Lower Green River Basin (12)
April 2001

Snow
Snow Water Equivalent in the Lower Green, as of April 1, is below average. SWE in the Hams Fork is 60 percent of average (71% of last year). Blacks Fork SWE is currently 66 percent of average (73 percent of last year). The Henry's fork SWE is currently 84 percent of average (89 percent of last year). The basin, as a whole, is 63 percent of average (72 percent of last year). For more information see Basin Summary of Snow Courses at beginning of this report.

Precipitation
Precipitation was below average for the 3 reporting stations during March. Precipitation ranged from 28 to 75 percent of average for the month. The entire basin received 61 percent of average for the month (83 percent of last year). The basin year-to-date precipitation is currently 59 percent of average (84 percent of last year). Year to date percentages range from 55 to 68.

Reservoir
Usable storage in Fontenelle Reservoir this month is 110,300 acre feet ( 70 percent of average and 105 percent of last year. Flaming Gorge is currently at 3,025,000 acre feet of usable storage. There is no average established for Flaming Gorge. Viva Naughton is currently at 32,200 acre feet of usable storage (119 percent of average).

Streamflow
Expected yields vary from 37 to 74 percent of average across the basin. The following forecast values are based on a 50 percent chance probability for the April through July forecast period. Green River near Green River is forecast to yield about 460,000-acre feet (51 percent of average). Blacks Fork near Robertson is forecast to yield 70,000-acre feet (74 percent of average). East Fork of Smiths Fork near Robertson is estimated to yield 22,000 acre-feet (73 percent of average). The estimated yield for Hams Fork near Frontier is 28,000- acre feet (42 percent of average). Viva Naughton Reservoir inflow will be about 33,000-acre feet (37 percent of average). Flaming Gorge Reservoir inflow will be about 620,000-acre feet (52 percent of average). 

==================================================================================================================================
                                                     LOWER 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 nr Green River, WY       APR-JUL       244       373    |      460        51    |       547       676            899
                                                                    |                       |
Blacks Fork nr Robertson             APR-JUL        47        61    |       70        74    |        79        93             95
                                                                    |                       |
EF of Smiths Fork nr Robertson       APR-JUL      17.4        20    |       22        73    |        24        28             30
                                                                    |                       |
Hams Fk blw Pole Ck nr Frontier      APR-JUL      16.7        23    |       28        42    |        33        42             66
                                                                    |                       |
Hams Fk Inflow to Viva Naughton Res  APR-JUL        23        29    |       33        37    |        44        59             89
                                                                    |                       |
Flaming Gorge Reservoir Inflow       APR-JUL       319       498    |      620        52    |       742       921           1196
                                                                    |                       |
==================================================================================================================================
                         LOWER GREEN RIVER BASIN                        |                 LOWER 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
========================================================================|=========================================================
FONTENELLE                                      NO REPORT               |   HAMS FORK RIVER             4        71        60
                                                                        |
FLAMING GORGE                         3749.0   3025.0   3199.0      --- |   BLACKS FORK                 5        73        66
                                                                        |
VIVA NAUGHTON RES                       42.4     32.2     33.4     27.1 |   HENRYS FORK                 3        89        84
                                                                        |
                                                                        |   GREEN above Flaming Gorge  26        72        63
                                                                        |
==================================================================================================================================
 * 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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