Presentation Abstract

The Swinomish agricultural area, along the Swinomish Channel, is part of the Skagit River Delta, a major agrarian region in Puget Sound. Historically a complex system of tidal channels serving as salmon habitat, the tidelands have since been diked and drained. In 2005, the Swinomish Indian Tribal Community (SITC) began restoration to demonstrate compatibility of fish habitat and agriculture. Muted tidal regulators (MTRs) operated to optimize tidal inundation and fish passage, replaced traditional tidegates, and prompted a study to evaluate soil conductivity impacts on agriculture. Objectives included electromagnetic (EM) surveying of soil conductivity, qualitatively assessing EM results utilizing two additional methods, and assessing local crop suitability and restoration effectiveness for fish habitat and agriculture compatibility. All methods showed low conductivity throughout the majority of the area with isolated elevated levels adjacent to drainage ditches, the main Channel dike, and in low-lying depressional areas. Designed for periodic inundation, a restoration area yielded some of the highest conductivity levels. Using conversion formulas applicable to each conductivity measurement method, conductivity values were converted to salinity classes to evaluate potential adverse crop effects. The areas described above ranged from primarily ‘slightly saline’ and ‘moderately saline’ (many crop yields restricted), to ‘strongly saline’, with marginal ‘very strongly saline’ areas along the main dike and in the restoration area. However, the vast majority of the agricultural area could be categorized as ‘non-saline’, with negligible crop effects. These results indicate that the restoration designed to enhance fish habitat resulted in limited salinity intrusion to the adjacent cropland. This study, along with concurrent projects in the Swinomish agricultural area, suggests that fish and farming, two economically and culturally significant symbols of the region, may not only survive, but thrive in the same space.

Session Title

Posters: Habitat Restoration & Protection

Keywords

Soil conductivity, Soil salinity, Agriculture, Electromagnetic surveys, Muted tidal regulators, Tide gates, Fish habitat

Conference Track

SSE18: Posters

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE18-81

Start Date

5-4-2018 11:30 AM

End Date

5-4-2018 1:30 PM

Type of Presentation

Poster

Contributing Repository

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

Geographic Coverage

Salish Sea (B.C. and Wash.)

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.

Type

text

Language

English

Format

application/pdf

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Apr 5th, 11:30 AM Apr 5th, 1:30 PM

Soil conductivity study and implications for fish and farming compatibility in the Swinomish agricultural area

The Swinomish agricultural area, along the Swinomish Channel, is part of the Skagit River Delta, a major agrarian region in Puget Sound. Historically a complex system of tidal channels serving as salmon habitat, the tidelands have since been diked and drained. In 2005, the Swinomish Indian Tribal Community (SITC) began restoration to demonstrate compatibility of fish habitat and agriculture. Muted tidal regulators (MTRs) operated to optimize tidal inundation and fish passage, replaced traditional tidegates, and prompted a study to evaluate soil conductivity impacts on agriculture. Objectives included electromagnetic (EM) surveying of soil conductivity, qualitatively assessing EM results utilizing two additional methods, and assessing local crop suitability and restoration effectiveness for fish habitat and agriculture compatibility. All methods showed low conductivity throughout the majority of the area with isolated elevated levels adjacent to drainage ditches, the main Channel dike, and in low-lying depressional areas. Designed for periodic inundation, a restoration area yielded some of the highest conductivity levels. Using conversion formulas applicable to each conductivity measurement method, conductivity values were converted to salinity classes to evaluate potential adverse crop effects. The areas described above ranged from primarily ‘slightly saline’ and ‘moderately saline’ (many crop yields restricted), to ‘strongly saline’, with marginal ‘very strongly saline’ areas along the main dike and in the restoration area. However, the vast majority of the agricultural area could be categorized as ‘non-saline’, with negligible crop effects. These results indicate that the restoration designed to enhance fish habitat resulted in limited salinity intrusion to the adjacent cropland. This study, along with concurrent projects in the Swinomish agricultural area, suggests that fish and farming, two economically and culturally significant symbols of the region, may not only survive, but thrive in the same space.