LOCATION.-- Lat 41°07'44", long 90°55'09" (NAD of 1927), in SE1/4SE1/4 sec.11, T.13 N., R.5 W., Mercer County, Hydrologic Unit 07080104, on right bank at downstream side of bridge on County Road 900 E, 1.8 mi northeast of Keithsburg, and at mile 3.0.

DRAINAGE AREA.-- 174 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1934 to September 1986. Monthly discharge only for some periods, published in WSP 1308. Seven-month period (March to September), water years 1987-90. October 1990 to September 1996. October 1997 to current year.

STAGE: Water years 1994-1996;1998 to current year.

REVISED RECORDS.-- WSP 1508: 1935-37(M), 1938, 1939-43(M). WDR IL-81-1: Drainage area.

GAGE.-- Water-stage recorder, U.S. Army Corps of Engineers satellite telemeter, and crest-stage gage. Datum of gage is 524.07 ft above NGVD of 1929 (levels by U.S. Army Corps of Engineers). Prior to Aug. 1, 1975, nonrecording gage and crest-stage gage at site 1,000 ft upstream at same datum. Aug. 1, 1975 to Aug. 24, 1981, water-stage recorder at site 500 ft downstream at same datum.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 8,900 ft³/s, Apr. 22, 1973, gage height, 27.88 ft, from graph based on gage readings at site 1,000 ft upstream at same datum; maximum gage height, 29.25 ft, Feb. 9, 2001, estimated discharge, 3,250 ft³/s, ice jam; minimum daily discharge, 0.53 ft³/s, Aug. 6, 1989.