Upper Green River Basin (11)
May 2001

Snow
The Upper Green River Basin snow water equivalent (SWE), above Fontenelle Reservoir, is about 56 percent of average (86 percent of last year). The Green River basin SWE above Warren Bridge is 44 percent of normal (84 percent of last year). SWE on the west side of the Upper Green River basin is about 58 percent of normal, 82 percent of this time last year. Newfork River SWE is now about 68 percent of normal (132 percent of last year). Big Sandy-Eden Valley SWE is about 67 percent of average (94 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 111 percent of the April average (191 percent of last year at this time). April precipitation varied from 59 to 178 percent of average. Water year-to-date precipitation is about 88 percent of average (63 percent of last year). Year to date percentage of average ranges from 56 to 75 percent for the reporting stations.

Reservoir
Usable storage in Big Sandy Reservoir is 11,100 acre-feet (46 percent of average and 29 percent of the total capacity). Eden Reservoir water level is too low to measure. Usable storage in Fontenelle Reservoir is 117,200 acre feet (72 percent of average and 34 percent of capacity. Flaming Gorge Reservoir is currently storing 3,041,200 acre feet -- 85 percent of last year and 81 percent of capacity. No average has been 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 much below average. Green River at Warren Bridge is expected to yield about 175,000 acre-feet (66 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 38,000 acre-feet (67 percent of normal). 

==================================================================================================================================
                                                     UPPER GREEN RIVER BASIN
                                               Streamflow Forecasts - May 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       138       160    |      175        66    |       190       212            266
                                                                    |                       |
Pine Creek abv Fremont Lake          APR-JUL        67        75    |       80        77    |        85        93            104
                                     MAY-JUL        66        74    |       79        78    |        84        92            101
                                                                    |                       |
New Fork River nr Big Piney          APR-JUL       155       206    |      240        62    |       274       325            385
                                                                    |                       |
Fontenelle Reservoir Inflow          APR-JUL       346       406    |      450        53    |       496       567            849
                                                                    |                       |
Big Sandy River nr Farson            APR-JUL        24        32    |       38        67    |        44        52             57
                                                                    |                       |
==================================================================================================================================
                         UPPER GREEN RIVER BASIN                        |                 UPPER GREEN RIVER BASIN
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 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                                       NO REPORT               |   GREEN above Warren Bridge   4        89        47
                                                                        |
EDEN                                            NO REPORT               |   UPPER GREEN (West Side)     7        82        58
                                                                        |
FLAMING GORGE                         3749.0   3041.2   3196.9      --- |   NEWFORK RIVER               3       132        68
                                                                        |
FONTENELLE                             344.8    117.2    118.6    161.8 |   BIG SANDY/EDEN VALLEY       2        94        67
                                                                        |
                                                                        |   GREEN above Fontenelle     14        87        57
                                                                        |
==================================================================================================================================
 * 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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