Shoshone and Clarks Fork River Basin
March 1997

Snow
Snowfall in the basin has been very good this year. SWE is 160 percent of average (1 percent above last year) in the Shoshone River basin, and 157 percent of average (11 percent above last year) in the Clarks Fork drainage. All sites are reporting well above average snowpack as of March 1. 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 9 percent above normal. Deaver had 6 times more precipitation than normal (3300 percent of February 1996). Year-to-date precipitation figures for the basin are also very high. They range from 73 percent at Cody 21SW to 201 percent of average at Clark 7NE. The basin year-to-date precipitation is now 171 percent of average (6 percent more than last year).

Reservoir
Current storage in Buffalo Bill Reservoir is about 24 percent above average. Currently about 485,600 acre feet is stored in Buffalo Bill Reservoir (about 96 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 drainage's 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 yield of about 410,000 acre feet (52 percent above normal) and at Buffalo Bill Reservoir the fifty percent chance yield it is expected to be 365,000 (59 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 880,000 acre feet (49 percent above average). 

==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - March 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       764       818    |      855       164    |       892       946            520
                                                                    |                       |
SF SHOSHONE RIVER near Valley        APR-SEP       353       387    |      410       152    |       433       467            269
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   APR-SEP       278       330    |      365       159    |       400       452            229
                                                                    |                       |
SHOSHONE RIVER blw Buffalo Bill (2)  APR-SEP      1135      1189    |     1250       156    |      1311      1350            799
                                                                    |                       |
CLARKS FORK RIVER near Belfry        APR-SEP       779       839    |      880       149    |       921       981            590
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of February              |        Watershed Snowpack Analysis - March 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    485.6    507.4    391.2 |   SHOSHONE RIVER              6       101       160
                                                                        |
                                                                        |   CLARKS FORK in WY           7       111       157
                                                                        |
==================================================================================================================================
 * 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.
To March 1997 Basin Outlook Report Contents Page