Importance of the lower Willamette River

The Willamette River provides key habitat for a host of wildlife and fish species. However, the natural environment of the river has been heavily altered by development of hydropower / flood control dams, channelization and water pollution. As a result of development the river has been channelized, wetlands drained and riparian forests cleared to provide farm land and to allow navigation of the river. However, the river, its tributaries and floodplain continue to provide important habitats for many species and life stages and are significant contributors to the health of the Columbia Basin ecosystem and salmonid fishes.

Habitat changes have been especially significant in the lower Willamette, defined as the watershed downstream of Willamette Falls at River Mile 26. Environmental conditions in the lower Willamette have been degraded by both local and basin-scale factors. Most visible is the urbanization of the Portland metropolitan area. The channel has been confined and dredged to promote navigation, floodplains have been isolated and drained to allow development and water quality has been degraded by industrialization and urban runoff. Tributary streams such as Clear, Deep, Johnson and Tryon creeks have been degraded by similar activities. The Clackamas River has been cleaved into two isolated sections by hydropower dams. Tributaries below the Clackamas dams have been degraded by urbanization and agriculture while upper basin areas have been degraded by road construction and logging.

In addition to local factors that have impacted conditions, the lower Willamette is also the recipient of environmental problems resulting from human activities throughout the upper Willamette basin. Water passing Willamette Falls is degraded by pollution, high temperature and increased sediment resulting from human actions in the river and streams above the falls. The modified hydrograph and increased summer water temperatures resulting from flood control and hydropower dams in upper basin tributaries have impacted conditions throughout the Willamette River. These upper basin problems affect fish abundance in the lower river and the potential effectiveness of restoration actions in the lower river.

Despite these problems, the lower Willamette River remains key habitat for Columbia River salmon and lamprey. The Willamette confluence has been identified as a key focus of restoration in the Willamette River Subbasin Plan. This area provides essential and critical habitat for ESA listed salmon including Willamette River Chinook (Threatened), Willamette River steelhead (Threatened) and lower Columbia River coho (Threatened). Adult and juvenile lamprey move through the lower Willamette while the Clackamas and lower Willamette tributaries may support spawning and rearing for lamprey. The lower Willamette River provides important juvenile rearing habitat for Willamette River Chinook, steelhead and coho. The river and the Columbia Slough provide rearing habitat for downstream migrating salmon from upper Columbia River populations. The Willamette River, the Clackamas River and its tributaries and urban tributaries such as Johnson Creek, Tryon Creek and the Columbia Slough form a habitat complex that supports the one of only two currently viable naturally spawning coho population and has significant potential to support recovery of the lower Columbia River coho ESU.

Specific measures

The importance of the Willamette River to Columbia River salmon and lamprey points to the need to protect and restore habitat in the lower Willamette and its tributaries. While recent studies have demonstrated the value of the area to Willamette and Columbia River salmon, important questions remain that need to be addressed. The role of the Willamette in supporting lamprey is evident from the number of fish passing Willamette Falls, yet the biological requirements and limiting factors for lamprey have been little studied. Significant improvements to habitat conditions in the lower Willamette are feasible. Many of these are being supported and funded by the City of Portland, however, requests for additional support from Bonneville recognizes the basin scale contribution of the lower Willamette to Columbia Basin salmon and the non-local source of many habitat limitations.

Lower Willamette River

The lower Willamette River should be a focus area for the Council’s program because of its importance to the recovery of multiple Willamette and Columbia river salmon ESUs as well as one of the Columbia Basin’s strongest lamprey populations.

1. In conjunction with the City of Portland, Bonneville shall fund a study of the use of the lower Willamette River and its tributaries to the recovery of lower Columbia River coho, Willamette River Chinook and Willamette River steelhead. The study should build on previous work to address the following issues:

a. Use of the Columbia River slough by Willamette River and Columbia River salmonids

b. Identification and ranking of local and non-local factors contributing to currently identified conditions limiting salmon and lamprey in the lower Willamette River.

c. Extent of use of lower Willamette mainstem and tributaries by local and upper Willamette and Columbia river salmon populations including the use of tributaries as off-channel habitat.

2. In conjunction with the City of Portland, Bonneville shall fund an investigation of the opportunities and potential to improve conditions in the lower Willamette River as affected by local and non-local factors. The study should address the following issues:

a. Opportunities to increase connectivity within the lower Willamette River and tributaries

b. Opportunities to provide off channel and shallow water habitat in the lower Willamette River including enhancement to tributaries and sloughs as well as restoration or expansion of existing shallow water and secondary channel environments.

3. The Corps of Engineers shall conduct studies to investigate the potential to contribute to Willamette River temperature control through operation and design of tributary dams. These studies shall:

a. Synthesize existing information to summarize the impact of tributary dam operations on Willamette River temperatures

b. Identify the opportunities and potential to provide a more normative hydrograph through changed project operations or facility modifications of Willamette River tributary dams.


Given that the Willamette River presently supports the largest and potentially most viable lamprey population in the Columbia Basin, Bonneville should fund studies to address basic lamprey population biological and the effect of environmental conditions on the viability and restoration potential lamprey.

1. Bonneville shall fund a study of passage of lamprey at Willamette Falls and the opportunities to enhance lamprey passage at the falls. Bonneville should investigate the potential for cost sharing among public and private interests.

2. Bonneville shall fund studies to investigate the population structure of Willamette River lamprey and the geographic sources of current production.

3. Bonneville shall fund studies to investigate the basic life history of lamprey in Willamette River tributaries as well as studies of lamprey habitat preferences, limiting factors and potential restoration measures.