LOCATION.-- Lat 38°19'52", long 89°52'41" (NAD of 1983), in SW1/4NE1/4 sec.28, T.2 S., R.7 W., St. Clair County, Hydrologic Unit 07140204, on left bank at downstream side of bridge on State Highway 13 at New Athens, 0.6 mi downstream from Silver Creek and at mile 41.4.

DRAINAGE AREA.-- 5,220 mi², approximately.

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1909 to December 1912, October 1914 to September 1921, October 1934 to September 1971. Monthly discharge only for some periods, published in WSP 1308. Records for January 1907 to September 1909, published in WSP 265, have been found to be unreliable and should not be used.

REVISED RECORDS.-- WSP 805: 1935, WSP 1208: 1910-11, 1920. WSP 1508: 1912, 1915-16, 1919, 1921. See also PERIOD OF RECORD.

GAGE.-- Water-stage recorder. Datum of gage is 329.50 ft above NGVD of 1929 (329.05 ft NAVD 1988). Oct. 1, 1909, to Dec. 31, 1912, and June 22, 1914, to Sept. 30, 1921, nonrecording gage at site 0.2 mi upstream at same datum. Jan. 18, 1935, to May 24, 1967, water-stage recorder at site 0.5 mi downstream at same datum. May 25, 1967, to May 18, 1970, nonrecording gage at present site and datum. Since Oct. 1, 1937, auxiliary nonrecording gages on Mississippi River near mouth of Kaskaskia River 41 mi downstream.

REMARKS.-- Flow partially regulated since Apr. 1, 1967, by Carlyle Reservoir 65 mi above gage.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 83,000 ft³/s May 23, 1943, gage height, 39.35 ft (backwater from Mississippi River); minimum, 13 ft³/s Oct. 5, 1941, caused by backwater from Mississippi River; minimum, unaffected by backwater, 40 ft³/s Sept. 19, 1954. Maximum discharge since construction of Carlyle Reservoir, 32,800 ft³/s Dec. 26, 1967, gage height, 27.75 ft.