February 2002 Water Supply Outlook - Bighorn River Basin (4)

Bighorn River Basin (4)
February 2002

Snow
Snowpack in this basin is well below average for this time of year. The Nowood drainage SWE is 65 percent of average (125 percent of last year). Greybull River SWE is 63 percent of average (151 percent of last year). Shell Creek SWE is 77 percent of average (126 percent of last year). The basin SWE, as a whole, is currently 70 percent of average (128 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
January precipitation was 67 percent of the monthly average (215 percent of last year). Sites ranged from 53 to 130 percent of average for the month. Year-to-date precipitation is 79 percent of normal; that is 126 percent of last year at this time. Year to date percentages, from the 10 reporting stations, range from 62 to 93.

Reservoir
Boysen Reservoir is currently storing 87,000-acre feet (15 percent of average). Bighorn Lake is now at 82 percent of average (701,100-acre feet). Boysen is currently storing 81 percent of last year at this time and Big Horn Lake is storing 60 percent of last year's volume.

Streamflow
The 50 percent chance April through September runoff is anticipated to be below normal. The Boysen Reservoir inflow is forecast to yield 455,000 acre feet (56 percent of average); the Greybull River nr Meeteese should yield 90,000 acre feet (45 percent of average); Shell Creek near Shell should yield 37,000 acre feet (51 percent of average) and the Bighorn River at Kane should yield 575,000 acre feet (52 percent of average).

==================================================================================================================================
                                               SHOSHONE & CLARKS FORK RIVER BASINS
                                               Streamflow Forecasts - February 1, 2002
==================================================================================================================================
                                              |  <<====== 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       255       309    |      345        66    |       381       435            520
                                                                    |                       |
SF SHOSHONE RIVER nr Valley          APR-SEP        95       128    |      150        57    |       172       205            265
                                                                    |                       |
SF SHOSHONE RIVER abv Buffalo Bill   APR-SEP        37        83    |      115        51    |       147       193            225
                                                                    |                       |
BUFFALO BILL DAM Inflow (2)          APR-SEP       322       437    |      515        64    |       593       708            805
                                                                    |                       |
CLARKS FORK RIVER nr Belfry          APR-SEP       290       350    |      390        66    |       430       490            595
                                                                    |                       |
==================================================================================================================================
                   SHOSHONE & CLARKS FORK RIVER BASINS                  |           SHOSHONE & CLARKS FORK RIVER BASINS
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 1, 2002
==================================================================================================================================
                                      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    280.2    370.2    292.6 |   SHOSHONE RIVER              6       171        75
                                                                        |
                                                                        |   CLARKS FORK in WY           7       166        79
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual volume will exceed the volumes in the table.

(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.

To February 2002 Basin Outlook Report Contents Page

Bighorn River Basin (4) February 2002

Bighorn River Basin (4)
February 2002