2004 USGS

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, 1,006,248 acre-ft, June 10, 11, gage height, 4,488.85 ft; minimum, 708,763 acre-ft, Feb. 8, gage height, 4,476.61 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	4,432	34,173	4,445	156,414	4,470	565,519
4,424	10,067	4,434	49,510	4,450	220,848	4,480	787,304
4,426	11,260	4,437	74,189	4,455	94,531	4,490	1,036,269
4,428	13,480	4,440	101,869	4,460	376,686	4,495.5	1,183,835
4,430	21,200

RESERVOIR STORAGE, ACRE FEET, WATER YEAR OCTOBER 2003 TO SEPTEMBER 2004 DAILY OBSERVATION AT 2400 HOURS
Day	Oct	Nov	Dec	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep

1	868474	830182	791961	787017	717405	771987	840054	914432	991756	989432	931199	853381
2	866274	827784	791254	785607	717405	773635	842230	917432	993308	987884	928189	852171
3	866030	826108	790076	783730	715125	774813	844652	920438	995120	986595	925435	849994
4	867007	824422	787957	781621	714214	776464	847563	923435	996674	985564	922686	848292
5	866518	822974	787722	779049	712167	777645	850236	927438	999008	984277	920438	846592
6	866030	820082	791254	776936	711258	779049	852897	930195	1000303	982219	917432	844895
7	865541	818639	792669	775284	709443	780685	855320	932706	1002627	980164	915182	843441
8	865053	817917	792197	773399	708763	782324	857747	935975	1004178	979394	912435	841505
9	864321	818158	793141	771517	709670	784199	860179	939251	1005212	978368	909445	839813
10	863101	818398	795032	769167	710577	786077	862614	942534	1006248	978111	906708	838123

11	862858	818158	796924	766822	711486	787252	865297	945823	1006248	977599	904225	836917
12	861883	817437	797398	764949	712394	789134	867496	948611	1005730	976830	902241	834989
13	860665	817917	798109	762611	713759	792433	870923	950889	1005730	975293	899764	833305
14	859692	817917	800480	761211	714442	793378	872885	953415	1005212	974013	898026	831142
15	858476	815996	800006	758647	716264	795741	876078	956198	1004954	973757	895299	829462
16	856776	813118	799531	756553	721062	798820	877554	958478	1003661	971201	893071	828024
17	855320	811682	798583	754231	730715	801668	879771	960507	1001852	970435	890353	826587
18	854350	810247	797161	752144	736258	804521	881734	963047	1001335	968649	888132	826348
19	852897	808813	796688	751218	740383	807143	884192	964573	1000303	964828	885422	826348
20	851687	807143	795268	747288	743601	810486	886653	966865	999527	962031	882962	824422

21	850477	805712	793850	744061	748443	813597	889118	969159	998749	960000	880016	823457
22	848535	803569	791490	741532	749829	816476	891588	970946	997711	957717	877308	823457
23	847078	802143	789134	738548	751449	819120	893566	972990	996933	955185	874849	822251
24	845379	800480	790782	736716	755391	821768	896042	974525	995897	952910	872394	821286
25	843925	798346	790076	733949	761444	825388	898771	976317	995379	950889	869698	819842
26	842714	797161	788192	731638	764949	827784	901249	978111	994602	947850	867252	818398
27	841263	795978	786312	729792	766588	829462	903977	980678	993308	945317	864565	816956
28	839330	794795	784668	727489	768229	831863	906708	984020	990723	942534	862370	815516
29	836676	793850	787017	725190	769637	834027	908947	986079	990981	939756	859935	814556
30	834027	792669	787017	722895		835712	911936	987626	990465	936731	857747	813597
31	832584		785607	720147		837882		989690		934214	855320

MAX	868474	830182	800480	787017	769637	837882	911936	989690	1006248	989432	931199	853381
MIN	832584	792669	784668	720147	708763	771987	840054	914432	990465	934214	855320	813597
a	4481.90	4480.23	4479.93	4477.11	4479.25	4482.12	4485.14	4488.21	4488.24	4486.03	4482.84	4481.11
b	-37359	-39915	-7062	-65460	+49490	+68245	+74054	+77754	+775	-56251	-78894	-41723

  CAL YR 2003 MAX 1037316 MIN 761911 b -25096

  WTR YR 2004 MAX 1006248 MIN 708763 b -56346

   a Gage height, in feet, at end of month

   b Change in contents, in acre-feet