Historic Water Quality Monitoring Data
Access H2NOW Chicago’s Historic Data
We believe that water quality information for our local waterways should be accessible to everyone. In support of this effort, we’re making H2NOW Chicago’s historical water quality data free and available to access on our website, offering valuable insights into the health of Chicago's waterways over time. Explore the key indicators that inform our understanding of water quality and guide future actions for cleaner, safer waterways.
Access H2NOW Chicago’s historical water quality data from 2021 to 2025 by completing the form below. Once submitted, you will receive an email with links to view and download data sheets for each river branch, as well as future communications about H2NOW Chicago and Current.
If you don’t receive an email within 5 minutes, check your spam folder. Having trouble accessing the data or have questions? Reach out to us at h2now@currentwater.org
The most recent version of the historical water quality data was published on June 9, 2026. If you completed the form below prior to this date, you must resubmit the form to get access to the most recent version.
Key updates to this version of the historical water quality data are:
Addition of 2025 data for all four monitoring sites
Greater transparency and consistency in our data cleaning efforts, detailed in “About the Data,” as well as four new data cleaning parameters:
Removal of all sensor readings where TLF values exceeded 200 ppb, indicating an error
Removal of all sensor readings for timestamps where only one sensor reports a value, indicating an error
Adjustments for daylight savings time
Removal of duplicate timestamps
New corrections in alignment with updated data cleaning parameters and improved data management procedures, impacting the following data sheets:
Calumet River - Cal-Sag Channel - 2023
Calumet River - Cal-Sag Channel - 2023
Chicago River - Main Stem - 2021
Chicago River - Main Stem - 2022
Chicago River - Main Stem - 2024
Chicago River - North Branch - 2021
Chicago River - North Branch - 2022
Chicago River - North Branch - 2024
Thank you for your interest in the health of our waterways! If you publicly reference H2NOW data anywhere, please be sure to cite H2NOW as your data source. By submitting this form, you confirm that you have read and agree to our terms and conditions for data usage.