Blue Mesa Reservoir unlikely to fill this summer

Big releases support endangered fish downstream

Word on the street this spring was that Blue Mesa Reservoir would be bursting at its banks this summer. Predictions were based on official and unofficial reports of above-normal river flows. However, a 2012 Environmental Impact Statement (EIS) has changed how local dams are operated in wet years, in deference to endangered fish species downstream. This new operational protocol will preclude the reservoir from filling this year.

“The reservoir is now only scheduled to reach a maximum storage of around 80 percent capacity in 2014,” said Upper Gunnison River District manager Frank Kugel. The U.S. Bureau of Reclamation (BOR) began blasting water through Blue Mesa Dam last week, with simultaneous releases happening at Morrow Point and Crystal Reservoirs, a trifecta of water storage and management that makes up what’s known as the Aspinall Unit.
The Record of Decision (ROD) states, “The EIS modifies the operations of the Aspinall Unit to provide sufficient releases of water at times, quantities, and duration necessary to avoid jeopardy to endangered fish species and adverse modification of their designated critical habitat while maintaining and continuing to meet authorized purposes of the Aspinall Unit.”
Given this new norm of operations adapted by the bureau during wet years, will Blue Mesa ever fill again?
“That’s a valid question, since the reservoir often does not fill in dry years due to lack of supply, and now with the Aspinall EIS, it will have trouble filling in wet years,” said Kugel.
“We all signed onto this because we agreed it’s important to save these fish,” said Colorado Fish and Wildlife Aquatic Species coordinator Harry Crocket.

According to the BOR’s website, an update written by hydraulic engineer Paul Davidson, unregulated inflow to Blue Mesa is 126 percent of normal this year, April through July. That’s 850,000 acre-feet of water entering the lake during the runoff months. “This sets the senior Black Canyon Water Right call for a one-day spring peak flow of 6,400 cfs, the Aspinall 2012 ROD target at a 10-day peak flow of 14,350 cfs… Reclamation plans to operate the Aspinall Unit to meet both the water right and ROD recommendations,” said Davidson.

The Colorado pike minnow, bonytail chub, humpback chub and razorback sucker are the fish that stand to benefit. The big flows are expected to improve the fishes’ critical habitat, at a time when the fish will be looking to spawn. Water will inundate otherwise shallow or dry riverbank areas, creating calm, sheltered spots for hatchlings, and heavy flows will wash the larvae into those areas.
The Gunnison River, said Crocket, was “mostly omitted” from the EIS as critical habitat. However, he said, “Historically, it was home to at least a couple of these species.”
“It’s a highly migratory fish,” Crocket said of the Colorado pike minnow. “It’s adapted to this big river system.”
It’s a system irrefutably changed by humans. Critical habitat for the Colorado pike minnow includes 1,123.6 miles of river, to include stretches of the Green, Yampa and White rivers, from Rifle to Glen Canyon, and the Yampa River to its confluence with the Colorado River. “They [US Fish and Wildlife] did designate critical habitat [from the mouth of the Gunnison] to the Uncompahgre confluence [at Delta],” Crocket said.
The Colorado pike minnow called the Gunnison River home through the 1960s. “After that,” said Crocket, “it blinked out. It’s not been possible for it to be re-colonized.” A new fish passage at the Redlands structure, two miles upriver from the Gunnison-Colorado River confluence at Grand Junction, allows fish to make their way around the barrier and upstream, marking the first time in more than 100 years for those downstream fish to gain passage to the Gunnison.
Meanwhile, upstream, a form of collateral damage resulting from the big water releases at Blue Mesa worries Fish and Wildlife personnel. The number of fish sucked into and blown out through the dam is staggering. The technical term for this is entrainment.
“Bigger water years mean more water through the dam, and more fish entrained,” said Gunnison area Colorado Fish and Wildlife aquatic biologist Dan Brauch. “Certainly, loss of kokanee with those releases is a concern.”
Kokanee are at the greatest risk of entrainment because they are the most populous species in the lake. But any fish in the wrong place at the wrong time could meet this fate. The number of fish entrained depends on whether water is being released from the tubes, from a lower water level, or through surface gates, at a higher level, and where the fish happen to be during those releases. Nets to prevent fish from getting too close to dams are not only expensive but have proven ineffective, said Brauch.
Strobe lights are an experiment being conducted in some places, an attempt to keep fish away from dams’ intake areas by spooking them away. “Kokanee migrate daily,” Brauch said, “so there’s an opportunity to assess that.”
Brauch said a study some years ago indicated that about 10 percent of entrained fish survive the trip. “They contribute to the fishery below the dam,” he said, to include Morrow Point Reservoir. When it comes time for these fish to spawn, however, they butt up against the downstream side of Blue Mesa dam.
A study funded by the Bureau of Reclamation from 1994 to 1996 found an average of 61,000 kokanee entrained through the dam each year. This included the relatively wet year of 1995. To put that in perspective, Colorado Fish and Wildlife stocks the lake with 3.5 million kokanee every spring. According to a study conducted by Colorado State University graduate student Bill Pate, 1.4 million Blue Mesa kokanee meet their demise each year due to predation. Pate’s study has been accepted for publication in an upcoming edition of The North American Journal of Fisheries Management.
Releases from Blue Mesa and Morrow Point began last week. Peak flow of 9,500 cfs through the Black Canyon was expected Thursday, with the goal to maintain that rate until June 14.