Study goals
Stakeholders, including municipal stormwater permittees in Western Washington, want to know how stream health changes over time in small streams as the area urbanizes and stormwater controls are implemented more broadly.
Study design
The Puget Small Streams (PSS) study collects water and sediment chemistry, in-stream and riparian habitat information, benthic macroinvertebrate, and periphyton samples. Continuous monitoring of stream water level and temperature are monitored at each site to cover a full water year. See sampling locations map below.
The study design has been modified to improve monitoring efficiency and statistical power. Read more details about the design in the study design fact sheet.
Read the Quality Assurance Project Plan (2020) for more detailed information such as study design, plans, and schedules.
Study findings
Previous monitoring done in 2015 found that urban development negatively impacted nearly all of the stream health indicators. Key stressors driving poor B-IBI scores includes physical habitat characteristics, especially watershed-level canopy cover, urban development and sediemnt chemistry. See factsheet and completed studies list below for detail.
Sampling locations
33 randomly selected sites and two reference sites are monitored each year. The map has been updated regularly to include completed sampling sites every year.
The sites for 2020 summer sampling are a subset of past 2015 sampling sites that met the new study design criteria and grouped by the percent of impervious cover in contributing watershed.
Over 100 stream sites were monitored in this large project. It was coordinated by the SAM Coordinator and included staff from King and Skagit counties, San Juan Island Conservation District, U.S. Geological Survey (USGS), Ecology's Environmental Assessment Program, Puget Sound Partnership, and a myriad of laboratories.
Study questions
This first round of stream monitoring evaluated streams in specified urban growth areas (UGAs) and the outside UGAs to understand the status of stream health in the region and identify major stressors causing poor stream conditions.
Study findings
Urban development negatively impacted nearly all of the stream health indicators (B-IBI, periphyton, water and sediment chemistry). Key stressors driving poor B-IBI scores includes physical habitat characteristics, sediment zinc concentration, stream substrate characteristics, and nutrients. This study found that low canopy cover in the watershed is the most important stressors to B-IBI at the regional scale.