Routine freshwater monitoring data collected by the The WA State Department of Ecology's River and Stream Monitoring Program are summarized by a technique called the "Water Quality Index" (WQI). The WQI ranges from 1 (poor quality) to 100 (good quality). The WQI summary does not include non-standard elements like metals. For temperature, pH, oxygen, and fecal coliform bacteria, the WQI is based on criteria in Washington’s Water Quality Standards, WAC 173-201A.
For nutrient and sediment measures where standards are not specific, results are based on expected conditions in a given region. Multiple constituents are combined and results aggregated over time to produce a single score for each station and each year.
The WQI station map shows the WQI annual scores for all stations from 2013. These maps show status at the individual stations but also give a general sense of water quality conditions . This often doesn't apply higher in the watersheds where we have very little WQI-type data--though downstream results can provide clues about what's happening upstream.