LOCATION.-- Lat 42°00'44", long 87°47'44" (NAD of 1927), in SW1/4SE1/4 sec.30, T.41 N., R.13 E., Cook County, Hydrologic Unit 07120003, on right bank at downstream side of bridge on Touhy Avenue in Niles, 3.6 mi downstream from West Fork of North Branch, 7.9 mi upstream from North Shore Channel, and at mile 51.4.

DRAINAGE AREA.-- 100 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1950 to current year. Prior to October 1952, records published with those for streams in the St. Lawrence River basin (WSP 1207, 1237).

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1978 to 1991. Additional chemical data for water years 1972-77 are published in Water-Resources Investigations 78-22 and 79-23 as site HCC 07.

SEDIMENT: October 1984 to September 1986.

BIOLOGICAL

ALGAE: Pigment and biomass, Water years 1989 and 1990.

REVISED RECORDS.-- WDR IL-75-1: Drainage area.

GAGE.-- Water-stage recorder and phone telemeter. Datum of gage is 601.99 ft above NGVD of 1929.

REMARKS.-- Diurnal fluctuation at low flow caused by sewage-treatment plants.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 2,590 ft³/s, Aug. 14, 1987, gage height, 11.35 ft; minimum daily discharge, .10 ft³/s, Sept. 30, 1953.

SUSPENDED-SEDIMENT CONCENTRATIONS: Maximum daily mean, 285 mg/L July 15, 1985; minimum daily mean, 2 mg/L Jan. 23 to Feb. 21, 1985, and Jan. 30-31, 1986.

SUSPENDED-SEDIMENT LOADS: Maximum daily, 566 tons July 8, 1986; minimum daily, 0.14 ton Jan. 29, Jan. 31 to Feb. 4, Feb. 6-11, 15-19, 1985.