LOCATION.-- Lat 41°49'33", long 87°54'02" (NAD of 1927), in NE1/4SE1/4 sec.31, T.39 N., R.12 E., Cook County, Hydrologic Unit 07120004, on left pier at upstream side of bridge on Wolf Road, in Cook County Forest Preserve, 0.5 mi north of Western Springs, and at mile 8.8.

DRAINAGE AREA.-- 115 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1945 to current year.

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1978-91 and 1999 to current year.

MISCELLANEOUS: Contaminants in streambed sediments, August 1998; contaminants in fish tissue, August 1998.

BIOLOGICAL

ALGAE: Water years 1989, 1990, and 2002-03.

BENTHIC MACROINVERTEBRATES: Water years 1999 and 2002.

FISH: Water years 1999-2000 and 2002-04.

HABITAT: Water years 1999 and 2002-04.

REVISED RECORDS.-- WSP 1915: Drainage area. WRD IL-87-2: Drainage area. WRD IL-97-2: July 21 - Sept. 26, 1996.

GAGE.-- Water-stage recorder, phone telemeter, and crest-stage gage. Datum of gage is 624.93 ft above NGVD of 1929. Prior to July 26, 1946, nonrecording gage at same site and datum.

REMARKS.-- Occasional regulation by sewage treatment plants upstream from station. Since May 28, 1996, some flow temporarily diverted for flood control to Elmhurst Quarry Flood Control Reservoir 12.3 miles upstream from gage.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 3,540 ft³/s, Aug. 17, 1987, gage height, 10.54 ft; minimum, no flow, May 27, 1998, due to bridge construction.