March 1997 Water Supply Outlook - Upper Green River Basin

Upper Green River Basin
March 1997

Snow
Snowpack in the basin, as of March 1, is 148 percent of average. Snow Water Equivalent (SWE) for the Green River above Warren Bridge is 144 percent of average and 12 percent more than last year. SWE on the west side of the Upper Green River basin is about 50 percent more than normal, 12 percent more than last year. SWE in the New Fork drainage is 44 percent more than normal, which is about 26 percent more than last year. The Big Sandy and Eden Valley portion of the river basin is about 51 percent above normal and 39 percent more than 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 averaged 49 percent of average for February; precipitation was 35 percent less than February of last year. February precipitation varied from 83 percent below normal (Big Piney and New Fork Lake) to 24 percent below normal (Kendall RS). Water year-to-date precipitation, is 22 percent above normal (14 percent more than last year).

Reservoir
Big Sandy Reservoir is storing 16,200 acre feet (88 percent of normal) and Eden is storing 3,600 acre feet (88 percent of average). Fontenelle Reservoir is about 69 percent of average (119,000 acre feet). Flaming Gorge Reservoir has about 3,150,600 acre feet stored ( no average available). 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 80,000 acre feet (40 percent more than normal).

==================================================================================================================================
                                                     UPPER GREEN RIVER BASIN
                                               Streamflow Forecasts - March 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       290       324    |      340       128    |       356       391            266
                                                                    |                       |
PINE CK abv Fremont Lake             APR-JUL       112       125    |      130       125    |       135       148            104
                                                                    |                       |
NEW FORK R nr Big Piney              APR-JUL       431       520    |      550       143    |       580       670            385
                                                                    |                       |
FONTENELLE RESERVOIR INFLOW          APR-JUL      1036      1174    |     1250       147    |      1326      1460            849
                                                                    |                       |
BIG SANDY R nr Farson                APR-JUL        64        74    |       80       140    |        86        96             57
                                                                    |                       |
==================================================================================================================================
                         UPPER GREEN RIVER BASIN                        |                 UPPER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of February              |        Watershed Snowpack Analysis - March 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     16.2     28.7     18.4 |   GREEN above Warren Bridge   4       112       144
                                                                        |
EDEN                                    11.8      3.6      6.1      4.1 |   UPPER GREEN (West Side)     7       112       150
                                                                        |
FLAMING GORGE                         3749.0   3150.6   3194.4      --- |   NEWFORK RIVER               3       126       144
                                                                        |
FONTENELLE                             344.8    119.0    121.8    172.0 |   BIG SANDY/EDEN VALLEY       2       139       151
                                                                        |
                                                                        |   GREEN above Fontenelle     14       114       148
                                                                        |
==================================================================================================================================
 * 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 March 1997 Basin Outlook Report Contents Page

Upper Green River Basin March 1997

Upper Green River Basin
March 1997