LOCATION.-- Lat 40°49'42", long 88°34'29" (NAD of 1927), in SW1/4 sec.6, T.27 N., R.6 E., Livingston County, Hydrologic Unit 07130002, at county road bridge, 0.3 mi. east of McDowell, 0.4 mi. downstream from Turtle Creek, 7.3 mi downstream from confluence of North and South Branches, and at mile 68.4.

DRAINAGE AREA.-- 551 mi²

PERIOD OF RECORD.--

SURFACE-WATER QUALITY

CHEMICAL: Water years 1978-91.

BIOLOGICAL

BENTHIC MACROINVERTEBRATES: Water year 1997.

REMARKS.--Water-discharge records from the Vermilion River at Pontiac (Station 05554500) were used to estimate mean daily discharges for this station. Station established as a low-flow water-quality samping site in August 1997 as part of the National Water-Quality Assessment (NAWQA), Lower Illinos River Basin synoptic study.

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) 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 33 meters downstream from the 1400 N bridge and continues downstream for 176 meters. The surface area sampled at reach A was 0.27 m².