Rocky Mountain National Park to Implement Another Phase of the Poudre Headwaters Project; Some Areas in the Kawuneeche Valley Will Be Closed August 24-30

Rocky Mountain National Park will be implementing another phase of the Poudre Headwaters Project during the week of August 24-30, 2026. Young greenbacks require food, space, and protection from non-native predators and competitors, like brook trout, which outcompete greenbacks. Removal of brook trout is a key factor for recovery success.

This project takes place on the west side of RMNP and involves the removal of all non-native fish from the Grand Ditch and upstream and downstream tributaries inside the park. Once removed, native Greenback cutthroat trout will be reintroduced into its native range in the headwaters of the Cache la Poudre River.

The first phase of this project inside RMNP took place during August 2025. This year’s project will be very similar to last year’s project. Because of the level of activity associated with the implementation of the Poudre Headwaters Project, all areas and trails within the project zone will be closed to all uses beginning on Monday, August 24 through Sunday, August 30. The Colorado River Trail and the Grand Ditch will be closed.

To remove non-native fish, aquatic biologists will apply a piscicide called rotenone to the 14.3-mile Grand Ditch system and its upstream and downstream tributaries. Rotenone is commonly used by state and federal land management agencies. This project will be led by biologists with the U.S. Forest Service. Other partners include Colorado Parks and Wildlife and U.S. Fish and Wildlife Service. This project is possible thanks to support provided by Trout Unlimited and Rocky Mountain Conservancy.

While this project is underway, the following trails will remain open: East Inlet Trail, North Inlet/Tonohutu Trail, Green Mountain Trail, Coyote Valley Trail, Onahu Trail, and Timber Lake Trail. The Holzwarth Historic Site and Harbison Meadows Picnic Area will also remain open. Fishing access will remain open in all areas along the Colorado River located south of the Colorado River Trailhead, including near the Holzwarth Historic Site and Coyote Valley.

For detailed hiking information on all the trails on the west side of Rocky, please click here.

For a map of the closure, please click here.



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