Bighorn River Basin (4)
February 1998

Snow
The Nowood drainage is 65 percent of last year and 77 percent of average SWE for February 1. The Greybull River drainage SWE is 145 percent of average (89 percent of last year). Shell Creek SWE is about 91 percent of average (78 % of last year). The basin SWE, as a whole, is currently 92 percent the February 1 average (74 % of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Precipitation, for the water year, has been good and is now 109 percent of average. January precipitation was 117 percent of the monthly average. Powell Field Station was the highest reporting station at 492 percent of the January average and Shell Creek was the low at 88 percent of average. Year-to-date precipitation is 109 percent of normal; that is 91 percent of last year at this time.

Reservoir
Boysen Reservoir is currently storing 549,300 acre feet (95 percent of average). Bighorn Lake is now at 110 percent of average (926,000 acre feet). Boysen is currently storing 101 percent of last year at this time and Big Horn Lake is storing 112 percent of last years volume.

Streamflow
The remaining of the runoff season (April - September) should yield below average runoff. The Wind River below Boysen is forecast to yield 760,000 acre feet (94 percent of average); the Nowood River near Ten Sleep should yield near 45,000 acre feet (78 percent of normal); the Greybull River near Meeteese should yield 185,000 acre feet (92 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 1,020,000 acre feet (91 percent of average). 

==================================================================================================================================
                                                       BIGHORN RIVER BASIN
                                               Streamflow Forecasts - February 1, 1998
==================================================================================================================================
                                              |  <<====== 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)
====================================================================|=======================|=====================================
WIND RIVER below Boysen (2)          APR-SEP       438       630    |      760        94    |       890      1082            809
                                                                    |                       |
NOWOOD RIVER near Tensleep           APR-SEP       0.8        27    |       45        78    |        63        89             58
                                                                    |                       |
GREYBULL RIVER at Meeteetse          APR-SEP       141       167    |      185        92    |       203       229            201
                                                                    |                       |
SHELL CREEK near Shell               APR-SEP        59        65    |       70        93    |        75        81             75
                                                                    |                       |
BIGHORN RIVER at Kane (2)            APR-SEP       538       825    |     1020        91    |      1215      1502           1124
                                                                    |                       |
==================================================================================================================================
                           BIGHORN RIVER BASIN                          |                   BIGHORN RIVER BASIN
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 1, 1998
==================================================================================================================================
                                      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    549.3    542.9    580.7 |   NOWOOD RIVER                5        65        77
                                                                        |
BIGHORN LAKE                          1356.0    926.0    826.4    839.2 |   GREYBULL RIVER              2        89       145
                                                                        |
                                                                        |   SHELL CREEK                 4        78        91
                                                                        |
                                                                        |   BIGHORN (Boysen-Bighorn)   11        74        92
                                                                        |
==================================================================================================================================
 * 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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