2001 California Hydrologic Data Report
11399000 LAKE ALMANOR AT PRATTVILLE, CA.
LOCATION - Lat 40°12'46", long 121°09'43", in SW 1/4 NE 1/4 sec.11, T.27 N., R.7 E., Plumas County,
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 Canyondam.
DRAINAGE AREA - 491 mi2.
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.
REVISED RECORDS - WSP 1931: Drainage area.
GAGE - Nonrecording gage read once daily. Datum of gage is 10.23 ft below sea level (levels by Pacific
Gas & Electric Co.). Prior to June 1, 1965, nonrecording gage at site 4.7 mi southeast at same datum.
REMARKS - Lake is formed by earthfill dam; storage began in July 1913; dam raised to gage height 4,455
ft in 1917 and 4,515 ft in 1927. Usable capacity, 1,175,000 acre-ft, between gage heights 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.
COOPERATION - Records were collected by Pacific Gas & Electric Co., under general supervision of the
U.S. Geological Survey, in connection with a Federal Energy Regulatory Commission project. Contents
not rounded to U.S. Geological Survey standards.
EXTREMES FOR PERIOD OF RECORD - Maximum contents, 1,142,960 acre-ft, June 8, 1982, gage height, 4,494.00
ft; minimum, 5,230 acre-ft, Feb. 5, 1918, gage height, 4,416.1 ft.
EXTREMES FOR CURRENT YEAR - Maximum contents, 839,813 acre-ft, Oct. 1, 2, gage height, 4,482.20 ft; minimum,
662,618 acre-ft, Sept. 30, gage height, 4,474.55 ft.
Capacity table (gage height, in feet, and contents, in acre-feet)
(Based on surveys by Pacific Gas & Electric Co. in 1924 and 1926)
4,422 8,948 4,434 49,510 4,460 376,686
4,424 10,067 4,437 74,189 4,470 565,519
4,426 11,260 4,440 101,869 4,480 787,304
4,428 13,480 4,445 156,414 4,490 1,036,269
4,430 21,200 4,450 220,848 4,495.5 1,183,835
4,432 34,173 4,455 294,531
RESERVOIR STORAGE (ACRE-FEET), WATER YEAR OCTOBER 2000 TO SEPTEMBER 2001
DAILY OBSERVATION AT 2400 HOURS
DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
1 839813 796688 749829 724501 686041 690549 729101 768463 791961 766119 719918 679380
2 839813 794322 752144 722207 686041 690549 731407 768463 791961 763780 717633 679745
3 837399 791961 752144 719918 686041 692783 733718 770811 791961 763780 717633 680156
4 834989 789604 752144 719918 686041 692783 733718 773164 791961 761444 717633 680492
5 832584 789604 752144 717633 683788 697262 736030 773164 789604 759113 717633 680763
6 830182 787252 752144 715353 683788 699509 736030 775520 789604 756786 715353 680913
7 830182 787252 752144 713076 683788 699509 738319 775520 787252 756786 713076 681166
8 827784 784903 747519 713076 683788 699509 738319 777881 787252 756786 710804 681446
9 827784 784903 745213 710804 686041 699509 740613 780218 787252 754463 710804 681605
10 825388 782558 742911 710804 686041 701759 740613 780218 787252 752144 710710 682055
11 825388 782558 740613 710804 688298 704014 742911 782558 787252 752144 709462 682485
12 822974 780218 740613 708537 688298 704014 742911 782558 784903 749829 709132 683104
13 820564 775520 740613 706273 688298 706273 745213 782558 782558 747519 708612 683741
14 818158 770811 740613 706273 688298 706273 745213 784903 782558 747519 706763 684266
15 815756 768463 738319 704014 686041 708537 745213 784903 782558 745213 704598 684857
16 813358 766119 738319 701759 686041 708537 747519 787252 782558 742911 702558 685496
17 810964 763780 736030 701759 688298 710804 747519 787252 784903 742911 700212 685524
18 810964 761444 733718 699509 688298 713076 749829 787252 782558 742911 698348 684154
19 808574 761444 733718 697262 690549 713076 752144 787252 780218 740613 696861 683048
20 808574 761444 733718 697262 690549 713076 754463 789604 780218 738319 694657 681587
21 808574 761444 733718 695020 690549 715353 754463 789604 777881 738319 692448 679679
22 806189 759113 731407 692783 692783 715353 756786 791961 775520 736030 690352 677477
23 806189 759113 731407 692783 692783 717633 756786 791961 775520 736030 688232 674720
24 803807 759113 731407 692783 692783 719918 759113 791961 775520 733718 686407 672341
25 803807 759113 731407 692783 692783 722207 759113 794322 773164 731407 685045 671293
26 801430 759113 729101 692783 690549 724501 761444 794322 773164 731407 684294 669708
27 799057 756786 729101 692783 690549 724501 763780 794322 770811 729101 683207 667368
28 799057 754463 729101 690549 690549 724501 763780 794322 770811 726799 681615 665770
29 801430 754463 726799 690549 --- 726799 766119 796688 768463 724501 679960 664193
30 799057 752144 726799 688298 --- 726799 768463 794322 768463 724501 678960 662618
31 799057 --- 724501 688298 --- 729101 --- 794322 --- 722207 679007 ---
MAX 839813 796688 752144 724501 692783 729101 768463 796688 791961 766119 719918 685524
MIN 799057 752144 724501 688298 683788 690549 729101 768463 768463 722207 678960 662618
a 4480.50 4478.50 4477.30 4475.70 4475.80 4477.50 4479.20 4480.30 4479.20 4470.20 4475.31 4474.57
b -43657 -46913 -27643 -36203 +2251 +38552 +39362 +25859 -25859 -46256 -43200 -16389
CAL YR 2000 MAX 1090522 MIN 724501 b -104242
WTR YR 2001 MAX 839813 MIN 662618 b -180096
a Gage height, in feet, at end of month
b Change in contents, in acre-feet