LOCATION.-- Lat 41°49'20", long 87°49'15" (NAD of 1927), in SW1/4SW1/4 sec.36, T.39 N., R.12 E., Cook County, Hydrologic Unit 07120004, on left bank 400 ft downstream from bridge on Barry Point Road in Riverside, 500 ft downstream from Hoffman Dam, 4,000 ft downstream from Salt Creek, and at mile 44.3.

DRAINAGE AREA.-- 630 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1943 to current year. Monthly discharge only for some periods, published in WSP 1308.

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1987-92 and 1999 to 2004.

SEDIMENT: April 1979 to September 1982, January 2003 to current year.

MISCELLANEOUS: Contaminants in streambed sediments, August 1998; contaminants in fish tissue, August 1998; sediment concentration and particle size, water years 1998-2003.

BIOLOGICAL

ALGAE: Water years 1989, 1990, and 2002-03.

BENTHIC MACROINVERTEBRATES: Water years 1999 and 2002.

FISH: Water years 1999-2000 and 2002-04.

HABITAT: Water years 1999 and 2002-04.

REVISED RECORDS.-- WSP 1174: 1944, 1948. WSP 1308: 1944(M). WDR IL-75-1: Drainage area.

GAGE.-- Water-stage recorder, U.S. Army Corps of Engineers satellite telemeter, automatic water sampler, and rain gage, and concrete dam. Datum of gage is 594.68 ft above NGVD of 1929. Prior to Nov. 27, 1946, nonrecording gage at bridge 400 ft upstream at same datum.

REMARKS.-- Occasional regulation by gates at Hoffman Dam.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 9,770 ft³/s, Aug. 15, 1987, gage height, 9.90 ft; no flow Aug. 22-24, 1962, and part of Sept. 5, 1968, Aug. 31, 1974, Oct. 7, 1974.

SUSPENDED-SEDIMENT CONCENTRATIONS: Maximum daily mean, 297 mg/L Apr. 12, 1979; minimum daily mean, 3 mg/L Jan. 24, Feb. 1, 3, 4, 1982

SUSPENDED-SEDIMENT LOADS: Maximum daily, 3,240 tons Apr. 12, 1979; minimum daily, 1.5 tons Feb. 3, 4, 1982.

EXTREMES OUTSIDE PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Flood of Mar. 18, 1919, reached a discharge of 7,450 ft³/s, gage height, 9.43 ft., present datum, from information furnished by Metropolitan Water Reclamation District of Greater Chicago.

REMARKS FOR CURRENT YEAR.--Benthic macroinvertebrate community samples were collected as part of the National Water-Quality Assessment program (NAWQA) in the upper Illinois River Basin. One quantitative (Richest-Targeted Habitat) and one qualitative (Qualitative-Multiple Habitat) sample were collected in accordance with the NAWQA protocols (Moulton and others, 2002). The quantitative sample was a composite of macroinvertebrates from about 10 submerged tree branches. Branches were cut underwater, gathered in a 500µm mesh net, and invertebrates were washed or picked from the branches. The average length and average diameter of each branch were measured and used to calculate an approximate surface area. The qualitative sample was collected from many habitat types within the sampling reach to obtain as complete a list of invertebrate taxa as possible. All samples were processed by the USGS National Water-Quality Laboratory. Phylum, Class, Order, Suborder, Family, Subfamily, and Tribe are listed and arranged according to the USGS National Water-Quality Laboratory taxonomic hierarchy. Reach A is located 492 ft upstream of the Joliet Road bridge (1.48 mi downstream of gage) in Riverside, and continues upstream for 984 ft. The surface area sampled at reach A was 0.19 m².