LOCATION.-- Lat 41°42'28", long 87°57'47" (NAD of 1927), in NE1/4SW1/4 sec.10, T.37 N., R.11 E., Du Page County, Hydrologic Unit 07120004, on concrete abutment on right bank, 50 ft upstream from bridge on Bluff Road at south edge of Argonne National Laboratory, 2.5 mi northeast of Lemont, and at mile 1.

DRAINAGE AREA.-- 13.0 mi²

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: December 1985 to current year.

STAGE: Water years 1994 to current year.

PARTIAL RECORD: Annual maximum, water years 1961-79.

PRECIPITATION: April 1986 to current year.

SURFACE-WATER QUALITY

MISCELLANEOUS: Water year 2000; contaminants in streambed sediments, water year 2000.

BIOLOGICAL

BENTHIC MACROINVERTEBRATES: Water year 2000.

FISH: Water year 2001.

HABITAT: Water year 2000.

REVISED RECORDS.-- WDR IL-77-1: 1961-76(M).

GAGE.-- Water-stage recorder, phone telemeter, unheated tipping-bucket rain gage, and crest-stage gage. Datum of gage is 630.00 ft above NGVD of 1929. Oct. 11, 1961, to Sept. 30, 1976, crest-stage gage on bridge 50 ft downstream at datum 11.22 ft higher.

REMARKS.-- For precipitation records, snowfall-affected data can result during cold weather when snow fills the rain-gage funnel and then melts as temperatures rise. Snowfall-affected data are subject to appreciable errors.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 3,070 ft³/s, July 18,1996, gage height, 17.53 ft; no flow at times in most years.

PRECIPITATION: Maximum daily total, 6.17 in., July 17, 1996.

REMARKS FOR CURRENT YEAR.--Fish community samples were collected as part of the National Water-Quality Assessment program (NAWQA) in the upper Illinois River Basin. Collections were made with a single pass of the entire reach with a backpack electroshocker with supplementary seine hauls and kicks. Fishes were identified by C. A. Taylor, Illinois Natural History Survey, Champaign. Reach A begins 85 feet downstream of Old Bluff Road and continues downstream for 492 feet.