Shoshone and Clarks Fork River Basin (5)
February 2000

Snow
Snow Water Equivalent (SWE) is 81 percent of the February 1 average (62 percent of last year) in the Shoshone River basin. The Clarks Fork River basin SWE is 91 percent of the February 1 average (75 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 January was 126 percent of normal (79 percent of last year). Monthly percentages range from 50 to 441 percent of average. The basin year-to-date precipitation is now 93 percent of average (69 percent of last year). Year-to-date percentages range from 36 to 163 percent of average.

Reservoir
Current storage in Buffalo Bill Reservoir is 108 percent of average (101 percent of last year's storage). Currently, about 449,000 acre-feet are stored in the reservoir compared to 445,000 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 (April through September period) for North Fork Shoshone River at Wapiti is expected to be 425,000 acre-feet (82 percent of average). South Fork of the Shoshone River near Valley is estimated to yield of 180,000 acre-feet (67 percent of average), and South Fork above Buffalo Bill Reservoir is expected to be 113,000 acre-feet (49 percent of average). At the Buffalo Bill Reservoir, the fifty percent chance yield for the Shoshone River is expected to be about 600,000 acre-feet (75 percent of average). The fifty-percent chance yield for the Clarks Fork of the Yellowstone near Belfry, Montana is expected to be about 535,000 acre- feet (91 percent of average). 

==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - February 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          APR-SEP       335       389    |      425        82    |       461       515            520
                                                                    |                       |
SF SHOSHONE RIVER nr Valley          APR-SEP       125       158    |      180        67    |       202       235            269
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   APR-SEP        35        81    |      113        49    |       145       191            229
                                                                    |                       |
BUFFALO BILL DAM Inflow (2)          APR-SEP       407       522    |      600        75    |       678       793            804
                                                                    |                       |
CLARKS FORK RIVER nr Belfry          APR-SEP       435       495    |      535        91    |       575       635            590
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 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    449.0    445.0    416.0 |   SHOSHONE RIVER              6        62        81
                                                                        |
                                                                        |   CLARKS FORK in WY           7        75        91
                                                                        |
==================================================================================================================================
 * 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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