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QUADRANGLE: Leonore, 7.5' series

LOCATION: Lat. 41 12'30", long 88 55'51", in SW1/4 SW1/4 sec. 30, T.32 N., R.3 E., La Salle County, Hydrologic Unit 07130002, on left downstream side of bridge on County Highway 57 (Red, White and Blue Bridge Road), 3.0 miles northeast of Leonore, 6.2 miles downstream from Otter Creek, 8.0 miles northwest of Streator, and at mile 17.2.

ESTABLISHMENT AND HISTORY: Digital water-stage recorder (ADR), and bubble gage installed Oct. 28, 1971. Two crest-stage gages (CSG’s) installed October 1973. Both CSG’s were replaced May 20, 1997. Graphic water-stage backup recorder installed Nov. 23, 1976. U.S. Army Corp. of Engineers installed a data-collection platform (DCP) in December 1985. Wire-weight gage destroyed July 1983 and reinstalled March 1991. Graphic recorder has since been removed.

Station operated 6.7 miles downstream at Lowell from 1931- 1971 with a drainage area of 1,278 sq. mi. Records equivalent.

DRAINAGE AREA: 1,251 sq. mi. (from USGS topographic maps)

GAGE: Digital water-stage recorder (ADR), satellite telemeter (DCP) and bubble gage in 64" X 64" Armco steel shelter. Outside base gage is a wire-weight gage located on the downstream side of the bridge, 140 feet right of the gage house. Two crest-stage gages are located about 40 ft. and 60 ft. downstream of the gage and about 15 ft. landward. Electric service is provided to the gage.

GAGE DATUM: Datum of gage is 520.58 ft. above NGVD of 1929.

CHANNEL AND CONTROL: Bed of stream is composed of sand, gravel, and bedrock. The channel approaches the gage at an angle and curves to the left at the gage. The channel is straight 200 to 2000 ft. downstream. Both banks are high and confine all flow to the bridge opening.

The low-stage control is a gravel bar about 2200 ft. downstream, created from the outwash of a tributary which enters the channel from the left. Medium and high stages are channel controlled.

DISCHARGE MEASUREMENTS: Low stages may be measured 125 ft. upstream from gage at a gravel riffle. Higher stages may be measured from the downstream side of the bridge which is marked off every 5.0 ft. starting from the left abutment.

Traffic safety: The attached traffic safety plan must be followed when making discharge measurements from the bridge. It documents the appropriate sign(s), cones, and possibly flag persons needed to prevent traffic-related accidents. Vehicle hazard lights must be used when approaching the traffic-safety site and continued until after personnel and vehicles have safely left the site.

FLOODS: July 15, 1958, 33,500 cfs (gage height 15.30 ft. at Lowell), Dec. 4, 1982, 31,800 cfs (gage height 27.13 ft. at present site).

POINT OF ZERO FLOW: Approximately 2.3 ft. gage datum.

WINTER FLOW: Considerable ice effect during winter months.

REGULATION AND DIVERSIONS: Low flows are occasionally affected by fluctuating water withdrawals by Northern Illinois Water Corporation at Streator, IL.