Lower Green River Basin (12)
February 1999

Snow
The Blacks Fork drainage snow water equivalent (SWE) is 91 percent of average (83 % of last year). SWE in the Hams Fork, as of February 1, is 90 percent of average (95% of last year). Henry's Fork is 122 percent of average (75 percent of last year). The basin, as a whole, is 94 percent of average (103 % of last year). For more information see Basin Summary of Snow Courses at beginning of this report.

Precipitation
Precipitation was below average for the 4 reporting stations during January. Precipitation ranged from 72 to 89 percent of average for the month. The entire basin received 84 percent of average for the month (62 percent of last year). The basin year-to-date precipitation is currently 77 percent of average (104 percent of last year). Year to date percentages range from 71 to 83.

Reservoir
Fontenelle Reservoir is currently storing 180,900 acre feet; this is 92 percent of average (103 % of last year). Flaming Gorge is currently storing 3,341,000 acre feet (at this time last year the reservoir was storing 3,279,000 acre feet). Flaming Gorge has a maximum capacity of 3,749,000 acre feet. Viva Naughton is currently storing 31,400 acre feet (109 percent of average).

Streamflow
Expected yields vary from 83 to 92 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 830,000-acre feet (92 percent of average). East Fork of Smiths Fork near Robertson is estimated to yield 25,000 acre-feet (83 percent of average). The estimated yield for Hams Fork near Frontier is 58,000-acre feet (88 percent of average). Viva Naughton Reservoir inflow will be about 76,000-acre feet (85 percent of average). 

==================================================================================================================================
                                                     LOWER GREEN RIVER BASIN
                                               Streamflow Forecasts - February 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       539       724    |      830        92    |       936      1124            899
                                                                    |                       |
EF of Smiths Fork nr Robertson       APR-JUL      18.7        22    |       25        83    |        28        33             30
                                                                    |                       |
Hams Fk blw Pole Ck nr Frontier      APR-JUL        35        48    |       58        88    |        69        86             66
                                                                    |                       |
Hams Fk Inflow to Viva Naughton Res  APR-JUL        39        61    |       76        85    |        91       113             89
                                                                    |                       |
==================================================================================================================================
                         LOWER GREEN RIVER BASIN                        |                 LOWER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 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    180.9    176.1    196.2 |   HAMS FORK RIVER             4        95        90
                                                                        |
FLAMING GORGE                         3749.0   3341.0   3279.0      --- |   BLACKS FORK                 2        83        91
                                                                        |
VIVA NAUGHTON RES                       42.4     31.4     25.0     28.7 |   HENRYS FORK                 2        75       122
                                                                        |
                                                                        |   GREEN above Flaming Gorge  22       103        94
                                                                        |
==================================================================================================================================
 * 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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