Lower Green River Basin
April 1997

Snow
The Blacks Fork drainage snow water equivalent (SWE) is 96 percent of average, currently the lowest in the basin. Henrys Fork is about 97 percent of average. Snowpack in the Hams Fork, as of April 1, is 132 percent of average. The basin as a whole is 131 percent of average. This is 6 percent ahead of last year at this time. For more information see Basin Summary of Snow Courses at beginning of this report.

Precipitation
Precipitation was light throughout the basin during March. Precipitation ranged from 53 percent of average at Church Buttes to 107 percent of average at Kelley RS. The entire basin received 79 percent of average for the month (80 percent of last year). The basin year to date precipitation is currently 124 percent of average; sites range from 108 to 141 percent of average.

Reservoir
Fontenelle Reservoir is currently storing 120,800 acre feet; this is 77 percent of average storage. Flaming Gorge currently is storing 3,184,900 acre feet. There is no average established for Flaming Gorge. Viva Naughton did not report this month.

Streamflow
Water users can expect above average yields in the basin this season. The following forecast values are based on a 50 percent chance probability for the April to July forecast period. Yields will range from 107 percent of average for State Line Reservoir inflow (32,000 acre feet) to 156 percent of average (103,000 acre feet) at Hams Fork near Frontier. Green River near Green River is forecast to yield 1,300,000 acre feet (145 percent of average). Meeks Cabin Reservoir inflow is estimated to flow 105,000 acre feet (109 percent of average). Viva Naughton Reservoir inflow will be about 142,000 acre feet (153 percent of average). Flaming Gorge Reservoir inflow should be near 1,700,000 acre feet (142 percent of average. 

==================================================================================================================================
                                                     LOWER GREEN RIVER BASIN
                                               Streamflow Forecasts - April 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 nr Green River, WY           APR-JUL      1133      1242    |     1300       145    |      1358      1474            899
                                                                    |                       |
MEEKS CABIN RESERVOIR Inflow         APR-JUL        91        99    |      105       109    |       111       119             96
                                                                    |                       |
STATE LINE RESERVOIR INFLOW          APR-JUL        23        29    |       32       107    |        36        41             30
                                                                    |                       |
HAMS FORK nr Frontier                APR-JUL        86        96    |      103       156    |       110       120             66
                                                                    |                       |
VIVA NAUGHTON RES inflow             APR-JUL       119       133    |      142       153    |       151       165             93
                                                                    |                       |
FLAMING GORGE RES INFLOW             APR-JUL      1363      1598    |     1700       142    |      1802      2045           1196
                                                                    |                       |
==================================================================================================================================
                         LOWER GREEN RIVER BASIN                        |                 LOWER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1997
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
FONTENELLE                             344.8    120.8     97.4    157.9 |   HAMS FORK RIVER             4       115       132
                                                                        |
FLAMING GORGE                         3749.0   3184.9   3151.0      --- |   BLACKS FORK                 5        71        96
                                                                        |
VIVA NAUGHTON RES                               NO REPORT               |   HENRYS FORK                 3        86        97
                                                                        |
                                                                        |   GREEN above Flaming Gorge  26       106       131
                                                                        |
==================================================================================================================================
 * 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 April 1997 Basin Outlook Report Contents Page