LOCATION.-- Lat 41°12'30", long 88°55'51" (NAD of 1927), in SW1/4SW1/4 sec.30, T.32 N., R.3 E., La Salle County, Hydrologic Unit 07130002, on left downstream side of bridge on County Highway 57 (Red, White and Blue Bridge Road), 3 mi northeast of Leonore, 6.2 mi downstream from Otter Creek, 8 mi northwest of Streator, and at mile 17.2.

DRAINAGE AREA.-- 1,251 mi². Area at site used prior to October 1971, 1,278 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: May 1931 to current year. Prior to October 1971, published as "at Lowell."

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1978 to 1991.

SEDIMENT: June 1980 to September 1981.

MISCELLANEOUS: Contaminants in streambed sediments, July 1996; contaminants in fish tissue, July 1996.

REVISED RECORDS.-- WSP 745: 1931-32. WSP 1308: 1932(M), 1935-38(M), 1940(M), 1942(M). WDR IL-75-1: Drainage area.

GAGE.-- Water-stage recorder, U.S. Army Corps of Engineers satellite telemeter and crest-stage gage. Datum of gage is 520.58 ft above NGVD of 1929 (520.40 ft NAVD 1988). Prior to Aug. 20, 1952, nonrecording gage at site 6.8 mi downstream at datum 19.97 ft lower. Aug. 20, 1952 to Sept. 30, 1971, nonrecording gage at site 6.7 mi downstream at datum 19.97 ft lower.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 33,500 ft³/s, July 15, 1958, gage height, 15.30 ft, from graph based on gage readings, site and datum then in use; maximum gage height, 27.13 ft, Dec. 4, 1982, present site and datum (discharge 31,800 ft³/s); minimum discharge, 2.6 ft³/s, Aug. 3, 1988.

SUSPENDED-SEDIMENT CONCENTRATIONS: Maximum daily mean, 6,730 mg/L Aug. 15, 1981; minimum daily mean, 1 mg/L Feb. 5, 1981.

SUSPENDED-SEDIMENT LOADS: Maximum daily, 209,000 tons Aug. 15, 1981; minimum daily, 0.24 ton Feb. 5, 1981.