Shoshone and Clarks Fork River Basin (5)
June 2000

Snow
Snow Water Equivalent (SWE) is 40 percent of the June 1 average (26 percent of last year) in the Shoshone River basin. The Clarks Fork River basin SWE is 68 percent of the June 1 average (58 percent of last year). For more information see the Basin Summary of Snow Course Data at the beginning of this report.

Precipitation
Precipitation for the month of May was 124 percent of normal (156 percent of last year). Monthly percentages range from 72 to 165 percent of average. The basin year-to-date precipitation is now 98 percent of average (83 percent of last year). Year-to-date percentages range from 54 to 129 percent of average.

Reservoir
Current storage in Buffalo Bill Reservoir is 134 percent of average (129 percent of last year's storage). Currently, about 504,000 acre-feet are stored in the reservoir compared to 392,100 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 yield (June through September period) for North Fork Shoshone River at Wapiti is expected to be 255,000 acre-feet (70 percent of average). South Fork of the Shoshone River near Valley is estimated to yield of 130,000 acre-feet (61 percent of average), and South Fork above Buffalo Bill Reservoir is expected to be 115,000 acre-feet (66 percent of average). At the Buffalo Bill Reservoir, the fifty percent chance yield for the Shoshone River is expected to be about 470,000 acre-feet (78 percent of average). The fifty-percent chance yield for the Clarks Fork of the Yellowstone near Belfry, Montana is expected to be about 350,000 acre- feet (77 percent of average). 

==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - June 1, 2000
==================================================================================================================================
                                              |  <<====== 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)
====================================================================|=======================|=====================================
NF SHOSHONE RIVER at Wapiti          JUN-SEP       207       235    |      255        70    |       275       303            365
                                                                    |                       |
SF SHOSHONE RIVER nr Valley          JUN-SEP        58       101    |      130        61    |       159       202            215
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   JUN-SEP      16.0        75    |      115        66    |       155       214            175
                                                                    |                       |
BUFFALO BILL DAM Inflow (2)          JUN-SEP       382       434    |      470        78    |       506       558            606
                                                                    |                       |
CLARKS FORK RIVER nr Belfry          JUN-SEP       295       328    |      350        77    |       372       405            453
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 2000
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
BUFFALO BILL                           646.6    504.0    392.1    375.6 |   SHOSHONE RIVER              6        26        40
                                                                        |
                                                                        |   CLARKS FORK in WY           7        58        68
                                                                        |
==================================================================================================================================
 * 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.
To June 2000 Basin Outlook Report Contents Page