USGS Water-Year Summary 2021
04087440 LAKE MICHIGAN AT CHICAGO LOCK AT CHICAGO, IL
LOCATION - Lat 41°53'18", long 87°36'27" referenced to North American Datum of 1927, in NE 1/4 NE 1/4 SE 1/4 sec.10, T.39 N., R.14 E., Cook County, IL, Hydrologic Unit 04060200, on the lake side of the downstream right guidewall, approximately due North of the riverside gates of the Chicago Lock.
DRAINAGE AREA - Indeterminate.
PERIOD OF RECORD -
STAGE: August 1997 to September 2003 and October 2007 to current.
GAGE - Water-stage recorder and cellular telemeter. Datum of gage is 579.48 ft above NGVD of 1929 (Chicago City Datum) (579.19 ft NAVD 1988).
EXTREMES FOR PERIOD OF RECORD -
Maximum gage height, 5.32ft, May 17, 2020; minimum, -4.07 ft., Jan. 18, 2013,
may be exaggerated by wave action.