Upper Green River Basin (11)
April 2001

Snow
The Upper Green River Basin snow water equivalent (SWE), above Fontenelle Reservoir, is about 61 percent of average (71 percent of last year). The Green River basin SWE above Warren Bridge is 63 percent of normal (71 percent of last year). SWE on the west side of the Upper Green River basin is about 57 percent of normal, 68 percent of this time last year. Newfork River SWE is now about 76 percent of normal (83 percent of last year). Big Sandy-Eden Valley SWE is about 57 percent of average (65 percent of last year). For more information see the Basin Summary of Snow Courses at the beginning of this report.

Precipitation
The 11 reporting precipitation sites in the basin were 64 percent of the March average (82 percent of last year at this time). March precipitation varied from 40 to 91 percent of average. Water year-to-date precipitation is about 58 percent of average (79 percent of last year). Year to date percentage of average ranges from 52 to 65 percent for the reporting stations.

Reservoir
Usable storage in Big Sandy Reservoir is 7,700 acre-feet (39 percent of average and 52 percent of the total capacity). Eden Reservoir is storing 0 acre-feet (0 percent of average and 0 percent of the total capacity). Usable storage in Fontenelle Reservoir is 110,300 acre feet (70 percent of average and 46 percent of capacity. Flaming Gorge Reservoir is currently storing 3,025,000 acre feet -- 95 percent of last year and 81 percent of capacity. There is no average established for Flaming Gorge. 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 165,000 acre-feet (62 percent of normal). Pine Creek above Fremont Lake is expected to yield 80,000 acre-feet (77 percent of normal). New Fork River near Big Piney is expected to yield about 240,000 acre-feet (62 percent of normal). Fontenelle Reservoir Inflow is estimated to be 450,000 acre-feet (53 percent of average), and Big Sandy near Farson is expected to be about 35,000 acre-feet (61 percent of normal). 

==================================================================================================================================
                                                     UPPER GREEN RIVER BASIN
                                               Streamflow Forecasts - April 1, 2001
==================================================================================================================================
                                              |  <<====== 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 River at Warren Bridge         APR-JUL       122       148    |      165        62    |       182       208            266
                                                                    |                       |
Pine Creek abv Fremont Lake          APR-JUL        65        74    |       80        77    |        86        95            104
                                                                    |                       |
New Fork River nr Big Piney          APR-JUL       134       197    |      240        62    |       283       346            385
                                                                    |                       |
Fontenelle Reservoir Inflow          APR-JUL       335       401    |      450        53    |       502       583            849
                                                                    |                       |
Big Sandy River nr Farson            APR-JUL      17.8        28    |       35        61    |        42        52             57
                                                                    |                       |
==================================================================================================================================
                         UPPER GREEN RIVER BASIN                        |                 UPPER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 2001
==================================================================================================================================
                                      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      7.7     21.1     19.9 |   GREEN above Warren Bridge   4        72        63
                                                                        |
EDEN                                            NO REPORT               |   UPPER GREEN (West Side)     7        68        57
                                                                        |
FLAMING GORGE                         3749.0   3025.0   3199.0      --- |   NEWFORK RIVER               3        83        76
                                                                        |
FONTENELLE                                      NO REPORT               |   BIG SANDY/EDEN VALLEY       2        65        57
                                                                        |
                                                                        |   GREEN above Fontenelle     14        71        61
                                                                        |
==================================================================================================================================
 * 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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