The Columbia River

COLUMBIA RIVER

Written by Marion E. Marts

Emeritus Professor of Geography, University of Washington, Seattle.The Editors of Encyclopedia Britannica

Last Updated: Dec 26, 2023

Columbia River Gorge, Oregon-Washington border

Columbia River: Largest river flowing into the Pacific Ocean from North America. It is exceeded in discharge on the continent only by the Mississippi, St. Lawrence, and Mackenzie rivers. The Columbia is one of the world’s greatest sources of hydroelectric power and, with its tributaries, represents a third of the potential hydropower of the United States. In addition, its mouth provides the first deepwater harbor north of San Francisco. Two-fifths of the river’s course, some 500 miles (800 km) of its 1,240-mile (2,000-km) length, lies in Canada, between its headwaters in British Columbia and the U.S. border.

Physiography and hydrology

The Columbia drains some 258,000 square miles (668,000 square km), of which about 85 percent is in the northwestern United States. Major tributaries are the Kootenay, Snake, Pend Oreille, Spokane, Okanogan, Yakima, Cowlitz, and Willamette rivers. High flows occur in late spring and early summer, when snow melts in the mountainous watershed. Low flows occur in autumn and winter, causing water shortages at the river’s hydroelectric plants.

The Columbia flows from its source in Columbia Lake, at an elevation of 2,700 feet (820 metres), in British Columbia near the crest of the Rocky Mountains, to the Pacific Ocean at Astoria, Oregon. For the first 190 miles (305 km), its course is northwesterly. It then flows to the south for 270 miles (435 km) to the border of Canada and the United States (elevation 1,290 feet [390 meters), where it enters northeastern Washington. It traverses east-central Washington in a sweeping curve known as the Big Bend, its prehistoric course having been disarranged first by lava flows and later by ice sheets. The ice sheets were instrumental in creating the Channelled Scablands, a series of coulees (steep-walled ravines) trending northeast-southwest in the northern part of the Columbia Plateau; Grand Coulee is the largest of these. The scablands were formed as immense torrents of water, released intermittently from ice-dammed lakes upstream, swept down-valley. Shortly below the confluence with the Snake River, its largest tributary, the Columbia turns west and continues 300 miles (480 km) to the ocean as the boundary between Oregon and Washington; in this last stretch the river has carved the spectacular Columbia River Gorge through the Cascade Range.

Tides flow upriver for 140 miles (225 km). Portland, Oregon (about 110 miles [180 km] from the mouth), and Vancouver, Washington (100 miles [160 km]), are the upper limit of oceangoing navigation, aided by a dredged channel. Through the use of a series of locks, barge traffic is made possible to Lewiston, Idaho, more than 460 miles (740 km) inland from the river’s mouth at the junction of the Clearwater and Snake rivers.

NW Power and Conservation Council

Columbia River: Description, Creation, and Discovery

Description

The Columbia River, fourth-largest by volume in North America (annual average of 192 million acre-feet at the mouth) begins at Columbia Lake in the Rocky Mountain Trench of southeastern British Columbia at about 2,656 feet above sea level. The geographic coordinates at the head of the lake are 50°13’ north latitude, 115°51 west longitude.

The river flows north for some 200 miles (322 kilometers) and then turns south and flows for about 270 miles (434 kilometers) before crossing the border into Washington at River Mile 749, that is, 749 miles (1,205 kilometers) inland from the Pacific Ocean. More precisely, according to the BC Freshwater Atlas, the Columbia River in British Columbia is 760.356 kilometers long (472.463 miles).

For its first approximately 150 miles (241 kilometers) in the United States, the Columbia forms the reservoir behind Grand Coulee Dam. The river then bends west, south and east through central Washington, turns south and then west, and forms the border between Oregon and Washington to the Pacific Ocean. The mouth of the river is about 10 miles (16 kilometers) west of Astoria, Oregon. The geographic coordinates at the mouth (near Cape Disappointment, Washington) are 124.09344 west longitude, 46.246922 north latitude (these are the coordinates the U.S. Army Corps of Engineers cites as River Mile Zero). The total length of the river is about 1,243 miles (about 2,000 kilometers). The drainage basin covers 259,000 square miles (670,810 square kilometers), approximately the size of France, drains portions of seven states and British Columbia, and covers three degrees of latitude and nine degrees of longitude. 

The Columbia mainstream has numerous tributaries, large and small. The biggest of these, in terms of length and volume, are: longest:

1. Snake (1,078 miles)

2. Kootenai/y (485 miles)

3. Deschutes (252 miles)

4. Yakima (214 miles)

5. Willamette (187 miles)

The largest by average annual discharge volume:

1. Snake (54,830 cubic feet per second (cfs) at Ice Harbor Dam)

2. Willamette (33,010 cfs at the Morrison Bridge in downtown Portland)

3. Kootenay/i (27,616 cfs at Cora Linn Dam near Nelson, British Columbia)

4. Pend Oreille (26,320 cfs at Box Canyon Dam in northern Washington)

   
   

Because of its unique situation close to the ocean and laced with tall mountain ranges, the Columbia evolved as one of the great rivers of the world in terms of its runoff and the diversity of its habitat. From its headwaters to its mouth, the river drops steadily at a rate of about two feet per mile, and most of its course is through rock-walled canyons. Down these rocky canyons the Columbia pours prodigious volumes of water, emptying an annual average of 192 million acre-feet into the Pacific; much of its volume originates in its middle and upper reaches. The Canadian portion of the basin, for example, contributes about 20 percent of the river’s total volume (this includes the water from rivers that begin or pass through the United States before entering the Columbia in Canada, such as the Clark Fork/Pend Oreille system and the Kootenay, which is spelled Kootenai in the United States).

The combination of high volume and stable canyons made the Columbia an ideal hydropower river. Today there are 14 dams on the mainstream Columbia, beginning with Bonneville at river mile 146 and ending with Mica at river mile 1,018, and more than 450 dams throughout the basin. Dams on the Columbia and its major tributaries, primarily the Snake River, at approximately 1,078 miles its longest feeder stream, produce half of the electricity consumed in the Pacific Northwest. The Columbia River dams inundated many of the river's dangerous rapids, well-described and named by early settlers and travelers on the river for their often treacherous passage — Dalles des Morts (Death Rapids), Hell Gate, White Cap, Rock Slide, Boulder, Surprise.

Hopefully this will help us locate the geographical areas and locations of waterways that the mighty Columbia River flows through in our Washington State in order to direct our prayer missles to hit the target.