. “Willows create shade for the creek. And they could not build cofferdams. If they aren’t done properly, dams create silt traps, and you end up with less fish habitat than you had before.”

Fact is, dozens of agencies and civic groups have keen and specific interests in a robust Bear Creek, as does every soul from Rosedale to Red Rocks who ever boiled an ear of corn, washed out their dirty socks, or took a shower. And it’s another fact that no one of them can single-handedly assure the stream’s future well-being.

“Evergreen Metro is only responsible for 1cfs, so there’s only so much that private water conservation can do to impact stream flow,” Schulte points out. “But cutting back on water use in general will definitely benefit the stream.”