The U.S. Army Corps of Engineers (Corps) is preparing a Programmatic Environmental Impact Statement (PEIS) to assess the effects of the continued operations and maintenance of the Willamette Valley System (WVS). The Corps requested that the Independent Scientific Advisory Board (ISAB) review a set of models for their scientific strengths and weaknesses in assessing potential responses of ESA-listed spring Chinook salmon and winter steelhead to alternative management actions. The ISAB focused on the fish response models used for the Draft Programmatic Environmental Impact Statement (DPEIS or Draft EIS) for the Willamette Valley System and did not evaluate the merits of the management alternatives or the Corps’ decisions on these alternatives.
Four independent modeling teams developed or updated existing models for spring Chinook salmon and steelhead to assess responses to the management alternatives. This ISAB report describes individual strengths and weaknesses of the following models and also provides suggestions for their collective use.
- University of British Columbia Integrated Passage Assessment Models (UBC models)
- NOAA Upper Willamette River Life Cycle Models (NOAA models)
- ICF Ecosystem Diagnosis and Treatment Models (EDT models)
- Oregon State University Flow and Fish Survival Models (OSU models)
The ISAB commends the Corps and the modeling groups for developing an innovative multi-model approach for assessing spring Chinook salmon and winter steelhead responses to management alternatives as part of preparing the EIS for the Willamette Valley System. Multiple models can offer an approach for more accurately quantifying uncertainties and lead to more informed decision-making.
The ISAB determined that the models for spring Chinook salmon and steelhead developed by the four modeling groups include the major processes influencing spring Chinook salmon and steelhead life histories and are scientifically sound. The models have some important differences, emphases, or areas of overlap. The collection of supporting and primary models provides valuable information for assessing potential responses of spring Chinook salmon and steelhead to the operational alternatives. The ISAB identified several crosscutting issues that apply across most, if not all, of the primary models, including calibration and validation, representation of mortality, scale of predictions, climate change, and future use of the models.
In summary, the four primary models are scientifically sound, and the multi-model approach used by the Corps to date is an excellent approach for assessing alternatives in the EIS process for the WVS. Going forward, the strengths and weaknesses of the four models and how the models are combined in the multiple model analysis should be recognized in assessing EIS alternatives. In addition to any further use for the EIS, the multiple models can be very useful for the Biological Assessment, implementation decisions related to the project, monitoring design, and adaptive management.
Note: Report was updated May 22, 2023. See page 2 of the PDF for details.