Trout Unlimited Joins With National Park Service to Remove Diversion Dam near Grand Teton National Park

The National Park Service, with help from Trout Unlimited, is going to remove the Spread Creek Dam near Grand Teton National Park. Its removal will free up 50 miles of trout stream. NPS photos.

For four decades the Spread Creek Dam has blocked the migratory route of a unique species of cutthroat trout in waters that flow into Grand Teton National Park. That's all about to change thanks to a partnership between Trout Unlimited and the National Park Service.

Removal of the diversion dam will open a 50-mile stretch of Spread Creek to the Snake River fine-spotted cutthroat trout, a state and federally recognized sensitive species, park officials said in a release.

The diversion dam is located in the Bridger-Teton National Forest to the east of the park, but the Park Service manages the structure. The project involves the removal of the dam, installation of natural-design and fish-friendly rock weirs, and the restoration of stream channel contours and vegetation.

The Park Service and the Wyoming Game and Fish Department had identified the dam as a priority for restoration activities because Spread Creek provides habitat for the Snake River fine-spotted cutthroat trout. Ever since the diversion dam was built 40 years ago it has created a year-round barrier to fish migration because it spans the width of the creek and blocks tributary spawning and rearing habitat for native fish such as cutthroat trout, mountain suckers and whitefish, according to a park release.

Grand Teton will work in partnership with TU, a nonprofit 501(c) (3) corporation dedicated to protecting, reconnecting, restoring and sustaining native trout habitat. TU’s Wyoming Water Project is securing the funding for the project and will oversee and conduct restoration activities, including the removal of the existing diversion structure, construction of a water delivery system, and restoration of the natural stream channel.

This project involves removal of the dam by mechanical means. Workers will bury a portion of the old concrete edifice to help support a new irrigation infrastructure. In place of the dam, three rock weirs will be installed to maintain water level at a new headgate that will divert irrigation water to authorized users in the park. The weirs are designed to allow for native fish to either pass over or through the structures to access historic spawning and rearing areas.

Once the dam is removed and the rock weirs are in place, the Spread Creek channel will be reconstructed to establish its natural hydrology, which has been interrupted for decades. Restoration of the channel downstream of the rock weirs will reflect the natural elevation and contour of the streambed and encourage native re-vegetation.

“This is an historic step toward correcting a long-term disruption to fish migration and an important action for restoring Spread Creek’s hydrology,” said Grand Teton Superintendent Mary Gibson Scott. “We appreciate and applaud the work of Trout Unlimited and their funding partners in making this milestone project possible. We also appreciate the cooperation we’ve received from historic water users, Bridger-Teton National Forest staff and the Wyoming Game and Fish Department as we launch this project to improve critical fish habitat outside and inside Grand Teton National Park.”