LOCATION.-- Lat 42°18'10", long 89°37'10" (NAD of 1927), in SE1/4 sec.30, T.27 N., R.8 E., Stephenson County, Hydrologic Unit 07090003, on right bank on property of Commonwealth Edison Company in Freeport, 0.3 mi upstream from Stephenson Street Bridge, 5 mi upstream from Yellow Creek, and at mile 61.9.

DRAINAGE AREA.-- 1,326 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: September 1914 to current year.

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1978-91.

REVISED RECORDS.-- WSP 1175: 1944, 1948. WSP 1508: 1915(M), 1917(M), 1921(M), 1924(M), 1928(M), 1930(M), 1935-37. WDR IL-75-1: Drainage area.

GAGE.-- Water-stage recorder, and U.S. Army Corps of Engineers satellite telemeter and rain gage. Datum of gage is 743.18 ft above NGVD of 1929. Prior to Jan. 15, 1935, nonrecording gage at site 0.9 mi downstream at datum 4.2 ft lower. July 13, 1943, to Aug. 25, 1982, auxiliary nonrecording gage read once daily 0.9 mi down stream.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 18,400 ft³/s, Mar. 16, 1929, gage height, 19.76 ft, site and datum then in use; minimum, 82 ft³/s, Dec. 11, 1957, result of freezeup.