Shoshone and Clarks Fork River Basin
February 1997

Snow
Snowfall in the basin has been very good this year. Snow water equivalent (SWE) has been falling at a record rate. SWE is 179 percent of average (11 percent above last year) in the Shoshone River basin, and 174 percent of average (19 percent above last year) in the Clarks Fork drainage. All sites are reporting well above average snowpack as of February 1. 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 very high. The Nine reporting sites averaged 72 percent more than normal for the month. Parkers Peak had 3 times more precipitation than normal. Year-to-date precipitation figures for the basin are also very high. They range from 99 percent at Buffalo Bill Dam to 206 percent of average at Parkers Peak. The basin year-to-date precipitation is now 186 percent of average (12 percent more than last year).

Reservoir
Current storage in Buffalo Bill Reservoir is about 23 percent above average. Currently about 513,500 acre feet is stored in Buffalo Bill Reservoir (about 98 percent of last year's storage amount). Detailed reservoir data is shown on the following page and on the reservoir storage summary at the beginning of this report.

Streamflow
Runoff from all drainages should be much above average this season. The fifty percent yield (April to September Period) for North Fork at Wapiti is expected to be 855,000 acre feet (64 percent more than normal). South Fork of the Shoshone near Valley has an estimated 50 percent chance yield of about 415,000 acre feet (54 percent above normal) and at Buffalo Bill Reservoir the fifty percent chance yield it is expected to be 370,000 (62 percent more than normal). Below Buffalo Bill Reservoir, the fifty percent chance yield for the Shoshone River is expected to be about 1,250,000 acre feet (56 percent above average). The fifty percent chance yield for the Clarks Fork of the Yellowstone near Belfry, Montana is expected to be about 810,000 acre feet (37 percent above average). 

==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - February 1, 1997
==================================================================================================================================
                                              |  <<====== 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       732       805    |      855       164    |       905       978            520
                                                                    |                       |
SF SHOSHONE RIVER near Valley        APR-SEP       354       391    |      415       154    |       439       476            269
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   APR-SEP       279       333    |      370       162    |       407       461            229
                                                                    |                       |
SHOSHONE RIVER blw Buffalo Bill (2)  APR-SEP      1057      1172    |     1250       156    |      1328      1443            799
                                                                    |                       |
CLARKS FORK RIVER near Belfry        APR-SEP       675       755    |      810       137    |       865       945            590
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 1, 1997
==================================================================================================================================
                                      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    513.5    521.8    416.0 |   SHOSHONE RIVER              6       111       179
                                                                        |
                                                                        |   CLARKS FORK in WY           7       119       174
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual flow 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 flow - actual flow may be affected by upstream water management.
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