11441001 UNION VALLEY RESERVOIR NEAR RIVERTON, CA
LOCATION.-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.
CHEMICAL ANALYSES.-June to September 1996.
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, 272,159 acre-ft, July 4, elevation, 4,868.23 ft; minimum, 147,049
acre-ft, Dec. 25, elevation, 4,816.13 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 1998 TO SEPTEMBER 1999
DAILY OBSERVATION AT 2400 HOURS
DAY OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP
1 164962 154665 151168 148831 175973 210745 187990 186051 247467 270534 242284 183438
2 164983 153746 152211 149289 175306 211139 186523 187448 248519 271036 241278 182462
3 164142 152909 153961 149403 174640 212373 184976 187741 248657 271479 239384 181115
4 164080 152017 154881 149308 174576 212571 184061 187832 248990 272159 237179 180236
5 163365 151361 154979 149212 174833 212596 182351 189511 249852 271390 234936 178727
6 163365 150802 155195 149308 175715 212348 181115 191636 251470 270741 232206 178073
7 163039 151457 154704 150015 180038 211805 179885 193340 252029 269828 230626 176794
8 162713 151631 154920 149766 184016 211237 178836 194288 252197 268330 228272 175607
9 162855 150648 154900 150207 189329 209567 177965 194985 252646 267833 225908 173934
10 163079 150360 154371 150284 192004 209297 176686 195287 253123 266431 223640 173059
11 162509 149785 153844 150015 193872 208028 175370 196360 253432 266081 221669 171299
12 162448 149422 153376 150418 195893 206521 174084 197812 254587 265034 219052 170328
13 162042 148565 153961 150860 196523 205191 172868 199721 255434 264222 216057 169425
14 162327 147730 153473 151380 197694 204757 172549 201072 256085 263152 213836 168317
15 162042 148071 152463 152114 198847 203412 172379 202383 256879 262027 211040 167193
16 161556 147635 152521 153298 200076 201572 172379 202741 256794 260475 209297 166013
17 161880 147181 152288 154626 204540 201025 173806 204108 257305 259844 207127 165209
18 161091 147087 151592 158162 206763 200289 174898 205988 258387 259387 204637 163773
19 160748 147332 151303 161657 207711 199083 176275 208028 259701 258701 202550 162733
20 160567 147389 150744 166178 208320 198188 177617 210548 260704 257618 200787 161536
21 160104 147597 150207 168213 208686 197014 178705 212942 261825 256993 199532 160406
22 159823 147068 149862 169677 208028 196360 179578 216282 263556 255632 197929 159261
23 158901 147162 148546 172188 208149 194822 179797 220523 264976 254502 191246 158282
24 159261 147540 147332 173528 207687 193918 179753 224669 265586 253854 193409 157566
25 158063 147484 147049 174790 208442 192694 181137 228141 266547 252871 192233 156515
26 157685 147465 147768 175306 208540 192510 182484 231231 267540 251694 191063 155431
27 156377 147654 148090 176189 208637 191636 183638 234882 268213 249880 189556 154019
28 155844 147805 147578 176383 209273 190880 184484 237447 268946 248768 188466 152851
29 155372 148546 147749 176405 --- 189624 184641 239816 269857 246777 187402 151979
30 154783 150264 148318 176102 --- 189033 184752 242392 270652 244934 186546 150226
31 154371 --- 148223 175715 --- 188058 --- 245236 --- 243620 184976 ---
MAX 164983 154665 155195 176405 209273 212596 187990 245236 270652 272159 242284 183438
MIN 154371 147068 147049 148831 174576 188058 172379 186051 247467 243620 184976 150226
a 4819.94 4817.82 4816.75 4830.33 4844.93 4835.92 4834.45 4858.79 4867.72 4858.20 4834.55 4817.80
b -10632 -4107 -2041 +27492 +33558 -21215 -3306 +60484 +25416 -27032 -58644 -34750
c 16380 15680 30720 9060 37640 72070 66110 54280 40600 40820 68100 48390
CAL YR 1998 MAX 276027 MIN 131720 b +10996 c 583600
WTR YR 1999 MAX 272159 MIN 147049 b -14777 c 499900
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