Freshwater quality refers to many aspects of water in rivers and streams including dissolved oxygen, pH, temperature, bacteria, nitrogen, phosphorus, suspended sediment, and turbidity. Freshwater quality throughout Puget Sound is affected by many different factors including weather and climate patterns, water withdrawals and diversions, erosion and stormwater runoff, discharges from wastewater treatment plants and industries, nutrient input and other pollution.

This Vital Sign tells us about the condition of the fresh water that is vital to people, fish and wildlife populations and helps understand whether efforts to reduce excessive sediments and nutrients out of our rivers and streams are effective.


Key Vital Sign Messages

  • Overall freshwater quality, as measured by the Water Quality Index (WQI), has not changed substantially since 1997 at river and stream monitoring stations across Puget Sound watersheds. In 2019 one-third of the 27 monitored stations had a WQI score indicating good stream health.
  • The Benthic Index of Biotic Integrity (B-IBI) indicator uses the diversity and abundance of invertebrates – the insects, snails, and worms that live in the stream bed – to measure stream health. The B-IBI is correlated with land use conversion and urbanization. Scores tend to be lower in areas with more urban development and less tree canopy cover in the watershed.
  • The Interdisciplinary Team of regional experts leading development of the B-IBI Implementation Strategy identified four priority strategies likely to improve stream condition. The strategies focus on 1) increasing capacity of local stormwater management programs, 2) coordinating watershed planning across jurisdictions, 3) encouraging restoration through education and incentives, and 4) preserving land for forestry and farming.
  • Stormwater runoff from urban and urbanizing areas is one of the biggest threats to streams, lakes, and Puget Sound. The Stormwater Action Monitoring (SAM) program is a collaborative, regional monitoring program that measures stormwater quality throughout Puget Sound watersheds with the goal to improve stormwater management.

Contributing Partners