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Water Quality Index

Water quality monitoring networks collect thousands of chemical, physical, and biological measurements of water each year. Individually, these data do not give us an indication of trends in water quality over time and across geographic areas. A concise, quick way to draw meaning from these numbers is needed. Water quality indices provide a way to distill thousands of records of environmental data into meaningful values that indicate the health of water resources and create a yardstick for measuring and assessing water quality.

Currently, water quality in Iowa rivers is ranked on 2 water indices: the National Sanitation Foundation Water Quality Index (NSFWQI) and the Iowa Water Quality Index (IWQI).

Click here for National Sanitation Foundation Water Quality Index (Google map).

For the IWQI, the Iowa DNR - Water Monitoring and Assessment Section calculates the IWQI score for each month, as well as a total average for all years sampled to date.

Click here for Iowa Water Quality Index - Monthly Score (Google map).

Click here for Iowa Water Quality Index - All Years Average (Google map).