Upper Green River Basin (11)
April 1998

Snow
The Upper Green River Basin snow water equivalent (SWE), above Fontenelle Reservoir, is 88 percent of average (62 percent of last year). SWE for the Green River above Warren Bridge is 86 percent of average and 57 percent of last year at this time. SWE on the west side of the Upper Green River basin is about 89 percent of normal, 64 percent of this time last year. Newfork River SWE is about 87 percent of normal -- about 63 percent of last year at this time. SWE for Big Sandy - Eden Valley area is 73 percent of normal and 51 percent of last year. For more information see the Basin Summary of Snow Courses at the beginning of this report.

Precipitation
The 12 reporting precipitation sites in the basin were 141 percent of average for March; precipitation was 138 percent of last year at this time. March precipitation varied from 107 percent of normal (Spring Greek Divide SNOTEL) to 351 percent above normal (Fontenelle Dam). Water year-to-date precipitation is about 78 percent of average (65 percent of last year).

Reservoir
Big Sandy Reservoir is storing 24,700 acre feet (124 percent of average) and Eden is storing 3,500 acre feet (74 percent of average). Fontenelle Reservoir is about 73 percent of average (115,600 acre feet). Flaming Gorge reservoir contains about 3,235,000 acre feet this year compared to 3,184,900 acre feet last year. 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 upper Green River basin is forecast below average. Green River at Warren Bridge is expected to yield about 230,000 acre feet (87 percent of normal). Pine Creek above Fremont Lake is expected to yield 95,000 acre feet (91 percent of normal). New Fork River near Big Piney is expected to yield about 325,000 acre feet (84 percent of normal). The 50 percent chance inflow to Fontenelle Reservoir is about 700,000 acre feet, which is about 82 percent of normal. Big Sandy near Farson is expected to be about 50,000 acre feet (88 percent of normal). 

==================================================================================================================================
                                                     UPPER 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 at Warren Bridge             APR-JUL       184       211    |      230        87    |       249       276            266
                                                                    |                       |
PINE CK abv Fremont Lake             APR-JUL        86        91    |       95        91    |        99       104            104
                                                                    |                       |
NEW FORK R nr Big Piney              APR-JUL       267       302    |      325        84    |       348       383            385
                                                                    |                       |
FONTENELLE RESERVOIR INFLOW          APR-JUL                        |      700        82    |                                849
                                                                    |                       |
BIG SANDY R nr Farson                APR-JUL        36        44    |       50        88    |        56        64             57
                                                                    |                       |
==================================================================================================================================
                         UPPER GREEN RIVER BASIN                        |                 UPPER 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
========================================================================|=========================================================
BIG SANDY                               38.3     24.7     26.7     19.9 |   GREEN above Warren Bridge   4        57        86
                                                                        |
EDEN                                    11.8      3.5      6.1      4.7 |   UPPER GREEN (West Side)     7        64        89
                                                                        |
FLAMING GORGE                         3749.0   3235.0   3184.9      --- |   NEWFORK RIVER               3        63        87
                                                                        |
FONTENELLE                             344.8    115.6    120.8    157.9 |   BIG SANDY/EDEN VALLEY       2        51        73
                                                                        |
                                                                        |   GREEN above Fontenelle     14        62        88
                                                                        |
==================================================================================================================================
 * 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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