LOCATION.-- Lat 41°16'19", long 90°22'39" (NAD of 1927), in NE1/4SE1/4 sec.21, T.15 N., R.1 E., Henry County, Hydrologic Unit 07080104, on left bank at downstream side of bridge on U.S. Highway 150, 1.5 mi north of Opheim, 5.5 mi south of Orion, and at mile 51.5.

DRAINAGE AREA.-- 155 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1940 to current year. Monthly discharge only for some periods, published in WSP 1308.

STAGE: Water years 1994 to current year.

REVISED RECORDS.-- WSP 1175: 1947(P). WSP 1508: 1942. WDR IL-75-1: Drainage area.

GAGE.-- Water-stage recorder, phone telemeter and crest-stage gage. Datum of gage is 653.96 ft above NGVD of 1929 (U.S. Army Corps of Engineers bench mark). Prior to Apr. 4, 1941, and Apr. 8 to Nov. 11, 1981, nonrecording gage at same site and datum.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 8,910 ft³/s, Feb. 19, 1951, gage height, 13.41 ft, from floodmarks; maximum gage height, 15.52 ft, June 23, 1974, discharge, 5,760 ft³/s; minimum discharge, 0.3 ft³/s, Oct. 6, 1956.

EXTREMES OUTSIDE PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Flood of August 1924 reached a stage of 20.2 ft, from floodmarks.