Powder and Tongue River Basins
April 1997

Snow
The basin is in good shape as far as snowpack is concerned. All drainage's within the Powder and Tongue River basin are above average. The entire basin, in Wyoming, is now 116 percent of average Snow Water Equivalent (SWE). The upper Tongue River drainage is about 16 percent above normal; the Goose Creek drainage is about 4 percent ahead of normal; the Clear Creek drainage is 8 percent above normal; the Crazy Woman Drainage is 17 percent above normal. The Upper Powder is 21 percent above normal. For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Year-to-date precipitation is 13 percent above average in the basin; this is 2 percent better than it was last year at this time. March precipitation was 7 percent below average (64 percent of last year). Precipitation for the year ranges from 56 to 134 percent of average.

Reservoir
Storage in the Tongue River Reservoir this month is 25,500 acre feet (71 percent of average).

Streamflow
The following values are for the 50 percent probability during the April to September forecast period. The Tongue River near Dayton is estimated to yield 130,000 acre feet (13 percent above normal). Water users on the Middle Fork near Barnum should have a yield near 23,000 acre feet (17 percent above normal). The North Fork of the Powder near Hazelton should yield about 11,500 acre feet (14 percent above normal). Clear Creek near Buffalo is estimated to yield 45,000 acre feet (15 percent above average). Rock Creek near Buffalo will yield about 26,000 acre feet (8 percent above normal) and Piney Creek at Kearny should yield about 60,000 acre feet (118 percent above average). 

==================================================================================================================================
                                                   POWDER & TONGUE RIVER BASINS
                                               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)
====================================================================|=======================|=====================================
TONGUE RIVER near Dayton (2)         APR-SEP       107       121    |      130       113    |       139       153            115
                                                                    |                       |
MIDDLE FORK POWDER near Barnum       APR-SEP      16.1        20    |       23       117    |        26        30           19.7
                                                                    |                       |
NORTH FORK POWDER near Hazelton      APR-SEP       8.3      10.2    |     11.5       114    |      12.8      14.7           10.1
                                                                    |                       |
CLEAR CREEK near Buffalo             APR-SEP        39        43    |       45       115    |        48        51             39
                                                                    |                       |
ROCK CREEK near Buffalo              APR-SEP        21        24    |       26       108    |        28        32             24
                                                                    |                       |
PINEY CREEK at Kearny                APR-SEP        37        51    |       60       118    |        69        83             51
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             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
========================================================================|=========================================================
TONGUE RIVER                            68.0     25.5     40.0     36.1 |   UPPER TONGUE RIVER          9        99       112
                                                                        |
                                                                        |   GOOSE CREEK                 3        97       104
                                                                        |
                                                                        |   CLEAR CREEK                 4        88       108
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           3       106       117
                                                                        |
                                                                        |   UPPER POWDER RIVER          5       124       121
                                                                        |
                                                                        |   POWDER RIVER in WY          9       108       116
                                                                        |
==================================================================================================================================
 * 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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