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.
The Puget Small Streams (PSS) study collects water and sediment chemistry, in-stream and riparian habitat information, benthic macroinvertebrate, and periphyton samples.
Sites are selected following a random probabilistic survey design which allows spatial characterization of large areas across the study region that would not otherwise be possible. It also uses modest funding and resources.
Read the Quality Assurance Project Plan (2020) for detailed information such as study design, plans, and schedules.
Study design adjustment
For studies starting in 2020, we made a few study design adjustments to better answer regional status and trend questions and to improve monitoring efficiency. These include:
- Stream conditions sampled every year at fewer random sites (n=33) to year variability and improve trend detection power.
- Sites are stratified by percent impervious surface of the contributing watershed into four categories to better represent the full range of urban and urbanizing conditions in the region.
- Sites are sampled in the summer only for watershed health (biota, stream, and riparian condition) with targeted water and sediment quality parameters.Monthly water quality was dropped.
- Continuous monitoring of stream water level starting the October before the summer sampling to calculate flows or flow metrics at each site.
Read the study design fact sheet for more information on these changes.
33 randomly selected sites two reference sites are monitored each 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.