LOCATION.-- Lat 41°23'04", long 88°47'21" (NAD of 1927), in SW1/4SE1/4 sec.29, T.34 N., R.4 E., La Salle County, Hydrologic Unit 07120007, on left bank under County Highway 18 bridge in Dayton, and at mile 5.2.

DRAINAGE AREA.-- 2,642 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: November 1914 to current year. Prior to April 1925, published as "at Wedron." Monthly discharge only for some periods, published in WSP 1308.

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1978-92 and 1996.

SEDIMENT: February 2003 to current year.

MISCELLANEOUS: Sediment concentration and particle size, water years 1996-97, 2003.

REVISED RECORDS.-- WSP 730: 1931. WSP 1208: 1930, 1935, 1939. WSP 1308: 1916(M), 1922(M), 1926-31(M), 1934-40(M), 1946-47(M). WDR IL-75-1: Drainage area. WDR IL-76-1: 1969.

GAGE.-- Water-stage recorder, phone telemeter, U.S. Army Corps of Engineers satellite telemeter, automatic water sampler, and crest-stage gage. Datum of gage is 462.30 ft above NGVD of 1929. Prior to Apr. 13, 1925, nonrecording gage at site 4.1 mi upstream at datum 496.80 ft above Memphis datum. Apr. 13, 1925, to Sept. 30, 1942, nonrecording gage at site 1,000 ft upstream at datum 7.70 ft below NGVD of 1929. Oct. 1, 1942, to Apr. 10, 1951, nonrecording gage, and Apr. 11, 1951, to Sept. 30, 1978, water-stage recorder, at site 1.000 ft upstream at same datum. Oct. 1, 1978 to June 11, 1997, water-stage recorder at site 500 ft upstream at same datum.

REMARKS.-- Regulation by hydropower plant upstream from gage.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 55,400 ft³/s, July 19, 1996, gage height, 24.47 ft, from rating curve extended above 43,000 ft³/s; affected by dam failure 500 ft upstream from gage then in use. Maximum gage height, 36.47 ft, Jan. 25, 1960, ice jam; minimum daily discharge, 1.0 ft³/s, Aug. 29, 1934, when turbines were shut down; minimum daily with plant operating, 78 ft³/s, Oct. 29, 1956.

SUSPENDED-SEDIMENT CONCENTRATIONS: Maximum daily, 2,380 mg/L, June 1, 2004; minimum daily, 4 mg/L, Feb. 18-20, 2003.

SUSPENDED-SEDIMENT LOADS: Maximum daily, 90,100 tons, June 1, 2004; minimum daily, 2.6 tons, Feb. 18, 2003.

REMARKS FOR CURRENT YEAR.-- Records fair except those for estimated daily discharges, which are poor.

A - When turbines were shut down; lowest daily mean with plant operating, 78 ft³/s, Oct. 29, 1956.

B - Gage height, 24.47 ft, from rating curve extended above 43,000 ft³/s, affected by dam failure 500 ft. upstream from gage then in use.

C - Ice jam.

D - Result of regulation by hydropower plant.

Table of Contents

Introduction

Station Descriptions

Surface-Water Data

Ground-Water Data

Meteorological Data

Biological Data