This summary report is a key step in the process of establishing ecological flow requirements for the Middle and Coast Forks of the Willamette River. The report synthesizes background information on the flow needs for key ecosystems, communities and exemplar species of the Middle Fork, Coast Fork and upper mainstem Willamette River.
The summary report provides the information basis for a Flow Recommendation Workshop which will develop ecosystem-based flows in the lower Middle and Coast Forks as well as the mainstem Willamette River immediately downstream of their confluence. The ultimate goals of this workshop will be to provide the U.S. Army Corps of Engineers (USACE) with recommendations for new flow paradigms incorporating changes to timing, magnitude and duration of dam discharges. The Nature Conservancy and USACE have categorized four major environmental flow components to be addressed in the Summary Report and during the Workshop:
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low flows (seasonal, annual and extreme low flows);
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high flow pulses (up to bankfull discharge);
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small floods (overbank flows, approximately 2- to 10-year return period);
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large floods (floodplain maintenance flows, > approximately 10-year return period).