Illinois River

Last Updated: May 3, 2026

Total streamflow across the Illinois River was last observed at 132,157 cfs, and is expected to yield approximately 262,130 acre-ft of water today; about 102% of normal. Average streamflow for this time of year is 130,087 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 Valley City reporting a streamflow rate of 52,000 cfs. However, the streamgauge with the highest stage along the river is the Illinois River At Henry with a gauge stage of 20.18 ft. 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.

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


15-Day Long Term Forecast


River Details

Last Updated 2026-05-03
Discharge Volume 262,130 ACRE-FT
Streamflow 132,157.0 cfs
Past 24 Hours: -4125.0 cfs (-3.03%)
Percent of Normal 101.59%
Maximum 632,800.0 cfs
2015-12-28
Seasonal Avg 130,087 cfs
       
River Streamflow Levels
Streamgauge Streamflow Gauge Stage 24hr Change (%) % Normal Minimum (cfs) Maximum (cfs) Air Temp Elevation
Illinois River Near Kerby
USGS 14377100
374 cfs 3.03 ft -4.59
Illinois River At Savoy
USGS 07194800
189 cfs 3.09 ft -20.59
Illinois River At Hwy. 16 Near Siloam Springs Ar
USGS 07195400
642 cfs 7.18 ft -15.53
Illinois River South Of Siloam Springs
USGS 07195430
206 cfs 3.93 ft 0.98
Illinois River Near Watts
USGS 07195500
901 cfs 3.93 ft -15
Illinois River At Chewey
USGS 07196090
1220 cfs 4.27 ft -16.44
Illinois River Near Tahlequah
USGS 07196500
2050 cfs 6.91 ft -20.85
Illinois River Near Gore
USGS 07198000
3970 cfs 11.29 ft 1.28
Illinois River At Marseilles
USGS 05543500
13400 cfs 13.52 ft -6.29
Illinois River At Kingston Mines
USGS 05568500
33200 cfs 15.48 ft -2.64
Illinois River At Henry
USGS 05558300
24400 cfs 20.18 ft -8.61
Illinois River At Valley City
USGS 05586100
52000 cfs 15.18 ft 1.96
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.