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USGS Water-Year Summary 2024
12372000 FLATHEAD RIVER NEAR POLSON, MT
LOCATION - Lat 47°40'49.03", long 114°14'48.22" referenced to North American Datum of 1983, in SW 1/4 NE 1/4 SE 1/4 sec.11, T.22 N., R.21 W., Lake County, MT, Hydrologic Unit 17010212, on left bank 0.5 mi downstream from Kerr Dam, 4.0 mi west of Polson, 5.0 mi downstream from Flathead Lake, and at river mile 71.5.
DRAINAGE AREA - 7,079 mi².
REVISIONS HISTORY - Water Supply Paper (WSP) 652: 1926. WSP 752: 1932. WSP 1182: 1948. WSP 1216: Drainage area. WSP 1246: 1928, maximum discharge. WSP 1636: 1958, adjusted runoff.
SURFACE-WATER RECORDS
PERIOD OF RECORD - July 1907 to current year.
GAGE - Water-stage recorder. Elevation of gage is 2,692.70 ft, referenced to the National Geodetic Vertical Datum of 1929 (levels by The Montana Power Co.). Prior to Oct. 1, 1941, nonrecording gages or water-stage recorder at several sites near highway bridge at old site of Michell's ferry 6 mi downstream from present site, all at elevation 2,629.20 ft (from river-profile survey). U.S. Geological Survey satellite telemeter is located at the station.
REMARKS - Flow is regulated by Flathead Lake (Kerr Dam) since April 1938 (station number 12371500) and Hungry
Horse Reservoir (station number 12362000) since September 1951. Numerous diversions for irrigation occur upstream from station.
Flathead project pumps can divert water for irrigation of lands downstream from station.
EXTREMES OUTSIDE PERIOD OF RECORD - Flood in June 1894 reached a stage of about 21 ft, present elevation; discharge, about 110,000 ft³/s, from lake elevation-discharge study.
AVERAGE DISCHARGE FOR PERIOD OF RECORD - 107 years, 11,570 ft³/s, 22.14 in/yr, 8,382,000 acre-ft/yr, adjusted for change in contents in Hungry Horse Reservoir and Flathead Lake.
