Lower Green River Basin (12)
June 1999

Snow
Cool weather has slowed the normal melting of snow -- consequently the comparison to average, and last year, could appear exaggerated. The Blacks Fork drainage snow water equivalent (SWE) is 138 percent of average (113 % of last year). SWE in the Hams Fork, as of June 1, is 157 percent of average (199% of last year). The Henry's Fork is melted out. SWE for the basin, as a whole, is 147 percent of average (218 % of last year). For more information see Basin Summary of Snow Courses at beginning of this report.

Precipitation
Precipitation was above average for the 4 reporting stations during May. Precipitation ranged from 44 to 291 percent of average for the month. The entire basin received 129 percent of average for the month (117 percent of last year). The basin year-to-date precipitation is currently 116 percent of average (134 percent of last year). Year to date percentages range from 106 to 209.

Reservoir
Fontenelle Reservoir is currently storing 134,100 acre feet; this is 105 percent of average (114 % of last year). Flaming Gorge did not report this month. Flaming Gorge reservoir is presently storing about 3,236,995 acre-feet (reservoir capacity is 3,749,000 acre-feet). Viva Naughton is currently storing about 34,300 acre feet (81 percent of capacity); this is about 101 percent of average ( the same as last year).

Streamflow
Expected yields vary from 93 to 130 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 1140,000-acre feet (127 percent of average). East Fork of Smiths Fork near Robertson is estimated to yield 28,000 acre-feet (93 percent of average). The estimated yield for Hams Fork near Frontier is 75,000-acre feet (114 percent of average). Viva Naughton Reservoir inflow will be about 100,000-acre feet (112 percent of average). 

==================================================================================================================================
                                                     LOWER GREEN RIVER BASIN
                                               Streamflow Forecasts - June 1, 1999
==================================================================================================================================
                                              |  <<====== 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      1002      1084    |     1140       127    |      1196      1278            899
                                                                    |                       |
Blacks Fork nr Robertson             APR-JUL        79        85    |       90        95    |        95       102             95
                                                                    |                       |
EF of Smiths Fork nr Robertson       APR-JUL        25        27    |       28        93    |        30        32             30
                                                                    |                       |
Hams Fk blw Pole Ck nr Frontier      APR-JUL        60        69    |       75       114    |        81        91             66
                                                                    |                       |
Hams Fk Inflow to Viva Naughton Res  APR-JUL        81        92    |      100       112    |       108       119             89
                                                                    |                       |
Flaming Gorge Reservoir Inflow       APR-JUL      1360      1473    |     1550       130    |      1627      1740           1196
                                                                    |                       |
==================================================================================================================================
                         LOWER GREEN RIVER BASIN                        |                 LOWER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 1999
==================================================================================================================================
                                      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    206.0    180.8    195.5 |   HAMS FORK RIVER             3       199       157
                                                                        |
FLAMING GORGE                                   NO REPORT               |   BLACKS FORK                 2       113       138
                                                                        |
VIVA NAUGHTON RES                       42.4     34.3      ---     34.0 |   HENRYS FORK                 2         0         0
                                                                        |
                                                                        |   GREEN above Flaming Gorge  18       218       147
                                                                        |
==================================================================================================================================
 * 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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