Upper Green River Basin (11)
June 1997

Snow
Snow water equivalent (SWE) in the basin, as of June 1 is 115 percent of average. SWE for the Green River above Warren Bridge is 59 percent of average and 17 percent less than last year at this time. SWE on the west side of the Upper Green River basin is about 28 percent more than normal, 26 percent less than this time last year. SWE for the Green River above Fontenelle Reservoir is 15 percent above average and 30 percent less than last year at this time. For more information see the Basin Summary of Snow Courses at the beginning of this report.

Precipitation
The 12 reporting precipitation sites in the basin averaged 13 percent below average for May; precipitation was nearly half (51 percent) of last year. May precipitation varied from 7 percent of normal (Big Piney) to 128 percent above normal (New Fork Lake). Water year-to-date precipitation, is 17 percent above normal (3 percent more than last year).

Reservoir
Big Sandy Reservoir is storing 40,300 acre feet (42 percent above normal) and Eden is storing 12,200 acre feet (56 percent above average). Fontenelle Reservoir is about 9 percent above average (212,900 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 basin, is forecast above average to much above average. Green River at Warren Bridge is expected to yield about 340,000 acre feet (28 percent more than normal). Pine Creek above Fremont Lake is expected to yield 130,000 acre feet ( 25 percent more than normal). New Fork River near Big Piney is expected to yield about 550,000 acre feet or 43 percent more than normal. The 50 percent chance inflow to Fontenelle Reservoir is about 1,250,000 acre feet, which is about 47 percent more than normal. Big Sandy near Farson is expected to be about 75,000 acre feet (32 percent more than normal). 

==================================================================================================================================
                                                     UPPER GREEN RIVER BASIN
                                               Streamflow Forecasts - June 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 at Warren Bridge             APR-JUL       306       322    |      340       128    |       358       375            266
                                                                    |                       |
PINE CK abv Fremont Lake             APR-JUL       119       127    |      130       125    |       133       141            104
                                                                    |                       |
NEW FORK R nr Big Piney              APR-JUL       458       533    |      550       143    |       567       639            385
                                                                    |                       |
FONTENELLE RESERVOIR INFLOW          APR-JUL      1121      1202    |     1250       147    |      1298      1384            849
                                                                    |                       |
BIG SANDY R nr Farson                APR-JUL        63        70    |       75       132    |        80        87             57
                                                                    |                       |
==================================================================================================================================
                         UPPER GREEN RIVER BASIN                        |                 UPPER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 1997
==================================================================================================================================
                                      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     40.3     33.0     28.3 |   GREEN above Warren Bridge   4        17        59
                                                                        |
EDEN                                    11.8     12.2      6.5      7.8 |   UPPER GREEN (West Side)     5        74       128
                                                                        |
FLAMING GORGE                                   NO REPORT               |   NEWFORK RIVER               2         0         0
                                                                        |
FONTENELLE                             344.8    212.9    131.0    195.5 |   BIG SANDY/EDEN VALLEY       1         0         0
                                                                        |
                                                                        |   GREEN above Fontenelle     11        60       115
                                                                        |
==================================================================================================================================
 * 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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