Identifying Stressor Risk to Biological Health in Streams and Small Rivers of Western Washington

An essential step in watershed management is the identification of key natural and anthropogenic stressors influencing important biological indicators of watershed health, such as the benthic index of biotic integrity, or B-IBI. Relative risk analysis provides quantifiable associations between biological response and stressors of concern, making this a useful tool to identify potential risks to aquatic biota. For this project, water quality, sediment chemistry, and physical habitat data (146 sites) from the Washington State Department of Ecology’s Status and Trends Monitoring for Watershed Health and Salmon Recovery Program were used to determine the relative importance and strength of relationship between benthic macroinvertebrate metrics and environmental stressors in western Washington streams and small rivers. The results presented here provide essential information needed to protect sites in excellent biological health and identify potential sources of impairment, which complement monitoring programs and support watershed management decisions.