2003 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, 1,037,316 acre-ft, June 10, gage height, 4,490.04 ft; minimum, 662,618 acre-ft, Sept. 30, gage height, 4,474.55 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 2002 TO SEPTEMBER 2003 DAILY OBSERVATION AT 2400 HOURS
Day	Oct	Nov	Dec	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep

1	765885	716036	713986	761911	804759	784668	844167	918433	1022110	1022894	974013	920187
2	762378	714897	712622	763312	806427	784903	846592	921438	1025509	1019761	973502	917682
3	760045	713076	711258	763780	808336	786077	849021	925435	1028652	1017675	971457	914932
4	757949	711486	710351	765183	809769	787017	851929	928690	1030487	1016373	969414	913184
5	757018	710124	709217	766119	808813	787957	853381	931450	1032062	1015592	967119	911687
6	755856	710351	708084	766354	808097	789134	854835	934465	1033113	1014812	965082	912435
7	752839	716036	707404	767056	807381	790311	857262	939504	1033639	1013252	963047	913184
8	750986	718775	707404	767525	805474	791254	859206	943039	1034690	1011693	961523	913933
9	748905	721520	706726	768463	803569	792197	860665	946076	1036269	1010135	959492	912685
10	746596	723812	706726	769872	801430	793614	862614	949119	1037316	1009357	957464	910441

11	744522	725190	706273	770811	798820	795032	864321	951647	1036792	1008061	955944	907703
12	743141	725649	705821	772458	796451	795978	870433	954173	1036269	1006766	953921	905714
13	742221	726339	710351	775049	796451	797398	873867	956704	1036269	1005212	952404	902736
14	740383	726799	719461	776464	796924	802856	876078	958731	1035216	1003144	950385	900259
15	739007	726799	724960	777409	797872	807620	878047	960761	1035216	1001077	949119	898274
16	738090	724960	731638	778815	799768	809769	880016	964319	1034690	999268	947343	895299
17	736030	724271	734180	779750	799057	811203	881734	967119	1034427	997711	946330	892824
18	734875	723353	735801	780218	798820	812400	883700	969925	1034164	996156	944810	890353
19	733718	722666	737861	779750	798583	813597	885422	972990