The Water Quality Index (WQI) for rivers and streams combines measures of dissolved oxygen, pH, temperature, fecal coliform bacteria, nitrogen, phosphorus, suspended sediment, and turbidity into a single score for individual monitoring stations across Puget Sound watersheds. The WQI ranges from 1 to 100, where a higher number is indicative of better water quality.
Annual Water Quality Index (WQI) for 16 long-term monitoring stations across Puget Sound watersheds. The index is based on monthly monitoring at individual stations and can range from 1 to 100 where a higher number is indicative of better water quality.
Key Vital Sign Indicator Results
Between 1997 and 2019, there has been no clear upward or downward trend in the average freshwater WQI. Thus, indicator progress toward the 2020 target is categorized as ‘Not Improving’. On average, index values have remained stable along with a decreasing trend in variability for annual WQI between the years.
While most of the 16 long-term monitoring stations in Puget Sound show little change in overall water quality, a few locations do show a significant trend in index values over the most recent 20-year period (2000-2019). The WQI has improved at the Elwha River near Port Angeles, and declined at three sites: Snohomish River at Snohomish, Snoqualmie River at Snoqualmie, and Puyallup River at Meridian Street.
The WQI indicator is below the 2020 recovery target. In 2019, one-third of the 27 monitored stations were at or above the target value of 80.
By 2020, at least half of all monitored stations should score 80 or above on the Water Quality Index.