Presentation Abstract

In 2015, the condition of Puget Sound Lowland streams was evaluated by collecting data for stream invertebrates, algae, water and sediment quality, and instream and riparian habitat. The study was designed and implemented as part of the Stormwater Action Monitoring program, a collaborative, regional stormwater monitoring program funded by more than 90 Western Washington cities and counties, the ports of Seattle and Tacoma, and the Washington State Department of Transportation. The goal of this long term program is to inform stakeholders on the status and trends of small streams within the Puget Lowlands and to track whether stream condition improves as a result of stormwater management practices in the region. A comparable number of sites were randomly selected inside and outside the Urban Growth Area (UGA). Benthic invertebrate taxa were used to calculate the benthic multi-metric index (B-IBI) and three stressor index scores for each of the 104 sites. All sites showed that sites within UGAs had poorer invertebrate condition compared to sites outside the UGA. Similar patterns were shown for algae, with the Trophic Diatom Index (TDI) indicating elevated nutrients inside the UGA compared to outside the UGA. We used boosted regression trees and a relative risk/attributable risk analysis to determine the most important human and natural factors influencing biological condition in the region. For the B-IBI, the most important factors influencing scores were December precipitation, watershed percent urban development, percent of watershed and riparian canopy cover, and stream substrate. For the TDI, the most important factors influencing condition were mean summer total phosphorus and nitrogen concentrations and watershed percent urban development. The intent is to use this status year of data to refine the sample design, and begin trend monitoring in the coming years with the goal to determine if streams are getting better or worse over time.

Session Title

Monitoring Stormwater Impacts on Contaminants in Receiving Waters

Keywords

Puget Sound lowland streams, Stormwater monitoring, Stormwater management

Conference Track

SSE3: Fate, Transport, and Toxicity of Chemicals

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE3-396

Start Date

6-4-2018 2:45 PM

End Date

6-4-2018 3:00 PM

Type of Presentation

Oral

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 6th, 2:45 PM Apr 6th, 3:00 PM

Assessing biological condition in small streams of the Puget Sound lowlands through collaborative regional monitoring

In 2015, the condition of Puget Sound Lowland streams was evaluated by collecting data for stream invertebrates, algae, water and sediment quality, and instream and riparian habitat. The study was designed and implemented as part of the Stormwater Action Monitoring program, a collaborative, regional stormwater monitoring program funded by more than 90 Western Washington cities and counties, the ports of Seattle and Tacoma, and the Washington State Department of Transportation. The goal of this long term program is to inform stakeholders on the status and trends of small streams within the Puget Lowlands and to track whether stream condition improves as a result of stormwater management practices in the region. A comparable number of sites were randomly selected inside and outside the Urban Growth Area (UGA). Benthic invertebrate taxa were used to calculate the benthic multi-metric index (B-IBI) and three stressor index scores for each of the 104 sites. All sites showed that sites within UGAs had poorer invertebrate condition compared to sites outside the UGA. Similar patterns were shown for algae, with the Trophic Diatom Index (TDI) indicating elevated nutrients inside the UGA compared to outside the UGA. We used boosted regression trees and a relative risk/attributable risk analysis to determine the most important human and natural factors influencing biological condition in the region. For the B-IBI, the most important factors influencing scores were December precipitation, watershed percent urban development, percent of watershed and riparian canopy cover, and stream substrate. For the TDI, the most important factors influencing condition were mean summer total phosphorus and nitrogen concentrations and watershed percent urban development. The intent is to use this status year of data to refine the sample design, and begin trend monitoring in the coming years with the goal to determine if streams are getting better or worse over time.