LOCATION.-- Lat 39°44'32", long 89°34'02" (NAD of 1927), in NE1/4NW1/4 sec.20, T.15 N., R.4 W., Sangamon County, Hydrologic Unit 07130007, on right bank at city of Springfield dam, 100 ft downstream from Horse Creek, 1.7 mi southwest of Rochester, and at mile 7.4. Auxiliary gage 1.2 miles downstream.

DRAINAGE AREA.-- 867 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: July 1949 to current year.

STAGE: Water years 1994 to current year.

REVISED RECORDS.-- WDR IL-75-1: Drainage area.

GAGE.-- Water-stage recorder, U.S. Army Corps of Engineers satellite telemeter, and crest-stage gage. Datum of gage is 511.30 ft above NGVD of 1929. Prior to Oct. 1, 1964, water-stage recorder, and Oct. 1, 1964, to Apr. 12, 1966, non-recording gage, at site 1.8 mi downstream at same datum. Auxiliary water-stage recorder at site 1.2 mi downstream. Prior to May 19, 1950, auxiliary non-recording gage at site 6.2 mi downstream. May 19, 1950 to Apr. 29, 1975, auxiliary non-recording gage at site 1.2 mi downstream.

REMARKS.-- Beginning Apr. 14, 1955, diversion for Springfield's public-water supply periodically occurs upstream from the station and upstream from the dam between the confluence of Horse Creek and the gage. The water is diverted to Lake Springfield. Occasional regulation occurs due to operation of the gate at the diversion dam. Pumpage from Lake Taylorville into stream generally occurs during the fall upstream from the gage.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 20,300 ft³/s, Apr. 14, 1994, gage height, 32.40 ft; maximum gage height, 33.65 ft, May 13, 2002, discharge 14,100 ft³/s; no flow Nov. 4-6, 1985, Sept. 9, 1987, and for many days in 1988-90, 92, and 2000.