The Puget Sound region is a unique network of mountain peaks, plateaus, rivers, lakes, and marine waters. These natural wonders make Pierce County a beautiful place to visit, live, work and play. Maintaining healthy water quality in the streams, rivers and lakes that connect the Cascade Mountains to Puget Sound is essential to the quality of life and prosperity of Pierce County residents, businesses and wildlife.
Water quality has declined in most areas of Pierce County as the population and development have grown over the past century. The most common water quality concerns in Pierce County streams are high levels of bacteria, nitrogen and phosphorus, elevated summer temperatures and low dissolved oxygen concentrations.
Our water quality specialists go out in the field monthly to monitor water quality at streams throughout Pierce County. We also collect benthic samples from a subset of streams every summer. Below are 2021 results from our stream monitoring program. This graphic below summarizes results between October 1, 2020, and September 30, 2021.
Watershed health is classified into three categories — Poor, Moderate and Good — using Benthic Index of Biotic Integrity (BIBI) scores and Water Quality Index (WQI) scores. Click on the tabs above to learn more about how these data points paint a water quality picture.
The Benthic Index of Biotic Integrity (BIBI) score is calculated using benthic macroinvertebrate (bugs living on the bottom of streams) samples. We collect these samples from specific streams every several years with the help of the Pierce Conservation District.
Macroinvertebrates are useful indicators of stream quality because they generally spend their life cycles in a small area, have a short life span and are sensitive to subtle changes in water quality or habitat. Different macroinvertebrate species have various levels of tolerance to pollution. Some species that are important food sources for salmon, such as mayflies, stoneflies, and caddis flies, are very intolerant to pollution. In an unhealthy stream the amount of these species will decline while the numbers of more pollution-tolerant species like leeches and black fly larvae, which salmon do not eat, will increase.
The BIBI scores listed below represent the most recent data available. The scores reflect information collected in the 2016-2021 timeframe.
The Water Quality Index (WQI) score is calculated using monthly stream water quality sampling for bacteria, pH, dissolved oxygen, temperature, turbidity, total suspended solids, total nitrogen and total phosphorus.
It is a measure of eight common parameters that are known to impact the health of freshwater streams. By observing the chemical and physical properties of the stream, we can better understand stream health and the impacts it may have on humans, fish and wildlife.
Carol Falkenhayn Maloy
Water Quality Supervisor
Phone: (253) 377-6866
7:30 a.m.–4:00 p.m.
2702 S 42nd St, Ste 109
Tacoma, WA 98409-7322