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River & stream water quality index

How is your river doing? The Water Quality Index, or WQI, summarizes and presents water-quality data as a number ranging from 1 to 100, with a higher number indicating better water quality. The WQI can be found on individual station pages in the Statewide Water Quality Monitoring Network data application.

See below to learn more about the Water Quality Index, its development, and how to calculate a WQI based on your own data.

See how your river or stream is doing

Data  presented in the Water Quality Index, or WQI, helps indicate whether water quality is good, meeting standards to protect aquatic life, whether it is of moderate concern or is poor and doesn't meet expectations. The Index ranges from 1 to 100; a higher number indicates better water quality.

WQI Score


Color code on station pages
80 and above Good - meets expectations - lowest concern blue
40 - 80 Moderate concern beige
40 and below Poor - does not meet expectations - highest concern red

The WQI graphs show blue for low concern, beige for moderate concern, and red for high concern or poor water quality. 

KEY says blue is good, beige is moderate, and red is poor. N/A is not sampled or not calculated. Higher scores mean better water quality and the maximum score is 100.

Find the Water Quality Index

The Water Quality Index is in a tab on individual station pages in the Statewide Water Quality Monitoring Network application. Select your station of interest from the application map, and click the blue link to get to the station page. The tabs are toward the bottom of the page. Click on the Water Quality Index tab to find the WQI graphs.

Row of tabs includes Station overview, Water Quality Index, Criteria, Finalized data, Preliminary data, and Temperature. Water Quality Index is the selected tab.

Most pages show trends over time, though the amount of time covered varies by station. Each page has four graphs: scores for the most recent water year (October through September), scores by constituent, scores by month, and general WQI score trends for that station year-by-year. The "scores by constituent" include eight analytes/parameters, including fecal coliform bacteria, dissolved oxygen, and temperature.

Calculate WQI based on your own data

The Water Quality Index spreadsheet (Version 6) is a downloadable tool for calculating a WQI score based on your own data.

Learn about the methodology

A Water Quality Index for Ecology's Stream Monitoring Program is a report that describes the development of and the methodology for the Water Quality Index.