Lower Green River Basin
May 1997

Snow
The Blacks Fork drainage snow water equivalent (SWE) is 97 percent of average, currently the lowest in the basin. Henry's Fork is about 154 percent of average. Snowpack in the Hams Fork, as of May 1, is 150 percent of average. The basin as a whole is 142 percent of average. This is 8 percent ahead of last year at this time. For more information see Basin Summary of Snow Courses at beginning of this report.

Precipitation
Precipitation was heavy throughout the basin during April. Precipitation ranged from 164 to 270 percent of average from the 3 reporting stations. The entire basin received 196 percent of average for the month (203 percent of last year). The basin year to date precipitation is currently 131 percent of average; sites range from 124 to 144 percent of average.

Reservoir
Fontenelle Reservoir is currently storing 134,100 acre feet; this is 83 percent of average storage. Flaming Gorge currently is storing 3,087,000 acre feet. There is no average established for Flaming Gorge. Viva Naughton is currently at 11,800 acre feet (45 percent of average).

Streamflow
Water users can expect above average yields in the basin this season. The following forecast values are based on a 50 percent chance probability for the April to July forecast period. Yields will be 107 percent of average for State Line Reservoir inflow (32,000 acre feet) 167 percent of average (110,000 acre feet) at Hams Fork near Frontier. Green River near Green River is forecast to yield 1,300,000 acre feet (145 percent of average). Meeks Cabin Reservoir inflow is estimated to flow 105,000 acre feet (109 percent of average). Viva Naughton Reservoir inflow will be about 150,000 acre feet (161 percent of average). Flaming Gorge Reservoir inflow should be near 1,800,000 acre feet (151 percent of average).

==================================================================================================================================
                                                     LOWER GREEN RIVER BASIN
                                               Streamflow Forecasts - May 1, 1997
==================================================================================================================================
                                              |  <<====== 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 R nr Green River, WY           APR-JUL      1151      1252    |     1300       145    |      1348      1447            899
                                                                    |                       |
MEEKS CABIN RESERVOIR Inflow         APR-JUL        92       100    |      105       109    |       110       118             96
                                                                    |                       |
STATE LINE RESERVOIR INFLOW          APR-JUL        25        29    |       32       107    |        35        39             30
                                                                    |                       |
HAMS FORK nr Frontier                APR-JUL        95       104    |      110       167    |       116       125             66
                                                                    |                       |
VIVA NAUGHTON RES inflow             APR-JUL       130       142    |      150       161    |       158       170             93
                                                                    |                       |
FLAMING GORGE RES INFLOW             APR-JUL      1495      1714    |     1800       151    |      1886      2105           1196
                                                                    |                       |
==================================================================================================================================
                         LOWER GREEN RIVER BASIN                        |                 LOWER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 1, 1997
==================================================================================================================================
                                      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    134.1    112.1    161.8 |   HAMS FORK RIVER             4       123       150
                                                                        |
FLAMING GORGE                         3749.0   3087.0   3107.3      --- |   BLACKS FORK                 5        74        97
                                                                        |
VIVA NAUGHTON RES                       42.4     11.8     19.8     26.5 |   HENRYS FORK                 3       134       154
                                                                        |
                                                                        |   GREEN above Flaming Gorge  26       108       142
                                                                        |
==================================================================================================================================
 * 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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