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

Provisional Monthly Streamflow Network - Tabular Data: October 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	3,001	3,619	3,049	1,093	6,262	5437500
Rock River near Joslin	9,549	86	3,383	5,168	4,268	1,665	8,879	5446500
Pecatonica River at Freeport	1,326	111	701	808	664	319	1,371	5435500
Green River near Geneseo	1,003	90	86	403	218	67	978	5447500
Edwards River near New Boston	445	91	28	148	48	13	456	5466500
Kankakee River at Momence	2,294	113	1,028	1,282	922	599	2,646	5520500
Iroquois River near Chebanse	2,091	102	78	747	232	63	2,035	5526000
Fox River at Dayton	2,642	111	774	1,259	898	340	2,365	5552500
Vermilion River at Pontiac	579	83	0	169	27	3	637	5554500
Spoon River at Seville	1,636	111	64	534	177	58	1,407	5570000
LaMoine River at Ripley	1,293	104	20	433	112	22	1,584	5585000
Bear Creek near Marcelline	349	82	3	123	13	1	492	5495500
Mackinaw River near Congerville	767	81	10	211	30	9	700	5567500
Salt Creek near Greenview	1,804	84	125	544	221	111	1,698	5582000
Sangamon River at Monticello	550	116	0	175	34	6	600	5572000
So. Fork Sangamon near Rochester	867	76	9	199	25	2	623	5576000
Illinois River at Valley City	26,743	87	6,772	13,160	8,067	5,617	30,100	5586100
Macoupin Creek near Kane	868	97	15	245	38	6	663	5587000
Vermilion River near Danville	1,290	104	53	379	108	44	1,133	3339000
Kaskaskia River at Vandalia	1,940	56	102	552	177	53	1,781	5592500
Shoal Creek near Breese	735	83	58	184	48	10	716	5594000
Embarras River at Ste. Marie	1,516	114	42	427	108	30	1,227	3345500
Skillet Fork at Wayne City	464	108	39	105	12	0	379	3380500
Little Wabash below Clay City	1,131	111	107	234	52	7	814	3379500
Big Muddy at Plumfield	794	55	60	155	77	34	464	5597000
Cache River at Forman	244	103	91	61	17	1	195	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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