Bighorn River Basin (4)
June 1999

Snow
Snowpack in this basin is above average for this time of year. Cool weather has slowed the normal melting of snow -- consequently the comparison to average, and last year, could appear exaggerated. The Nowood drainage is 192 percent of average SWE. The Greybull River drainage SWE is 266 percent of average (2014 percent of last year). Shell Creek SWE is 131 percent of average (296 percent of last year). The basin SWE, as a whole, is currently 152 percent of average (406 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
May precipitation was 123 percent of the monthly average (335 percent of last year). Sites ranged from 43 to 196 percent of average for the month. Year-to-date precipitation is 127 percent of normal; that is 138 percent of last year at this time. Year to date percentages, from the 15 reporting stations, range from 100 to 162.

Reservoir
Boysen Reservoir is currently storing 490,400-acre feet (90 percent of average). Bighorn Lake is now at 107 percent of average (911,500-acre feet). Boysen is currently storing 110 percent of last year at this time and Big Horn Lake is storing 106 percent of last year's volume. Streamflow
The 50 percent chance June through September runoff is anticipated to be near normal. The Wind River at Boysen is forecast to yield 825,000 acre feet (136 percent of average); the Nowood River near Ten Sleep should yield near 24,500 acre feet (117 percent of normal); the Greybull River at Meeteese should yield 215,000 acre feet (129 percent of average); Shell Creek near Shell should yield 60,000 acre feet (109 percent of average) and the Bighorn River at Kane should yield 1,115,000 acre feet (138 percent of average). 
==================================================================================================================================
                                                       BIGHORN RIVER BASIN
                                               Streamflow Forecasts - June 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)          JUN-SEP       618       741    |      825       136    |       909      1032            609
                                                                    |                       |
NOWOOD RIVER nr Tensleep (D)         JUN-SEP      17.8        22    |       25       117    |        27        31             21
                                                                    |                       |
GREYBULL RIVER nr Meeteetse          JUN-SEP       204       210    |      215       129    |       220       226            167
                                                                    |                       |
SHELL CREEK nr Shell                 JUN-SEP        50        56    |       60       109    |        64        70             55
                                                                    |                       |
BIGHORN RIVER at Kane (2)            JUN-SEP       741       964    |     1115       138    |      1266      1489            811
                                                                    |                       |
==================================================================================================================================
                           BIGHORN RIVER BASIN                          |                   BIGHORN RIVER BASIN
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 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    490.4    447.6    546.4 |   NOWOOD RIVER                2         0       192
                                                                        |
BIGHORN LAKE                          1356.0    911.5    859.7    855.6 |   GREYBULL RIVER              2       2014      266
                                                                        |
                                                                        |   SHELL CREEK                 3       296       131
                                                                        |
                                                                        |   BIGHORN (Boysen-Bighorn)    7       406       152
                                                                        |
==================================================================================================================================
 * 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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