Lower Green River Basin (12)
April 1998

Snow
The Blacks Fork drainage snow water equivalent (SWE) is 107 percent of average (112 % of last year). SWE in the Hams Fork, as of March 1, is 87 percent of average (65 % of last year). Henry's Fork is 134 percent of the April 1 average (138 % of last year). The basin as a whole is 93 percent of average (71 % of last year). For more information see Basin Summary of Snow Courses at beginning of this report.

Precipitation
Precipitation was well above average for the three reporting stations during March. Precipitation ranged from 114 to 178 percent of average. The entire basin received 137 percent of average for the month (166 percent of last year). The basin year-to-date precipitation is currently 82 percent of average (64 % of last year).

Reservoir
Fontenelle Reservoir is currently storing 115,600 acre feet; this is 46 percent of average storage (96 % of last year). Flaming Gorge is storing 3,235,000 acre feet (no average established). Flaming Gorge has a maximum capacity of 3,749,00 acre feet. Viva Naughton did not report their storage this month.

Streamflow
Expected yields vary for 80 to 113 percent of average across the basin. The following forecast values are based on a 50 percent chance probability for the April to July forecast period. Green River near Green River is forecast to yield 715,000 acre feet (80 percent of average). Meeks Cabin Reservoir inflow is estimated to flow 100,000 acre feet (104 percent of average). Yield for the State Line Reservoir inflow will be about 34,000 acre feet (113 percent of average). The estimated yield for Hams Fork near Frontier is 55,000 acre feet (83 percent of average). Viva Naughton Reservoir inflow will be about 75,000 acre feet (81 percent of average). Flaming Gorge Reservoir inflow should be near 1,000,000 acre feet (84 percent of average).

==================================================================================================================================
                                                     LOWER GREEN RIVER BASIN
                                               Streamflow Forecasts - April 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 nr Green River, WY           APR-JUL       571       657    |      715        80    |       773       859            899
                                                                    |                       |
MEEKS CABIN RESERVOIR Inflow         APR-JUL        86        94    |      100       104    |       106       114             96
                                                                    |                       |
STATE LINE RESERVOIR INFLOW          APR-JUL        25        31    |       34       113    |        38        43             30
                                                                    |                       |
HAMS FORK nr Frontier                APR-JUL        38        48    |       55        83    |        62        72             66
                                                                    |                       |
VIVA NAUGHTON RES inflow             APR-JUL        52        66    |       75        81    |        84        98             93
                                                                    |                       |
FLAMING GORGE RES INFLOW             APR-JUL                        |     1000        84    |                               1196
                                                                    |                       |
==================================================================================================================================
                         LOWER GREEN RIVER BASIN                        |                 LOWER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1998
==================================================================================================================================
                                      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    115.6    120.8    157.9 |   HAMS FORK RIVER             4        65        87
                                                                        |
FLAMING GORGE                         3749.0   3235.0   3184.9      --- |   BLACKS FORK                 5       112       107
                                                                        |
VIVA NAUGHTON RES                               NO REPORT               |   HENRYS FORK                 3       138       134
                                                                        |
                                                                        |   GREEN above Flaming Gorge  26        71        93
                                                                        |
==================================================================================================================================
 * 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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