LOCATION.-- Lat 40°40'18", long 90°22'33" (NAD of 1927), in SW1/4 SW1/4 SE1/4 sec.15, T.8 N., R.1 E., Fulton County, Hydrologic Unit 07130005. Located at CR20, 3.1 miles east of Avon.

DRAINAGE AREA.-- 271.2 mi²

PERIOD OF RECORD.--

BIOLOGICAL

BENTHIC MACROINVERTEBRATES: Water year 1997.

REMARKS.--Station established as a low-flow water-quality sampling site in August 1997 as part of the National Water-Quality Assessment (NAWQA), Lower Illinois River Basin synoptic study.

REMARKS FOR CURRENT YEAR.-- Biological samples were collected downstream from the CR20 bridge. 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) sample was collected in accordance with the NAWQA protocols (Cuffney and others, 1993). The quantitative sample was a composite of macroinvertebrates from about 10 submerged tree branches. Branches were cut underwater, gathered in a 425µm 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. 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 downstream from the SR 41 bridge and continues downstream for about 100 meters. The surface area sampled at reach A was 0.39 m².