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USGS Water-Year Summary 2024
05443500 ROCK RIVER AT COMO, IL
LOCATION - Lat 41°46'20", long 89°44'44" referenced to North American Datum of 1983, in NW 1/4 NW 1/4 NW 1/4 sec.31, T.21 N., R.7 E., Whiteside County, IL, Hydrologic Unit 07090005, downstream side of Route 30 bridge, slightly left of the center, 0.5 mi upstream from Como, 2.5 mi downstream from Rock Falls, 3 mi upstream from Elkhorn Creek, and at mile 68.5.
DRAINAGE AREA - 8,753 mi².
REVISIONS HISTORY - WSP 1308: 1915(M), 1917-18(M), 1922(M), 1924(M), 1926(M), 1928(M), 1931-32(M), 1934(M). WDR IL-79-1: Drainage area. WDR IL-97-l: 1996 (Dec. 12-23).
Revisions: Gage datum was updated to 603.13 ft NAVD88 on September 15, 2022, based on a GNSS Level II survey using GEOID18.
Revisions: Gage datum was updated to 603.13 ft NAVD88 on September 15, 2022, based on a GNSS Level II survey using GEOID18.
SURFACE-WATER RECORDS
PERIOD OF RECORD -
SURFACE-WATER DISCHARGE AND STAGE
DISCHARGE: March to December 1905, October 1914 to September 1971,
October 1977 to September 1986. Water years 1987-90, seven-month period
(March to September). October 1990 to current.
Published as "at Sterling" 1905-6 and as "at Lyndon" 1914-34.
Records published for both sites December 1933 to September 1934.
Monthly discharge only for some periods, published in WSP 1308.
STAGE: Water years 1994 to current.
PARTIAL RECORD: Annual maximum, water years 1972-77.
SURFACE-WATER QUALITY
CHEMICAL: Water years 1978-91 and 2009-2011.
SURFACE-WATER DISCHARGE AND STAGE
DISCHARGE: March to December 1905, October 1914 to September 1971,
October 1977 to September 1986. Water years 1987-90, seven-month period
(March to September). October 1990 to current.
Published as "at Sterling" 1905-6 and as "at Lyndon" 1914-34.
Records published for both sites December 1933 to September 1934.
Monthly discharge only for some periods, published in WSP 1308.
STAGE: Water years 1994 to current.
PARTIAL RECORD: Annual maximum, water years 1972-77.
SURFACE-WATER QUALITY
CHEMICAL: Water years 1978-91 and 2009-2011.
GAGE - Water-stage recorder and U.S. Army Corps of Engineers satellite telemeter. Datum of gage is 603.13 ft. NAVD of 1988. September 30, 1934, to September 17, 2014, site located 0.7 mi upstream, at datum 0.62 ft. higher. November 24, 1914, to September 30, 1934, nonrecording gage at Lyndon, 15.8 mi downstream at datum 22.46 ft lower. January 6, 1905, to February 17, 1906, nonrecording gage at Sterling, 3.7 mi upstream at different datum.
REMARKS - Some diurnal fluctuation caused by dam and powerplants upstream from station.
Accuracy of records is discussed in the annual Station Analysis archived at the USGS IL Water Science Center.
EXTREMES FOR PERIOD OF RECORD - SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 59,700 ft³/s, April 21, 1973, gage height, 15.66 ft , site and datum then in use; maximum gage height, 17.51 ft, February 7, 1938, ice jam, site and datum then in use; minimum discharge, 390 ft³/s, July 27, 2003 and July 12, 2005, result of regulation.
