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

Provisional Monthly Streamflow Network - Tabular Data: July 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	3,936	4,428	3,166	1,425	9,651	5437500
Rock River near Joslin	9,549	86	5,912	6,936	5,296	2,351	14,730	5446500
Pecatonica River at Freeport	1,326	111	1,074	1,009	786	387	1,861	5435500
Green River near Geneseo	1,003	90	801	619	451	180	1,345	5447500
Edwards River near New Boston	445	91	308	315	191	48	699	5466500
Kankakee River at Momence	2,294	112	2,575	1,591	1,382	733	2,836	5520500
Iroquois River near Chebanse	2,091	103	523	1,378	749	139	3,142	5526000
Fox River at Dayton	2,642	111	3,308	1,477	1,094	404	3,522	5552500
Vermilion River at Pontiac	579	83	249	333	176	36	770	5554500
Spoon River at Seville	1,636	111	861	1,055	732	184	2,320	5570000
LaMoine River at Ripley	1,293	105	421	813	374	62	2,370	5585000
Bear Creek near Marcelline	349	82	34	261	89	3	770	5495500
Mackinaw River near Congerville	767	81	611	386	225	43	1,006	5567500
Salt Creek near Greenview	1,804	84	1,269	1,255	828	276	3,049	5582000
Sangamon River at Monticello	550	117	393	299	163	27	942	5572000
So. Fork Sangamon near Rochester	867	77	181	397	227	24	998	5576000
Illinois River at Valley City	26,743	87	40,177	23,444	19,910	8,846	46,690	5586100
Macoupin Creek near Kane	868	98	218	371	140	19	1,149	5587000
Vermilion River near Danville	1,290	105	824	782	519	76	1,933	3339000
Kaskaskia River at Vandalia	1,940	56	2,071	1,389	1,325	138	2,573	5592500
Shoal Creek near Breese	735	83	185	349	166	32	868	5594000
Embarras River at Ste. Marie	1,516	114	838	820	560	107	1,934	3345500
Skillet Fork at Wayne City	464	110	42	206	76	4	679	3380500
Little Wabash below Clay City	1,131	111	1,131	594	280	30	1,864	3379500
Big Muddy at Plumfield	794	55	198	517	466	86	1,063	5597000
Cache River at Forman	244	102	1,111	111	44	6	287	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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