From Steve Schweitzer's A Fly Fishing Guide To Rocky Mountain National Park, flyfishingrmnp.com:
Trailhead to Granite Falls
This creek offers the day hiker the chance at a trout trifecta of brookies, browns, and generic cutthroat (most likely of Colorado River cutthroat strain). From the trail's ...
US-34 to W Portal Rd to Tonahutu/North Inlet Trailheads. The average trail slope of grade 6 can be deceiving. It is weighted more towards the section of trail below Granite Falls. From Granite Falls to Haynach Lakes the average grade is nine, with the Haynach Lakes Trail a steeper grade eleven. The closer you get to Haynach Lakes, the steeper the trail becomes. The first five miles of the trail offers a gentle rise following picturesque Tonahutu Creek. Big Meadows is aptly named - it seems to take forever traversing from one end to the other. The trail meets up with Tonahutu Creek again just after west Big Meadows, and follows the creek closely until Granite Falls, where the trail and creek meet intermittently until the trail breaks northward to Haynach Lakes Trail.