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

Provisional Monthly Streamflow Network - Tabular Data: July 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	4,713	4,424	3,120	1,425	9,651	5437500
Rock River near Joslin	9,549	86	7,094	6,935	5,176	2,351	14,730	5446500
Pecatonica River at Freeport	1,326	111	1,204	1,007	781	387	1,861	5435500
Green River near Geneseo	1,003	90	363	622	456	175	1,345	5447500
Edwards River near New Boston	445	91	327	314	191	48	699	5466500
Kankakee River at Momence	2,294	113	1,215	1,595	1,387	733	2,836	5520500
Iroquois River near Chebanse	2,091	102	582	1,386	758	141	3,257	5526000
Fox River at Dayton	2,642	111	1,427	1,477	1,094	404	3,522	5552500
Vermilion River at Pontiac	579	83	121	336	178	36	770	5554500
Spoon River at Seville	1,636	111	1,056	1,055	715	184	2,320	5570000
LaMoine River at Ripley	1,293	104	967	812	358	62	2,370	5585000
Bear Creek near Marcelline	349	82	172	262	80	4	882	5495500
Mackinaw River near Congerville	767	81	131	389	229	43	1,006	5567500
Salt Creek near Greenview	1,804	84	711	1,261	834	276	3,049	5582000
Sangamon River at Monticello	550	116	51	301	165	27	942	5572000
So. Fork Sangamon near Rochester	867	76	323	398	217	24	998	5576000
Illinois River at Valley City	26,743	87	14,876	23,543	19,930	8,846	46,690	5586100
Macoupin Creek near Kane	868	97	1,491	360	140	19	1,041	5587000
Vermilion River near Danville	1,290	104	231	787	523	76	1,933	3339000
Kaskaskia River at Vandalia	1,940	56	1,966	1,379	1,277	276	2,901	5592500
Shoal Creek near Breese	735	83	732	344	164	32	868	5594000
Embarras River at Ste. Marie	1,516	114	1,003	818	550	107	1,934	3345500
Skillet Fork at Wayne City	464	108	846	200	74	4	679	3380500
Little Wabash below Clay City	1,131	111	2,419	577	279	30	1,727	3379500
Big Muddy at Plumfield	794	55	616	515	457	86	1,063	5597000
Cache River at Forman	244	103	123	111	43	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 2023.

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Streamflow Data

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