LOCATION.-- Lat 40°01'51", long 88°35'20" (NAD of 1927), in NE1/4SW1/4 sec.12, T.18 N., R.5 E., Piatt County, Hydrologic Unit 07130006, on right downstream side of highway bridge, 0.5 mi west of Monticello, and at mile 162.2.

DRAINAGE AREA.-- 550 mi².

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: February 1908 to December 1912, June 1914 to current year. Monthly discharge only for some periods, published in WSP 1308. Published as "near Monticello" 1910-12.

STAGE: Water years 1994 to current year.

SURFACE-WATER QUALITY

CHEMICAL: Water years 1990-92, 1997-98, and 2001 to current year.

MISCELLANEOUS: Contaminants in streambed sediments, July 1996; contaminants in fish tissue, July 1996; streambank sediment size, October 1997; streambed sediment size, October 1997.

BIOLOGICAL

ALGAE: Water years 1996-98 and 2002-03.

BENTHIC MACROINVERTEBRATES: Water years 1996-98 and 2002.

FISH: Water years 1997-98 and 2002-04.

HABITAT: Water years 1996-98 and 2002-04.

REVISED RECORDS.-- WSP 525: 1920. WSP 1115: 1946-47. WSP 1208: 1915-16, 1918-20, 1927, 1929, 1939. WSP 1508: 1908(M), 1917, 1928(M). WDR IL-81-2: 1909(P), 1912(P), 1915(P), 1919-32(P), 1935(P), 1937-38(P), 1940-41(P), 1944(P), 1946-47(P). WDR IL-89-2: 1988.

GAGE.-- Water-stage recorder, phone telemeter, and crest-stage gage. Datum of gage is 625.89 ft above NGVD of 1929. Prior to Sept. 30, 1964, nonrecording gage at site 0.2 mi downstream at same datum. Oct. 1, 1964, to Oct. 22, 1971, nonrecording gage at present site and datum.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 19,000 ft³/s, Oct. 4, 1926, gage height, 18.50 ft, from graph based on gage readings, site then in use; maximum gage height, 19.06 ft, Apr. 13, 1994, discharge, 15,900 ft³/s; no flow Aug. 28, Sept. 5, 11, 17, 18, Oct. 30, 31, Nov. 1, 1988.

REMARKS FOR CURRENT YEAR.--Benthic macroinvertebrate community samples were collected as part of the National Water-Quality Assessment program (NAWQA) in the lower 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 ten 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 begins 820 ft upstream of the gage, and continues upstream for 915 ft. The surface area sampled was 0.20 m².