Bighorn River Basin (4)
June 2001

Snow
Snowpack in this basin is well below average for this time of year. The Nowood and Greybull River drainages are melted out as of June 1. Shell Creek SWE is 3 percent of average (4 percent of last year). The basin SWE, as a whole, is currently 2 percent of average (4 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
May precipitation was 39 percent of the monthly average (39 percent of last year). Sites ranged from 6 to 79 percent of average for the month. Year-to-date precipitation is 66 percent of normal; that is 70 percent of last year at this time. Year to date percentages, from the 12 reporting stations, range from 44 to 81.

Reservoir
Usable storage in Boysen Reservoir is currently 413,900-acre feet (76 percent of average). Bighorn Lake is now at 98 percent of average (839,700-acre feet). Boysen is currently storing 76 percent of last year at this time and Big Horn Lake is storing 89 percent of last year's volume.

Streamflow
The 50 percent chance June through September runoff is anticipated to be below normal. The Boysen Reservoir inflow is forecast to yield 175,000 acre feet (29 percent of average); the Greybull River nr Meeteese should yield 42,000 acre feet (25 percent of average); Shell Creek near Shell should yield 18,700 acre feet (34 percent of average) and the Bighorn River at Kane should yield 175,000 acre feet (22 percent of average). 

==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - June 1, 2001
==================================================================================================================================
                                              |  <<====== 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          JUN-SEP       165       180    |      190        52    |       210       238            365
                                                                    |                       |
SF SHOSHONE RIVER nr Valley          JUN-SEP        56        73    |       85        40    |       114       157            215
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   JUN-SEP      16.0        29    |       38        22    |        78       137            175
                                                                    |                       |
BUFFALO BILL DAM Inflow (2)          JUN-SEP       214       235    |      250        41    |       286       338            606
                                                                    |                       |
CLARKS FORK RIVER nr Belfry          JUN-SEP       123       133    |      140        31    |       162       195            453
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 2001
==================================================================================================================================
                                      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    406.9    504.0    375.6 |   SHOSHONE RIVER              6         4         2
                                                                        |
                                                                        |   CLARKS FORK in WY           7         8         6
                                                                        |
==================================================================================================================================
 * 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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