LOCATION.-- Lat 41°34'06", long 87°36'28" (NAD of 1927), in SE1/4NW1/4 sec.34, T.36 N., R.14 E., Cook County, Hydrologic Unit 07120003, on right bank at downstream side of bridge on Margaret Street in Thornton, 1.0 mi downstream from North Creek, and at mile 4.2.

DRAINAGE AREA.-- 104 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: May 1948 to current year. Prior to October 1974, records published with those for streams in the St. Lawrence River basin (WSP 1307, 1727, 1911, 2111, WDR IL 1971-74).

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1979-91.

REVISED RECORDS.-- WSP 1707: Drainage area.

GAGE.-- Water-stage recorder, phone telemeter, and crest-stage gage. Datum of gage is 586.43 ft above NGVD of 1929. Prior to Dec. 18, 1948, nonrecording gage at same site and datum.

REMARKS.-- Effluent from sewage-treatment plant upstream consists of publicly supplied water from Lake Michigan and ground water sources.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 4,700 ft³/s, July 13, 1957, gage height, 16.00 ft; maximum gage height, 17.06 ft, June 14, 1981, discharge, 4,140 ft³/s, minimum daily discharge, 4.4 ft³/s, Sept. 11, 1949.

EXTREMES OUTSIDE PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Flood of Apr. 5, 1947, reached a stage of 14.34 ft (from floodmark), discharge, 4,200 ft³/s.