Event Title

Long-term water quality trend analysis in the Lone Tree Creek watershed and surrounding marine waters

Presentation Abstract

The Lone Tree Creek watershed is located on the Reservation of the Swinomish Indian Tribal Community (SITC) and is an important area both ecologically and culturally. Lone Tree Creek and the surrounding Skagit Bay nearshore environment provide important salmon and shellfish habitats, as well as recreation areas, and therefore have been the focus for ongoing research since 1997. Water quality parameters in the creek, lagoon, and two bay sites have been monitored since the late 1990s and early 2000s, and an additional pocket estuary site was added to monitoring efforts in 2007. This study used Mann-Kendall analysis to determine how water quality (pH, DO, temperature, salinity, turbidity, and Fecal coliform bacteria) has changed at these sites over time. Seasonal Mann-Kendall was used at all sites with the exception of the intermittent creek. At creek sites Mann-Kendall analysis was run individually on seasons that had adequate flow for water quality data collection. Pettit’s Homogeneity Test was used to assess if there were any homogeneity breaks in trend where the time series analysis should be divided. Overall trend analysis at all stations suggests a shift toward decreasing water quality around 2010/-2011. Some sites show improving water quality from 2004-2010 prior to the 2010 shift. Restoration that occurred on Lone Tree Creek in 2006 and 2007 did not coincide with any homogeneity breaks in the data. Although the restoration did lead to water quality improvements, they were not significant on the time scale considered in trend analyses. Possible explanations for the shift in water quality occurring around 2010 include: changes in land-use and forestry practices, new management practices at the campground in the creek watershed, and effects related to climate stressors. Understanding such shifts in water quality are essential for effectively moving forward with monitoring programs and the development of future restoration projects.

Session Title

Posters: Monitoring: Species & Habitats

Conference Track

SSE18: Posters

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE18-94

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

Long-term water quality trend analysis in the Lone Tree Creek watershed and surrounding marine waters

The Lone Tree Creek watershed is located on the Reservation of the Swinomish Indian Tribal Community (SITC) and is an important area both ecologically and culturally. Lone Tree Creek and the surrounding Skagit Bay nearshore environment provide important salmon and shellfish habitats, as well as recreation areas, and therefore have been the focus for ongoing research since 1997. Water quality parameters in the creek, lagoon, and two bay sites have been monitored since the late 1990s and early 2000s, and an additional pocket estuary site was added to monitoring efforts in 2007. This study used Mann-Kendall analysis to determine how water quality (pH, DO, temperature, salinity, turbidity, and Fecal coliform bacteria) has changed at these sites over time. Seasonal Mann-Kendall was used at all sites with the exception of the intermittent creek. At creek sites Mann-Kendall analysis was run individually on seasons that had adequate flow for water quality data collection. Pettit’s Homogeneity Test was used to assess if there were any homogeneity breaks in trend where the time series analysis should be divided. Overall trend analysis at all stations suggests a shift toward decreasing water quality around 2010/-2011. Some sites show improving water quality from 2004-2010 prior to the 2010 shift. Restoration that occurred on Lone Tree Creek in 2006 and 2007 did not coincide with any homogeneity breaks in the data. Although the restoration did lead to water quality improvements, they were not significant on the time scale considered in trend analyses. Possible explanations for the shift in water quality occurring around 2010 include: changes in land-use and forestry practices, new management practices at the campground in the creek watershed, and effects related to climate stressors. Understanding such shifts in water quality are essential for effectively moving forward with monitoring programs and the development of future restoration projects.