Cowlitz River

Cowlitz River
Name	Cowlitz River
Country	United States
State	Washington
Length	105 mi (169 km)
Source	Confluence of Cispus and Toutle rivers
Source1 location	Southwest of Mount St. Helens, Cascade Range
Mouth	Columbia River
Mouth location	Near Kelso and Longview
Basin size	2,800 sq mi (7,252 km2)
Tributaries left	Cispus River, Tilton River
Tributaries right	Toutle River, Nisqually (note: not main)
Cities	Mossyrock, Morton, Randle, Packwood, Kelso, Longview

Cowlitz River is a major tributary of the Columbia River in southwestern Washington (state), draining portions of the Cascade Range including the flanks of Mount Rainier and Mount St. Helens. The river system supports industrial centers such as Longview, Washington and Kelso, Washington while sustaining salmon runs, hydroelectric projects, and forestry operations tied to agencies like the U.S. Army Corps of Engineers and the Bonneville Power Administration. Its basin intersects the traditional territories of Indigenous nations including the Cowlitz Indian Tribe, Yakama Nation, and Confederated Tribes and Bands of the Yakama Nation.

Course

The river begins at the confluence of the Cispus River and the Toutle River near Randle, Washington and flows generally southwest through communities such as Mossyrock, Washington and Morton, Washington before reaching the Columbia River near Longview, Washington and Kelso, Washington. Major tributaries entering along its course include the Tilton River, the Skookumchuck River, and the Kalama River system, connecting to regional corridors like Interstate 5 and state routes including Washington State Route 504 and U.S. Route 12. The channel navigates valleys carved by Pleistocene glaciation and volcanic episodes from Mount St. Helens eruption (1980) and earlier eruptions of Mount Mazama and Cascade Volcanoes.

Hydrology and Watershed

The basin encompasses headwaters on the slopes of Mount Rainier National Park and the Gifford Pinchot National Forest, receiving alpine snowmelt, glacial runoff, and rainfall influenced by the Pacific Ocean and the Olympic Mountains rain shadow. Flow regimes are regulated by dams such as Mayfield Dam and Mossyrock Dam, which provide reservoirs including Mayfield Lake and Riffe Lake used for hydroelectricity by entities like Puget Sound Energy and the Washington Department of Ecology. Seasonal discharge varies with spring snowmelt and episodic events tied to El Niño–Southern Oscillation phases and Pacific extratropical cyclones. Sediment loads surged after the 1980 Mount St. Helens eruption, prompting engineering responses by the U.S. Geological Survey, the U.S. Army Corps of Engineers, and the Environmental Protection Agency to monitor turbidity, nutrient fluxes, and channel morphology.

History and Human Use

Indigenous peoples including the Cowlitz people and bands of the Chinookan peoples and Salish peoples historically used the river for trade, salmon fishing, and cultural practices, interacting with explorers from the Lewis and Clark Expedition era and later Hudson's Bay Company fur trading networks. Euro-American settlement accelerated with the Oregon Trail, the Donation Land Claim Act, and railroad expansion by companies such as the Northern Pacific Railway and the Great Northern Railway. Hydropower development in the 20th century involved corporations like Seattle City Light and public agencies leading to construction of Mayfield Dam and Mossyrock Dam, affecting navigation and spawning habitats. Industrialization in Longview, Washington and timber operations tied to firms like Weyerhaeuser shaped economic patterns alongside policy actions by the U.S. Forest Service and state institutions such as the Washington State Department of Natural Resources.

Ecology and Wildlife

The river supports anadromous fish including Chinook salmon, Coho salmon, Chum salmon, and steelhead with runs historically harvested by the Cowlitz Indian Tribe and commercial fisheries licensed by the National Oceanic and Atmospheric Administration and the Washington Department of Fish and Wildlife. Riparian zones host species such as bald eagle, great blue heron, river otter, and mammals like black bear and elk within habitats cataloged by the U.S. Fish and Wildlife Service and conservation groups like The Nature Conservancy and Audubon Society. Aquatic ecology has been altered by barriers, hatchery programs run by the Cowlitz Tribal Hatchery and state hatcheries, invasive species management coordinated with the Washington Invasive Species Council, and restoration projects influenced by legislation including the Endangered Species Act regarding listings and recovery plans.

Recreation and Transportation

Recreational uses include angling for salmon and trout sanctioned by the Washington Department of Fish and Wildlife, whitewater boating on stretches monitored by local outfitters in Cowlitz County, Washington and Lewis County, Washington, and hiking trails connected to Gifford Pinchot National Forest and Mount St. Helens National Volcanic Monument. Transportation corridors parallel portions of the river, integrating the Port of Longview, barge traffic on the Columbia River, rail lines owned historically by BNSF Railway, and freight operations serving timber and pulp facilities such as those formerly operated by International Paper. Public access sites are administered by agencies including the Washington State Parks and Recreation Commission and county parks departments.

Conservation and Management

Management involves multi-jurisdictional coordination among the Cowlitz Indian Tribe, state agencies like the Washington State Department of Ecology, federal bodies including the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, and non-governmental organizations such as American Rivers and Backcountry Hunters & Anglers. Initiatives focus on dam passage improvements, habitat restoration projects funded through programs like the Bonneville Power Administration mitigation efforts, watershed planning with the Southwest Washington Regional Transportation Council, and climate resilience strategies aligned with Washington State Department of Natural Resources projections. Ongoing litigation and agreements have involved entities such as the Bonneville Power Administration and tribal governments addressing fishery compensation, while scientific monitoring by the U.S. Geological Survey and academic partners at University of Washington and Washington State University informs adaptive management.

Category:Rivers of Washington (state)