LOCATION.-- Lat 42°09'59", long 88°17'25" (NAD of 1927), in NE1/4NW1/4 sec.34, T.43 N., R.8 E., McHenry County, Hydrologic Unit 07120006, on right bank 20 ft upstream from bridge on State Highway 62 (Algonquin Road) in Algonquin, 140 ft upstream from Algonquin Dam, and at mile 81.6.

DRAINAGE AREA.-- 1,403 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1915 to current year. Monthly discharge only for some periods, published in WSP 1308.

STAGE: Water years 1994 to current year.

BIOLOGICAL

ALGAE: Pigment and biomass, Water year 1989.

REVISED RECORDS.-- WSP 1175: 1916. WDR IL-75-1: Drainage area.

GAGE.-- Water-stage recorder, phone telemeter, and concrete dam with adjustable gate. Datum of gage is 729.48 ft above NGVD of 1929. Prior to Oct. 20, 1933, nonrecording gage at site 20 ft downstream at same datum.

REMARKS.-- Flow regulated by gate in Algonquin Dam, Stratton Lock and Dam (previously known as McHenry Dam), 16 mi upstream from station, and occasionally affected by wind action.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 6,720 ft³/s, May 22, 2004, gage height 3.09 ft, due to regulation; maximum gage height, 4.50 ft, April 1, 1916; from graph based on gage readings; no flow, Nov. 26, 1952, Nov. 20, 1953, Oct. 25, 1956 and Sept. 9, 14, 1958, result of windstorm.