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USGS Water-Year Summary 2024
11399000 Lake Almanor at Prattville, CA
LOCATION - Lat 40°12'46", long 121°09'43" referenced to North American Datum of 1927, in SW 1/4 NE 1/4 sec.11, T.27 N., R.7 E., Plumas County, CA, Hydrologic Unit 18020121, Lassen National Forest, at intake tower to Butt Valley Tunnel at Prattville, 4.7 mi northwest of Lake Almanor Dam, and 5.6 mi northwest of Canyon Dam.
DRAINAGE AREA - 491 mi².
REVISIONS HISTORY - WSP 1931: Drainage area.
SURFACE-WATER RECORDS
PERIOD OF RECORD - July 1913 to current year. Monthly contents only for some periods, published in WSP 1315-A. Published as "near Prattville" 1937-60. Prior to October 1964, records published as usable contents.
GAGE - Datum of gage is 10.23 ft below NGVD of 1929 (levels by Pacific Gas and Electric Company). Prior to June 1, 1965, nonrecording gage at site 4.7 mi southeast at same datum.
COOPERATION - Records were collected by Pacific Gas and Electric Company, under general supervision of the U.S. Geological Survey, in connection with Federal Energy Regulatory Commission project no. 2105.
REMARKS - Lake is formed by earth-fill dam; storage began in July 1913; dam raised to elevation 4,455 ft in 1917 and 4,515 ft in 1927. Contents based on capacity table dated 1926. Usable capacity, 1,175,000 acre-ft, between elevations 4,422 ft, invert of outlet, and 4,495.5 ft, maximum storage limit. Dead storage, 8,948 acre-ft. Water is diverted by tunnel and penstock to Butt Valley Powerplant (station 11400600) and then is used for power development in the North Fork Feather River. Figures given, including extremes, represent total contents at 2400 hours. See schematic diagram of North Fork Feather River Basin available from the California Water Science Center.
EXTREMES FOR PERIOD OF RECORD - Maximum contents, 1,142,960 acre-ft, June 8, 1982, elevation, 4,494.00 ft; minimum, 5,230 acre-ft, Feb. 5, 1918, elevation, 4,416.1 ft.
