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

Provisional Monthly Streamflow Network - Tabular Data: December 2025

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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	3,084	3,706	3,311	1,288	6,242	5437500
Rock River near Joslin	9,549	86	4,987	5,703	5,185	1,984	10,200	5446500
Pecatonica River at Freeport	1,326	111	704	761	637	305	1,426	5435500
Green River near Geneseo	1,003	89	N/A	529	423	87	1,373	5447500
Edwards River near New Boston	445	91	N/A	203	120	18	432	5466500
Kankakee River at Momence	2,294	111	N/A	2,061	1,802	857	3,780	5520500
Iroquois River near Chebanse	2,091	102	N/A	1,612	1,115	134	4,045	5526000
Fox River at Dayton	2,642	111	N/A	1,644	1,384	496	3,401	5552500
Vermilion River at Pontiac	579	83	N/A	387	160	8	1,070	5554500
Spoon River at Seville	1,636	111	143	733	400	65	1,790	5570000
LaMoine River at Ripley	1,293	104	N/A	537	229	28	1,472	5585000
Bear Creek near Marcelline	349	81	N/A	157	33	1	487	5495500
Mackinaw River near Congerville	767	81	18	457	204	16	1,398	5567500
Salt Creek near Greenview	1,804	84	152	1,096	624	106	2,837	5582000
Sangamon River at Monticello	550	115	4	368	165	12	1,118	5572000
So. Fork Sangamon near Rochester	867	76	10	560	143	7	1,694	5576000
Illinois River at Valley City	26,743	87	5,455	18,530	15,400	6,778	37,150	5586100
Macoupin Creek near Kane	868	97	18	501	151	8	1,514	5587000
Vermilion River near Danville	1,290	104	N/A	970	560	62	2,625	3339000
Kaskaskia River at Vandalia	1,940	56	288	1,900	1,539	159	5,294	5592500
Shoal Creek near Breese	735	83	N/A	606	209	19	1,762	5594000
Embarras River at Ste. Marie	1,516	114	46	1,293	777	39	3,501	3345500
Skillet Fork at Wayne City	464	107	8	464	214	5	1,264	3380500
Little Wabash below Clay City	1,131	111	47	1,085	514	22	2,706	3379500
Big Muddy at Plumfield	794	55	49	671	363	50	1,877	5597000
Cache River at Forman	244	103	26	357	214	13	931	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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Provisional Monthly Streamflow Network - Data Details, Illinois State Water Survey

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