2000
California Hydrologic Data Report
b Change in contents, in acre-feet.
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 mi 2 .
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, 1,090,522 acre-ft, June 8, 11, 13, gage height, 4,492.05
ft; minimum, 823,457 acre-ft, Jan. 7, gage height, 4,481.52 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 94,531
RESERVOIR STORAGE (ACRE-FEET), WATER YEAR OCTOBER 1999 TO SEPTEMBER 2000
DAILY OBSERVATION AT 2400 HOURS
DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
1 954173 933208 880507 828743 869209 934717 974269 1042296 1085716 1058111 982219 903480
2 955438 930195 878293 827545 870188 936983 975549 1045448 1086517 1056259 979394 901745
3 956198 926937 875586 827066 872149 936479 975549 1048079 1087052 1054145 976317 896538
4 955185 924185 872640 825630 872640 935723 977599 1050978 1087052 1051241 972735 894308
5 955438 920688 870188 824664 873867 934968 979908 1053088 1087586 1048869 970691 892824
6 956957 917933 867496 824905 874112 935723 981705 1055995 1088121 1047290 967629 889859
7 957717 915182 865053 823457 874358 937738 984020 1058376 1087854 1045448 965082 887639
8 958985 913683 862858 824664 872885 939756 986337 1062085 1090522 1043609 962031 885422
9 959746 911438 860665 825888 872640 943798 988142 1064200 1090255 1040460 958731 884192
10 960761 909196 858476 826587 875095 945317 990206 1066843 1089989 1038101 955691 883946
11 959239 906708 856048 829462 877554 947090 993049 1068961 1090522 1036269 952910 881734
12 959746 904721 853866 829462 879525 948611 995379 1069755 1090255 1033376 949880 881243
13 960507 901993 852655 829223 884192 950889 999268 1070815 1090522 1031537 946583 879525
14 961523 901250 850236 830662 888378 952152 1002627 1072406 1089989 1028652 944810 878293
15 961777 898771 849508 831623 891835 953921 1005471 1073733 1088923 1025509 941271 875832
16 959492 898026 849021 835953 895299 955185 1008839 1074795 1085983 1022110 937234 873867
17 958985 897034 847564 837882 898026 956704 1012732 1075061 1084647 1020544 934968 873130
18 958985 895051 845622 840296 899764 958985 1015072 1076124 1083580 1016894 934465 871413
19 956198 894556 843925 842957 902489 961015 1018457 1076389 1081447 1015072 933208 869698
20 953921 893813 842957 844895 904969 963047 1021588 1076655 1079848 1013252 932454 868964
21 952657 891094 840296 846835 907703 964573 1024724 1076389 1077985 1010135 932706 865053
22 952152 888625 838605 848049 912186 966101 1027603 1076921 1076655 1008061 932957 861639
23 950637 886407 837882 850719 914932 966610 1030225 1076655 1075061 1005730 930446 858233
24 949372 883700 837640 855078 916682 967374 1032325 1076389 1073733 1003919 927688 855563
25 947597 884930 836676 856776 918934 967629 1033113 1078783 1072937 1001335 923935 852655
26 945823 885176 834749 858476 923435 968649 1034427 1080381 1071080 997452 920688 849994
27 948357 885914 833305 859935 927939 968904 1034427 1080381 1069490 995120 918684 846835
28 944557 883454 832103 860909 930446 969925 1036792 1081713 1067373 992273 915931 844168
29 941776 880998 829942 862370 932957 970946 1039149 1083046 1064729 990465 912186 844410
30 938747 882471 829942 866274 --- 971457 1039935 1084114 1062085 987884 908698 842714
31 936227 --- 828743 867741 --- 972735 --- 1084647 --- 984792 906957 ---
MAX 961777 933208 880507 867741 932957 972735 1039935 1084647 1090522 1058111 982219 903480
MIN 936227 880998 828743 823457 869209 934717 974269 1042296 1062085 984792 906957 842714
a 4486.11 4483.95 4481.74 4483.35 4485.98 4487.55 4490.14 4491.83 4490.98 4488.02 4484.94 4482.32
b -20984 -53756 -53728 +38998 +65216 +39778 +67200 +44712 -22562 -77293 -77835 -64243
CAL YR 1999 MAX 1109782 MIN 821074 b -10364
WTR YR 2000 MAX 1090522 MIN 823457 b -114497