Presentation Title

Characterizing salt intrusion and habitat zones in the Snohomish River estuary using extensive field data and hydrodynamic modeling

Session Title

Session S-01A: Current Salish Sea Water Quality

Conference Track

Marine Water Quality

Conference Name

Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Start Date

30-4-2014 10:30 AM

End Date

30-4-2014 12:00 PM

Abstract

Tidal flooding is the primary driver of physical attributes (e.g., hydrology, elevation, channel morphology, and soil chemistry) that determine the biological characteristics of estuarine ecosystems (e.g., vegetation and animal assemblages), but many of the specific cause and effect relationships are not well established. Uncertainties concerning restoration response/effectiveness, habitat-biota relationships, and climate change impacts on estuarine ecosystems are often related to unquantified hydrological parameters. The Snohomish River estuary is the focus of numerous restoration projects; including 241 hectares of completed projects; 529 hectares of projects that are in process or have completed designs; 156 hectares of projects with 30-60% completed designs; and an additional 1,067 hectares of projects that are in the conceptual, feasibility, or preliminary design phase. To support restoration design and monitoring in the Snohomish River estuary, we synthesized data from multiple sources to improve our understanding of salt intrusion and habitat characteristics in the estuary. We used data collected from discrete surface water sampling, discrete water column profiling, continuous water sensor monitoring, and hydrodynamic modeling efforts to classify mixohaline habitats in the estuary; polyhaline (18 – 30 ppt), mesohaline (5 – 18 ppt), oligohaline (0.5 – 5 ppt), and freshwater (0 – 0.5 ppt). Previous descriptions of salt intrusion in the Snohomish River estuary suggested that salt intrusion was limited to areas downstream of the Steamboat Slough bifurcation and the Ebey/Union/Steamboat slough bifurcation/confluence complex at Otter Island. Our results indicate that salt intrusion is much more extensive in the Snohomish Estuary and that oligohaline habitat conditions can extend through the entire estuary complex to approximately 2.0 km upstream of the first primary bifurcation along the mainstem that forms upper Ebey Slough. Application of our mixohaline habitat classifications may improve spatial data for historical and current vegetation extents and we apply this analysis to completed and planned restoration projects within the estuary.

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Language

English

Format

application/pdf

Type

Text

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Apr 30th, 10:30 AM Apr 30th, 12:00 PM

Characterizing salt intrusion and habitat zones in the Snohomish River estuary using extensive field data and hydrodynamic modeling

Room 615-616-617

Tidal flooding is the primary driver of physical attributes (e.g., hydrology, elevation, channel morphology, and soil chemistry) that determine the biological characteristics of estuarine ecosystems (e.g., vegetation and animal assemblages), but many of the specific cause and effect relationships are not well established. Uncertainties concerning restoration response/effectiveness, habitat-biota relationships, and climate change impacts on estuarine ecosystems are often related to unquantified hydrological parameters. The Snohomish River estuary is the focus of numerous restoration projects; including 241 hectares of completed projects; 529 hectares of projects that are in process or have completed designs; 156 hectares of projects with 30-60% completed designs; and an additional 1,067 hectares of projects that are in the conceptual, feasibility, or preliminary design phase. To support restoration design and monitoring in the Snohomish River estuary, we synthesized data from multiple sources to improve our understanding of salt intrusion and habitat characteristics in the estuary. We used data collected from discrete surface water sampling, discrete water column profiling, continuous water sensor monitoring, and hydrodynamic modeling efforts to classify mixohaline habitats in the estuary; polyhaline (18 – 30 ppt), mesohaline (5 – 18 ppt), oligohaline (0.5 – 5 ppt), and freshwater (0 – 0.5 ppt). Previous descriptions of salt intrusion in the Snohomish River estuary suggested that salt intrusion was limited to areas downstream of the Steamboat Slough bifurcation and the Ebey/Union/Steamboat slough bifurcation/confluence complex at Otter Island. Our results indicate that salt intrusion is much more extensive in the Snohomish Estuary and that oligohaline habitat conditions can extend through the entire estuary complex to approximately 2.0 km upstream of the first primary bifurcation along the mainstem that forms upper Ebey Slough. Application of our mixohaline habitat classifications may improve spatial data for historical and current vegetation extents and we apply this analysis to completed and planned restoration projects within the estuary.