Bighorn River Basin (4)
January 2001

Snow
Snowpack in this basin is well below average for this time of year. The Nowood drainage SWE is 68 percent of average (82 percent of last year). Greybull River SWE is 57 percent of average (154 percent of last year). Shell Creek SWE is 72 percent of average (77 percent of last year). The basin SWE, as a whole, is currently 68 percent of average (84 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
December precipitation was 75 percent of the monthly average (62 percent of last year). Sites ranged from 0 to 91 percent of average for the month. Year-to-date precipitation is 77 percent of normal; that is 95 percent of last year at this time. Year to date percentages, from the 10 reporting stations, range from 71 to 86.

Reservoir
Boysen Reservoir is currently storing 457,100-acre feet (75 percent of average). Bighorn Lake is now at 99 percent of average (881,000-acre feet). Boysen is currently storing 84 percent of last year at this time and Big Horn Lake is storing 92 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 575,000 acre feet (71 percent of average); the Greybull River nr Meeteese should yield 120,000 acre feet (60 percent of average); Shell Creek near Shell should yield 62,000 acre feet (83 percent of average) and the Bighorn River at Kane should yield 840,000 acre feet (75 percent of average). 

==================================================================================================================================
                                                       BIGHORN RIVER BASIN
                                               Streamflow Forecasts - January 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)
====================================================================|=======================|=====================================
BOYSEN RESERVOIR Inflow (2)          APR-SEP       223       433    |      575        71    |       717       927            809
                                                                    |                       |
GREYBULL RIVER nr Meeteetse          APR-SEP        88       107    |      120        60    |       133       152            201
                                                                    |                       |
SHELL CREEK nr Shell                 APR-SEP        51        58    |       62        83    |        66        73             75
                                                                    |                       |
BIGHORN RIVER at Kane (2)            APR-SEP       382       634    |      840        75    |      1046      1304           1124
                                                                    |                       |
==================================================================================================================================
                           BIGHORN RIVER BASIN                          |                   BIGHORN RIVER BASIN
             Reservoir Storage (1000 AF) - End of December              |        Watershed Snowpack Analysis - January 1, 2001
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
BOYSEN                                 596.0    457.1    547.0    613.5 |   NOWOOD RIVER                2        82        68
                                                                        |
BIGHORN LAKE                          1356.0    881.0    960.3    891.8 |   GREYBULL RIVER              2       154        57
                                                                        |
                                                                        |   SHELL CREEK                 3        77        72
                                                                        |
                                                                        |   BIGHORN (Boysen-Bighorn)    7        84        68
                                                                        |
==================================================================================================================================
 * 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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