USGS
Water Resources Data - California, Water Year 1994
11441001 UNION VALLEY RESERVOIR NEAR RIVERTON, CA
LOCATION (REVISED).--Lat 38`51'33", long 120`26'13", in NW 1/4 NW 1/4 sec.29, T.12 N., R.14 E., El Dorado County,
Hydrologic Unit 18020129, Eldorado National Forest, in valve control house near left bank at Union Valley Dam
on Silver Creek, 0.7 mi upstream from Little Silver Creek, and 6.6 mi north of Riverton.
DRAINAGE AREA.--83.7 mi2.
PERIOD OF RECORD.--October 1962 to current year.
GAGE.--Water-stage recorder. Datum of gage is sea level (levels by Sacramento Municipal Utility District).
REMARKS.--Reservoir is formed by earthfill dam completed in December 1962; storage began May 1962. Usable
capacity, 269,514 acre-ft between elevations 4,645.0 ft, minimum operating level, and 4,870.0 ft, top of
radial spillway gates. Dead storage, 7,921 acre-ft. Reservoir receives water from the South Fork Rubicon
River via Robbs Peak Powerplant (station 11429300) and from South Fork Silver Creek, since April 1985, via
Jones Fork Powerplant (station 11440900). Water is used for power development in the South Fork American
River basin. Discharge to Union Valley Powerplant (station 11441002) is shown as a line item below this
table. Records, including extremes, represent total contents. See schematic diagrams of Middle Fork American
and Rubicon River basins and South Fork American River basin.
COOPERATION.--Records were collected by Sacramento Municipal Utility District, 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, 279,100 acre-ft, July 9, 1974, elevation, 4,870.6 ft; minimum
since reservoir first filled, 18,300 acre-ft, Jan. 13, 1977, elevation, 4,683.3 ft.
EXTREMES FOR CURRENT YEAR.--Maximum contents, 185,827 acre-ft, Oct. 16, elevation, 4,835.12 ft; minimum,
117,167 acre-ft, Feb. 26, elevation, 4,799.22 ft.
Capacity table (elevation, in feet, and contents, in acre-feet)
(Based on table provided by Sacramento Municipal Utility District, recomputed October 1991)
4,680 17,675 4,780 89,926
4,700 25,160 4,800 118,894
4,720 35,266 4,820 154,489
4,740 48,883 4,840 197,460
4,760 66,841 4,870 277,435
RESERVOIR STORAGE (ACRE-FEET), WATER YEAR OCTOBER 1993 TO SEPTEMBER 1994
DAILY OBSERVATION AT 2400 HOURS
DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
1 182683 177639 154508 130129 126399 118428 148964 166178 179382 162002 150879 138720
2 182993 177010 153434 129579 125861 119183 149231 166633 178879 161394 150533 138557
3 183104 176534 151979 129031 125341 120104 150456 167152 178552 160607 150379 138071
4 183326 175693 150360 128774 125057 121096 151361 167463 178313 159762 149805 137567
5 183460 175005 148451 128535 124523 122685 151689 167817 177986 159221 149250 136904
6 183571 174490 147389 128092 124074 123825 152211 168860 177487 158442 148888 136315
7 183793 173891 146333 127566 123676 124241 152075 170223 177530 157904 149098 135639
8 183949 173400 145508 127007 122998 124723 152404 170961 176729 157625 148603 135071
9 184261 172910 145227 126467 122833 125057 152928 171891 176081 157109 148413 134258
10 184641 172188 144797 126029 122603 126046 153006 173144 175650 156476 148204 133537
11 184819 171658 143867 125542 121913 127566 152715 174169 174984 156219 147881 132749
12 184864 170982 142738 125107 121716 128416 153142 174769 174726 156061 147484 131894
13 184842 170371 142332 124723 121340 128842 153356 175715 174084 155667 146785 131391
14 185043 169404 141817 124523 120802 130353 153902 175995 173507 155293 146220 130474
15 185580 168547 140956 124707 120510 131842 154959 176361 173123 154999 145695 129905
16 185827 167526 140207 124307 120137 133239 156002 176189 172825 154763 145171 129596
17 185625 166488 139245 123859 120039 133765 157248 176275 172082 154606 144816 129219
18 185199 165621 138594 123263 119716 134753 158162 176902 171595 154274 144294 128433
19 185020 164654 138017 122225 119183 136672 159642 177053 170813 153746 144071 127854
20 184328 163732 136583 121815 118797 138395 160607 177205 170181 153863 143885 127294
21 183860 162916 136725 121684 118621 140189 161536 177509 169425 153668 143403 126686
22 183238 162164 136511 122373 118380 141799 161961 177812 168547 153434 143126 126517
23 182750 161273 135727 123527 117980 143015 162815 177878 168150 153123 143015 125811
24 182262 160224 134682 124324 117549 144406 163181 178030 167671 152579 142738 125141
25 181489 159301 133976 125392 117342 145096 163528 178095 166882 152327 142314 124290
26 180895 158481 133449 125794 117167 144965 163794 178639 166075 151862 141688 123660
27 180389 157804 133099 125912 117310 144928 163876 179229 165250 151631 141267 123329
28 179994 157070 132277 126248 117469 145657 164736 179141 164306 151014 140499 122652
29 179403 156397 131720 126517 --- 146766 165209 179032 163344 150841 140062 122718
30 178879 155313 131183 126787 --- 147768 165394 178923 162754 151033 139589 122258
31 178400 --- 130681 126855 --- 148223 --- 178923 --- 151361 139281 ---
MAX 185827 177639 154508 130129 126399 148223 165394 179229 179382 162002 150879 138720
MIN 178400 155313 130681 121684 117167 118428 148964 166178 162754 150841 139281 122258
a 4831.60 4820.72 4807.37 4805.13 4799.41 4817.05 4825.72 4832.08 4824.36 4818.59 4812.13 4802.27
b -4283 -23087 -24632 -3826 -9386 +30754 +17171 +13529 -16169 -11393 -12080 -17023
c 18310 25590 32780 18340 17830 8150 11540 11400 20930 22600 24150 23230
CAL YR 1993 MAX 273285 MIN 73535 b +54257 c 439700
WTR YR 1994 MAX 185827 MIN 117167 b -60425 c 234800
a Elevation, in feet, at end of month.
b Change in contents, in acre-feet.
c Diversion, in acre-feet, to Union Valley Powerplant, provided by Sacramento Municipal Utility District.
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U.S. Geological
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