months, stage and discharge may be affected by ice in the
channel. Data values reported on these pages may be
significantly higher or lower than the actual streamflow.
Adjustments to the data will be done after detailed analyses.
Ice affected values identified on graphs (•) may be viewed by choosing the table
output format. If you have questions about these values,
please contact the
Idaho Water Data Maintainer.
LOCATION.--Lat 48° 37'04", long 116° 02'47", in
NW1/4 NW1/4 NW1/4 sec.20, T.33 N., R.34 W., principal Meridian,
Lincoln County, Montana, Leonia quad, Hydrologic Unit 17010104, on
right bank at Leonia, 450 ft east of Montana-Idaho State line, 0.5 mi
upstream from Boulder Creek, and at mile 171.6.
DRAINAGE AREA.--11,740 mi2, approximately.
PERIOD OF RECORD.--March 1928 to current year.
GAGE.--Water-stage recorder. Datum of gage is 1,790.25 ft above
NGVD of 1929 or converted to NAVD 88 is 1794.118 ft. Prior to Oct. 1,
1970, at datum 90 ft lower. Prior to Nov. 13, 1928, nonrecording gage
on bridge 250 ft upstream at datum 90.41 ft lower.
REMARKS.--Diversions above station for irrigation of about 14,600
acres. Flow regulated by Libby Dam and power plant since Mar. 21,
EXTREMES FOR PERIOD OF RECORD.-- UNREGULATED PERIOD (1929-71):
Maximum discharge prior to regulation by Libby Dam, and powerplant,
123,000 ft3/s May 28, 1948, gage height, 33.40 ft;
minimum, 996 ft3/s Dec. 9, 1936, minimum gage height, 7.56
ft, Dec. 10, 1929.
REGULATED PERIOD (1972 to current year): Maximum discharge since
regulation began, 62,000 ft3/s Jan. 16, 1974, gage height,
24.15 ft; maximum gage height, 25.87 ft, June 17, 18, 2006; minimum
daily discharge, 2,270 ft Dec. 9, 1972.
EXTREMES OUTSIDE PERIOD OF RECORD.--Floods of June 1894 and 1916
reached stages of 34.6 and 31.6 ft, respectively, present datum, from
information by Great Northern Railway.