LOCATION.-- Lat 42°11'40", long 88°59'56" (NAD of 1983), in NE1/4NE1/4 sec.21, T.43 N., R.2 E., Winnebago County, Hydrologic Unit 07090006, on left bank at upstream side of bridge on Blackhawk Road, 1.4 mi downstream from South Branch Kishwaukee River, 2 mi southwest of Perryville, 7.1 mi upstream from Killbuck Creek, and at mile 9.6.

DRAINAGE AREA.-- 1,099 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1939 to current year.

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1978-91.

SEDIMENT: April 1979 to September 1981.

REVISED RECORDS.-- WSP 1175: 1941(P), 1942. WSP 1508: 1941, 1949. WDR IL-75-1: Drainage area.

GAGE.-- Water-stage recorder, phone telemeter, and U.S. Army Corps of Engineers satellite telemeter and rain gage. Datum of gage is 692.13 ft above NGVD of 1929 (levels by U.S. Army Corps of Engineers) (691.96 ft NAVD 1988). Prior to Apr. 30, 1949, nonrecording gage at same site and datum.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 24,200 ft³/s, July 18, 1996, gage height 23.54 ft; minimum discharge, 46 ft³/s, Oct. 6, 7, 10, 1956.

SUSPENDED-SEDIMENT CONCENTRATION: Maximum daily mean, 1,860 mg/L June 7, 1980; minimum daily mean, 13 mg/L Sept. 17, 1981.

SUSPENDED-SEDIMENT LOADS: Maximum daily, 24,000 tons Apr. 1, 1979; minimum daily, 11 tons Sept. 17, 1981.

EXTREMES OUTSIDE PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Flood in January 1938 reached a stage of 23.85 ft, from information by the U.S. Army Corps of Engineers.