Upper Green River Basin (11)
January 1998

Snow
Upper Green River Basin snow water equivalent (SWE), as of Jan 1, is 53 percent of average (24 percent of last year). SWE for the Green River above Warren Bridge is 49 percent of average and 21 percent of last year at this time. SWE on the west side of the Upper Green River basin is about 52 percent of normal, 26 percent of this time last year. SWE for Big Sandy - Eden Valley area is 63 percent of normal and 31 percent of last year. 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 32 percent of average for December; precipitation was only 12 percent of last year at this time. December precipitation varied from 26 percent of normal (Triple Peak SNOTEL) to 80 percent above normal (Big Piney). Water year-to-date precipitation is about 48 percent above normal (29 percent of last year).

Reservoir
Big Sandy Reservoir is storing 21,100 acre feet (122 percent of average) and Eden is storing 3,500 acre feet (83 percent of average). Fontenelle Reservoir is about 107 percent of average (223,100 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 below average. Green River at Warren Bridge is expected to yield about 180,000 acre feet (68 percent of normal). Pine Creek above Fremont Lake is expected to yield 78,000 acre feet ( 75 percent of normal). New Fork River near Big Piney is expected to yield about 230,000 acre feet (60 percent of normal). The 50 percent chance inflow to Fontenelle Reservoir is about 475,000 acre feet, which is about 56 percent of normal. Big Sandy near Farson is expected to be about 38,000 acre feet (67 percent of normal). 

==================================================================================================================================
                                                     UPPER GREEN RIVER BASIN
                                               Streamflow Forecasts - January 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       125       148    |      180        68    |       212       260            266
                                                                    |                       |
PINE CK abv Fremont Lake             APR-JUL        60        71    |       78        75    |        85        96            104
                                                                    |                       |
NEW FORK R nr Big Piney              APR-JUL       116       184    |      230        60    |       276       344            385
                                                                    |                       |
FONTENELLE RESERVOIR INFLOW          APR-JUL       334       359    |      475        56    |       591       762            849
                                                                    |                       |
BIG SANDY R nr Farson                APR-JUL        23        32    |       38        67    |        44        53             57
                                                                    |                       |
==================================================================================================================================
                         UPPER GREEN RIVER BASIN                        |                 UPPER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of December              |        Watershed Snowpack Analysis - January 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     21.1     15.8     17.3 |   GREEN above Warren Bridge   4        21        49
                                                                        |
EDEN                                    11.8      3.5      3.6      4.2 |   UPPER GREEN (West Side)     5        26        52
                                                                        |
FLAMING GORGE                                   NO REPORT               |   NEWFORK RIVER               2        29        64
                                                                        |
FONTENELLE                             344.8    223.1    186.2    208.3 |   BIG SANDY/EDEN VALLEY       1        31        63
                                                                        |
                                                                        |   GREEN above Fontenelle     11        24        53
                                                                        |
==================================================================================================================================
 * 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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