Promoting stewardship of Willamette River resources.

Click here to access the WMC Documents page.

Click here to access the State of the Willamette information.

Click here to access our Story Map of Willamette Activities.

Click here to view the Benton SWCD 2014-2015 Annual Report with a focus on the Willamette!

Who We Are

The Willamette Mainstem Cooperative is a collaboration of landowners, organizations, and volunteers working together to promote, facilitate, and foster long-term stewardship of Willamette River resources with a focus on the Corvallis to Albany river reach.

What We Do

1. COLLABORATE with stakeholders to raise awareness about native and invasive plants along the river and address weed control priorities.

We provide information and opportunities for people to work together to achieve shared goals for river health.

  • Community Events – weed pulls, stakeholder meetings, workshops, and presentations

    Above: Workshop attendees learn about native and invasive aquatic plant impacts and efforts along the Willamette River to control noxious aquatic weeds. See here for upcoming Love Your River Events!

  • Outreach Materials – aquatic weed guide, webpage, and landowner reports of survey findings
  • Partners


2. PLAN for the short and long-term management of aquatic and terrestrial invasives and PRIORITIZE species focus based on invasive plant population size and habitat impacts.

We surveyed close to 3,000 acres of riparian and aquatic habitats between Corvallis and Albany to identify high quality habitats and map populations of priority invasive plants.


Species Found in Small Patches Species Abundant, Yet Controllable High Quality Habitat
Japanese knotweed English ivy ~15% or 385 acres of area surveyed
Purple loosestrife False brome Mostly on public land
Scotch broom Water primrose species Mostly in relatively undisturbed sites
Spotted knapweed Old man’s beard Patches average six acres

3. PROTECT high quality habitat through control and containment of target invasive plants.

We apply integrated techniques to control priority invasive plants on the Willamette River. Efforts have spanned from volunteer weed pulls to technical control methods implemented by contracted and licensed experts. Pictures below depict volunteers and contractors removing invasive plants along the Willamette River.

Top left: Volunteers pull invasive water primrose (Ludwigia hexapetala). Top right: Licensed contractor treats invasive water primrose on Willamette River slough. Bottom left: Volunteers remove invasive English ivy to protect native riparian trees at Takena Landing Park. Event done in coordination with Benton County CWMA. Bottom right: Goats graze invasive plants in public park in the river (see blog on grazing project);

4. MONITOR post-treatment site changes for impacts, success, and future management needs.


Top: Photo monitoring Uruguayan primrose-willow (Ludwigia hexapetala) in open marsh habitat on the Willamette River (pre-treatment on left, post-treatment on right). Bottom left: U.S. Geological Survey conducts pre- and post-treatment water quality monitoring. Bottom right: Portland State University conducts vegetation surveys to assess aquatic plant community conditions at treated site.

5. PLANT and encourage natural recruitment of appropriate native aquatic and terrestrial plant species following invasive weed control treatments.

Top left: Native wapato (Sagittaria latifolia) tuber collection at local farmer/wetland restoration practitioner’s property. Top right: Two wapato tubers up close. Bottom left: Wapato tubers being planted at Willamette River slough after several years of invasive water primrose control treatments at site. Bottom right: Wapato flower and leaves. Blog post here about tuber collection.


This project would not have been possible without the help of the following organizations:


Contact Information

If you have any questions please contact Michael Ahr via email or call (541) 753-7208 ext. 202.