The 20,000 acre ACEC includes the South Fork from Palisades Dam to the confluence with the Henry?s Fork, the Henry?s Fork from the confluence to St. Anthony, and the main stem from the confluence south to Lewisville Knolls. The region surrounding the river has a variety of populated areas, ranging from Idaho Falls with a population of 45,000, to small towns and uninhabited forestlands. Many farms and ranches are along the river. The upper section near Palisades Dam is a mountain valley; the middle section on the South Fork, a rugged canyon; and the lower section (including the Henrys Fork and main stem) a wide river with a broad dynamic floodplain. These different sections provide gentle forested uplands, rugged mountains, cliffs, islands in the river channel, a cottonwood gallery forest, Douglas fir, aspen, and juniper/sagebrush vegetation. The Snake River ACEC supports the most extensive cottonwood gallery forest remaining in Idaho and probably the largest such ecosystem in the intermountain west. The USFWS rated it as the most unique and biodiverse ecosystem in Idaho. In 1985 the BLM designated the public lands along the corridor as an Area of Critical Environmental Concern.

Federal land within the Snake River ACEC are cooperatively managed by the BLM and USFS under the guidance of the Snake River Activity/Operations Plan ? a multiple resource plan keying in on riparian habitat, wildlife values, and recreation. The South Fork is a world famous, blue ribbon fishery and supports the largest native cutthroat trout fishery outside of Yellowstone National Park. BLM participates in several cooperative efforts along the river corridors, including research projects involving Bald Eagles, neotropical birds, the cottonwood ecosystem, and others.

Ornithological Summary

The Snake River ACEC produces one third of the Bald Eagles in the Greater Yellowstone Ecosystem (GYE), supporting 19 nesting territories. It also supports the largest Bald Eagle winter roost in the GYE. Three Peregrine Falcon eyries have established along the South Fork since 1991. Recent passerine and raptor inventory and research have identified 126 different species of birds, the majority (67%) being neotropical migrants which inhabit the rich and diverse vegetation associated with the rivers. This includes 21 raptor species and 33 avian species of concern. The main Snake River and the Henrys Fork are significant migration resting areas for thousands of swans, geese, and ducks, as well as a variety of shorebirds. The rivers also produce large numbers of waterfowl annually, and are home to 13 Great Blue Heron rookeries.

Conservation Issues

Although critically important habitat, the Snake River ACEC has many conservation issues, including dams, irrigation diversions, levees, subdivision, resort, and agricultural development, noxious weed invasion, excessive livestock grazing, and increasing recreational use. All of these issues and activities have fragmented and degraded this ecosystem. However, much is being done to counteract these problems. Congress designated this area as a Land and Water Conservation Fund Project in 1992. Eleven habitat improvement projects are underway and an Adopt-A-Wetland program maintains waterfowl nesting areas and cleans up litter along the rivers. Use of federal land within the ACEC is managed under the Snake River Activity/ Operations Plan which keys in on acceptable limits of recreation and livestock grazing, limits riparian vegetation degradation, and protects wildlife habitat. To date, 14 fee title acquisitions and one conservation easement acquisition have been purchased by the BLM. In addition, BLM has worked with IDFG and BPA to acquire two river parcels in fee title. The acquisition of key parcels from willing sellers preserves the integrity and ecological values of the rivers. The BLM also participates with an interagency noxious weed control team, which has implemented an aggressive biological control program to abate noxious weed invasion. As a result of new cottonwood ecology research, the Bureau of Reclamation has made an effort to release water to mimic pre-dam floods to facilitate cottonwood seedling establishment along the rivers to perpetuate valuable wildlife habitat. And most recently, with the help of a large 2005 NAWCA Grant, partners will work to protect and restore wetlands along the 125-mile-long Henrys Fork river corridor. These funds will be used to abate the prime threat along the corridor, urbanization, by acquiring conservation easements on 4,463 acres of private lands and to restore 1,020 additional acres.


The landscape changes from a mountain valley along the upstream section, to a rugged canyon in the middle section to Heise, to a wide river with a broad and dynamic flood plain along the lower section (including the Henrys Fork and main Snake River). The rivers, particularly the South Fork, have many islands formed by multiple dynamic channels. The climate is characterized by relatively low annual precipitation of 14-16 inches, most of which comes in the form of snowfall in the winter. Soils within the floodplain are primarily silt, sandy loams and cobbles. The river corridor vegetation is dominated by narrow-leaf cottonwoods in the canopy, with a woody understory of red-osier dogwood, silverberry, willows, and water birch. Adjacent uplands include habitats of Douglas fir, juniper, aspen, and agricultural lands.

Land Use

Recreational uses - Fishing is the primary recreational activity, although river floating, camping, hiking, horseback riding, off-highway vehicle use, picnicking, bird watching, and sight-seeing are increasing (200,000 visits per year). These recreational (again primarily fishing) uses, both outfitted and non-outfitted, provides local employment and brings an estimated $6,000,000 into the local economy. Public grazing provides 30 permittees with a total income of $200,000. Historical sites abound along the rivers, such as stones marked with fur trades initials, Native American art, Vardis Fisher historical sites, Beaver Dick Lee historic site, and ferry sites.

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