Upper Green River Basin (11)
June 1998

Snow
The Upper Green River Basin snow water equivalent (SWE), above Fontenelle Reservoir, is 69 percent of average (54 percent of last year). The Green River above Warren Bridge is has melted out. SWE on the west side of the Upper Green River basin is about 84 percent of normal, 57 percent of this time last year. Newfork River and Big Sandy - Eden Valley area snow courses have melted out. For more information see the Basin Summary of Snow Courses at the beginning of this report.

Precipitation
The 13 reporting precipitation sites in the basin were 115 percent of average for May; precipitation was 140 percent of last year at this time. May precipitation varied from 84 percent of normal (Triple Peak SNOTEL) to 171 percent of normal (New Fork Lake SNOTEL). Water year-to-date precipitation is about 83 percent of average (72 percent of last year).

Reservoir
Big Sandy Reservoir is storing 30,900 acre feet (109 percent of average and 81 percent of capacity). Eden is storing 5,700 acre feet (73 percent of average and 48 percent of capacity). Fontenelle Reservoir had no report this monthis storing about 131,600 acre feet (81 percent of average and about 38 percent of capacity). The 3,749,000 acre feet capacity Flaming Gorge reservoir had no reportcontains about 3,190,600 acre feet; this year compared to 3,087,000 acre feet last year. 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 below average. Green River at Warren Bridge is expected to yield about 250,000 acre feet (94 percent of normal). Pine Creek above Fremont Lake is expected to yield 100,000 acre feet (96 percent of normal). New Fork River near Big Piney is expected to yield about 350,000 acre feet (91 percent of normal). The 50 percent chance inflow to Fontenelle Reservoir is about 750,000 acre feet, which is about 88 percent of normal. Big Sandy near Farson is expected to be about 50,000 acre feet (88 percent of normal). 

==================================================================================================================================
                                                     UPPER GREEN RIVER BASIN
                                               Streamflow Forecasts - June 1, 1998
==================================================================================================================================
                                              |  <<====== 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 at Warren Bridge             APR-JUL       215       236    |      250        94    |       264       285            266
                                                                    |                       |
PINE CK abv Fremont Lake             APR-JUL        93        97    |      100        96    |       103       107            104
                                                                    |                       |
NEW FORK R nr Big Piney              APR-JUL       307       333    |      350        91    |       367       393            385
                                                                    |                       |
FONTENELLE RESERVOIR INFLOW          APR-JUL                        |      750        88    |                                849
                                                                    |                       |
BIG SANDY R nr Farson                APR-JUL        42        47    |       50        88    |        53        58             57
                                                                    |                       |
==================================================================================================================================
                         UPPER GREEN RIVER BASIN                        |                 UPPER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 1998
==================================================================================================================================
                                      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     30.9     40.3     28.3 |   GREEN above Warren Bridge   4         0         0
                                                                        |
EDEN                                    11.8      5.7     12.2      7.8 |   UPPER GREEN (West Side)     4        57        84
                                                                        |
FLAMING GORGE                                   NO REPORT               |   NEWFORK RIVER               2         0         0
                                                                        |
FONTENELLE                             344.8    180.8    212.9    195.5 |   BIG SANDY/EDEN VALLEY       1         0         0
                                                                        |
                                                                        |   GREEN above Fontenelle     10        54        69
                                                                        |
==================================================================================================================================
 * 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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