LOCATION.-- Lat 41°29'20", long 90°09'27" (NAD of 1927), in NE1/4SW1/4 sec.4, T.17 N., R.3 E., Henry County, Hydrologic Unit 07090007, on right bank at upstream side of bridge on State Highway 82, 1.4 mi upstream from Geneseo Creek, 2.4 mi north of Geneseo, and at mile 14.9.

DRAINAGE AREA.-- 1,003 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: March 1936 to current year.

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

SEDIMENT: March 1978 to September 1981.

CHEMICAL: Water years 1978-91.

REVISED RECORDS.-- WSP 875: 1938. WSP 1508: 1937, 1939-41(M), 1946(P), 1947-49. WDR IL-74-1: Drainage area.

GAGE.-- Water-stage recorder, U.S. Army Corps of Engineers satellite telemeter and crest-stage gage. Datum of gage is 577.66 ft above NGVD of 1929 (levels by U.S. Army Corps of Engineers). Prior to Oct. 1, 1939, nonrecording gage at present site at datum 27.00 ft. lower. Oct. 1, 1939 to Apr. 3, 1940, nonrecording gage at present site at datum 3.0 ft. higher. Apr. 3, 1940 to Sept. 30, 1997, recording gage at present site at datum 3.0 ft. higher.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 12,100 ft³/s, June 22, 1974, gage height, 19.75 ft, present datum; maximum gage height, 21.59 ft, present datum, Jan. 23, 1969, ice jam; minimum daily discharge, 22 ft³/s, Jan. 18, 1977.

SUSPENDED-SEDIMENT CONCENTRATION: Maximum daily mean, 8,620 mg/L Apr. 14, 1981; minimum daily mean, 17 mg/L Jan. 15, 16, 1979.

SUSPENDED-SEDIMENT LOADS: Maximum daily, 132,000 tons Apr. 14, 1981; minimum daily, 7.3 tons Jan. 15, 16, 1979.