ILLINOIS FLOW REPORT

Last Updated: December 26, 2025

The state of Illinois is currently experiencing a variety of streamflow conditions, with many waterways reporting significantly lower than average flows. Areas along major rivers such as the Illinois River at Marseilles, with a current streamflow of 3,730 cubic feet per second (cfs) and a gage height of 11.21 feet, are witnessing flow values much below normal (-57.59%). Similarly, the Mississippi River at Thebes is recording a streamflow of 87,200 cfs, which is also below its typical range (-48.87%). These low flows could affect recreational activities and water enthusiasts might find popular whitewater trails and paddling spots less accessible, with potential implications for local ecosystems and municipalities that rely on these rivers.

Conversely, the Kaskaskia River at Vandalia has seen a significant 24-hour increase in streamflow, up by 242.29 cfs to a current flow of 599 cfs, though it still remains below the normal range (-60.85%). Such sudden increases could indicate potential flooding risks, especially in nearby urban areas like Vandalia. The Rock River, another significant waterway, shows varying conditions with a notable increase in streamflow at Byron, rising by 36.94 cfs to 4,300 cfs, yet also remaining below the normal level (-41.03%). This variation in streamflow data across Illinois rivers calls for vigilant monitoring, as both flow droughts and large increases can have substantial impacts on recreational river use, water resource management, and the overall health of the state's aquatic ecosystems.