Spread Creek Dam removal to improve trout habitat
Project near national park will open up 50 miles of stream to migrating cutthroat.
Spread Creek Dam will be demolished to improve trout habitat and return the area to a more natural state. NEWS&GUIDE PHOTO / PRICE CHAMBERSView our entire photo gallery >>
By Cory Hatch, Jackson Hole, Wyo.
September 1, 2010
Just north of Triangle X Ranch and a few miles down a gravel road, a 13-foot-tall, 125-foot-long concrete and metal dam rises from Spread Creek’s cobbles. Located just outside Grand Teton National Park and surrounded by national forest, it seems a monstrosity — out of place with the surrounding environment.
The structure is clearly crumbling. Four decades’ worth of water has scoured holes in the dam’s concrete apron large enough for a tree trunk, or a person, to fit through. The closed metal floodgates leak water through the spillway, and the rickety metal walkway and railing have begun to rust.
Fish pool at the bottom of the dam, some jumping in vain at the structure’s concrete apron.
“This is a complete barrier to fish passage,” said Sue Consolo-Murphy, Grand Teton’s chief of science and resources management, who led a recent tour.
Now a restoration project is underway, one that will return Spread Creek to a more natural flow. The dam will be removed, opening some 50 miles of Spread Creek and its tributaries to free movement of native Snake River fine-spotted cutthroat trout.
Federal and state wildlife managers call the species “sensitive.” The National Park Service and Wyoming Game and Fish Department identified the dam as a priority for restoration.
The Spread Creek area is vast. The north and south forks of Spread Creek drain the Mount Leidy Highlands and parts of Togwotee Pass. They circle the landmark peaks of Mount Leidy and Grouse Mountain and comprise an important part of the Jackson Hole backcountry: a timbered mountain drainage 40 miles long and 15 miles wide.
Forty-three years ago, the Spread Creek Dam was part of an ambitious irrigation project that would have shunted water to pastureland around what is now the eastern portion of Grand Teton National Park. Back then, there was little worry about cutthroat habitat. There was no such thing as endangered species like grizzly bears that fed on them. The challenge was for ranchers eking out a living.
Over the years, however, the need to divert water from Spread Creek has gradually diminished, rendering the dam obsolete. Restoration will be possible only through years of conservation work and interagency cooperation. Significant ranch lands encompassed by Grand Teton when it was expanded in the middle of the last century are now public.
“By acquiring most of the lands in the Elk Ranch area, we acquired most of the water rights,” Consolo-Murphy said. Grand Teton manages the dam, although it is located on the Bridger-Teton National Forest.
The massive structure has two irrigation diversions; the south ditch now serves Triangle X Ranch and Moosehead Ranch and the north ditch serves the park. Some grazing rights remain there.
The amount of water diverted — right now the maximum water right is 60 cubic feet per second — is a pittance compared to the overall capacity of the dam.
“The way this is designed, you could shut the river off,” said Nick Kraus, a project engineer with Quadrant Consulting.
Both the Triangle X Ranch and the Moosehead Ranch agreed to a project that will demolish the dam this fall. Under Kraus’ supervision, construction crews will use a hydraulic hammer to cut the dam into pieces, which will then be removed from the stream bed or buried.
The $500,000 project, which officials said will start in mid-September and finish “before the snow flies.” It also will restore the stream bed to its historic elevation.
Diversion structures will be moved upstream to a more suitable location and built to allow fish movement and to fit in with the natural environment.
“To create the diversion, we’re using boulders that will span the river,” Kraus said. Gates will divert water into the existing irrigation ditches.
Water from the south gate will actually travel to the north ditch through a pipe buried underneath the river.
“It’s restoration to more of a natural condition,” Consolo-Murphy said. “And it’ll be a simpler, safer system to maintain.”
Once the project is complete, the new structure will allow an isolated native cutthroat trout fishery above the dam to mix with trout from the rest of the watershed, said Scott Yates, director of Trout Unlimited’s Wyoming Water Project.
The project really boils down to genetic diversity, said Rob Gipson, regional fisheries supervisor for the Wyoming Game and Fish Department.
“The biggest benefit is, when it comes down to long-term survivability of Snake River cutthroat, you’re connecting 50 miles of habitat,” he said. “You’re getting that genetic exchange that hasn’t been there since the dam was constructed.”
While fish are currently able to drift downstream over the dam, they can’t return to their native spawning ground in the upper portion of the creek. Hence the fish gathering in the pools at the bottom of the structure.
“The more genetic diversity you have, the better the chance the species has to adapt to change whether climate change or catastrophic fire,” Gipson said. “We like to think long-term, too. We’re here for the long haul, and genetic diversity is important in that regard.”
Both Yates and Gipson said there is little risk of a nonnative species like rainbow trout making its way up the watershed and contaminating the genetically pure cutthroat trout population there.
“In the Upper Snake River, we have a fairly intact hydrology,” Yates said, explaining that cutthroat, not rainbows, favor the large fluctuations in water flow that are present in places like Spread Creek. “There are not many rainbows above the Gros Ventre.”
Gipson agreed that the threat from rainbows is small.
“You could make that argument for any connected habitat, but the benefits far outweigh the potential negatives,” he said.
And trout aren’t the only beneficiaries of the dam’s removal.
“This could benefit non-game species too,” Gipson said. Sculpin, longnose dace and mountain suckers also will have more freedom to move in the watershed.
Trout Unlimited’s Wyoming Water Project secured the funding and will oversee removal and restoration. Numerous groups have coordinated expertise and funding under the Trout Unlimited umbrella, including the Jackson Hole One Fly Foundation/National Fish and Wildlife Foundation, the Wyoming Wildlife and Natural Resource Trust, Wyoming Game and Fish and the Jackson Hole Chapter of Trout Unlimited.
Grand Teton National Park Superintendent Mary Gibson Scott called the dam removal “an historic step toward correcting a long-term disruption to fish migration and an important action for restoring Spread Creek’s hydrology,” and she praised cooperation, including that of the water users.
Gipson also appears satsified.
“It’s been a great collaborative process for us,” he said. “It’s nice to see what can happen when agencies and the landowners are on the same page.
“It’s nice to have something that is a large project. But it’s relatively small and doable. The bang for the buck is definitely there.”