Bighorn River Basin (4)
May 2000

Snow
Snowpack in this basin is well below average for this time of year. The Nowood drainage is 61 percent of average SWE (63 percent of last year). The Greybull River drainage SWE is 51 percent of average (33 percent of last year). Shell Creek SWE is 90 percent of average (88 percent of last year). The basin SWE, as a whole, is currently 74 percent of average (69 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
April precipitation was 101 percent of the monthly average (58 percent of last year). Sites ranged from 47 to 176 percent of average for the month. Year-to-date precipitation is 91 percent of normal; that is 71 percent of last year at this time. Year to date percentages, from the 14 reporting stations, range from 49 to 107.

Reservoir
Boysen Reservoir is currently storing 501,400-acre feet (100 percent of average). Bighorn Lake is now at 111 percent of average (877,600- acre feet). Boysen is currently storing 106 percent of last year at this time and Big Horn Lake is storing 114 percent of last year's volume.

Streamflow
The 50 percent chance May through September runoff is anticipated to be well below normal. The Boysen Reservoir inflow is forecast to yield 530,000 acre feet (70 percent of average); the Greybull River nr Meeteese should yield 94,000 acre feet (48 percent of average); Shell Creek near Shell should yield 64,000 acre feet (89 percent of average) and the Bighorn River at Kane should yield 730,000 acre feet (70 percent of average). 
==================================================================================================================================
                                                       BIGHORN RIVER BASIN
                                               Streamflow Forecasts - May 1, 2000
==================================================================================================================================
                                              |  <<====== 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)          MAY-SEP       271       425    |      530        70    |       635       789            758
                                                                    |                       |
GREYBULL RIVER nr Meeteetse          MAY-SEP        54        78    |       94        48    |       110       134            195
                                                                    |                       |
SHELL CREEK nr Shell                 MAY-SEP        54        60    |       64        89    |        68        75             72
                                                                    |                       |
BIGHORN RIVER at Kane (2)            MAY-SEP       353       577    |      730        70    |       883      1107           1039
                                                                    |                       |
==================================================================================================================================
                           BIGHORN RIVER BASIN                          |                   BIGHORN RIVER BASIN
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 1, 2000
==================================================================================================================================
                                      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    501.4    474.8    502.6 |   NOWOOD RIVER                3        64        72
                                                                        |
BIGHORN LAKE                          1356.0    877.6    771.3    789.2 |   GREYBULL RIVER              2        33        51
                                                                        |
                                                                        |   SHELL CREEK                 4        88        90
                                                                        |
                                                                        |   BIGHORN (Boysen-Bighorn)    9        70        79
                                                                        |
==================================================================================================================================
 * 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.


	SHOSHONE & CLARKS FORK RIVER BASINS as of May 1, 2000
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