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 1997 to current year. 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.

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) (523.85 ft NAVD 1988). 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.