January 1997 Water Supply Outlook - Upper Green River Basin

Upper Green River Basin
January 1997

Snow
Snowpack in the basin, as of January 1, is over 200 percent of average. Snow Water Equivalent (SWE) for the Green River above Warren Bridge is about 227 percent of average and about 55 percent more than last year. SWE on the west side of the Upper Green River basin is about 102 percent more than normal, about 38 percent more than last year. SWE in the New Fork drainage is 120 percent more than normal, which is about 71 percent more than last year. For more information see the Basin Summary of Snow

Precipitation
The 13 reporting precipitation sites in the basin averaged 150 percent more than normal for December. December precipitation varied from 23 percent below normal (Big Piney) to 257 percent above normal (Kendal RS). Water year-to-date precipitation, is about 61 percent above normal (about 45 percent more than last year).

Reservoir
When current storage is compared to average for this time of the year, storage varies from 86 to 91 percent of average. Current storage compared to average for the three storage reservoirs in the basin is as follows; Big Sandy 91% (15,800 acre feet), Eden 86% (3,600 acre feet), and Fontenelle 89% (186,200). Big Sandy and Eden Reservoir is about 41 percent below last years storage amount, while Fontenelle is 24 percent less than last year at this time. Detailed reservoir data is shown on the following page and on the reservoir storage summary at the beginning of this report.

Streamflow
Runoff yield in the basin is forecast above average to much above average. The fifty percent chance April through July runoff at Green River at Warren Bridge is expected to yield about 350,000 acre feet (32 percent more than normal). Pine Creek above Fremont Lake is expected to yield 145,000 acre feet or 45 percent more than normal. New Fork River near Big Piney has a 50 percent chance yield of 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 80,000 acre feet (40 percent more than normal).

==================================================================================================================================
                                                     UPPER GREEN RIVER BASIN
                                               Streamflow Forecasts - January 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       261       318    |      350       132    |       382       439            266
                                                                    |                       |
PINE CK abv Fremont Lake             APR-JUL       114       138    |      145       139    |       152       176            104
                                                                    |                       |
NEW FORK R nr Big Piney              APR-JUL       354       504    |      550       143    |       596       747            385
                                                                    |                       |
FONTENELLE RESERVOIR INFLOW          APR-JUL       798      1134    |     1250       147    |      1366      1698            849
                                                                    |                       |
BIG SANDY R nr Farson                APR-JUL        55        74    |       80       140    |        86       105             57
                                                                    |                       |
==================================================================================================================================
                         UPPER GREEN RIVER BASIN                        |                 UPPER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of December              |        Watershed Snowpack Analysis - January 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     15.8     26.7     17.3 |   GREEN above Warren Bridge   4       155       227
                                                                        |
EDEN                                    11.8      3.6      6.1      4.2 |   UPPER GREEN (West Side)     4       138       202
                                                                        |
FLAMING GORGE                         3749.0   3249.0   3279.0      --- |   NEWFORK RIVER               2       171       220
                                                                        |
FONTENELLE                             344.8    186.2    216.0    208.3 |   BIG SANDY/EDEN VALLEY       1       146       202
                                                                        |
                                                                        |   GREEN above Fontenelle     10       147       213
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual flow 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 flow - actual flow may be affected by upstream water management.

To Jaunary 1997 Basin Outlook Report Contents Page

Upper Green River Basin January 1997

Upper Green River Basin
January 1997