USGS Water-Year Summary for Site 12301933

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	Available Parameters
	00010 Temperature, water(Min.,Mean,Max.)
	00060 Discharge(Mean)
	00095 Specific cond at 25C(Mean,Max.,Min.)
	00300 Dissolved oxygen(Mean,Min.,Max.)
	00400 pH(Max.,Med.,Min.)
	63680 Turbidity, Form Neph(Mean,Min.,Max.)

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Water year 2024: 2024-10-01 to 2025-09-30

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USGS Water-Year Summary 2024

12301933 KOOTENAI RIVER BELOW LIBBY DAM, NEAR LIBBY, MT

LOCATION - Lat 48°24'02.39", long 115°19'07.39" referenced to North American Datum of 1983, in SW 1/4 SW 1/4 SW 1/4 sec.33, T.31 N., R.29 W., Lincoln County, MT, Hydrologic Unit 17010101, Kootenai National Forest, on right bank 0.7 mi downstream from Libby Dam, 2.8 mi upstream from Fisher River, 11 mi east of Libby, and at river mile 221.4.

DRAINAGE AREA - 8,999 mi².

REVISIONS HISTORY - Dissolved Oxygen (% saturation) data for the periods of July 31 2019, Nov. 14, 2022, were removed from publication on Apr. 5, 2023, as they were unable to be corrected to compensate for continuous changes in barometric pressure.

SURFACE-WATER RECORDS

PERIOD OF RECORD - October 1971 to current year.

GAGE - Water-stage recorder. Elevation of gage is 2,100 ft, referenced to the National Geodetic Vertical Datum of 1929 (U.S. Army Corps of Engineers bench mark). Prior to Feb. 13, 1974, nonrecording gage at site 0.4 mi upstream at same elevation.

REMARKS -

Flow has been completely regulated by Lake Koocanusa since Mar. 21, 1972. Irrigation diversions 
occur from tributaries in Canada and the United States upstream from the station.

WATER-QUALITY RECORDS

PERIOD OF DAILY RECORD -
WATER TEMPERATURE: July 2019 to February 2023.

TURBIDITY: July 2019 to February 2023.

SPECIFIC CONDUCTANCE: July 2019 to February 2023.

pH: July 2019 to February 2023.

DISSOLVED OXYGEN mg/L: July 2019 to February 2023.

CHLOROPHYLL: July 2019 to November 2021.

PHYCOCYANIN: July 2019 to December 2020.

REMARKS -

Sampling Location (WQ):

Discrete water samples are collected from the cableway at a single point at the thalweg of the cross-section, approximately 45’ from REW (location 145’ on cable, painted red).

Daily water quality samples are pumped up to the gage house from a point approximately 15-30’ (depending on stage) from the REW, where there is good flow.

EXTREMES FOR PERIOD OF DAILY RECORD -

WATER TEMPERATURE: Maximum, 18.1°C, August 21, 2022; minimum, 1.9°C, March 1, 2022.
TURBIDITY: Maximum, 4.4 formazin nephelometric units (FNU) on June 24, 2020, November 8, and 15, 2021; Minimum, less than 0.5 FNU for multiple days during the period of record.
SPECIFIC CONDUCTANCE: Maximum, 292 uS/cm on May 13, 2022; Minimum, 218 uS/cm on August 28, 2022.
pH: Maximum, 8.7 pH units on September 10, 2019; Minimum, 7.9 pH units on November 26, 2019 & October 18, 2021.
DISSOLVED OXYGEN mg/L: Maximum, 12.7 mg/L on April 29, 2022; Minimum, 8.1 mg/L on October 7, 2021.
DISSOLVED OXYGEN %SATURATION: Maximum, 102 %SAT on August 27, 2019; Minimum, 71 %SAT on December 01, 2021.
CHLOROPYLL: Maximum, 2.23 relative fluorescence units (RFU) July 22, 2020; Minimum, less than 0.05 RFU many days throughout the period. .
PHYCOCYANIN: Maximum, 0.53 relative fluorescence units (RFU) January 26, 2020; Minimum, less than 0.05 RFU many days throughout the period.