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

Provisional Monthly Streamflow Network - Tabular Data: June 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	4,900	5,304	4,366	1,734	10,190	5437500
Rock River near Joslin	9,549	86	6,486	8,675	7,161	3,128	17,450	5446500
Pecatonica River at Freeport	1,326	111	898	1,155	955	388	2,218	5435500
Green River near Geneseo	1,003	90	428	1,022	871	239	2,431	5447500
Edwards River near New Boston	445	91	281	506	389	68	1,241	5466500
Kankakee River at Momence	2,294	113	1,862	2,323	2,077	1,002	3,931	5520500
Iroquois River near Chebanse	2,091	102	2,033	2,284	1,724	417	5,013	5526000
Fox River at Dayton	2,642	111	1,384	2,216	1,794	675	5,221	5552500
Vermilion River at Pontiac	579	83	847	612	406	96	1,612	5554500
Spoon River at Seville	1,636	111	859	1,752	1,153	284	3,898	5570000
LaMoine River at Ripley	1,293	104	541	1,316	779	99	3,090	5585000
Bear Creek near Marcelline	349	82	160	351	132	7	1,130	5495500
Mackinaw River near Congerville	767	81	698	806	594	117	1,961	5567500
Salt Creek near Greenview	1,804	84	1,544	1,993	1,410	486	3,964	5582000
Sangamon River at Monticello	550	116	373	553	404	83	1,241	5572000
So. Fork Sangamon near Rochester	867	76	403	957	569	107	2,539	5576000
Illinois River at Valley City	26,743	87	20,257	32,291	28,390	10,480	66,270	5586100
Macoupin Creek near Kane	868	97	374	629	340	58	1,730	5587000
Vermilion River near Danville	1,290	104	1,086	1,358	1,050	229	2,956	3339000
Kaskaskia River at Vandalia	1,940	56	739	1,826	1,673	327	4,658	5592500
Shoal Creek near Breese	735	83	249	591	327	59	1,469	5594000
Embarras River at Ste. Marie	1,516	114	727	1,461	997	215	3,509	3345500
Skillet Fork at Wayne City	464	108	487	352	148	11	1,117	3380500
Little Wabash below Clay City	1,131	111	726	959	475	70	2,578	3379500
Big Muddy at Plumfield	794	55	1,164	818	652	169	1,809	5597000
Cache River at Forman	244	103	959	216	154	9	461	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 2023.

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Streamflow Data

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