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

Provisional Monthly Streamflow Network - Tabular Data: February 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	N/A	4,238	3,564	1,739	7,336	5437500
Rock River near Joslin	9,549	86	N/A	7,045	5,894	2,705	12,660	5446500
Pecatonica River at Freeport	1,326	111	661	1,152	906	436	2,075	5435500
Green River near Geneseo	1,003	89	N/A	803	695	131	1,545	5447500
Edwards River near New Boston	445	91	N/A	380	318	52	791	5466500
Kankakee River at Momence	2,294	111	1,684	2,612	2,537	1,073	4,482	5520500
Iroquois River near Chebanse	2,091	102	N/A	2,608	2,133	372	6,256	5526000
Fox River at Dayton	2,642	111	N/A	2,186	1,915	618	4,020	5552500
Vermilion River at Pontiac	579	83	N/A	544	414	40	1,401	5554500
Spoon River at Seville	1,636	111	N/A	1,453	1,336	241	2,936	5570000
LaMoine River at Ripley	1,293	104	N/A	1,020	738	95	2,197	5585000
Bear Creek near Marcelline	349	81	2	260	171	14	603	5495500
Mackinaw River near Congerville	767	81	N/A	676	539	62	1,616	5567500
Salt Creek near Greenview	1,804	84	125	1,721	1,362	260	4,359	5582000
Sangamon River at Monticello	550	115	5	595	444	52	1,345	5572000
So. Fork Sangamon near Rochester	867	76	14	868	592	31	2,068	5576000
Illinois River at Valley City	26,743	87	9,050	25,470	23,990	8,753	48,910	5586100
Macoupin Creek near Kane	868	97	19	740	455	39	1,752	5587000
Vermilion River near Danville	1,290	104	N/A	1,513	1,090	229	3,308	3339000
Kaskaskia River at Vandalia	1,940	56	N/A	2,755	2,365	459	5,650	5592500
Shoal Creek near Breese	735	83	72	893	583	85	2,147	5594000
Embarras River at Ste. Marie	1,516	114	N/A	1,951	1,600	240	4,117	3345500
Skillet Fork at Wayne City	464	107	111	674	518	49	1,758	3380500
Little Wabash below Clay City	1,131	111	365	1,556	1,180	163	3,683	3379500
Big Muddy at Plumfield	794	55	N/A	1,075	1,077	198	2,048	5597000
Cache River at Forman	244	103	N/A	521	441	78	1,050	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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