Provisional Monthly Streamflow Network - Data Details, Illinois State Water Survey

Provisional Monthly Streamflow Network - Tabular Data: April 2026

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				Long-term monthly flows for period of record (cfs)
Station	Drainage area (sq. mi.)	Years of record	Monthly mean flow (cfs)	Mean flow*	Median (50% exceedence) flow	90% exceedence flow	10% exceedence flow	USGS Station No.
Rock River at Rockton	6,363	86	12,705	7,828	6,894	3,161	12,840	5437500
Rock River near Joslin	9,549	86	19,269	11,442	10,305	4,700	18,870	5446500
Pecatonica River at Freeport	1,326	111	2,269	1,319	1,108	514	2,210	5435500
Green River near Geneseo	1,003	90	2,022	1,093	984	385	2,170	5447500
Edwards River near New Boston	445	90	865	567	450	156	1,230	5466500
Kankakee River at Momence	2,294	113	4,957	3,488	3,491	1,807	5,393	5520500
Iroquois River near Chebanse	2,091	102	3,193	3,156	2,982	936	5,591	5526000
Fox River at Dayton	2,642	111	7,464	3,414	3,132	1,207	5,845	5552500
Vermilion River at Pontiac	579	83	657	796	673	191	1,644	5554500
Spoon River at Seville	1,636	111	2,834	1,923	1,532	448	3,851	5570000
LaMoine River at Ripley	1,293	105	2,575	1,570	1,279	234	3,284	5585000
Bear Creek near Marcelline	349	82	642	421	304	18	844	5495500
Mackinaw River near Congerville	767	81	1,179	1,053	919	233	1,984	5567500
Salt Creek near Greenview	1,804	84	2,421	2,384	2,001	793	4,521	5582000
Sangamon River at Monticello	550	116	392	790	674	194	1,648	5572000
So. Fork Sangamon near Rochester	867	76	927	1,090	860	153	2,243	5576000
Illinois River at Valley City	26,743	87	42,253	37,635	34,680	15,840	61,280	5586100
Macoupin Creek near Kane	868	98	1,745	1,142	730	129	2,864	5587000
Vermilion River near Danville	1,290	104	2,466	1,901	1,620	537	3,786	3339000
Kaskaskia River at Vandalia	1,940	56	3,352	2,691	2,236	515	5,594	5592500
Shoal Creek near Breese	735	83	714	1,073	739	174	2,346	5594000
Embarras River at Ste. Marie	1,516	114	2,628	2,330	1,834	543	4,825	3345500
Skillet Fork at Wayne City	464	108	370	849	733	117	1,928	3380500
Little Wabash below Clay City	1,131	111	1,193	1,798	1,332	235	3,840	3379500
Big Muddy at Plumfield	794	55	219	1,582	1,313	431	3,412	5597000
Cache River at Forman	244	103	50	598	528	112	1,220	3612000

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Station Numbers are linked to the U.S. Geological Survey, providing more information about each station.

Notes:
Much below normal flow = 90-100% chance of exceedence.
Below normal flow = 70-90% chance of exceedence.
Normal flow = 30-70% chance of exceedence.
Above normal flow = 10-30% chance of exceedence.
Much above normal flow = 0-10% chance of exceedence.
* As reported in U.S. Geological Survey (USGS) Water Resources Data, Illinois, Water Year 2024.

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Streamflow Data

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