USGS Water-Year Summary for Site 12355000

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	00060 Discharge(Mean)

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Water year 2023: 2022-10-01 to 2023-09-30

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USGS Water-Year Summary 2023

12355000 FLATHEAD RIVER AT FLATHEAD, BRITISH COLUMBIA

LOCATION - Lat 49°00'04.47", long 114°28'32.39" referenced to North American Datum of 1983, UNSPECIFIED, Hydrologic Unit is unknown, Lat 49°00'06" N, long 114°28'30" W referenced to North American Datum of 1927, on left bank 200 ft north of international boundary at Flathead, British Columbia, 1.6 mi upstream from Sage Creek, 6.5 mi northwest of Trail Creek, MT, and at river mile 216.6. Hydrologic Unit is 17010206.

DRAINAGE AREA - 429 mi².

REVISIONS HISTORY - The maximum gage height (affected by backwater) for water year 2009 was deleted, based upon reanalysis of gage-height record.

SURFACE-WATER RECORDS

PERIOD OF RECORD - March 1929 to June 1995 (no winter records prior to 1952), October 1999 to current year. Prior to 1934, published as "Flathead River near Trail Creek, MT." October 1970 to September 1972, published as "North Fork Flathead River at Flathead, British Columbia." Gage was reestablished in October 1999 and is operated by the U.S. Geological Survey at site on left bank in British Columbia.

GAGE - Water-stage recorder. Elevation of gage is 3,964.95 ft, referenced to the National Geodetic Vertical Datum of 1929. Prior to Sept. 1, 1949, nonrecording gage and Sept. 1, 1949 to Oct. 4, 1964, water-stage recorder was located at a site 1,200 ft upstream at an elevation 11.01 ft higher. Oct. 5, 1964, to Aug. 1, 1973, water-stage recorder was located at a site on left bank 155 ft upstream at an elevation 1.79 ft higher. Aug. 2, 1973 to June 28, 1995 operated by Water Survey Canada at site on right bank at elevation 3.21 ft. higher. October 1999 to current year, located at site 200 ft upstream from the international border in British Columbia on left bank.

REMARKS -

WATER-QUALITY RECORDS

PERIOD OF RECORD - Water years 1949-50, 1965, 1970, 1975-93 and August 1999 to current year.

PERIOD OF DAILY RECORD - SPECIFIC CONDUCTANCE: November 1974 to September 1981. WATER TEMPERATURE: November 1974 to September 1991. SUSPENDED-SEDIMENT DISCHARGE: April 1975 to October 1978, August 1985 to June 1991.

REMARKS -

EXTREMES FOR PERIOD OF DAILY RECORD - SPECIFIC CONDUCTANCE: Maximum daily, 309 microsiemens per centimeter (uS/cm) at 25.0°C, Jan. 12, 28, 1975, Jan. 20, 1980; minimum daily, 130 uS/cm at 25.0°C, May 20, 1976. WATER TEMPERATURE: Maximum 19.5°C, Aug 2, 1977; minimum 0.0°C on many days during winters. SEDIMENT CONCENTRATION: Maximum daily mean, 1,310 mg/L, June 20, 1975; minimum daily mean, 1 mg/L on many days most years. SEDIMENT LOAD: Maximum daily, 36,100 tons, June 20, 1975; minimum daily, 0.24 ton, Feb. 1 and 23, 1988.