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Winter Chloride Watchers

Winter Chloride Watchers

3682 Observations
0 Issues
111 Locations


Bruce M Colravy
3230 Points
Jean Reddington
1090 Points
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Across the northern US, salt is commonly spread on roads during the winter to prevent the build-up of snow and ice. The salt dissolves in the melt water and travels into streams and groundwater, increasing the concentration of chloride (one of the main components in the salt) in local waterways. The large amounts of salt spread on roads in urban and suburban areas can lead to concentrations that are toxic to many fish and invertebrates. In the State of Illinois, 475 stream miles were listed as “impaired” in 2018 due to chloride. This means that these streams do not meet water quality standards.

A scientific study published in 2022 ( used data from community scientists in the St. Louis area to understand how road salt is impacting stream invertebrates. We found that the winter concentrations of chloride were often unsafe for aquatic animals in watersheds where roads covered at least 5% of the land area.

The Illinois RiverWatch Network is working to increase the amount of chloride data available across Illinois. You can explore the data that have been collected so far by exploring the interactive maps on this site. If you are interested in participating in this project, reach out to RiverWatch staff at

Areas monitored

One Confluence Way
East Alton, IL