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Invasive species, Aquatic ecology -- Research -- United States, Environmental monitoring -- Pacific Northwest


The Clackamas River Hydroelectric Project No. 2195 (Project) is located on the Oak Grove Fork of the Clackamas River and the mainstem of the Clackamas River in Clackamas County, Oregon. Reservoirs included in the Project include Timothy Lake, Lake Harriet, North Fork Reservoir, Faraday Lake, and Estacada Lake. The operator of the Project, Portland General Electric (PGE), was issued a license on December 21, 2010 by the Federal Energy Regulatory Commission (FERC) for continued operations and maintenance. The Final Environmental Impact Statement (FEIS) for the license noted that regular surveys for invasive aquatic weed species would be conducted as part of the Project’s Vegetation Management Plan.

The term “aquatic weed” is used here to refer to any non-native aquatic plant species. Information from repeated aquatic surveys will help determine native species distributions and the need for treatment of problematic aquatic weed species, particularly hydrilla (Hydrilla verticillata), Brazilian elodea (Egeria densa), and Eurasian watermilfoil (Myriophyllum spicatum).

Surveys conducted for PGE by Portland State University (PSU) in Timothy Lake, Lake Harriet, and North Fork Reservoir in 2011 did not locate any problematic submerged or floating leaved aquatic weed species. Earlier surveys of Timothy Lake, and Timothy Lake and Lake Harriet, also indicated the reservoirs were free of aquatic weeds. Heaton et al. (1996) noted that the native species Bidens beckii was present and had the potential to become weedy, however, this species was not found during the 2004 or 2011 surveys.

This report covers the results of follow up aquatic vegetation surveys conducted in Lake Harriet, Timothy Lake, and North Fork Reservoir between August 14 and August 21, 2014, as well as new surveys of Faraday Lake and Estacada Lake. Shoreline surveys for emergent invasive species such as yellow flag iris (Iris pseudacorus) and purple loosestrife (Lythrum salicaria) were included in surveys for the first time.


This is the final report. Prepared for: Portland General Electric, Clackamas River Hydroelectric Project

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