Shoshone and Clarks Fork River Basin (5)
February 1998

Snow
Snow in the basin is near average for this time of year. SWE is 108 percent of average (60 percent of last year) in the Shoshone River basin, and 97 percent of average (56 percent of last year) in the Clarks Fork drainage. 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 156 percent of normal. Cody 12 SE had the lowest percentage of average for the month (127%). Year-to-date precipitation figures for the basin range from 84 percent at Cody 21 SW to 209 percent of average at Cody. The basin year-to-date precipitation is now 113 percent of average (64 percent of last year).

Reservoir
Current storage in Buffalo Bill Reservoir is 129 percent of average. Currently 535,800 acre feet is stored in the reservoir. This is 104 percent of last year's storage at this time. 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 drainage's should be near average this season. The fifty percent yield (April to September period) for North Fork at Wapiti is expected to be 520,000 acre feet (100 percent of average). South Fork of the Shoshone near Valley has an estimated yield of 255,000 acre feet (95 percent of average), and South Fork above Buffalo Bill Reservoir is expected to be 230,000 acre feet (100 percent of average). Below Buffalo Bill Reservoir, the fifty percent chance yield for the Shoshone River is expected to be about 745,000 acre feet (93 percent of average). The fifty percent chance yield for the Clarks Fork of the Yellowstone near Belfry, Montana is expected to be about 575,000 acre feet (98 percent above average). 
==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - February 1, 1998
==================================================================================================================================
                                              |  <<====== 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       397       470    |      520       100    |       570       643            520
                                                                    |                       |
SF SHOSHONE RIVER near Valley        APR-SEP       194       231    |      255        95    |       279       316            269
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   APR-SEP       139       193    |      230       100    |       267       321            229
                                                                    |                       |
SHOSHONE RIVER blw Buffalo Bill (2)  APR-SEP       552       667    |      745        93    |       823       938            804
                                                                    |                       |
CLARKS FORK RIVER near Belfry        APR-SEP       440       520    |      575        98    |       630       710            590
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 1, 1998
==================================================================================================================================
                                      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    535.8    513.5    416.0 |   SHOSHONE RIVER              6        60       108
                                                                        |
                                                                        |   CLARKS FORK in WY           7        56        97
                                                                        |
==================================================================================================================================
 * 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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