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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