Lower Green River Basin (12)
April 2000

Snow
The Blacks Fork drainage snow water equivalent (SWE) is 91 percent of average (102 % of last year). SWE in the Hams Fork, as of April 1, is 84 percent of average (84% of last year). The Henry's Fork SWE for the basin is 95 percent of average (121 % of last year). The basin, as a whole, is 88 percent of average (87 percent of last year). For more information see Basin Summary of Snow Courses at beginning of this report.

Precipitation
Precipitation was above average for the 3 reporting stations during March. Precipitation ranged from 57 to 126 percent of average for the month. The entire basin received 73 percent of average for the month (91 percent of last year). The basin year-to-date precipitation is currently 71 percent of average (78 percent of last year). Year to date percentages range from 64 to 76.

Reservoir
Fontenelle Reservoir is currently storing 105,100 acre feet; this is 67 percent of average (86 % of last year). Flaming Gorge does not have an average established. Flaming Gorge is currently storing 3,199,000 acre feet. Last year at this time there was 3,190,600 acre feet in storage at Flaming Gorge. Viva Naughton is currently storing 33,400 acre feet; this is 123 percent of average (112 % of last year).

Streamflow
Expected yields vary from 73 to 84 percent of average across the basin. The following forecast values are based on a 50 percent chance probability for the April through July forecast period. Green River near Green River is forecast to yield about 740,000-acre feet (82 percent of average). Blacks Fork near Robertson is forecast to yield 75,000-acre feet (79 percent of average). East Fork of Smiths Fork near Robertson is estimated to yield 22,000 acre-feet (73 percent of average). The estimated yield for Hams Fork near Frontier is 50,000-acre feet (76 percent of average). Viva Naughton Reservoir inflow will be about 65,000-acre feet (73 percent of average). Flaming Gorge Reservoir inflow will be about 1,000,000-acre feet (84 percent of average). 

==================================================================================================================================
                                                     LOWER GREEN RIVER BASIN
                                               Streamflow Forecasts - April 1, 2000
==================================================================================================================================
                                              |  <<====== Drier ======  Future Conditions  =======  Wetter =====>>  |             
                                              |                                                                     |
  Forecast Point                     Forecast |  ==================== Chance Of Exceeding * ======================  |
                                      Period  |    90%       70%    |  50% (Most Probable)  |      30%       10%    |  30-Yr Avg.
                                              | (1000AF)  (1000AF)  |   (1000AF)  (% AVG.)  |    (1000AF)  (1000AF) |    (1000AF)
====================================================================|=======================|=====================================
Green River nr Green River, WY       APR-JUL       566       653    |      740        82    |       827       908            899
                                                                    |                       |
Blacks Fork nr Robertson             APR-JUL        52        66    |       75        79    |        84        98             95
                                                                    |                       |
EF of Smiths Fork nr Robertson       APR-JUL      17.4        20    |       22        73    |        24        28             30
                                                                    |                       |
Hams Fk blw Pole Ck nr Frontier      APR-JUL        34        43    |       50        76    |        57        69             66
                                                                    |                       |
Hams Fk Inflow to Viva Naughton Res  APR-JUL        39        54    |       65        73    |        76        91             89
                                                                    |                       |
Flaming Gorge Reservoir Inflow       APR-JUL       658       878    |     1000        84    |      1122      1340           1196
                                                                    |                       |
==================================================================================================================================
                         LOWER GREEN RIVER BASIN                        |                 LOWER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 2000
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
FONTENELLE                             344.8    105.1    122.9    157.9 |   HAMS FORK RIVER             4        84        84
                                                                        |
FLAMING GORGE                         3749.0   3199.0   3190.6      --- |   BLACKS FORK                 5       102        91
                                                                        |
VIVA NAUGHTON RES                       42.4     33.4     29.7     27.1 |   HENRYS FORK                 3       121        95
                                                                        |
                                                                        |   GREEN above Flaming Gorge  26        87        88
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual volume will exceed the volumes in the table.

The average is computed for the 1961-1990 base period.

(1) - The values listed under the 10% and 90% Chance of Exceeding are actually 5% and 95% exceedance levels.                  
(2) - The value is natural volume - actual volume may be affected by upstream water management.
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