Flathead Water

The Flathead River is one of North America’s wildest rivers. It originates in the remote interior of southeast British Columbia and flows through the uninhabited Flathead River Valley in B.C. across the border into the state of Montana, where it empties into Flathead Lake. In Montana, the Flathead River is a federally designated Wild and Scenic River and forms the western boundary of Glacier National Park.

The transboundary Flathead supports important native fish populations, including bull trout and westslope cutthroat trout, species that are shared by the U.S. and Canada. Bull trout are a sensitive species, native to cold, clear waters like those in the Flathead River. They spend their adult life in Flathead Lake in Montana, then migrate up-river (up to 275 km) to spawn in select tributaries throughout the B.C. Flathead, as well as in the Montana tributaries. Bull trout have highly specialized habitat requirements and are very sensitive to water temperature and any form of habitat degradation. Bull trout are listed as threatened under the U.S. Endangered Species Act and blue-listed in British Columbia (a list under B.C.’s Endangered Species strategy for species not immediately threatened with extinction but of special concern because of sensitivity to human activities or natural disturbances). The tributary streams and main stem of the Flathead in B.C. provide critical spawning and rearing habitat for bull trout, westslope cutthroat trout, mountain whitefish and sculpin.

In addition to native fish species, the Flathead supports a population of tailed frogs, the most primitive frog in the world. Like the native fish, the tailed frog is sensitive to habitat degradation and is the only stream-dwelling frog in Canada. The tailed frog is blue-listed in British Columbia.

In addition to the river itself, the rich, riparian (the zone where the river meets the land) valley and floodplains of the Flathead support a large diversity of plant communities and wildlife. The Flathead supports a greater diversity and abundance of carnivores - including mountain lion, grizzly bear, lynx and wolverine - than any other area in North America. The riparian floodplain is a natural travel corridor for wildlife, allowing seasonal movement in the rugged topography of the Rocky Mountains. In addition to connecting critical habitat, the floodplain and riparian areas contain important bear food with abundant early spring and late fall foods.

Fast Facts

  • The watershed encompasses 4,134 square kilometres with 38 per cent of the drainage in B.C., and 62 per cent in Montana.
  • The watershed supports more than 300 species of aquatic insects, 10 species of native fish and 12 species of introduced fish.
  • The Flathead River flows south across the border to form the western boundary of Waterton-Glacier International Peace Park, a World Heritage Site and two designated UNESCO Biosphere Reserves.
  • British Columbia blue-listed species in the Flathead include: grizzly bear, Rocky Mountain bighorn sheep, northern goshawk, turkey vulture, Lewis’ wood pecker, tailed frog, bull trout and mottled sculpin
  • U.S. threatened species in the Flathead include: grizzly bear, lynx, bald eagle and bull trout
  • U.S. endangered species in the Flathead include the wolf and peregrine falcon
  • In 2003, the B.C. portion of the Flathead basin supported approximately 55per cent of the total bull trout spawning population in the transboundary Flathead River.


“The B.C portion of the transboundary Flathead is a regional stronghold for (genetically pure) westslope cutthroat trout populations.” (Muhlfeld et al, 2005) and both bull trout and westslope cutthroat use the entire drainage as critical spawning and rearing habitat (Fraley and Shepard, 1989)

“The health of the aquatic environment is dependent upon the management of the terrestrial resources of the basin.” - Recommendations of the Steering Committee for the Flathead River Basin Environmental Impact Study, 1983 

“The Flathead River is the ecological engine of the Crown of the Continent Ecosystem.” -Transboundary Flathead Research Needs Workshop, West Glacier, MT, Executive Summary, 2005 

"On a continental scale, the entire Flathead is a biodiversity hotspot with a range of important habitats." - The State of the Crown of the Continent Ecosystem: Transboundary Bioregion. Flathead Transboundary Network, 2001 

“A unique community of carnivore species resides in the Transboundary flathead region that appears unmatched in North America for its variety, completeness, use of bottomlands, and density of species that are rare elsewhere.” - Dr. John Weaver 

“The “shifting habitat mosaic” mediates very high biodiversity and bioproduction. Indeed I hypothesize that the highest level of species diversity in the Rocky Mountains, if not the entire continent may occur in these floodplains.” - Dr. Jack Stanford

“The transboundary Flathead has one of the most outstanding large mammal assemblages in North America, including 16 carnivore and six ungulate species.” - Transboundary Flathead Research Needs Workshop, West Glacier, MT, Executive Summary, 2005 


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