Bighorn Lake

Bighorn Lake
Name	Bighorn Lake
Location	Big Horn County, Sheridan County, Hot Springs County, Big Horn County, Custer County
Type	reservoir
Inflow	Bighorn River
Outflow	Bighorn River
Basin countries	United States

Bighorn Lake is a reservoir impounded on the Bighorn River within the Bighorn Canyon National Recreation Area straddling Wyoming and Montana. Created by the construction of Yellowtail Dam in the mid-20th century, the lake lies within a matrix of Bighorn Mountains, Big Horn Basin, and arid plains, forming a corridor for regional hydrology, ecology, and recreation. The impoundment and surrounding public lands intersect with federal agencies and regional communities, influencing resource management, indigenous history, and outdoor tourism.

Geography

Bighorn Lake occupies a canyon corridor cut by the Bighorn River through the Bighorn Mountains, between landmarks such as Bighorn Canyon, Devils Canyon, and the Crow Indian Reservation. The reservoir extends near jurisdictions including Yellowtail, the town of Thermopolis, the city of Billings, and Hardin, and lies downstream of tributary confluences like Little Bighorn River and Nowood River. Adjacent public lands include Bighorn Canyon National Recreation Area, Shoshone National Forest, Custer Gallatin National Forest, and Bureau of Land Management tracts, while nearby protected areas include Medicine Wheel/Medicine Mountain National Historic Landmark and Wind River Reservation borders. Transportation corridors providing access include U.S. Route 14A, U.S. Route 310, and regional corridors linking Interstate 90 and Interstate 25.

Hydrology and Geology

The reservoir converts fluvial dynamics of the Bighorn River into a managed impoundment regulated by Yellowtail Dam, an infrastructure project implemented under laws such as the Flood Control Act of 1944 and coordinated by the Bureau of Reclamation. The lake receives snowmelt runoff from the Absaroka Range, Beartooth Mountains, and Bighorn Mountains, with seasonal discharge patterns influenced by Columbia River Basin-adjacent climate regimes and continental precipitation gradients. Geologically, the canyon showcases strata of Paleozoic and Mesozoic age, including Madison Limestone, Bighorn Dolomite, and Powder River Basin outcrops; structural controls reflect Laramide orogeny episodes tied to the uplift responsible for the Rocky Mountains. Sedimentation, hypolimnetic mixing, and reservoir thermal stratification are monitored relative to downstream allocations under compacts like the Yellowstone River Compact and interstate water law precedents.

Ecology

Bighorn Lake and its riparian corridor support assemblages of aquatic and terrestrial species including sport fishes such as rainbow trout, brown trout, and cutthroat trout, with native populations of pallid sturgeon in connected basin reaches and potential habitat for lake sturgeon in tributary systems. Riparian vegetation includes cottonwood, willow, and sedge communities supporting avifauna like bald eagle, peregrine falcon, great blue heron, and migratory stopovers on flyways used by American white pelican and Canada goose. Upland fauna encompass elk, mule deer, bighorn sheep, pronghorn, black bear, and mountain lion, while aquatic invertebrate assemblages include mayfly, caddisfly, and stonefly taxa important for trout diets. Invasive species concerns involve zebra mussel, quagga mussel, and nonnative centrarchids, with associated monitoring by agencies like the U.S. Fish and Wildlife Service and U.S. Geological Survey.

History and Human Use

The canyon and reservoir sit within territories long used by Indigenous nations including the Crow Nation, Northern Arapaho, Shoshone Tribe, and Sioux. Euro-American exploration by fur traders and explorers such as John Colter and overland routes like the Bozeman Trail brought settlement pressure prior to 20th-century water projects. Yellowtail Dam, named for Robert S. Yellowtail of the Crow Tribe, was built in partnership with the Bureau of Reclamation and represents mid-century federal water policy that engaged stakeholders including the National Park Service, U.S. Army Corps of Engineers, and regional irrigation districts serving agriculture in the Big Horn Basin and Powell County. The reservoir affected archeological sites, traditional fishing areas, and ranching operations tied to historic homesteaders and companies such as Anaconda Copper in the broader regional economy.

Recreation and Access

Recreational amenities around the lake are administered by National Park Service units and local outfitters, offering boating, fly-fishing, rafting, hunting, and wildlife viewing. Anglers pursue trout species using techniques linked to schools and guides from communities like Lovell, Fort Smith, and Basin, while river runners navigate whitewater stretches below Yellowtail Dam under seasonal release schedules coordinated with agencies including the U.S. Fish and Wildlife Service and National Park Service. Access nodes include marinas, boat ramps, campgrounds, and trailheads connected to historic routes such as Oregon Trail corridors; nearby visitor centers provide interpretive exhibits on geology, paleontology, and indigenous cultures. Regional tourism intersects with events in Billings, Sheridan, and Cody that draw outfitters and visitors.

Conservation and Management

Management of the reservoir involves interagency coordination among the Bureau of Reclamation, National Park Service, U.S. Fish and Wildlife Service, Bureau of Land Management, and tribal governments such as the Crow Tribe of Indians. Conservation priorities address habitat restoration, invasive species prevention through programs modeled on Aquatic Nuisance Species protocols, water quality monitoring by the Environmental Protection Agency and U.S. Geological Survey, and cultural resource protection under laws like the National Historic Preservation Act. Collaborative initiatives include riparian restoration projects informed by research from institutions such as Montana State University, University of Wyoming, and the Smithsonian Institution, while regional planning engages entities like the Upper Missouri River Basin Association and state natural resource departments to balance recreation, irrigation, and ecological integrity.

Category:Reservoirs in Wyoming Category:Reservoirs in Montana