Bighorn River Basin (4)
February 1999

Snow
Snowpack in this basin is near average, except for the Greybull River drainage, which is 20 percent above average. The Nowood drainage is 90 percent (116 percent of last year). The Greybull River drainage SWE is 120 percent of average (82 percent of last year). Shell Creek SWE is 105 percent of average (115 percent of last year). The basin SWE, as a whole, is currently 101 percent of average (109 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
January precipitation was 133 percent of the monthly average (114 percent of last year). Sites ranged from 32 percent to 204 percent of average for the month. Year-to-date precipitation is 129 percent of normal; that is 121 percent of last year at this time. Year to date percentages, from the 16 reporting stations, range from 102 to 220.

Reservoir
Boysen Reservoir is currently storing 569,300-acre feet (98 percent of average). Bighorn Lake is now at 103 percent of average (864,100-acre feet). Boysen is currently storing 104 percent of last year at this time and Big Horn Lake is storing 93 percent of last year's volume.

Streamflow
The 50 percent chance April through September runoff is anticipated to be near normal. The Wind River at Boysen is forecast to yield 860,000 acre feet (106 percent of average); the Nowood River near Ten Sleep should yield near 66,000 acre feet (114 percent of normal); the Greybull River at Meeteese should yield 215,000 acre feet (107 percent of average); Shell Creek near Shell should yield 70,000 acre feet (93 percent of average) and the Bighorn River at Kane should yield 1,170,000 acre feet (104 percent of average). 

==================================================================================================================================
                                                       BIGHORN RIVER BASIN
                                               Streamflow Forecasts - February 1, 1999
==================================================================================================================================
                                              |  <<====== 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       538       730    |      860       106    |       990      1182            809
                                                                    |                       |
NOWOOD RIVER nr Tensleep (D)         APR-SEP        34        53    |       66       114    |        79        98             58
                                                                    |                       |
GREYBULL RIVER nr Meeteetse          APR-SEP       181       201    |      215       107    |       229       249            201
                                                                    |                       |
SHELL CREEK nr Shell                 APR-SEP        59        65    |       70        93    |        75        81             75
                                                                    |                       |
BIGHORN RIVER at Kane (2)            APR-SEP       787       975    |     1170       104    |      1365      1551           1124
                                                                    |                       |
==================================================================================================================================
                           BIGHORN RIVER BASIN                          |                   BIGHORN RIVER BASIN
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 1, 1999
==================================================================================================================================
                                      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    569.3    549.3    580.7 |   NOWOOD RIVER                5       116        90
                                                                        |
BIGHORN LAKE                          1356.0    864.1    926.0    839.2 |   GREYBULL RIVER              2        82       120
                                                                        |
                                                                        |   SHELL CREEK                 4       115       105
                                                                        |
                                                                        |   BIGHORN (Boysen-Bighorn)   11       109       101
                                                                        |
==================================================================================================================================
 * 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.
To February 1999 Basin Outlook Report Contents Page