1999
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, 1,174,887 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, 1,109,782 acre-ft, June 16, gage height, 4,492.77 ft; minimum,
821,074 acre-ft, Jan. 16, gage height, 4,481.42 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 1998 TO SEPTEMBER 1999
DAILY OBSERVATION AT 2400 HOURS
DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
1 951399 924945 903487 839832 860444 883952 954439 1012757 1080914 1102002 1053617 974781
2 948362 922190 903735 838383 860200 888634 956214 1015619 1084914 1100128 1050978 975293
3 945834 919438 905475 837418 860444 892091 957229 1017963 1088923 1101199 1048869 976317
4 943308 916439 903984 835731 860444 895306 958498 1019527 1091853 1100664 1046500 976830
5 940785 913194 903239 833803 863125 898525 960785 1020831 1093985 1098257 1042982 977599
6 938516 912446 901501 832840 867030 901005 962565 1022657 1096654 1096921 1040197 978624
7 937005 911698 899021 830675 870208 903487 964092 1024746 1098806 1095853 1037316 978624
8 935494 911698 897286 829713 873391 905972 968170 1026314 1100931 1093027 1034165 977599
9 933984 909456 894069 829232 878297 909954 969701 1028668 1102994 1091415 1032850 977599
10 931973 908211 891597 828992 878297 911698 971745 1030761 1104949 1091146 1030487 976830
11 929963 905475 888881 828031 877560 913693 973535 1031809 1107096 1088215 1028652 976573
12 927955 902494 886415 826110 877560 915690 974814 1032071 1107096 1087854 1025771 975805
13 926199 899764 883706 822991 878542 917438 977120 1032071 1108707 1084381 1022633 974781
14 924945 899021 881737 822512 880754 919438 978658 1032071 1108976 1081980 1019761 973502
15 923192 896543 879279 822033 881983 921189 980967 1033381 1109244 1082513 1017155 972735
16 920188 894069 878051 821074 882229 923192 982509 1032857 1109782 1080381 1014292 970946
17 918438 892832 876333 824190 881737 923442 984308 1034168 1108976 1078251 1011953 969159
18 919688 890115 873636 826830 882229 925697 986367 1036528 1108438 1075858 1008061 968904
19 920438 887401 870942 831637 881000 927453 987654 1038891 1108170 1075061 1005730 967119
20 921438 884444 868252 834767 881000 930214 990231 1042044 1107901 1075326 1002110 966101
21 922941 881983 865565 837177 880016 931973 992294 1044410 1107633 1073998 1000045 964319
22 923943 881983 861418 840314 877560 934488 994875 1045200 1107364 1072671 996933 963810
23 925196 884937 860687 844907 875842 936501 996167 1048622 1106291 1071611 993308 961777
24 927704 888141 860931 847086 874616 939524 999011 1052577 1104145 1069490 991240 962793
25 928708 888141 854363 849267 874126 941542 1000046 1056008 1104345 1069755 988916 961777
26 930214 891597 850964 850964 875842 943308 1003412 1060500 1103073 1068166 986853 960761
27 931470 893821 848297 852905 877560 945076 1005486 1064204 1103264 1065786 983248 959746
28 932476 893574 845875 853877 881000 946592 1008080 1068444 1103609 1063672 980678 959239
29 933733 895553 842489 854849 --- 948109 1008859 1071363 1103073 1061820 978624 957971
30 930968 902990 840314 856307 --- 950385 1014418 1075348 1103073 1059435 976061 957211
31 928206 --- 839107 857523 --- 952665 --- 1078539 --- 1056755 975549 ---
MAX 951399 924945 905475 857523 882229 952665 1014418 1078539 1109782 1102002 1053617 978624
MIN 918438 881983 839107 821074 860200 883952 954439 1012757 1080914 1056755 975549 957211
a 4485.79 4484.78 4482.17 4482.93 4483.89 4486.76 4489.01 4491.60 4492.52 4490.77 4487.66 4486.94
b -24966 -25216 -63883 +18416 +23477 +71665 +61753 +64121 +24534 -46318 -81206 -18338
CAL YR 1998 MAX 1123508 MIN 625736 b +214881
WTR YR 1999 MAX 1109782 MIN 821074 b +4039