Willamette River

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Willamette River
The Willamette passing through downtown Portland
Origin	Oregon Coast Range and Cascade Range
Mouth	Columbia River
Length	187 mi (301 km)
Source elevation	450 ft (140 m)
Mouth elevation	sea level plus river stage
Avg. discharge	Annual: 33,816 cu ft/s (957.6 m³/s)[1] December: 67,800 cu ft/s (1,920 m³/s) August: 8,480 cu ft/s (240 m³/s)[2]
Basin area	11,100 sq mi (29,000 km²)[3]

Coordinates: 44°37′11, N°123′10

The Willamette River (pronounced wɨˈlæmɨt (help·info)) is a tributary of the Columbia River, 187 miles (301 km) long,^[4] in northwestern Oregon in the United States. Flowing northward between the Coastal Range and Cascade Range, the river and its tributaries form a basin called the Willamette Valley containing 70% of Oregon's population,^[5] including its largest city Portland, which sits along both sides of the river near its mouth on the Columbia. Its lush valley is fed by prolific rainfall on the western side of the Cascades, forming one of the most fertile agricultural regions of North America that was the destination for many if not most of the emigrants along the Oregon Trail. The river was an important transportation route throughout much of the early history of the state, furnishing a means of conveying the vast timber and agricultural resources of the state to the outside world.

Part of the river's floodplain (the Willamette Floodplain) was established as a National Natural Landmark in 1987; ten years later the river was named as one of ten national American Heritage Rivers.

Contents 1 Description 2 Environmental issues 3 Big Pipe Project 4 See also 5 References 6 External links

[edit] Description

The Willamette rises in three separate forks in the mountains south and southeast of Eugene, at the southern end of the Willamette Valley. The Middle Fork and North Fork rise on the western side of the Cascades between Three Sisters south to Diamond Peak, with the Middle Fork receiving the North Fork northwest of Oakridge and flowing northwest through the mountains to the southern end of the Willamette Valley. The Coast Fork rises in the lower mountains south of Cottage Grove, flowing north to join the Middle Fork 2 mi (3.2 km) southeast of Eugene.

From Eugene, the combined river flows NNW across the plain of the southern Willamette Valley to Corvallis, then follows a zigzag course past Albany and around the isolated hills in the central valley, passing west of downtown Salem. From Salem it flows north in a meandering course across the northwest plain of the valley, reaching the hills at Newberg, where it turns sharply ENE along the hills, passing through an opening in the hills at Oregon City, the location of the Willamette Falls and the head of navigation. From Oregon City it flows northwest, past Lake Oswego and Milwaukie on the south edge of Portland, then passing between east and west Portland, where it is spanned by a series of urban bridges. Downstream of downtown Portland it flows northwest through the industrial port area of Portland Harbor, then splitting into two channels around Sauvie Island, both of which hook around to enter the Columbia from the west, with the main channel entering on the north edge of Portland and the smaller Multnomah Channel entering approximately 15 mi (24 km) NNW at St. Helens.

The river's many tributaries drain the surrounding valley as well as portions of the Cascades and the Coastal Range. Downstream from the confluence of its forks, it is joined by McKenzie on the north side of Eugene, and by the Long Tom River from the southwest approximately 10 mi (16 km) south of Corvallis. It is joined by the Marys from the west at Corvallis, and the Calapooia from the southeast 5 mi (8 km) northeast of Corvallis, and It is joined by the Santiam from the east and the Luckiamute from the west within 1 mi (1.6 km) of each other approximately 5 mi (8 km) north of Albany. It is joined by the Yamhill from the west at Dayton, by the Molalla from the southeast near Canby, by the Tualatin from the west at West Linn, and by the Clackamas from the southeast at Gladstone.

The river forms part of the boundary of the following counties: Benton, Linn, Polk, Marion, Yamhill and Clackamas. Tributaries of the Willamette River also drain some or all of Lane, Washington and Multnomah counties.

Although riverboats navigated the upstream part of the Willamette into the first decades of the 20th century, currently there is little commercial traffic on the river above the Willamette Falls. The Willamette Falls Locks allow boat traffic, primarily recreational vessels, around the falls. The river is crossed by three ferries along its route in the Willamette Valley. The three ferries are located (from south to north) at Buena Vista, Wheatland, and Canby. The only locks on the river are located at Oregon City.

The Willamette River is prone to periodic floods. Notable floods include events in 1861 (which destroyed Linn City, Oregon), 1899, 1964, and the Willamette Valley Flood of 1996.

The river below Willamette Falls is subject to semidiurnal tides caused by the Pacific Ocean, but also with the effects of dams on the Columbia River and Willamette river basin which are regulated for hydroelectric power generation. Reverse flow has been observed as far upstream as Ross Island (river mile 15).^[6]

The lower river flow rate varies considerably by season and due to weather. Warm winter rains, for example, cause extensive mountain snow melt which significantly raises the river level and flow rate. The Willamette Valley Flood of 1996 was an extreme combination of saturated ground, snow melt and heavy rain: The maximum flow rate is not known, however 283,000 cubic feet per second (8010 m³/s) was estimated on January 18, 1974 at river stage 23.84 feet (7.27 m). The peak river stage (measured at the Morrison Bridge gauge in downtown Portland) on February 9, 1996 was 27.74 feet (8.46 m). Flood stage is 18.0 feet (5.5 m). The other extreme occurred during a drought on July 10, 1978 at 4,200 cu ft/s (120 m³/s).^[3] The Willamette's mean discharge rate is approximately 32,000 cu ft/s (910 m³/s).^[7]

[edit] Environmental issues

The Portland Harbor section of the Willamette River between downtown Portland and its terminus at the Columbia River is heavily polluted from years of industrial development of the river and its banks. Historical and current activities include shipbuilding, creosote manufacture, lead processing, and transfer and storage of petroleum products. State studies in the 1990s identified a wide variety of pollutants in the river bottom, including heavy metals, polychlorinated biphenyls (PCBs), and pesticides. As a result of these studies, this section of the river was designated a Superfund site in 2000,^[8] involving the United States Environmental Protection Agency in cleanup of the river bottom.^[9] The initial cleanup and containment of the pollutants is focused on the portion between Swan Island and Sauvie Island.^[10]

The Superfund site is downstream from most of the river however and lies less than twelve miles from where the Willamette ends at the Columbia river. Further upstream the pressing environmental issues have been mainly variations in pH and dissolved oxygen.^[11] In the Portland Metropolitan Area, these issues are exacerbated by sewer overflow events during periods of high rainfall. The city has embarked on expanding the sewer system in order to minimize these events through construction of the Big Pipe Project part of the river renaissance project.

Even further upstream however, the Willamette is not heavily polluted and is used by communities, such as the City of Tigard, for drinking water. The major contaminants are from agricultural runoff.

[edit] Big Pipe Project

Following an agreement between the City of Portland and the State of Oregon to reduce Combined sewer overflows (CSOs) dramatically in 1991,^[12] the Office of Sustainable Development began work on what it dubbed the "Big Pipe Project".

The project consisted primarily of two large pipes on either side of the river. The project was part of a larger effort by the Bureau of Environmental Services to reduce CSOs through a series of combined efforts, which had already netted results of a 53% reduction in CSO volume by 2003.^[12]

The west side pipe, which is approximately 14 feet in diameter and travels from SW Clay Street to the Swan Island Pumping Station, was completed in 2006.^[12][13] The pipe connects to the Southwest Parallel Interceptor, another pipe project approximately six feet in diameter, at SW Clay Street, which then continues on south for several more miles, covering the Portland Metro South Waterfront area.

As of June 2008, the east side pipe is under construction and is slated for completion in December 2011.^[14] The pipe, like its cousin, will connect to the Swan Island Pumping Station, but will extend a full six miles south down the east bank.^[15] The east side pipe, serving a much larger segment of population, is 22 feet wide and will be able to hold over 83 million gallons of storm water and sewage.^[15][14]

Together the pipes and other CSO projects will provide a 94% reduction in CSO volume by 2011, dramatically reducing one of the largest pollutants of the Willamette River.^[15][14]

[edit] See also

• List of crossings of the Willamette River
• List of Oregon rivers
• Oregon Country
• Steamboats of the Willamette River

[edit] References

[edit] External links

• Portland Harbor DEQ cleanup - Oregon state Department of Environmental Quality
• Willamette Riverkeeper - Working to protect and restore the Willamette River
• City of Portland River Renaissance - Renewing Portlanders' connections to the River