LOCATION.-- Lat 41°32'11", long 88°04'57" (NAD of 1983), in NE1/4NE1/4 sec. 9, T.35 N., R.10 E., Will County, Hydrologic Unit 07120004, on the downstream side of State Highway 53 (Ruby St.) bridge, and at river mile 15.7.

DRAINAGE AREA.-- 1,503 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: February 2005 to current year.

STAGE: February 2005 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1982-87.

GAGE.-- Water-stage recorder, acoustic-velocity meter, and satellite telemeter. Datum of gage is 0.00 ft above NGVD of 1929 (-0.29 ft NAVD 1988) (U.S. Army Corps of Engineers bench mark).

REMARKS.-- Flow regulated by navigation dams upstream and downstream from the gage. Since Jan. 17, 1900, flow includes diversion from Lake Michigan through the Chicago Sanitary and Ship Canal.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 11,500 ft³/s, Aug. 20, 2005, gage height, 539.82 ft; maximum gage height, 539.91 ft, Aug. 20, 2005, discharge, 10,100 ft³/s; periods of no flow or reverse flow are possible at this site.

EXTREMES OUTSIDE PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum measured discharge, 28,000 ft³/s, July 18, 1996, gage height unknown; maximum observed gage height, 539.96 ft, Jan. 13, 2005.