Fall flush concern: Water over dam?
GSPI News Editor
On an October day in Glenwood Canyon last year, Sherman Hebein looked into the Colorado River and was appalled.
“I saw this big batch of sediment coming down the river and I said, ‘What’s going on?'”
It was more than just a question of idle curiosity. Hebein, based in Montrose, is senior aquatic biologist on the Western Slope for the Colorado Division of Wildlife.
He, other DOW officials and Western Slope anglers all are concerned about Xcel Energy’s decision to flush sand out of the reservoir behind the Shoshone Dam in Glenwood Canyon last fall.
The result was a heavy load of sediment dumped downstream during the brown trout spawning season.
“It was just a mudflow,” said Jeff Dysart, co-owner of Alpine Angling in Carbondale and Roaring Fork Anglers in Glenwood Springs.
The DOW has taken its concerns to Xcel, which uses the reservoir to divert water through tunnels to its Shoshone hydroelectric plant three miles downstream in the canyon. The power company has responded with a promise to try to do future flushes in the spring rather than the fall, when runoff from snowmelt boosts flows and reduces the environmental impacts.
“We will make every attempt possible to try to limit and not do any releases and flush water out of the dam in the fall,” said Dan Brown, the plant production supervisor for Xcel’s Colorado hydro operations.
Pat Tucker, area manager in Glenwood for the DOW, said some anglers would prefer to hear more ironclad assurances from Xcel.
For now, he said, “The proof will be when they have to do this again, how do they handle it.”
Meanwhile, the U.S. Army Corps of Engineers has begun looking into whether it has any authority under the Clean Water Act to require Xcel to obtain a federal permit before future flush operations.
Some maintenance activities on a reservoir are exempted from permitting, said Mark Gilfillan, biologist and regulatory project manager for the Army Corps of Engineers’ Colorado/Gunnison Basin regulatory office in Grand Junction.
The Corps of Engineers was notified of the flushing Oct. 27, immediately after it began.
“Some of the activity that we observed may be exempt from the Clean Water Act and some of it may not,” said Gilfillan.
“We do have, obviously, concerns; we’re still collecting information,” he said.
to a small flush’
Hebein said the concerns behind such a sediment flush in the fall are many-fold.
The abrupt change in water flow is one. Brown trout spawn on the edges of the river. If the trout spawn while the reservoir is being flushed, and then the water reverts to normal level, many of the brown trout eggs can be left high and dry.
A fall sediment flush also contaminates the river far more than in the spring, because the lower water volume increases the concentration of the sediment in the river.
Hebein said spores of a fungus that attacks brown trout also back up in reservoirs, but are released during a flush, threatening fish downstream. Trout already are weakened during spawning. The sediment-filled water makes them further stressed and vulnerable to the fungus.
Sediment also smothers some aquatic insects, killing off food that can be important to trout during their various life stages, Hebein said.
“All told, there can be a serious consequence to a small flush,” he said.
Dysart agreed. “It’s not good to have three or four inches of mud sitting on the bottom of the river all winter,” he said.
Hebein said he didn’t hear of many dead fish floating on the surface due to the flush, and doesn’t think its impacts were that direct or easy to quantify. It could take another year of population counts to get a better sense of the damage done.
Also, an average or above-average runoff this spring would help to clean out the river and reduce the impacts of the sediment, Hebein said.
Besides threatening trout, last year’s flush made the water too muddy to fish, Dysart said. He said the timing of the flush didn’t hurt his guide business much because it came at the end of the season. But he added, “A lot of the locals that like to get out and fish, they couldn’t do it.”
During the spring runoff, the Colorado is muddy and unfishable anyway. And the high water would carry the sediment from flushing the reservoir much farther downstream, all the way to Lake Powell, Dysart said.
“It just makes sense,” he said of flushing the reservoir in the spring.
Staff turnover a factor
The flushing isn’t required every year. Xcel releases water about every four years to eliminate a sandbar that forms near the intake tubes leading to its power plant.
The fact that the reservoir isn’t flushed more frequently may be part of the problem.
Tucker began his Glenwood job in September 1999. Brown started on his job at Xcel in June. So neither of them knows anything about past fall releases, or any possible agreements to try to avoid them.
Meanwhile, the Colorado River “has become more of a player” among anglers in recent years, for a variety of factors, Dysart and Tucker agreed. That has made the consequences of endangering the fishery more severe.
In a letter to Tucker, Brown commits Xcel to making “reasonable efforts” to flush the reservoir in the spring rather than fall.
He said the company also will make the same commitment in the case of routine maintenance, upgrades, inspections and similar work. Brown said Xcel will notify departments and individuals responsible for scheduling this work so they are aware of the timing sensitivities involved.
Lastly, Brown said that in emergency situations, Xcel will work to resolve the problem quickly. It also will notify the state Division of Water Resources of any operational changes at Shoshone, so DWR can notify the DOW and other state agencies as necessary.
Contact Dennis Webb: 945-8515, ext. 516
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