Illinois River River Levels

Last Updated: December 20, 2025

The Illinois River is a 273-mile-long tributary of the Mississippi River that flows through the state of Illinois.


Summary

Total streamflow across the Illinois River was last observed at 15,240 cfs, and is expected to yield approximately 30,228 acre-ft of water today; about 34% of normal. River levels are low and may signify a drought. Average streamflow for this time of year is 45,125 cfs, with recent peaks last observed on 2015-12-28 when daily discharge volume was observed at 632,800 cfs.

Maximum discharge along the river is currently at the Illinois River At Henry reporting a streamflow rate of 5,340 cfs. This is also the highest stage along the Illinois River, with a gauge stage of 14.59 ft at this location. This river is monitored from 12 different streamgauging stations along the Illinois River, the highest being situated at an altitude of 1,202 ft, the Illinois River Near Kerby.

River Details

Last Updated 2025-12-20
Discharge Volume 30,228 ACRE-FT
Streamflow 15,240.0 cfs
-5570.0 cfs (-26.77%)
Percent of Normal 33.77%
Maximum 632,800.0 cfs
2015-12-28
Seasonal Avg 45,125 cfs
       
River Streamflow Levels
Streamgauge Streamflow Gauge Stage 24hr Change (%) % Normal Minimum (cfs) Maximum (cfs) Air Temp Elevation
Illinois River Near Kerby
USGS 14377100
4920 cfs 11.05 ft 115.79
Illinois River At Savoy
USGS 07194800
40 cfs 2.17 ft -2.42
Illinois River At Hwy. 16 Near Siloam Springs Ar
USGS 07195400
248 cfs 6.11 ft -1.2
Illinois River South Of Siloam Springs
USGS 07195430
215 cfs 2.66 ft -2.27
Illinois River Near Watts
USGS 07195500
282 cfs 2.51 ft -2.76
Illinois River At Chewey
USGS 07196090
312 cfs 2.84 ft -1.27
Illinois River Near Tahlequah
USGS 07196500
371 cfs 5.12 ft 2.49
Illinois River Near Gore
USGS 07198000
80 cfs 6.6 ft -19.66
Illinois River At Marseilles
USGS 05543500
3900 cfs 11.25 ft -33.56
Illinois River At Kingston Mines
USGS 05568500
4310 cfs 2.73 ft -18.53
Illinois River At Henry
USGS 05558300
5340 cfs 14.59 ft 21.36
Illinois River At Valley City
USGS 05586100
4980 cfs 2.26 ft 67.68
Seasonal Discharge Comparison
Maximum Streamflow Discharge
Streamflow Elevation Profile

The Illinois River (Miami-Illinois: Inoka Siipiiwi) is a principal tributary of the Mississippi River, approximately 273 miles (439 km) long, in the U.S. state of Illinois. The river drains a large section of central Illinois, with a drainage basin of 28,756.6 square miles (74,479 km2). The drainage basin extends into Wisconsin, Indiana, and a very small area of southwestern Michigan. This river was important among Native Americans and early French traders as the principal water route connecting the Great Lakes with the Mississippi. The French colonial settlements along the rivers formed the heart of the area known as the Illinois Country. After the construction of the Illinois and Michigan Canal and the Hennepin Canal in the 19th century, the role of the river as link between Lake Michigan and the Mississippi was extended into the era of modern industrial shipping. It now forms the basis for the Illinois Waterway.