1996
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, 1,129,715 acre-ft, May 27, 28, gage height, 4,493.51 ft; minimum,
864,344 acre-ft, Dec. 10, gage height, 4,483.21 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 1995 TO SEPTEMBER 1996
DAILY OBSERVATION AT 2400 HOURS
DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
1 954693 914941 867519 874126 898525 996167 1037840 1050731 1126474 1086526 1020048 950639
2 953679 911948 867519 873881 895801 998235 1038628 1052840 1127824 1084129 1017442 948615
3 952665 907962 868007 872656 896048 1001081 1037315 1054424 1127014 1081999 1015098 946087
4 951146 904978 868496 871921 901501 1006005 1036528 1056536 1127284 1079604 1013277 943813
5 948615 902245 868007 870942 905972 1008859 1036003 1058914 1126474 1077475 1009898 941542
6 947603 899021 868007 870698 909456 1010677 1035216 1060235 1126474 1075614 1008080 939524
7 945076 896543 866297 872656 913444 1012757 1035479 1062087 1125935 1073487 1005745 937760
8 945076 893574 865565 871677 914691 1014838 1036003 1063675 1125665 1071363 1004708 935746
9 946592 890609 864588 870942 917688 1017181 1036003 1065793 1125395 1069505 1001599 933733
10 948109 887648 864344 869719 920438 1020048 1036269 1067118 1123777 1066588 999011 931722
11 949374 885922 865565 868741 922941 1024485 1036003 1068709 1122969 1064469 996942 929963
12 950133 885183 872901 868252 925447 1028144 1036003 1070567 1121353 1062352 994359 927955
13 951652 884198 876088 868741 928206 1030761 1036269 1071894 1119738 1061089 992552 926199
14 953172 885676 876333 868985 930716 1031809 1036003 1074285 1118124 1059178 989715 924444
15 954439 886908 880508 870942 932727 1034692 1036791 1077741 1116243 1057064 987912 922691
16 954439 888141 881491 874616 935494 1037840 1038103 1085993 1114094 1054687 985337 920939
17 952919 888141 880754 877069 939776 1039941 1040204 1095597 1112483 1051785 982766 919188
18 950386 886908 879525 881000 946592 1040992 1039679 1104701 1110872 1049676 980197 917188
19 947603 885922 877560 882229 954186 1040729 1039679 1110604 1108457 1047306 977376 916189
20 945581 885183 875842 883213 962310 1040992 1039153 1114631 1106311 1045463 974814 914192
21 943561 883459 875352 884937 970212 1040729 1038891 1119738 1104165 1043358 972767 912446
22 940533 881737 873391 885676 974047 1039416 1038103 1123238 1102557 1041255 970723 910701
23 939020 879525 873636 887648 978914 1038365 1037578 1125395 1100145 1039941 969446 908958
24 936249 877806 874126 888388 981738 1040467 1038891 1127284 1099074 1037315 966895 907713
25 934236 875352 873636 890115 984565 1039153 1039679 1128364 1097469 1035479 965365 905972
26 932727 873146 872656 890115 987396 1038365 1040992 1128364 1095597 1033381 962819 904232
27 930214 870698 871187 893821 989457 1037315 1041781 1129715 1093460 1031285 960531 902494
28 927202 870698 870453 895058 992810 1037053 1043621 1129715 1091858 1028929 959006 900757
29 924444 869230 869474 897039 994617 1034954 1045463 1129174 1089991 1027883 956975 899269
30 921439 868496 872656 899269 --- 1033905 1047569 1128904 1088391 1025269 955200 897534
31 918438 --- 874126 899764 --- 1033643 --- 1128634 --- 1022918 952919 ---
MAX 954693 914941 881491 899764 994617 1040992 1047569 1129715 1127824 1086526 1020048 950639
MIN 918438 868496 864344 868252 895801 996167 1035216 1050731 1088391 1022918 952919 897534
a 4485.40 4483.38 4483.61 4484.65 4488.40 4489.90 4490.43 4493.47 4491.97 4489.49 4486.87 4484.56
b -35494 -49942 +5630 +25638 +94853 +39026 +13926 +81065 -40243 -65473 -69999 -55385
CAL YR 1995 MAX 1137013 MIN 695730 b +179072
WTR YR 1996 MAX 1129715 MIN 864344 b -56398
a Gage height, in feet, at end of month.
b Change in contents, in acre-feet.