In 2001, King County initiated a comprehensive study of the Green-Duwamish watershed, called the Green-Duwamish Watershed Water Quality Assessment (GDWQA) Comprehensive Monitoring Program. The primary purpose of the program was to collect and analyze water quality data within the Green-Duwamish watershed. As part of the GDWQA, King County implemented the microbial source tracking (MST) study described herein to address bacterial contamination in the watershed and to better understand the relationship between land use and bacterial loadings. Human sources were most prevalent in areas of low-density development (i.e., septic systems), canine/feline sources were most prevalent in areas of high density development, and livestock sources were most prevalent in agriculture areas. Bacteria sources among stations generally did not vary consistently with hydrologic condition (base flow versus storm flow) or season (winter versus summer). Avian bacteria sources represented the largest percentage (26.1 percent) of all ribotypes, and were the predominant source at eight of the nine monitoring stations.
Green – Duwamish Watershed Water Quality Assessment: Microbial Source Tracking Study Report
Reference: Herrera. 2006. Green - Duwamish Watershed Water Quality Assessment: Microbial Source Tracking Study Report. Prepared for King County Department of Natural Resources and Parks, by Herrera Environmental Consultants, Inc., Seattle, Washington.