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

Provisional Monthly Streamflow Network - Tabular Data: May 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	4,756	6,012	5,343	2,397	11,460	5437500
Rock River near Joslin	9,549	86	6,164	9,544	8,452	3,875	17,910	5446500
Pecatonica River at Freeport	1,326	111	831	1,112	926	465	1,977	5435500
Green River near Geneseo	1,003	90	480	1,106	905	301	2,189	5447500
Edwards River near New Boston	445	91	310	577	407	120	1,259	5466500
Kankakee River at Momence	2,294	113	1,880	2,987	2,851	1,468	4,749	5520500
Iroquois River near Chebanse	2,091	102	1,397	2,823	2,292	698	5,978	5526000
Fox River at Dayton	2,642	111	1,561	2,793	2,364	951	5,097	5552500
Vermilion River at Pontiac	579	83	294	798	597	191	1,740	5554500
Spoon River at Seville	1,636	111	802	1,974	1,386	424	4,334	5570000
LaMoine River at Ripley	1,293	104	600	1,580	885	208	3,969	5585000
Bear Creek near Marcelline	349	82	287	432	216	25	1,272	5495500
Mackinaw River near Congerville	767	81	261	997	835	248	2,142	5567500
Salt Creek near Greenview	1,804	84	1,313	2,497	2,008	624	5,516	5582000
Sangamon River at Monticello	550	116	327	735	545	185	1,637	5572000
So. Fork Sangamon near Rochester	867	76	654	1,183	784	158	2,919	5576000
Illinois River at Valley City	26,743	87	16,970	38,613	35,320	15,440	71,880	5586100
Macoupin Creek near Kane	868	97	1,170	1,069	531	86	3,138	5587000
Vermilion River near Danville	1,290	104	963	1,735	1,284	571	3,903	3339000
Kaskaskia River at Vandalia	1,940	56	1,880	2,076	1,585	273	5,323	5592500
Shoal Creek near Breese	735	83	774	970	691	105	2,076	5594000
Embarras River at Ste. Marie	1,516	114	1,810	2,018	1,284	380	5,170	3345500
Skillet Fork at Wayne City	464	108	931	668	339	38	2,070	3380500
Little Wabash below Clay City	1,131	111	1,660	1,527	859	91	4,670	3379500
Big Muddy at Plumfield	794	55	1,625	1,497	984	274	4,123	5597000
Cache River at Forman	244	103	328	456	328	27	1,124	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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