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Willamette River

Length: 187 miles
Basin area: approximately 11,400 square miles

The Willamette is a river in crisis. The river touches many Oregonians' lives and is worthy of renewed efforts to restore it.

Willamette Riverphoto by Vivian Johnson

The Willamette River is the 13th largest river by volume in the United States. The Willamette Basin is more than 11,000 square miles in area, and it is home to more than 70% of all Oregonians. The Willamette begins in the Cascade Mountains, and flows through Eugene, Corvallis, and Salem, before ending in Portland at its confluence with the Columbia River. The river's flow is modified by some 13 dams on its tributaries, 11 of which produce hydropower. The Willamette Valley has some of the richest farmland in the nation and produces about half of Oregon's yearly farm sales. Population in the Willamette Basin is expected to double to nearly 4.0 million by 2050.

A Closer Look

Over the past 80 years the Willamette River has been polluted by industry, agriculture, and cities. In the late 1960s Governor Tom McCall led a cleanup effort that reduced industrial pollution. The river is significantly cleaner today than it was then, but it still has a long way to go. In 2006 American Rivers listed the Willamette as the third most endangered river in the United States. Industries continue to discharge wastes into the river under authorized permits. Attention is being drawn to permits that allow “mixing zones” - areas where pollution is allowed to exceed water quality standards until it mixes with the receiving stream and becomes diluted. A six-mile stretch of the river in the Portland harbor is now a federal Superfund site. This area is highly polluted with toxins, heavy metals and other substances, and the cleanup will likely take a decade.

Human uses have dramatically altered land in the Willamette Basin from its natural state, removing forests, grasslands, prairies, and wetlands, and converting them to agricultural and urban uses, including nearly four miles of road for every square mile of land in the basin. The stream channel has been altered and confined by Army Corps of Engineers projects designed to control flooding, which has destroyed fish and wildlife habitat. Spring chinook and steelhead, the Willamette's native salmonids, are listed as threatened under the federal Endangered Species Act. The state advises against eating any species of resident fish due to mercury and PCB contamination. Resident fish include most fish except salmon, lamprey and sturgeon, which leave the river for the ocean during much of their lifespan.

Runoff from agricultural land and urban areas contributes more to the Willamette's pollution than industrial sources. There is a need to reduce pollution from agricultural runoff throughout the basin, and a portion of the Southern Willamette Valley is designated as a Groundwater Management Area due to nitrate contamination. Urban runoff is a particular problem in the Portland area because of the city's Combined Sewer Overflow (CSO) system. Parts of the city have an old sewer system where water that enters storm drains is mixed into the same pipe with raw sewage as it all makes its way to the treatment plant. When it rains, there is too much water for the pipe to hold and it overflows, sending raw sewage into the Willamette. The City of Portland is addressing this problem by investing in a “big pipe” project so overflows will occur much less frequently. But the pipe will still have limited capacity, so the City must continue to promote downspout disconnects and other techniques that keep rainwater from entering the sewer system.

DEQ has recently completed a Total Maximum Daily Load (TMDL) assessment for temperature, bacteria, and mercury in the Willamette Basin. The TMDL is an important step in the implementation of the Clean Water Act because it codifies how much pollution is too much for the river, and where the pollutants are coming from. The TMDL does not prescribe a specific plan for cleaning up the river. Instead, it includes general ideas and requires local government agencies to develop implementation plans by next year. The DEQ estimates it will take 20 years before the Willamette meets water quality standards for bacteria, 20 to 50 years to reduce instream temperatures to make them cold enough for endangered salmon, and 50 to 100 years to reduce mercury to low enough levels that resident fish are no longer hazardous to eat.

The Willamette River is more severely impacted by urban stormwater runoff than any other Oregon river because so much of the land in its basin is urbanized. When rainwater hits impervious surfaces such as streets, sidewalks, and roofs, it flows overland instead of soaking into the ground as it would in a natural area. Most stormwater systems were not designed with water quality in mind. They send untreated stormwater directly into streams or pump it underground at high volume and velocity, carrying all the pollutants picked up along the way. Common stormwater pollutants include eroded soil, oil, metals, bacteria, pesticides and fertilizers. Urban runoff can change stream flows, increase flooding, scour out stream banks and channels, and destroy fish habitat.

Today, builders are using new techniques to reduce impervious surface and filter stormwater before it ends up in our rivers. These “low impact development” techniques use soil and plants to filter and slow down rainwater, creating an urban system that functions more like a natural one. You can now find examples of pervious pavement, ecoroofs, raingardens, vegetated swales, and stormwater planters in cities around the state. They can be used in commercial and residential developments and on streets to change stormwater from a problem into an amenity and create attractive landscapes. Rainwater can also be harvested in rain barrels or cisterns and used for irrigation. Many of Oregon's local governments are leading the way in promoting low impact development and river-friendly cities. The Oregon Environmental Council is working to build upon these efforts to make sustainable stormwater management standard practice in cities and towns around the state.

Pervious Pavement

Water filters through the pervious asphalt installed on all the roads in Salem's Pringle Creek Community, reducing the streets' impact on the nearby creek. © Pringle Creek Community.

Curb Extension

Street runoff flows into these curb extensions on NE Siskiyou Street in Portland. They are landscaped with plants to filter pollutants, improve water quality, reduce stormwater flow, and look great. ©Environmental Services, City of Portland

Green Roof
The SeQuential Biofuels retail station, located just off Interstate 5 in Eugene, was built with a “living roof ” containing thousands of plants and five inches of soil to help to control rainwater runoff and cool theconvenience store during the summer. © SeQuential Biofuels.


Browse Oregon's other major rivers:

  1. Columbia
  2. Deschutes
  3. Grande Ronde
  4. John Day
  5. Malheur
  6. Owyhee
  7. Rogue
  8. Snake
  9. Umpqua


Pollutants in the Willamette River

Willamette River Data

Local Resources - Willamette River

Willamette Riverkeeper (Portland) | (503) 223-6418 |

Willamette Basin Explorer |

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