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The Willamette River ( ) is a major
tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drai ...
of the
Columbia River The Columbia River ( Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia ...
, accounting for 12 to 15 percent of the Columbia's flow. The Willamette's
main stem In hydrology, a mainstem (or trunk) is "the primary downstream segment of a river, as contrasted to its tributaries". Water enters the mainstem from the river's drainage basin, the land area through which the mainstem and its tributaries flow. ...
is long, lying entirely in northwestern
Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
in the United States. Flowing northward between the Oregon Coast Range and the
Cascade Range The Cascade Range or Cascades is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, ...
, the river and its tributaries form the
Willamette Valley The Willamette Valley ( ) is a long valley in Oregon, in the Pacific Northwest region of the United States. The Willamette River flows the entire length of the valley and is surrounded by mountains on three sides: the Cascade Range to the eas ...
, a basin that contains two-thirds of Oregon's population, including the state capital, Salem, and the state's largest city, Portland, which surrounds the Willamette's mouth at the Columbia. Originally created by
plate tectonics Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of larg ...
about 35 million years ago and subsequently altered by
volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called a ...
and erosion, the river's
drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
was significantly modified by the Missoula Floods at the end of the most recent ice age. Humans began living in the watershed over 10,000 years ago. There were once many tribal villages along the lower river and in the area around its mouth on the Columbia. Indigenous peoples lived throughout the upper reaches of the basin as well. Rich with sediments deposited by flooding and fed by prolific rainfall on the western side of the Cascades, the Willamette Valley is one of the most fertile agricultural regions in North America, and it was thus the destination of many 19th-century pioneers traveling west along the
Oregon Trail The Oregon Trail was a east–west, large-wheeled wagon route and emigrant trail in the United States that connected the Missouri River to valleys in Oregon. The eastern part of the Oregon Trail spanned part of what is now the state of Kans ...
. The river was an important transportation route in the 19th century, although Willamette Falls, just upstream from Portland, was a major barrier to boat traffic. In the 21st century, major highways follow the river, and roads cross the main stem on approximately 30 different bridges. More than half a dozen bridges not open to motorized vehicles provide separate crossings for bicycles and pedestrians, mostly in the Eugene area, and several others are exclusively for rail traffic. There are also ferries that convey cars, trucks, motorcycles, bicycles, and pedestrians across the river for a fare and provided river conditions permit. They are the
Buena Vista Ferry The Buena Vista Ferry connects Marion County and Polk County across the Willamette River in the U.S. state of Oregon. It is located a few miles south of Independence, near the community of Buena Vista. The river is approximately 720 feet (220 m) ...
between Marion County and Polk County south of Independence and Salem, the
Wheatland Ferry The Wheatland Ferry is a cable ferry that connects Marion County and Yamhill County across the Willamette River in the U.S. state of Oregon. The ferry travels approximately across the river, depending on the height of the river, and is powere ...
between Marion County and Polk County north of Salem and Keizer, and
Canby Ferry The Canby Ferry is a cable ferry in the U.S. state of Oregon that connects Canby, and Wilsonville/Stafford in Clackamas County across the Willamette River. The service has been in operation since 1914, except from 1946 to 1953. The specific v ...
in Clackamas County north of Canby. Since 1900, more than 15 large dams and many smaller ones have been built in the Willamette's drainage basin, 13 of which are operated by the
U.S. Army Corps of Engineers , colors = , anniversaries = 16 June (Organization Day) , battles = , battles_label = Wars , website = , commander1 = ...
(USACE). The dams are used primarily to produce
hydroelectricity Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined an ...
, to maintain reservoirs for recreation, and to prevent flooding. The river and its tributaries support 60 fish species, including many species of
salmon Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus '' Salmo'') and North Pacific (genus '' Onco ...
and
trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', '' Salmo'' and '' Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salm ...
; this is despite the dams, other alterations, and pollution (especially on the river's lower reaches). Part of the Willamette Floodplain was established as a National Natural Landmark in 1987, and the river was named as one of 14
American Heritage Rivers American Heritage Rivers were designated by the United States Environmental Protection Agency in the 1990s to receive special attention (coordinating efforts of multiple governmental entities) to further three objectives: natural resource and envir ...
in 1998.


Course

The upper tributaries of the Willamette originate in the mountains south and southeast of
Eugene, Oregon Eugene ( ) is a city in the U.S. state of Oregon. It is located at the southern end of the Willamette Valley, near the confluence of the McKenzie and Willamette rivers, about east of the Oregon Coast. As of the 2020 United States Census, ...
. Formed by the confluence of the
Middle Fork Willamette River The Middle Fork Willamette River is one of several forks that unite to form the Willamette River in the western part of the U.S. state of Oregon. It is approximately long, draining an area of the Cascade Range southeast of Eugene, which is at ...
and the Coast Fork Willamette River near Springfield, the
main stem In hydrology, a mainstem (or trunk) is "the primary downstream segment of a river, as contrasted to its tributaries". Water enters the mainstem from the river's drainage basin, the land area through which the mainstem and its tributaries flow. ...
Willamette meanders generally north for to the
Columbia River The Columbia River ( Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia ...
. The river's two most significant course deviations occur at Newberg, where it turns sharply east, and about downstream from Newberg, where it turns north again. Near its mouth north of downtown Portland, the river splits into two channels that flow around Sauvie Island. Used for navigation purposes, these channels are managed by the
U.S. federal government The federal government of the United States (U.S. federal government or U.S. government) is the national government of the United States, a federal republic located primarily in North America, composed of 50 states, a city within a f ...
. The main channel, which is the primary navigational conduit for Portland's harbor and riverside industrial areas, is deep and varies in width from , although the river broadens to in some of its lower reaches. This channel enters the Columbia about from the Columbia's mouth on the Pacific Ocean. The smaller
Multnomah Channel The Multnomah Channel is a distributary of the Willamette River. It diverges from the main stem a few miles upstream of the main stem's confluence with the Columbia River in Multnomah County in the U.S. state of Oregon. The channel flows northw ...
, a
distributary A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel. Distributaries are a common feature of river deltas. The phenomenon is known as river bifurcation. The opposite of a distributar ...
, is long, about wide, and deep. It ends about farther downstream on the Columbia, near St. Helens in Columbia County. Relevant map quadrangles include Eugene East, Coburg, Junction City, Harrisburg, Peoria, Riverside, Lewisburg, Albany, Monmouth, Salem West, Mission Bottom, Dayton, St. Paul, Newberg, Sherwood, Canby, Lake Oswego, Portland, Linnton, Sauvie Island, and Saint Helens. Proposals have been made for deepening the Multnomah Channel to in conjunction with roughly of tandem-maintained navigation on the Columbia River. Between the 1850s and the 1960s, channel-straightening and flood control projects, as well as agricultural and urban encroachment, cut the length of the river between the McKenzie River confluence and Harrisburg by 65 percent. Similarly, the river was shortened by 40 percent in the stretch between Harrisburg and Albany. Interstate 5 and three branches of Oregon Route 99 are the two major highways that follow the river for its entire length. Communities along the main stem include Springfield and Eugene in Lane County;
Harrisburg Harrisburg is the capital city of the Commonwealth of Pennsylvania, United States, and the county seat of Dauphin County. With a population of 50,135 as of the 2021 census, Harrisburg is the 9th largest city and 15th largest municipality in ...
in Linn County; Corvallis in Benton County; Albany in Linn and Benton counties;
Independence Independence is a condition of a person, nation, country, or state in which residents and population, or some portion thereof, exercise self-government, and usually sovereignty, over its territory. The opposite of independence is the stat ...
in Polk County; Salem in Marion County; Newberg in
Yamhill County Yamhill County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 107,722. The county seat is McMinnville. Yamhill County was named after the Yamhelas, members of the Kalapuya Tribe. Yamhill C ...
;
Oregon City ) , image_skyline = McLoughlin House.jpg , imagesize = , image_caption = The McLoughlin House, est. 1845 , image_flag = , image_seal = Oregon City seal.png , image_map ...
, West Linn,
Milwaukie Milwaukie is a city mostly in Clackamas County, Oregon, United States; a very small portion of the city extends into Multnomah County. The population was 20,291 at the 2010 census. Founded in 1847 on the banks of the Willamette River, the c ...
, and Lake Oswego in
Clackamas County Clackamas County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 421,401, making it Oregon's third-most populous county. Its county seat is Oregon City. The county was named after the Nati ...
; and Portland in Multnomah and
Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...
counties. Significant tributaries from source to mouth include the Middle and Coast forks and the McKenzie, Long Tom, Marys, Calapooia, Santiam, Luckiamute, Yamhill, Molalla, Tualatin, and Clackamas rivers. Beginning at above sea level, the main stem descends between source and mouth, or about 2.3 feet per mile (0.4 m per km). Source and mouth elevation derived from
Google Earth Google Earth is a computer program that renders a 3D computer graphics, 3D representation of Earth based primarily on satellite imagery. The program maps the Earth by superimposition, superimposing satellite images, aerial photography, and geog ...
search using GNIS source and mouth coordinates.
The gradient is slightly steeper from the source to Albany than it is from Albany to Oregon City.Benke, ''et al.'', p. 617 At Willamette Falls, between West Linn and Oregon City, the river plunges about . For the rest of its course, the river is extremely low-gradient and is affected by Pacific Ocean tidal effects from the Columbia. The main stem of the Willamette varies in width from about .


Discharge

With an average flow at the mouth of about , the Willamette ranks 19th in volume among rivers in the United States and contributes 12 to 15 percent of the total flow of the Columbia River. The Willamette's flow varies considerably season to season, averaging about in August to more than in December. The U.S. Geological Survey (USGS) operates five stream gauges along the river, at Harrisburg, Corvallis, Albany, Salem, and Portland. The average discharge at the lowermost gauge, near the Morrison Bridge in Portland, was between 1972 and 2013. Located at
river mile A river mile is a measure of distance in miles along a river from its mouth. River mile numbers begin at zero and increase further upstream. The corresponding metric unit using kilometers is the river kilometer. They are analogous to vehicle ro ...
(RM) 12.8 or river kilometer (RK) 20.6, the gauge measures the flow from an area of , roughly 97 percent of the Willamette basin. The highest flow recorded at this station was on February 9, 1996, during the Willamette Valley Flood of 1996, and the minimum was on July 10, 1978. The highest recorded flow of for the Willamette at a different gauge in Portland occurred during a flood in 1861. This and many other large flows preceded the Flood Control Act of 1936 and dam construction on the Willamette's major tributaries. The river below Willamette Falls, from the mouth, is affected by
semidiurnal tides Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables can ...
, and gauges have detected reverse flows (backwards river flows) below Ross Island at RM 15 (RK 24). The
National Weather Service The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...
issues tide forecasts for the river at the Morrison Bridge.


Geology

The Willamette River basin was created primarily by
plate tectonics Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of larg ...
and
volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called a ...
and was altered by erosion and sedimentation, including deposits from enormous glacial floods as recent as 13,000 years ago.Wallick, ''et al.'', pp. 495–97 The oldest rocks beneath the Willamette Valley are the
Siletz River Volcanics The Siletz River Volcanics, located in the Oregon Coast Range, United States, are a sequence of basaltic pillow lavas that make up part of Siletzia.subducted by the Farallon Plate beneath the
North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Paci ...
, creating the
forearc Forearc is a plate tectonic term referring to a region between an oceanic trench, also known as a subduction zone, and the associated volcanic arc. Forearc regions are present along a convergent margins and eponymously form 'in front of' the v ...
basin that would later become the Willamette Valley.Benke, ''et al.'', p. 616 The valley was initially part of the
continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...
, rather than a separate inland sea. Many layers of marine deposits formed in the forearc basin and cover the older Siletz River Volcanics. About 20 to 16 million years ago,
uplift Uplift may refer to: Science * Geologic uplift, a geological process ** Tectonic uplift, a geological process * Stellar uplift, the theoretical prospect of moving a stellar mass * Uplift mountains * Llano Uplift * Nemaha Uplift Business * Upli ...
formed the Coast Range and separated the basin from the Pacific Ocean.
Basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...
s of the Columbia River Basalt Group, from eruptions primarily in eastern Oregon, flowed across large parts of the northern half of the basin about 15 million years ago. They covered the Tualatin Mountains (West Hills), most of the
Tualatin Valley The Tualatin Valley is a farming and suburban region southwest of Portland, Oregon in the United States. The valley is formed by the meandering Tualatin River, a tributary of the Willamette River at the northwest corner of the Willamette Va ...
, and the slopes of hills further south, with up to of
lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or ...
. Later depositions covered the basalt with up to of silt in the Portland and Tualatin basins. During the
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
, beginning roughly 2.5 million years ago, volcanic activity in the Cascades combined with a cool, moist climate to produce further heavy sedimentation across the basin, and
braided river A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, ''aits'' or ''eyots''. Braided streams tend to occur in rivers with high sediment ...
s created alluvial fans spreading down from the east. Between about 15,500 and 13,000 years ago, the Missoula Floods—a series of large outpourings originating at Glacial Lake Missoula in Montana—swept down the Columbia River and backfilled the Willamette watershed. Each flood produced "discharges that exceeded the annual discharge of all the present-day rivers of the world combined". Filling the Willamette basin to depths of in the Portland region, each flood created a temporary lake, Lake Allison, that stretched from Lake Oswego to near Eugene.Orr (1999), pp. 212–13 The ancestral Tualatin Valley, part of the Willamette basin, flooded as well; water depths ranged from at Lake Oswego to as far upstream (west) as Forest Grove. Flood deposits of silt and clay, ranging in thickness from in the north to about in the south, settled from this muddy water to form today's valley floor. The floods carried Montana icebergs well into the basin, where they melted and dropped
glacial erratic A glacial erratic is glacially deposited rock differing from the type of rock native to the area in which it rests. Erratics, which take their name from the Latin word ' ("to wander"), are carried by glacial ice, often over distances of hundred ...
s onto the land surface. These rocks, composed of granite and other materials common to central Montana but not to the Willamette Valley, include more than 40 boulders, each at least in diameter.Orr (1999), p. 214 Before being partly chipped away and removed, the largest of these originally weighed about . The northern part of the watershed is underlain by a network of faults capable of producing earthquakes at any time, and many small quakes have been recorded in the basin since the mid-19th century.Orr (1999), pp. 215–19 In 1993, the Scotts Mills earthquake—the largest recent earthquake in the valley, measuring 5.6 on the
Richter scale The Richter scale —also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale—is a measure of the strength of earthquakes, developed by Charles Francis Richter and presented in his landmark 1935 ...
—was centered near Scotts Mills, about south of Portland. It caused $30 million in damage, including harm to the Oregon State Capitol in Salem. Evidence suggests that massive quakes of 8 or more on the Richter scale have occurred historically in the
Cascadia subduction zone The Cascadia subduction zone is a convergent plate boundary that stretches from northern Vancouver Island in Canada to Northern California in the United States. It is a very long, sloping subduction zone where the Explorer, Juan de Fuc ...
off the Oregon coast, most recently in 1700 CE, and that others as strong as 9 on the Richter scale occur every 500 to 800 years. The basin's high population density, its nearness to this subduction zone, and its loose soils, which tend to amplify shaking, make the Willamette Valley especially vulnerable to damage from strong earthquakes.


Watershed

The Willamette River drains a region of , which is 12 percent of the total area of Oregon. Bounded by the Coast Range to the west and the Cascade Range to the east, the river basin is about long and wide. Elevations within the watershed range from at Mount Jefferson in the Cascade Range to at the mouth on the Columbia River. Watersheds bordering the Willamette River basin are those of the
Little Deschutes River The Little Deschutes River is a tributary of the Deschutes River in the central part of the U.S. state of Oregon. It is about long, with a drainage basin of . It drains a rural area on the east side of the Cascade Range south of Bend. The Littl ...
to the southeast, the
Deschutes River Deschutes River may refer to: *Deschutes River (Oregon) **Little Deschutes River (Oregon), a tributary of the Deschutes River in Oregon *Deschutes River (Washington) The Deschutes River is a river in the U.S. state of Washington. Its headwater ...
to the east, and the Sandy River to the northeast; the North Umpqua and Umpqua rivers to the south; coastal rivers including (from south to north) the Siuslaw, the Alsea, the Yaquina, the Siletz, the Nestucca, the Trask, and the
Wilson Wilson may refer to: People *Wilson (name) ** List of people with given name Wilson ** List of people with surname Wilson * Wilson (footballer, 1927–1998), Brazilian manager and defender * Wilson (footballer, born 1984), full name Wilson R ...
to the west; the Nehalem and the Clatskanie to the northwest, and the Columbia River to the north. About 2.5 million people lived in the Willamette River basin as of 2010, about 65 percent of the population of Oregon. As of 2009, the basin contained 20 of the 25 most populous cities in Oregon. These cities include Springfield, Eugene, Corvallis, Albany, Salem, Keizer, Newberg, Oregon City, West Linn, Milwaukie, Lake Oswego, and Portland. The largest is Portland, with more than 500,000 residents. Not all of these cities draw water in part or exclusively from the Willamette for their municipal water supply. Other cities in the watershed (but not on the main-stem river) with populations of 20,000 or more are Gresham, Hillsboro, Beaverton, Tigard, McMinnville, Tualatin, Woodburn, and Forest Grove. Sixty-four percent of the watershed is privately owned, while 36 percent is publicly owned. The
U.S. Forest Service The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...
manages 30 percent of the watershed, the U.S.
Bureau of Land Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands. Headquartered in Washington DC, and with oversight over , it governs one eighth of the country's ...
5 percent, and the State of Oregon 1 percent. Sixty-eight percent of the watershed is forested; agriculture, concentrated in the Willamette Valley, makes up 19 percent, and urban areas cover 5 percent. More than of roads criss-cross the watershed.Benke, ''et al.'', pp. 616–17 In 1987, the
U.S. Secretary of the Interior The United States secretary of the interior is the head of the United States Department of the Interior. The secretary and the Department of the Interior are responsible for the management and conservation of most federal land along with natura ...
designated of the watershed in Benton County as a National Natural Landmark. This area is the Willamette Floodplain, the largest remaining unplowed native grassland in the North Pacific geologic province, which encompasses most of the Pacific Northwest coast.


History


First inhabitants

For at least 10,000 years, a variety of indigenous peoples populated the Willamette Valley. These included the Kalapuya, the Chinook, and the Clackamas. The territory of the Clackamas encompassed the northeastern portion of the basin, including the Clackamas River (with which their name is shared). Although it is unclear exactly when, the territory of the Chinook once extended across the northern part of the watershed, through the Columbia River valley. Indigenous peoples of the Willamette Valley were further divided into groups including the Kalapuyan-speaking Yamhill and Atfalati (Tualatin) (both Northern Kalapuya), Central Kalapuya like the Santiam, Muddy Creek (Chemapho), Long Tom (Chelamela), Calapooia (Tsankupi), Marys River (Chepenafa) and Luckiamute, and the Yoncalla or Southern Kalapuya, as well other tribes such as the Chuchsney-Tufti, Siuslaw and
Molala The Molala (also Molale, Molalla, Molele) are a people of the Plateau culture area in the Oregon Cascades and central Oregon, United States. They are one of the Confederated Tribes of the Grand Ronde Community of Oregon, with 141 of the 882 member ...
. The name ''Willamette'' is of indigenous origin, deriving from the French pronunciation of the name of a Clackamas Native American village.Bright, p. 567 However, Native American languages in Oregon were very similar, so the name may also be derived from Kalapuya dialects. Around the year 1850, the Kalapuya numbered between 2,000 and 3,000 and were distributed among several groups. These figures are only speculative; there may have been as few as eight subgroups or as many as 16. In that time period, the Clackamas' tribal population was roughly 1,800. The
U.S. Census Bureau The United States Census Bureau (USCB), officially the Bureau of the Census, is a principal agency of the U.S. Federal Statistical System, responsible for producing data about the American people and economy. The Census Bureau is part of the ...
estimated that the Chinook population was nearly 5,000, though not all of the Chinook lived on the Willamette. The Chinook territory encompassed the lower Columbia River valley and significant stretches of the Pacific coast on both the north and the south side of the Columbia's mouth. At times, however, the Chinook territory extended even farther south in the Willamette Valley. The total native population was estimated at 15,000. The indigenous peoples of the Willamette River practiced a variety of life ways. Those on the lower river, slightly closer to the coast, often relied on fishing as their primary economic mainstay.
Salmon Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus '' Salmo'') and North Pacific (genus '' Onco ...
was the most important fish to Willamette River tribes as well as to the Native Americans of the Columbia River, where white traders traded fish with the Native Americans. Upper-river tribes caught steelhead and salmon, often by building weirs across tributary streams. Tribes of the northern Willamette Valley practiced a generally settled lifestyle. The Chinooks lived in great wooden lodges,Ruby and Brown, p. 16 practiced
slavery Slavery and enslavement are both the state and the condition of being a slave—someone forbidden to quit one's service for an enslaver, and who is treated by the enslaver as property. Slavery typically involves slaves being made to perf ...
, and had a well-defined
caste Caste is a form of social stratification characterised by endogamy, hereditary transmission of a style of life which often includes an occupation, ritual status in a hierarchy, and customary social interaction and exclusion based on cultur ...
system. People of the south were more nomadic, traveling from place to place with the seasons. They were known for the controlled burning of woodlands to create meadows for hunting and plant gathering (especially camas).


Fur trade

The Willamette River first appears in the records of outsiders in 1792, when it was seen by British Lieutenant William Robert Broughton of the Vancouver Expedition, led by George Vancouver. From the 18th to the mid-19th century, much of the
Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Thou ...
and most of its rivers were involved in the
fur trade The fur trade is a worldwide industry dealing in the acquisition and sale of animal fur. Since the establishment of a world fur market in the early modern period, furs of boreal ecosystem, boreal, polar and cold temperate mammalian animals h ...
, in which fur trappers (mostly
French-Canadian French Canadians (referred to as Canadiens mainly before the twentieth century; french: Canadiens français, ; feminine form: , ), or Franco-Canadians (french: Franco-Canadiens), refers to either an ethnic group who trace their ancestry to Fre ...
s working for the
Hudson's Bay Company The Hudson's Bay Company (HBC; french: Compagnie de la Baie d'Hudson) is a Canadian retail business group. A fur trading business for much of its existence, HBC now owns and operates retail stores in Canada. The company's namesake business di ...
and the
North West Company The North West Company was a fur trading business headquartered in Montreal from 1779 to 1821. It competed with increasing success against the Hudson's Bay Company in what is present-day Western Canada and Northwestern Ontario. With great weal ...
, which later merged) hunted for
beaver Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers a ...
and
sea otter The sea otter (''Enhydra lutris'') is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of the weasel family, but among the smal ...
on rivers, streams, and coastlines. The pelts of these animals commanded substantial prices in either the United States, Canada or eastern Asia, because of their "thick, luxurious and water-repellent" qualities. Fur traders heavily exploited the Willamette River and its tributaries. During this period, the Siskiyou Trail (or California-Oregon Trail) was created. This trading path, over long, stretched from the mouth of the Willamette River near present-day Portland south through the Willamette Valley, crossing the Cascades and the
Siskiyou Mountains The Siskiyou Mountains are a coastal subrange of the Klamath Mountains, and located in northwestern California and southwestern Oregon in the United States. They extend in an arc for approximately from east of Crescent City, California, nort ...
, and south through the
Sacramento Valley , photo =Sacramento Riverfront.jpg , photo_caption= Sacramento , map_image=Map california central valley.jpg , map_caption= The Central Valley of California , location = California, United States , coordinates = , boundaries = Sierra Nevada (ea ...
to
San Francisco San Francisco (; Spanish for " Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the fourth most populous in California and 17t ...
.


19th-century development

In 1805, the
Lewis and Clark Expedition The Lewis and Clark Expedition, also known as the Corps of Discovery Expedition, was the United States expedition to cross the newly acquired western portion of the country after the Louisiana Purchase. The Corps of Discovery was a select gr ...
traveled thousands of miles across central North America in an attempt to map and explore the Louisiana Territory of the United States and the
Oregon Country Oregon Country was a large region of the Pacific Northwest of North America that was subject to a long dispute between the United Kingdom and the United States in the early 19th century. The area, which had been created by the Treaty of 1818, co ...
, which were then occupied mainly by Native Americans and settlers from Great Britain. As the expedition traveled down and back up the Columbia River, it missed the mouth of the Willamette, one of the Columbia's largest tributaries. It was only after receiving directions from natives along the Sandy River that the explorers learned about their oversight. William Clark returned down the Columbia and entered the Willamette River in April 1806. The
United States Exploring Expedition The United States Exploring Expedition of 1838–1842 was an exploring and surveying expedition of the Pacific Ocean and surrounding lands conducted by the United States. The original appointed commanding officer was Commodore Thomas ap Catesby ...
passed through the Willamette Valley in 1841 while traveling along the Siskiyou Trail. The expedition members noted extensive salmon fishing by natives at Willamette Falls, much like that at Celilo Falls on the Columbia River. In the middle part of the 19th century, the Willamette Valley's fertile soils, pleasant climate, and abundant water attracted thousands of settlers from the eastern United States, mainly the Upland South borderlands of Missouri, Iowa, and the Ohio Valley. Many of these emigrants followed the
Oregon Trail The Oregon Trail was a east–west, large-wheeled wagon route and emigrant trail in the United States that connected the Missouri River to valleys in Oregon. The eastern part of the Oregon Trail spanned part of what is now the state of Kans ...
, a trail across western North America that began at
Independence, Missouri Independence is the fifth-largest city in Missouri and the county seat of Jackson County, Missouri, Jackson County. Independence is a satellite city of Kansas City, Missouri, and is the largest suburb on the Missouri side of the Kansas City metro ...
, and ended at various locations near the mouth of the Willamette River. Although people had been traveling to Oregon since 1836, large-scale migration did not begin until 1843, when nearly 1,000 pioneers headed westward. Over the next 25 years, some 500,000 settlers traveled the Oregon Trail, braving the rapids of the
Snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more ...
and Columbia Rivers to reach the Willamette Valley. Starting in the 1820s,
Oregon City ) , image_skyline = McLoughlin House.jpg , imagesize = , image_caption = The McLoughlin House, est. 1845 , image_flag = , image_seal = Oregon City seal.png , image_map ...
developed near Willamette Falls. It was incorporated in 1844, becoming the first city west of the
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...
to have that distinction.
John McLoughlin John McLoughlin, baptized Jean-Baptiste McLoughlin, (October 19, 1784 – September 3, 1857) was a French-Canadian, later American, Chief Factor and Superintendent of the Columbia District of the Hudson's Bay Company at Fort Vancouver fr ...
, a Hudson's Bay Company (HBC) official, was one of the major contributors to the founding of the town in 1829. McLoughlin attempted to persuade the British government (which still held sway over the area) to allow American settlers to live on the land, and provided significant help to American colonization of the area, all against the HBC's orders. Oregon City prospered because of the
paper mill A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags, and other ingredients. Prior to the invention and adoption of the Fourdrinier machine and other types of paper machine that use an endless belt ...
s that were run by the water power of Willamette Falls, but the falls formed an impassable barrier to river navigation. Linn City (originally Robins Nest) was established across the Willamette from Oregon City. After Portland was incorporated in 1851, quickly growing into Oregon's largest city, Oregon City gradually lost its importance as the economic and political center of the Willamette Valley. Beginning in the 1850s,
steamboat A steamboat is a boat that is marine propulsion, propelled primarily by marine steam engine, steam power, typically driving propellers or Paddle steamer, paddlewheels. Steamboats sometimes use the ship prefix, prefix designation SS, S.S. or S/S ...
s began to ply the Willamette, despite the fact that they could not pass Willamette Falls. As a result, navigation on the Willamette River was divided into two stretches: the lower stretch from Portland to Oregon City—which allowed connection with the rest of the Columbia River system—and the upper reach, which encompassed most of the Willamette's length. Any boats whose owners found it absolutely necessary to get past the falls had to be
portage Portage or portaging (Canada: ; ) is the practice of carrying water craft or cargo over land, either around an obstacle in a river, or between two bodies of water. A path where items are regularly carried between bodies of water is also called a ...
d. This led to competition for business among steam portage companies. In 1873, the construction of the
Willamette Falls Locks The Willamette Falls Locks are a lock system on the Willamette River in the U.S. state of Oregon. Opened in 1873 and closed since 2011, they allowed boat traffic on the Willamette to navigate beyond Willamette Falls and the T.W. Sullivan Dam ...
bypassed the falls and allowed easy navigation between the upper and lower river. Each lock chamber measured long and wide, and the canal was originally operated manually before it switched to electrical power. Usage of the locks peaked in the 1940s, and by the early 21st century, the lock system was little used. Since 2011, the Willamette Falls Locks have been inactive. As commerce and industry flourished on the lower river, most of the original settlers acquired farms in the upper Willamette Valley. By the late 1850s, farmers had begun to grow crops on most of the available fertile land. The settlers increasingly encroached on Native American lands. Skirmishes between natives and settlers in the Umpqua and Rogue River (Oregon), Rogue valleys to the southwest of the Willamette River led the Government of Oregon, Oregon state government to remove the natives by military force. They were first led off their traditional lands to the Willamette Valley, but soon were marched to the Coast Indian Reservation. In 1855, Joel Palmer, an Oregon legislator, negotiated a treaty with the Willamette Valley tribes, who, although unhappy with the treaty, ceded their lands to non-natives. The natives were then relocated by the government to a part of the Coast Reservation that later became the Grande Ronde Reservation. Between 1879 and 1885, the Willamette River was charted by Cleveland S. Rockwell, a topographical engineer and cartographer for the U.S. National Geodetic Survey, U.S. Coast and Geodetic Survey. Rockwell surveyed the lower Willamette from the foot of Ross Island through Portland to the Columbia River and then downstream on the Columbia to Bachelor Island (Washington), Bachelor Island. Rockwell's survey was extremely detailed, including 17,782 hydrographic soundings. His work helped open the port of Portland to commerce. In the second half of the 19th century, the United States Army Corps of Engineers, USACE dredged channels and built locks and levees in the Willamette's watershed. Although products such as lumber were often transported on an existing network of railroads in Oregon, these advances in navigation helped businesses deliver more goods to Portland, feeding the city's growing economy. Trade goods from the Columbia basin north of Portland could also be transported southward on the Willamette due to the deeper channels made at the Willamette's mouth.


20th and 21st centuries

By the early 20th century, major river-control projects had begun to take place. Levees were constructed along the river in most urban areas, and Portland built concrete walls to protect its downtown sector. In the following decades, many large dams were built on Cascade Range tributaries of the Willamette. The Army Corps of Engineers operates 13 such dams, which affect flows from about 40 percent of the basin. Most of them do not have fish ladders. With development in and near the river came increased pollution. By the late 1930s, efforts to stem the pollution led to formation of a state sanitary board to oversee modest cleanup efforts. In the 1960s, Oregon Governor Tom McCall led a push for stronger pollution controls on the Willamette. In this, he was encouraged by Robert W. Straub, Robert (Bob) Straub—the state treasurer and future Oregon governor (1975)—who first proposed a Willamette Greenway program during his 1966 gubernatorial campaign against McCall. The Oregon State Legislature established the program in 1967. Through it, state and local governments cooperated in creating or improving a system of parks, trails, and wildlife refuges along the river. In 1998, the Willamette became one of 14 rivers designated an American Heritage River by U.S. President Bill Clinton. By 2007 the Greenway had grown to include more than 170 separate land parcels, including 10 state parks. Public uses of the river and land along its shores include camping, swimming, fishing, boating, hiking, bicycling, and wildlife viewing. In 2008, government agencies and the non-profit Willamette Riverkeeper organization designated the full length of the river as the Willamette River Water Trail. Four years later, the National Park Service added the Willamette water trail—expanded to to include some of the major tributaries—to its list of National Recreation Trail, national water trails. The water trail system is meant to protect and restore waterways in the United States and enhance recreation on and near them. A 1991 agreement between the City of Portland and the State of Oregon to dramatically reduce combined sewer overflows (CSOs) led to Portland's West Side CSO Tunnel, Big Pipe Project. The project, part of a related series of Portland CSO projects completed in late 2011 at a cost of $1.44 billion, separates the city's sanitary sewer lines from storm-water inputs that sometimes overwhelmed the combined system during heavy rains. When that occurred, some of the raw sewage in the system flowed into the river instead of into the city's wastewater treatment plant. The Big Pipe project and related work reduces CSO volume on the lower river by about 94 percent. In June 2014, Dean Hall became the first person to swim the entire length of the Willamette River. He swam from Eugene to the river mouth in 25 days.


Dams and bridges


Dams

There are more than 20 major dams on the Willamette's tributaries, as well as a complex series of levees, dikes, and channels to control the river's flow. The only dam on the Willamette's main stem is the Willamette Falls Dam, a low weir-type structure at Willamette Falls that diverts water into the headraces of the adjacent mills and a power plant. The Willamette Falls Locks, locks at Willamette Falls were completed in 1873. Elsewhere on the main stem, numerous minor flow-regulation structures force the river into a narrower and deeper channel to facilitate navigation and flood control. The dams on the Willamette's major tributaries are primarily large flood-control, water-storage, and power-generating dams. Thirteen of these dams were built from the 1940s through the 1960s and are operated by the United States Army Corps of Engineers (USACE). Of those 13, 11 produce hydropower. Flood-control dams operated by the USACE are estimated to hold up to 27 percent of the Willamette's runoff. They are used to regulate river flows so as to cut peaks off floods and increase low flows in late summer and autumn, and to divert water into deeper, narrower channels to prevent flooding. A relatively small of amount of the water stored in the reservoirs is used for irrigation. Cougar Dam on the South Fork McKenzie River and Detroit Dam on the North Santiam River are the two tallest dams in the Willamette River basin. Detroit Dam is high and stores of water. Lookout Point Dam on the
Middle Fork Willamette River The Middle Fork Willamette River is one of several forks that unite to form the Willamette River in the western part of the U.S. state of Oregon. It is approximately long, draining an area of the Cascade Range southeast of Eugene, which is at ...
, forming Lookout Point Lake, has the largest water storage capacity, at . The other 11 dams are Big Cliff Dam, Big Cliff on the North Santiam River; Green Peter Dam, Green Peter and Foster Dam, Foster on the Santiam River; Cougar on the South Fork McKenzie River; Blue River Reservoir, Blue River on the Blue River (Oregon), Blue River; Fern Ridge Reservoir, Fern Ridge on the Long Tom River; Hills Creek Dam, Hills Creek and Dexter Reservoir, Dexter on the Middle Fork Willamette River; Fall Creek Lake, Fall Creek on Fall Creek (Middle Fork Willamette River), Fall Creek; Cottage Grove Dam, Cottage Grove on the Coast Fork Willamette River, and Dorena Reservoir, Dorena on the Row River. Due to these tall dams, Chinook salmon and steelhead are blocked from roughly half of their historic habitat and spawn (biology), spawning grounds on the Willamette's major tributaries. Unable to live and reproduce as they once did, they have been "brought to the brink of extinction". Endangered species listings and a subsequent lawsuit by Willamette Riverkeeper led to a plan to improve fish passage and other actions to help native fish recover in 2008. Since then, work has proceeded slowly, and the Corps of Engineers, citing engineering difficulties and cost, may not meet the original agreed-upon deadline of 2023 for a system of effective remedies. Other major dams in the Willamette watershed are owned by other interests; for example, several hydroelectric facilities on the Clackamas River are owned by Portland General Electric. These include the River Mill Hydroelectric Project, the Oak Grove Hydroelectric Project, Oak Grove project, and the dam at Timothy Lake.


Bridges

The 50 or so List of crossings of the Willamette River, crossings of the Willamette River include many historic structures, such as the Van Buren Street Bridge, a swing bridge. Built in 1913, it carries Oregon Route 34 (Corvallis–Lebanon Highway) over the river upstream of RM 131 (RK 211) in Corvallis. The machinery to operate the swing span was removed in the 1950s. The Oregon City Bridge, built in 1922, replaced a Suspension bridge, suspension span constructed at the site in 1888. It carries Oregon Route 43 over the river at about RM 26 (RK 42) between Oregon City and West Linn. The Ross Island Bridge carries U.S. Route 26 in Oregon, U.S. Route 26 (Mount Hood Highway) over the river at RM 14 (RK 23). It is one of 10 highway bridges crossing the river in Portland. The bridge is the only Cantilever bridge, cantilevered deck truss in Oregon. Tilikum Crossing is a cable-stayed bridge that carries public transit, bicycles, and pedestrians, but no cars or trucks, over the river. It opened for general use on September 12, 2015, becoming the first new bridge built across the river in the Portland metropolitan area since 1973. Further downstream is the oldest remaining highway structure over the Willamette, the Hawthorne Bridge, built in 1910. It is the oldest vertical-lift bridge in operation in the United States and the oldest highway bridge in Portland. It is also the busiest bicycle and Transportation in Portland, Oregon, transit bridge in Oregon, with over 8,000 cyclists and 800 TriMet buses (carrying about 17,400 riders) daily. Another historic structure, the Steel Bridge, further downstream, was "the largest telescoping bridge in the world at the time of its opening" in 1912.Smith, ''et al.'', p. 208 It carries trains on its lower deck, MAX Light Rail, MAX (Metropolitan Area Express) light-rail trains and motorized vehicles on its upper deck, and foot and bicycle traffic on a cantilevered walkway attached to the lower deck. When small ships must pass under the bridge, its double vertical-lift span can raise a lower railway deck without disturbing traffic on the upper deck. Operators can raise both decks as high as above the water. The Steel Bridge is "believed to be the world's only double-lift span that can raise its lower deck independently of the upper deck." The Broadway Bridge (Portland, Oregon), Broadway Bridge, slightly downstream of the Steel Bridge, was the world's longest double-leaf Bascule bridge, bascule drawbridge at the time of its construction in 1913.Smith, ''et al.'', p. 116 Further downstream, the St. Johns Bridge, a steel suspension bridge built in 1931, replaced the last of the Willamette River ferry, ferries in Portland.Smith, ''et al.'', p. 113 At about RM 6 (RK 10), it carries the Special routes of U.S. Route 30#Portland bypass, U.S. Route 30 Bypass. The bridge has two Gothic architecture, Gothic towers supporting the span. The adjacent park and neighborhood of Cathedral Park, Portland, Oregon, Cathedral Park are named after the Gothic Cathedral-like appearance of the bridge towers. It is the tallest bridge in Portland, with tall towers and a navigational clearance.


Flooding

Due to the volume and seasonality of precipitation in western Oregon, the Willamette River has often flooded. Heavy rains and mountain snows are common in winter, and snowpack in the Cascade Range can rapidly melt during warmer winter storms. The greatest Willamette River flood in recorded history began in 1861, well before the construction of dams in the watershed. Rainstorms and warm temperatures in December 1861 combined with a well-above-average snowpack in the Cascades created the largest Willamette River flood in recorded history. An observer of the flood wrote, "The whole Willamette valley was a sheet of water". From Eugene to Portland, thousands of acres of farmland were washed away, and many towns in the valley were damaged or destroyed. The "Great Flood of 1862, Great Flood", as it is sometimes called, was massively destructive to human development because most of that development was located on the river's floodplain, which provided rich soils and ready access to water transportation. The 1861 flood peaked at —more than the Mississippi River usually discharges in the 21st century—and inundated some of land. This flood destroyed the town of Linn City. When the flood ended on December 14, only three homes remained standing in Linn City. No one died in the Linn City flood, but the destruction was too significant for the town to recover, and it was abandoned. Today the city of West Linn stands about where Linn City once was. Significant flooding recurred in the winter of early 1890, when the river rapidly rose and crested. Portland's main street was completely submerged, communication over the Cascades was cut off, and many rail lines were forced to shut down. Another major flood occurred on the Willamette in 1894, and although it too caused much damage, it was not as large as that of 1861. Throughout the 1940s the Willamette continued to flood its valley. It washed out five bridges in Lane County in December 1942, caused seven deaths in Portland and evacuations in Eugene in January 1943, flooded Corvallis in November 1946, contributed to the destruction of Vanport City, Oregon, Vanport City and the death of about 15 of its residents in May 1948, and nearly flooded parts of Salem in December 1948. Although the Willamette was, by the mid-20th century, heavily engineered and controlled by a complex system of dams, channels, and barriers, it experienced severe floods through the end of the century. Storms caused a Christmas flood of 1964, major flood that swelled the Willamette and other rivers in the Pacific Northwest from December 1964 through January 1965, submerging nearly of land. Before dawn on December 21, 1964, the Willamette reached , which was higher than the seawall on its banks in Portland. By this time, about 15 people had died as a result of the flooding, and about 8,000 had been forced to evacuate their homes. On December 24, 1964, President Lyndon B. Johnson ordered federal aid for the flooded areas, as the Willamette continued to rise. In the next couple of days, the river receded, but on December 27, it was at , which was still nearly above the flood stage. The river continued to pose flood threats through January 1965, and more stormy weather occurred along the Pacific Coast. In February 1996, heavy warm rains driven by a subtropical jet stream fell on a deep snowpack in the Willamette watershed. These conditions, similar to those that caused the 1861 flood, caused Willamette Valley Flood of 1996, some of the costliest flooding in the river's recorded history. An Associated Press journalist reported, "The river crested at one town after another—at Corvallis 3½ feet above flood stage, Oregon City 18 feet above, Portland 10.5 feet above—much like a meal moving through a boa constrictor." The flood was serious enough to interrupt the progress of Oregon's growing economy, but the inundated acreage was smaller than in 1964—only about . About 450 concrete flood-protection walls in Portland that had been constructed during the February flood, each weighing about , were removed in April 1996. In October, they were replaced by a larger steel wall that cost the city about $300,000. The new wall had removable steel plates designed to better prevent future flooding.


Pollution

Since as early as 1869, with the introduction of a federally funded "snag puller" designed to keep the waterway clear, human habitation has affected the ecology of the river basin. Domestic and industrial waste from the cities built up along the river "essentially [turned] the main-stem river into an open sewer by the 1920s." The construction of large federal dams on the Willamette's tributaries between 1941 and 1969 damaged the spawning grounds for spring Chinook salmon and steelhead. A 1927 City Club of Portland report labeled the waterway "filthy and ugly" and identified the City of Portland as the worst offender. The Oregon Anti-Stream Pollution League brought a pollution-abatement measure before the 39th Oregon Legislative Assembly in 1937. The bill passed, but Governor Charles Martin (Oregon politician), Charles Martin vetoed it. The Izaak Walton League and the Oregon affiliate of the National Wildlife Federation countered the governor's veto with a ballot initiative, which passed in November 1938. Governor Tom McCall, shortly after he was elected in 1966, ordered water quality tests on the Willamette, conducted his own research on the water quality, and became head of the Oregon State Sanitary Authority. McCall learned that the river was heavily polluted in Portland. In a television documentary, ''Pollution in Paradise'', he said, "The Willamette River was actually cleaner when the Oregon Sanitary Authority was created in 1938 than it was in 1962."Williams, p. 131 He then discouraged tourism in the state and made it harder for companies to qualify for a permit to operate near the river. He also regulated how much those companies could pollute and closed plants that did not meet state pollution standards.Williams, p. 132 Despite earlier cleanup efforts, state studies in the 1990s identified a wide variety of pollutants in the river bottom, including toxic heavy metal, heavy metals, polychlorinated biphenyls (PCBs), and pesticides along the lower of the river, in Portland. As a result, this section of the river was designated a Superfund site in 2000, involving the United States Environmental Protection Agency, U.S. Environmental Protection Agency (EPA) in cleanup of the river bottom. The area to be addressed stretches from the Fremont Bridge almost to the Columbia – spanning nearly 11 river miles. Reducing risk from the pollutants in this stretch will involve removing contaminated sediment from the river bottom and efforts to contain contaminated sediment by placing clean sediment on top (known as "capping"). Pollution has been exacerbated by combined sewer overflows, which the city has greatly reduced through its West Side CSO Tunnel, Big Pipe Project. Farther upstream, the pressing environmental issues have mainly been variations in pH and dissolved oxygen. The Willamette is nevertheless clean enough to be used by cities such as Corvallis and Wilsonville, Oregon, Wilsonville for drinking water. Since pollution concerns are primarily along the lower river, the Willamette in general scores relatively high on the Oregon Water Quality Index (OWQI), which is compiled by the Oregon Department of Environmental Quality (DEQ). The DEQ considers index scores of less than 60 to be very poor; the other categories are 60–79 (poor); 80–84 (fair); 85–89 (good), and 90–100 (excellent). The Willamette River's water quality is rated excellent near the source, though it gradually declines to fair near the mouth. Between 1998 and 2007, the average score for the upper Willamette at Springfield (RM 185, RK 298) was 93. At Salem (RM 84, RK 135), the score was 89, and good scores continued down to the Hawthorne Bridge in Portland (RM 13, RK 21) at 85. Scores were in the "fair" category farther downstream; the least favorable reading was 81 at the Swan Island Channel midpoint (RM 0.5, RK 0.8). By comparison, sites on the Winchuck River, the Clackamas, and the North Santiam all scored 95, and a site at a pump station on Klamath Strait Drain between Upper Klamath Lake and Lower Klamath Lake recorded the lowest score in Oregon at 19.Oregon Water Quality Index, pp. 7–10


Flora and fauna

Over the past 150 years, a significant change for the Willamette River has been the loss of its floodplain forests, which covered an estimated 89 percent of a band along each river bank in 1850. By 1990, only 37 percent of this zone was forested; the rest had been converted to farm fields or cleared for urban or suburban uses. The remaining forests close to the river include stands of Populus trichocarpa, black cottonwood, Fraxinus latifolia, Oregon ash, willow, and Acer macrophyllum, bigleaf maple.Benke, ''et al.'', p. 619 The central valley—a former perennial grass prairie interspersed with oak, Douglas fir, Pinus ponderosa, ponderosa pine, and other trees—is devoted almost entirely to farming. Douglas fir, Tsuga heterophylla, western hemlock, and Thuja plicata, western red cedar dominate the forest on the Coast Range side of the basin. Forests to the east in the Cascade Range are predominantly Douglas fir, Abies amabilis, Pacific silver fir, western hemlock, and western red cedar. Fish in the Willamette basin include 31 native species, among them Coastal cutthroat trout, cutthroat, Bull trout, bull, and rainbow trout, several species of
salmon Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus '' Salmo'') and North Pacific (genus '' Onco ...
, Catostomidae, sucker, minnow, sculpin, and lamprey, as well as sturgeon, stickleback, and others. Among the 29 non-native species in the basin, there are Brook trout, brook, Brown trout, brown, and lake trout, Largemouth bass, largemouth and Smallmouth bass, smallmouth bass, walleye, carp, bluegill, and others. In addition to fish, the basin supports 18 species of amphibians, such as the Pacific giant salamander. Beaver and North American river otter, river otter are among 69 mammal species living in the watershed, also frequented by 154 bird species, such as the American dipper, osprey, and harlequin duck. Garter snakes are among the 15 species of reptiles found in the basin. Species diversity is greatest along the lower river and its tributaries. Threatened, endangered, or sensitive species include spring Chinook salmon, winter steelhead, chum salmon, Coho salmon and Oregonichthys, Oregon chub.Benke, ''et al.'', pp. 620–21 In the central valley, several projects have been done to restore and protect wetlands in order to provide habitat for bald eagles, Fender's blue butterfly (of which 6,000 remain), Oregon chub, Lomatium bradshawii, Bradshaw's desert parsley, a variety of Erigeron decumbens, Willamette fleabane, and Lupinus sulphureus, Kincaid's lupine. In the early 21st century, osprey populations are increasing along the river, possibly because of a ban on the pesticide DDT and on the birds' ability to use power poles for nesting.Benke, ''et al.'', p. 621 Beaver populations, presumed to be much lower than historic levels, are increasing throughout the basin.


See also

* List of crossings of the Willamette River * List of longest streams of Oregon * List of rivers of Oregon * Steamboats of the Willamette River


References


Works cited

* �
"Oregon Water Quality Index Summary Report, Water Years 1998–2007"
(PDF), May 2008. Oregon Department of Environmental Quality. Retrieved April 10, 2011. * Benke, Arthur C., ed., and Cushing, Colbert E., ed.; Stanford, Jack A.; Gregory, Stanley V.; Hauer, Richard F.; Snyder, Eric B. (2005). "Chapter 13: Columbia River Basin" in ''Rivers of North America''. Burlington, Massachusetts: Elsevier Academic Press. . . * Bright, William (2004). ''Native American Placenames of the United States''. Norman, Oklahoma: University of Oklahoma Press. . . * Campbell, Lyle (1997). ''American Indian Languages''. New York, New York: Oxford University Press. . . * Deur, Douglas; Turner, Nancy J. (2005). ''Keeping it Living: Traditions of Plant Use and Cultivation on the Northwest Coast of North America''. Seattle: University of Washington Press. . . * Edwards, G. Thomas; Schwantes, Carlos A. (1986). ''Experiences in a Promised Land: Essays in Pacific Northwest History''. Seattle: University of Washington Press. . . * Engeman, Richard H. (2009). ''The Oregon Companion: A Historical Gazetteer of the Useful, the Curious, and the Arcane''. Portland, Oregon: Timber Press. . . * Gulick, Bill (2004). ''Steamboats on Northwest Rivers''. Caldwell, Idaho: Caxton Press. . . * Holman, Frederick Van Voorhies (1907). ''Dr. John McLoughlin, the Father of Oregon''. Cleveland, Ohio: A. H. Clark Company. . . * Laenen, Antonius; Dunnette, David A. (1997). ''River Quality: Dynamics and Restoration''. Boca Raton, Florida: CRC Press. . . * Loy, Willam G.; Allan, Stuart Allan; Buckley, Aileen R.; Meecham, James E. (2001) [1976]. ''Atlas of Oregon'' (2nd ed.). Eugene, Oregon: University of Oregon Press. . . * Mackie, Richard Somerset (1997). ''Trading Beyond the Mountains: the British Fur Trade on the Pacific, 1793–1843''. Vancouver: UBC Press. . . * McArthur, Lewis A.; McArthur, Lewis L. (2003) [1928]. ''Oregon Geographic Names'' (7th ed.). Portland, Oregon: Oregon Historical Society Press. . . * * Orr, Elizabeth L.; Orr, William N. (1999). ''Geology of Oregon'' (5th ed.). Dubuque, Iowa: Kendall/Hunt Publishing Company. . . * Orr, Elizabeth L.; Orr, William N. (2012). ''Oregon Geology'' (6th ed.). Corvallis, Oregon: Oregon State University Press. . . * * Samson, Karl (2010). ''Frommer's Oregon''. Hoboken, New Jersey: Wiley-Blackwell. . . * Smith, Dwight A.; James B. Norman, Norman, James B.; Dykman, Pieter T. (1989) [1986]. ''Historic Highway Bridges of Oregon'' (2nd ed.). Portland, Oregon: Oregon Historical Society Press. . . * Snipp, C. Matthew (1989). ''American Indians: The First of This Land''. New York, New York: Russell Sage Foundation. . . * Stenzel, Franz (1972). ''Cleveland Rockwell: Scientist and Artist, 1837–1907''. Portland, Oregon: Oregon Historical Society. . . * * * * * * * Wortman, Sharon Wood; Wortman, Ed.; Norman, James B. (2006). ''The Portland Bridge Book'' (3rd ed.). Portland, Oregon: Urban Adventure Press. . .


External links


City of Portland River Renaissance Strategy

Guiding the Willamette
[web archive], ''Think Out Loud'' radio program on Oregon Public Broadcasting, April 1, 2009
Historic river channels between Albany and Monmouth
nbsp;– Oregon Department of Geology and Mineral Industries lidar poster
Portland Harbor DEQ cleanup
nbsp;– Oregon State Department of Environmental Quality
Willamette Riverkeeper
nbsp;– Non-profit environmental organization {{authority control Willamette River, American Heritage Rivers Ferries of Oregon Rivers of Benton County, Oregon Rivers of Clackamas County, Oregon Rivers of Lane County, Oregon Rivers of Linn County, Oregon Rivers of Marion County, Oregon Rivers of Multnomah County, Oregon Rivers of Washington County, Oregon Rivers of Yamhill County, Oregon Rivers of Columbia County, Oregon Rivers of Oregon Tributaries of the Columbia River Willamette Valley