Green River (Colorado River tributary)

Green River (Colorado River tributary)
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Name	Green River
Source1 location	Wind River Range, Wyoming
Mouth location	Confluence with the Colorado River in Canyonlands National Park
Subdivision type1	Country
Subdivision name1	United States
Length	730 mi
Discharge1 avg	6180 cuft/s
Basin size	44800 sqmi

Green River (Colorado River tributary). The Green River is a major tributary of the Colorado River, flowing approximately 730 miles through the western United States. Originating in the Wind River Range of Wyoming, it traverses diverse landscapes in Colorado and Utah before joining the Colorado River in Canyonlands National Park. Its course has been central to the exploration, geology, and ecology of the Intermountain West.

Course

The river begins on the western slopes of the Continental Divide within the Bridger Wilderness of the Wind River Range. It flows south through the arid Green River Basin in Wyoming, passing the city of Green River. It then enters northeastern Utah, carving through the eastern flank of the Uinta Mountains in a series of dramatic canyons, including Flaming Gorge. The river continues southward, forming the boundary between the Colorado Plateau and the Uinta Basin, before crossing into northwestern Colorado near Dinosaur National Monument. It re-enters Utah, flowing through Desolation Canyon and Gray Canyon, before its final confluence with the Colorado River at The Confluence in the heart of Canyonlands National Park.

Hydrology

The Green River's flow is primarily fed by snowmelt from the high peaks of the Wind River Range and the Uinta Mountains. Major tributaries include the Yampa River, which joins at Steamboat Rock in Dinosaur National Monument, and the Duchesne River. The river's hydrology has been extensively altered by major water projects, most notably Flaming Gorge Dam, completed in 1964, which created Flaming Gorge Reservoir and regulates downstream flows for irrigation, hydroelectric power, and flood control. Other significant dams and diversions include the Fontenelle Dam and the Strawberry River trans-basin diversion project.

Geology

The river's course exposes a profound geologic history, cutting through sedimentary rock layers that record over 300 million years. In its upper reaches, it flows across Cretaceous and Tertiary formations of the Green River Basin, known for vast oil shale and trona deposits. Its passage through the Uinta Mountains reveals ancient Precambrian Uinta Mountain Group quartzite. The most iconic geologic features are found in its lower canyons, where it has incised deeply into the colorful Pennsylvanian- to Jurassic-age sandstones of the Colorado Plateau, such as the Weber Sandstone, Cedar Mesa Sandstone, and the sheer cliffs of the Canyonlands region.

History

The river corridor has been inhabited for millennia, with evidence of Fremont culture and later Ute and Shoshone presence. The first recorded European sighting was by Spanish explorers from the Domínguez–Escalante expedition in 1776. It was named the "Spanish River" on early maps. In 1825, William Ashley's fur trapping expedition descended the river, opening the Green River Rendezvous era. It was a critical route for subsequent explorers like John Wesley Powell, who famously mapped the river and its canyons during his 1869 and 1871 expeditions for the U.S. Geological Survey. The river valley later became a corridor for the Union Pacific Railroad and the focus of major Bureau of Reclamation water development in the 20th century.

Ecology

The river system supports a range of ecosystems, from montane forests in its headwaters to riparian corridors and desert aquatic habitats. It is home to several native fish species, including the endangered Colorado pikeminnow and razorback sucker, whose populations have declined due to dam construction and non-native species like rainbow trout and smallmouth bass. Riparian zones provide critical habitat for wildlife such as bald eagle, peregrine falcon, river otter, and mule deer. The riparian corridors, particularly in Labyrinth Canyon and Stillwater Canyon, are vital oases within the arid Colorado Plateau desert.

Recreation

The Green River is a premier destination for outdoor recreation. Flaming Gorge National Recreation Area offers world-class rainbow trout and lake trout fishing, along with boating and camping. The river's wilderness canyons, especially the sections within Dinosaur National Monument (Lodore Canyon), Desolation and Gray Canyons, and the flatwater stretches above Canyonlands National Park, are famous for multi-day whitewater rafting, kayaking, and canoeing trips. Significant hiking trails, including the Green River Trail in Wyoming and routes in Canyonlands, provide access to its remote shores, attracting thousands of visitors annually for adventure and solitude.

Category:Rivers of Colorado Category:Rivers of Utah Category:Rivers of Wyoming Category:Tributaries of the Colorado River