Bighorn River Basin (4)
April 2000

Snow
Snowpack in this basin is just below average for this time of year. The Nowood drainage is 88 percent of average SWE (97 percent of last year). The Greybull River drainage SWE is 70 percent of average (63 percent of last year). Shell Creek SWE is 95 percent of average (93 percent of last year). The basin SWE, as a whole, is currently 89 percent of average (91 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
March precipitation was 81 percent of the monthly average (125 percent of last year). Sites ranged from 3 to 123 percent of average for the month. Year-to-date precipitation is 88 percent of normal; that is 77 percent of last year at this time. Year to date percentages, from the 14 reporting stations, range from 29 to 106.

Reservoir
Boysen Reservoir is currently storing 523,600-acre feet (99 percent of average). Bighorn Lake is now at 114 percent of average (912,000- acre feet). Boysen is currently storing 111 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 April through September runoff is anticipated to be well below normal. The Boysen Reservoir inflow is forecast to yield 525,000 acre feet (65 percent of average); the Greybull River nr Meeteese should yield 130,000 acre feet (65 percent of average); Shell Creek near Shell should yield 68,000 acre feet (91 percent of average) and the Bighorn River at Kane should yield 690,000 acre feet (61 percent of average). 

==================================================================================================================================
                                                       BIGHORN RIVER BASIN
                                               Streamflow Forecasts - April 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)          APR-SEP       229       405    |      525        65    |       645       821            809
                                                                    |                       |
GREYBULL RIVER nr Meeteetse          APR-SEP        89       114    |      130        65    |       146       171            201
                                                                    |                       |
SHELL CREEK nr Shell                 APR-SEP        57        64    |       68        91    |        72        79             75
                                                                    |                       |
BIGHORN RIVER at Kane (2)            APR-SEP       272       521    |      690        61    |       859      1108           1124
                                                                    |                       |
==================================================================================================================================
                           BIGHORN RIVER BASIN                          |                   BIGHORN RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 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    523.6    473.8    529.3 |   NOWOOD RIVER                5        97        88
                                                                        |
BIGHORN LAKE                          1356.0    912.0    782.6    798.5 |   GREYBULL RIVER              2        63        70
                                                                        |
                                                                        |   SHELL CREEK                 4        93        95
                                                                        |
                                                                        |   BIGHORN (Boysen-Bighorn)   11        91        89
                                                                        |
==================================================================================================================================
 * 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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