LOCATION.-- Lat 40°19'49", long 90°53'46" (NAD of 1927), in SE1/4SW1/4 sec.18, T.4 N., R.4 W., McDonough County, Hydrologic Unit 07130010, on right bank at downstream side of bridge on State Highway 61, 0.2 mi downstream from a railroad bridge, 1 mi southwest of Colmar, 1.8 mi upstream from Troublesome Creek, and at mile 61.8.

DRAINAGE AREA.-- 655 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1944 to current year.

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1975-91 and 1998.

MISCELLANEOUS: Contaminants in streambed sediments, July 1997; contaminants in fish tissue, July 1997; streambank sediment size, October 1997; streambed sediment size, October 1997.

BIOLOGICAL

ALGAE: Water years 1996-98.

BENTHIC MACROINVERTEBRATES: Water years 1996-98.

FISH: Water year 1997-98.

HABITAT: Water years 1996-98, 2003.

GAGE.-- Water-stage recorder, U.S. Army Corps of Engineers satellite telemeter and crest-stage gage. Datum of gage is 491.53 ft above NGVD of 1929 (491.27 ft NAVD 1988). Prior to July 13, 1945, nonrecording gage at same site and datum.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 38,900 ft³/s, Mar. 5, 1985, gage height, 26.61 ft; maximum gage height, 27.03 ft, Jan. 3, 1965, ice jam; no flow part of each day Dec. 8, 9, 12, 13, 17, 21, 1955, due to temporary dam upstream; no flow Oct. 19, 1988.

REMARKS FOR CURRENT YEAR.--Fish community samples were collected as part of the National Water-Quality Assessment program (NAWQA), in the lower Illinois River Basin. Taxonomy is based on Robins and others (1991), except where modified for the family Moronidae (Johnson, 1984) and the order Cyprinidontiformes (Parenti, 1981). Common names were compared to the current Illinois fish species list posted by Illinois Natural History Survey. Collection methods followed Meador and others (1993). Collections were taken with a boat electroshocker and seine. Fishes were identified in the field by C. A. Taylor, Illinois Natural History Survey, Champaign. Representative specimens were preserved, identified, and vouchered at the Illinois Natural History Survey fish collection. The reach begins 1326 feet downstream of the State Highway 61 bridge (gage), and continues downstream 1283 feet.