Ecosystem Response to the Removal of the Elwha River Dams

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Webinar Essentials:
Ecosystem Response to the Removal of the Elwha River Dams
George Pess, Ph.D., Program Manager, Watershed Program at the United States National Oceanic and Atmospheric Administration (NOAA) Northwest Fisheries Science Center (NWFSC)
Tuesday, December 6 2022

One ecosystem restoration technique that can have a large-scale effect is dam removal. This single action allows for the re-connection of ecosystem processes such as upstream and downstream organism movement, the rapid transformation from lentic to lotic conditions in former reservoirs, rapid shifts in community structure and food webs, and accelerated habitat creation through sediment deposition.

Worldwide stream and watershed restoration efforts cost billions annually. These projects are typically local-scale activities that do not have a measurable effect on ecosystem function or services. In this webinar, George will present the results from the largest dam removal ever undertaken, and the measurable ecosystem changes which include:

-The release and subsequent downstream transport of tens of millions of metric tons of sediment from former reservoirs and the transformation and rebuilding of estuarine and riverine habitats.

-The resumption of free passage for aquatic organisms and re-established anadromous fishes to areas that have been void of such species for 100 years, and the rapid increase in salmonid life history diversity.

-Short-term effects due to large changes in sediment supply which temporally resulted in reductions in Chinook salmon productivity.

-Increased marine-derived nutrients entering the food webs and altering the migration patterns and fecundity of an aquatic songbird.

George has worked in fisheries since 1989 (A.B. in Economics and Environmental Science, Bowdoin College 1987, an M.S. in Forest Science, Yale University 1992, and a Ph.D. in Aquatic and Fishery Sciences, University of Washington, 2009). His primary research interest has been the examination of natural and land-use effects on salmon habitat and salmon production and his current research includes the ecosystem response to the removal of the Elwha River dams. A program manager for the watershed program at the United States National Oceanic and Atmospheric Administration (NOAA) Northwest Fisheries Science Center (NWFSC), he is also an affiliate professor at the University of Washington School of Aquatic and Fishery Sciences.

The Joint Committee on Fisheries Engineering and Science hosts a free webinar series as part of its mission to engage scientists and engineers on topics related to fish passage. The Committee consists of members of the American Fisheries Society Bioengineering Section (AFS-BES) and the American Society of Civil Engineers Environmental and Water Resources Institute (ASCE-EWRI). It was established in January 2011 to foster communication between the two groups, provide opportunities for engineers and biologists to share relevant knowledge and learn from one another, and to collaborate on projects related to fish passage.

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