Upper Green River Basin (11)
April 1999

Snow
The Upper Green River Basin snow water equivalent (SWE), above Fontenelle Reservoir, is 105 percent of average (123 percent of last year). The Green River above Warren Bridge is 103 percent of normal (110 percent of last year). SWE on the West Side of the Upper Green River basin is about 105 percent of normal, 127 percent of this time last year. Newfork River SWE is now 107 percent of normal (126 percent of last year). Big Sandy - Eden Valley is currently 114 percent of normal (156 percent of last year). For more information see the Basin Summary of Snow Courses at the beginning of this report.

Precipitation
The 11 reporting precipitation sites in the basin were 78 percent of the March average (56 percent of last year at this time). March precipitation varied from 37 to 104 percent of average. Water year-to-date precipitation is about 95 percent of average (120 percent of last year). Year to date percentage of average ranges from 80 to 108 for the 11 reporting stations.

Reservoir
Big Sandy Reservoir is storing 37,800 acre-feet (190 percent of average and 99 percent of capacity). Eden reservoir is storing 7,100 acre-feet (151 percent of average and 60 percent of capacity). Fontenelle Reservoir is storing 122,900 acre-feet (78 percent of average and 36 percent of the total capacity). Flaming Gorge reservoir is presently storing about 3,190,600 acre-feet (85 percent of capacity -- reservoir capacity is 3,749,000 acre- feet). Detailed reservoir data is shown on the following page and on the reservoir storage summary at the beginning of this report.

Streamflow
The fifty percent chance April through July runoff in the Upper Green River basin is forecast above average. Green River at Warren Bridge is expected to yield about 275,000 acre-feet (103 percent of normal). Pine Creek above Fremont Lake is expected to yield 105,000 acre-feet (101 percent of normal). New Fork River near Big Piney is expected to yield about 400,000 acre-feet (104 percent of normal). Inflow to Fontenelle Reservoir is expected to be about 900,000 acre feet (106 percent of average). Big Sandy near Farson is expected to be about 63,000 acre-feet (111 percent of normal).

 
==================================================================================================================================
                                                     UPPER GREEN RIVER BASIN
                                               Streamflow Forecasts - April 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 at Warren Bridge         APR-JUL       229       258    |      275       103    |       292       319            266
                                                                    |                       |
Pine Creek abv Fremont Lake          APR-JUL        89        99    |      105       101    |       111       121            104
                                                                    |                       |
New Fork River nr Big Piney          APR-JUL       285       357    |      400       104    |       443       516            385
                                                                    |                       |
Fontenelle Reservoir Inflow          APR-JUL       654       830    |      900       106    |       972      1146            849
                                                                    |                       |
Big Sandy River nr Farson            APR-JUL        47        56    |       63       111    |        70        79             57
                                                                    |                       |
==================================================================================================================================
                         UPPER GREEN RIVER BASIN                        |                 UPPER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1999
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
BIG SANDY                               38.3     37.8     24.7     19.9 |   GREEN above Warren Bridge   4       110       103
                                                                        |
EDEN                                    11.8      7.1      3.5      4.7 |   UPPER GREEN (West Side)     7       127       105
                                                                        |
FLAMING GORGE                         3749.0   3190.6   3235.0      --- |   NEWFORK RIVER               3       126       107
                                                                        |
FONTENELLE                             344.8    122.9    115.6    157.9 |   BIG SANDY/EDEN VALLEY       2       156       114
                                                                        |
                                                                        |   GREEN above Fontenelle     14       123       105
                                                                        |
==================================================================================================================================
 * 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.
(D) - The operational measurement of flow at this point has been discountinued. 

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