USGS Water-Year Summary for Site 05555300

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	Available Parameters
	00010 Temperature, water(Mean)
	00020 Temperature, air(Mean)
	00060 Discharge(Mean)
	00065 Gage height(Mean)

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Water year 2025: 2025-10-01 to 2026-09-30

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USGS Water-Year Summary 2025

05555300 VERMILION RIVER NEAR LEONORE, IL

LOCATION - Lat 41°12'30", long 88°55'50" referenced to North American Datum of 1983, in SW 1/4 SW 1/4 sec.30, T.32 N., R.3 E., LaSalle County, IL, Hydrologic Unit 07130002, on left downstream side of bridge on County Highway 57 (Red, White and Blue Bridge Road), 3 mi northeast of Leonore, 6.2 mi downstream from Otter Creek, 8 mi northwest of Streator, and at mile 17.2.

DRAINAGE AREA - 1,251 mi². at site prior to October 1971, 1,278 sq. mi.

REVISIONS HISTORY -

WSP 745: 1931-32. WSP 1308: 1932(M), 1935-38(M), 1940(M), 1942(M). WDR IL-75-1: Drainage area.

Revisions: Gage height and discharge for Aug, 29, 2019, were revised on Mar. 25, 2020, to fill a gap in the record.

Revisions: Gage datum was revised to 521.14 ft NAVD88 on June 6, 2023, as determined by a GNSS Level II survey using GEOID18. Oct. 1, 1971, to June 6, 2023, gage datum was published as 520.58 ft above NGVD of 1929 (520.40 ft NAVD 1988), furnished.

Revisions: Gage Height for the period of February 10 – April 1, 2025 was revised on August 14, 2025 to change primary reference from TRP-1 to TRP-2. TRP-1 was found unsettled by 0.28 ft during levels on August 12, 2025. Based on readings of both references back to December 2024, unsettling most likely occurred on February 10, 2025 due to shifting ice. TRP-2 was also unsettled by 0.018 ft, so a Set-1 datum correction was applied up the event on February 10 to 0.02 ft later that day. The correction was held constant through the end of analyzed record on April 1, 2025. Gage height corrections and measurement mean gage heights were redrawn to match readings of TRP-2. Readings of TRP-1 were deselected for publication and readings of TR-2 were adjusted by 0.02 ft.

Revisions: Discharge for the period of February 10 – April 1, 2025 was revised on August 14, 2025 to change shifts based on revision of the gage height due to unsettling of the primary reference. Shifts were matched to event timing and placement of measurements in this period with new mean gage heights. Ice estimation on February 10-March 5, 2025 was adjusted based on these changes to the discharge site in conjunction with comparison to upstream site 05554500.

SURFACE-WATER RECORDS

PERIOD OF RECORD -
SURFACE-WATER DISCHARGE AND STAGE
  DISCHARGE: May 1931 to current. Prior to October 1971, published as "at Lowell."
  STAGE: Water years 1994 to current.
SURFACE-WATER QUALITY
  CHEMICAL: Water years 1978 to 1991 and 2009 to 2011.
  SEDIMENT: June 1980 to September 1981.
  MISCELLANEOUS: Contaminants in streambed sediments, July 1996; contaminants in fish tissue,
    July 1996.

GAGE - Water-stage recorder, satellite telemeter and crest-stage gage. Datum of gage is 521.14 ft above NAVD of 1988. Prior to Aug. 20, 1952, nonrecording gage at site 6.8 mi downstream at datum of 500.61 ft NGVD29. Aug. 20, 1952, to Sept. 30, 1971, nonrecording gage at site 6.7 mi downstream, at datum of 500.61 ft NGVD29.

REMARKS - Accuracy of records is discussed in the annual Station Analysis archived at the USGS IL Water Science Center.

EXTREMES FOR PERIOD OF RECORD -
SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 38,900 ft³/s, Apr. 18, 2013, gage height, 30.25 ft; minimum, 2.6 ft³/s, Aug. 3, 1988.
SUSPENDED-SEDIMENT CONCENTRATIONS: Maximum daily mean, 6,730 mg/L Aug. 15, 1981; minimum daily mean, 1 mg/L Feb. 5, 1981.
SUSPENDED-SEDIMENT LOADS: Maximum daily, 209,000 tons Aug. 15, 1981; minimum daily, 0.24 ton Feb. 5, 1981.