Shoshone and Clarks Fork River Basin (5)
January 2000

Snow
Snow Water Equivalent (SWE) is 69 percent of the January 1 average (53 percent of last year) in the Shoshone River basin. The Clarks Fork River basin SWE is 87 percent of the January 1 average (77 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 December was 97 percent of normal (74 percent of last year). Monthly percentages range from 9 to 161 percent of average. The basin year-to-date precipitation is now 80 percent of average (66 percent of last year). Year-to-date percentages range from 35 to 100 percent of average.

Reservoir
Current storage in Buffalo Bill Reservoir is 105 percent of average (102 percent of last year's storage). Currently, about 457,500 acre-feet are stored in the reservoir compared to 447,900 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 440,000 acre-feet (85 percent of average). South Fork of the Shoshone River near Valley is estimated to yield of 170,000 acre-feet (63 percent of average), and South Fork above Buffalo Bill Reservoir is expected to be 170,000 acre-feet (74 percent of average). At the Buffalo Bill Reservoir, the fifty percent chance yield for the Shoshone River is expected to be about 650,000 acre-feet (81 percent of average). The fifty-percent chance yield for the Clarks Fork of the Yellowstone near Belfry, Montana is expected to be about 515,000 acre-feet (87 percent of average). 

==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - January 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       368       411    |      440        85    |       469       512            520
                                                                    |                       |
SF SHOSHONE RIVER nr Valley          APR-SEP       110       146    |      170        63    |       194       230            269
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   APR-SEP        84       135    |      170        74    |       205       256            229
                                                                    |                       |
BUFFALO BILL DAM Inflow (2)          APR-SEP       435       563    |      650        81    |       737       865            804
                                                                    |                       |
CLARKS FORK RIVER nr Belfry          APR-SEP       401       469    |      515        87    |       561       629            590
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of December              |        Watershed Snowpack Analysis - January 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    457.5    447.9    436.7 |   SHOSHONE RIVER              5        53        69
                                                                        |
                                                                        |   CLARKS FORK in WY           7        77        87
                                                                        |
==================================================================================================================================
 * 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.
(3) - Forecasts produced in cooperation with Alberta Forecasting Staff Canada
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