LOCATION.-- Lat 41°11'13", long 90°58'02" (NAD of 1927), at quarter corner between secs.21 and 28, T.14 N., R.5 W., Mercer County, Hydrologic Unit 07080104, on left bank at downstream side of bridge on State Highway 17, 1.5 mi northeast of New Boston, and at mile 4.6.

DRAINAGE AREA.-- 445 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1934 to current year. Monthly discharge only for some periods, published in WSP 1308.

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1978-91. Additional chemical data for water years 1959, 1971-77 are published in Water-Resources Investigations 78-23 and 79-24 as site LF 01.

SEDIMENT: January 1979 to September 1981.

REVISED RECORDS.-- WSP 1508: 1935-36(M), 1938-40(M), 1941, 1943. WDR IL-75-1: Drainage area.

GAGE.-- Water-stage recorder, U.S. Army Corps of Engineers satellite telemeter and crest-stage gage. Datum of gage is 529.92 ft above NGVD of 1929 (levels by U.S. Army Corps of Engineers). Prior to Mar. 1, 1941, nonrecording gage at same site and datum.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 18,000 ft³/s, Apr. 22, 1973, gage height, 23.33 ft; minimum, 1.2 ft³/s, Oct. 19, 20, 1988.

SUSPENDED-SEDIMENT CONCENTRATIONS: Maximum daily mean, 11,600 mg/L May 29, 1980; minimum daily mean, 9 mg/L Feb. 15, 1981.

SUSPENDED-SEDIMENT LOADS: Maximum daily, 75,400 tons Apr. 14, 1981; minimum daily, 1.4 tons Oct. 12, 13, 1979.