Shoshone and Clarks Fork River Basin (5)
March 1998

Snow
Snow in the basin is near average for this time of year. SWE is 92 percent of average (57 percent of last year) in the Shoshone River basin, and 84 percent of average (53 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 February was 37 percent of normal. Clarke 7NE had the lowest percentage of average for the month (0 %). Year-to-date precipitation figures for the basin range from 79 to 186 percent of average. The basin year-to-date precipitation is now 99 percent of average (60 percent of last year).

Reservoir
Current storage in Buffalo Bill Reservoir is 134 percent of average. Currently 525,900 acre feet is stored in the reservoir. This is 108 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 through 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 215,000 acre feet (94 percent of average). Below Buffalo Bill Reservoir, the fifty percent chance yield for the Shoshone River is expected to be about 750,000 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 485,000 acre feet (82 percent above average). 

==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - March 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       429       483    |      520       100    |       557       611            520
                                                                    |                       |
SF SHOSHONE RIVER near Valley        APR-SEP       198       232    |      255        95    |       278       312            269
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   APR-SEP       128       180    |      215        94    |       250       302            229
                                                                    |                       |
SHOSHONE RIVER blw Buffalo Bill (2)  APR-SEP       598       689    |      750        93    |       811       902            804
                                                                    |                       |
CLARKS FORK RIVER near Belfry        APR-SEP       384       444    |      485        82    |       526       586            590
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of February              |        Watershed Snowpack Analysis - March 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    525.9    485.6    391.2 |   SHOSHONE RIVER              5        57        92
                                                                        |
                                                                        |   CLARKS FORK in WY           7        53        84
                                                                        |
==================================================================================================================================
 * 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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