2002 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, 909,943 acre-ft, June 30, gage height, 4,485.06 ft; minimum, 604,959 acre-ft, Nov 9, 10, gage height, 4,471.89 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 2001 TO SEPTEMBER 2002 DAILY OBSERVATION AT 2400 HOURS
Day	Oct	Nov	Dec	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep

1	659,522	610,473	622,452	647,693	693,454	729,792	773,635	839,330	893,318	908,947	878,539	832,584
2	657,541	609,411	626,333	651,622	694,349	730,715	775,284	840,779	895,051	908,947	877,308	830,182
3	655,126	609,198	626,765	653,592	695,244	732,100	777,172	842,472	895,794	908,449	876,816	827,305
4	652,716	609,198	627,629	655,565	696,141	733,255	780,218	843,683	895,051	908,698	875,832	823,939
5	650,311	608,561	658,201	658,201	697,038	735,338	782,324	845,864	895,299	909,196	873,867	821,527
6	647,693	607,076	629,794	661,064	697,711	736,716	784,434	847,806	894,804	908,449	872,394	819,360
7	645,952	606,017	630,227	663,493	700,183	739,466	786,782	849,508	895,051	907,454	870,433	817,196
8	643,535	605,171	630,444	665,484	700,859	741,072	788,663	851,445	895,299	905,963	869,209	816,716
9	642,218	604,959	630,661	667,478	701,759	742,451	791,490	853,139	895,794	904,969	867,741	814,556
10	640,903	604,959	630,661	669,699	702,435	744,752	794,322	854,835	896,290	902,984	866,518	811,921

11	639,372	605,806	630,227	670,588	703,112	746,596	796,688	856,776	897,282	901,002	865,297	810,964
12	637,842	608,349	630,661	672,146	704,014	748,443	799,294	858,233	897,530	899,019	865,541	808,574
13	636,751	609,198	632,397	673,483	704,917	750,292	801,905	859,692	898,522	898,522	865,297	806,666
14	635,007	610,048	634,137	674,599	705,821	751,218	805,236	861,639	899,019	897,778	863,589	804,283
15	633,267	610,899	633,049	675,939	706,952	752,144	807,858	863,101	900,011	896,786	862,126	801,905
16	631,529	611,750	632,397	676,833	707,857	753,535	810,486	865,053	900,754	895,547	859,692	799,294
17	629,794	612,602	632,832	677,728	709,443	754,463	812,400	867,007	901,497	894,061	858,233	797,161
18	628,062	613,455	633,484	678,624	710,351	755,391	813,837	868,719	901,993	893,071	856,776	794,795
19	626,333	614,308	634,137	679,520	713,304	756,321	815,756	871,413	902,984	891,341	855,078	792,669
20	625,038	614,522	636,751	680,866	715,353	757,483	817,677	873,867	903,480	890,600	853,623	790,547

21	623,313	615,590	637,187	682,214	717,177	758,647	819,120	875,341	904,225	889,612	851,929