Shoshone and Clarks Fork River Basin (5)
June 2001

Snow
Nearly all snow has melted from the SNOTEL sites in this basin. Only one site has any snow. 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 61 percent of normal (49 percent of last year). Monthly percentages range from 7 to 94 percent of average. The basin year-to-date precipitation is now 74 percent of average (76 percent of last year). Year-to-date percentages range from 32 to 90 percent of average.

Reservoir
Current usable storage in Buffalo Bill Reservoir is 108 percent of average (81 percent of last year's storage) – the reservoir is about 63 percent of capacity. Currently, about 406,900 acre-feet of usable storage is in the reservoir compared to 504,000 acre feet last year – normally the reservoir stores about 375,600 acre feet at this time of the year. Detailed reservoir data is shown on the following page and on the reservoir storage summary at the beginning of this report.

Streamflow
Yield from the basin is expected to be much below average. Irrigators relying on direct diversion from a stream may experience shortages. The fifty percent yield (June through September period) for North Fork Shoshone River at Wapiti is expected to be 190,000 acre-feet (52 percent of average). South Fork of the Shoshone River near Valley is estimated to yield of 85,000 acre-feet (40 percent of average), and South Fork above Buffalo Bill Reservoir is expected to be 38,000 acre-feet (22 percent of average). At the Buffalo Bill Reservoir, the fifty-percent chance yield for the Shoshone River is expected to be about 250,000 acre-feet (41 percent of average). The fifty-percent chance yield for the Clarks Fork of the Yellowstone near Belfry, Montana is expected to be about 140,000 acre-feet (31 percent of average). 

==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - June 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)
====================================================================|=======================|=====================================
NF SHOSHONE RIVER at Wapiti          JUN-SEP       165       180    |      190        52    |       210       238            365
                                                                    |                       |
SF SHOSHONE RIVER nr Valley          JUN-SEP        56        73    |       85        40    |       114       157            215
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   JUN-SEP      16.0        29    |       38        22    |        78       137            175
                                                                    |                       |
BUFFALO BILL DAM Inflow (2)          JUN-SEP       214       235    |      250        41    |       286       338            606
                                                                    |                       |
CLARKS FORK RIVER nr Belfry          JUN-SEP       123       133    |      140        31    |       162       195            453
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 2001
==================================================================================================================================
                                      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    406.9    504.0    375.6 |   SHOSHONE RIVER              6         4         2
                                                                        |
                                                                        |   CLARKS FORK in WY           7         8         6
                                                                        |
==================================================================================================================================
 * 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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