Bighorn River Basin
April 1997

Snow
All drainage's in the basin are above average at this time. The Nowood drainage is 10 percent ahead of last year and 119 percent of average SWE for April 1. The Greybull River drainage is near last years SWE, with 134 percent of average. Shell Creek SWE is lower, at only 13 percent above average. The basin SWE, as a whole, is currently 118 percent of April 1 average. SWE for the entire basin is 2 percent ahead of April 1996 (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 117 percent of average. Only 3 sites are below average. March precipitation was 83 percent of the monthly average. The Middle Powder site was the highest reporting station at 131 percent of the March average.

Reservoir
Reservoir storage is good in the basin with Bighorn Lake at 95 percent of average and Boysen at 86 percent. Boysen is currently storing 456,200 acre feet and Bighorn Lake is at 761,000. This is just slightly less than what was being stored last year at this time.

Streamflow
All forecast points are predicted to be average to well above average. The Wind River below Boysen is forecast to yield 1,130,000 acre feet (140 percent of average); the Nowood River near Ten Sleep should yield near 78,000 acre feet (135 percent of normal); the Greybull River near Meeteese should yield 260,000 acre feet (129 percent of average); Shell Creek near Shell should yield 83,000 acre feet (111 percent of average) and the Bighorn River at Kane should yield 1,615,000 acre feet (144 percent of average). 

==================================================================================================================================
                                                       BIGHORN RIVER BASIN
                                               Streamflow Forecasts - April 1, 1997
==================================================================================================================================
                                              |  <<====== 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       834      1010    |     1130       140    |      1250      1426            809
                                                                    |                       |
NOWOOD RIVER near Tensleep           APR-SEP        46        65    |       78       135    |        91       110             58
                                                                    |                       |
GREYBULL RIVER at Meeteetse          APR-SEP       218       243    |      260       129    |       277       302            201
                                                                    |                       |
SHELL CREEK near Shell               APR-SEP        71        78    |       83       111    |        88        95             75
                                                                    |                       |
BIGHORN RIVER at Kane (2)            APR-SEP      1197      1446    |     1615       144    |      1784      2033           1124
                                                                    |                       |
==================================================================================================================================
                           BIGHORN RIVER BASIN                          |                   BIGHORN RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1997
==================================================================================================================================
                                      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    456.2    534.3    529.3 |   NOWOOD RIVER                5       110       119
                                                                        |
BIGHORN LAKE                          1356.0    761.0    783.3    798.5 |   GREYBULL RIVER              2        92       134
                                                                        |
                                                                        |   SHELL CREEK                 4       100       113
                                                                        |
                                                                        |   BIGHORN (Boysen-Bighorn)   11       102       118
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual flow 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 flow - actual flow may be affected by upstream water management.
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