Powder and Tongue River Basins (6)
February 1998

Snow
The Powder River basin, in Wyoming, is now 83 percent of average Snow Water Equivalent (SWE). The Upper Tongue River drainage is 94 percent of normal; the Goose Creek drainage is 90 percent of normal; the Clear Creek drainage is 93 percent of normal; the Crazy Woman Drainage is 77 percent of normal and the Upper Powder is 76 percent of average. For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Year-to-date precipitation is 102 percent of average in the basin; this is 18 percent less than it was last year at this time. January precipitation was 12 percent above average (85 percent of last year). Precipitation for the year ranges from 75 to 115 percent of average.

Reservoir
Storage in the Tongue River Reservoir this month is 5,100 acre feet (19 percent of average). Streamflow
The following values are for the 50 percent probability during the April through September forecast period. The Tongue River near Dayton is estimated to yield 107,000 acre feet (93 percent of normal). Water users on the Middle Fork near Barnum should have a yield near 14,500 acre feet (74 percent of normal). The North Fork of the Powder near Hazelton should yield about 8,700 acre feet (86 percent of normal). Clear Creek near Buffalo is estimated to yield 35,000 acre feet (90 percent of average). Rock Creek near Buffalo will yield about 20,000 acre feet (83 percent of normal) and Piney Creek at Kearny should yield about 48,000 acre feet (94 percent of average). 
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                                                   POWDER & TONGUE RIVER BASINS
                                               Streamflow Forecasts - February 1, 1998
==================================================================================================================================
                                              |  <<====== 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        78        95    |      107        93    |       119       136            115
                                                                    |                       |
MIDDLE FORK POWDER near Barnum       APR-SEP       7.3      11.6    |     14.5        74    |      17.4        22           19.7
                                                                    |                       |
NORTH FORK POWDER near Hazelton      APR-SEP       6.0       7.6    |      8.7        86    |       9.8      11.4           10.1
                                                                    |                       |
CLEAR CREEK near Buffalo             APR-SEP        28        32    |       35        90    |        38        42             39
                                                                    |                       |
ROCK CREEK near Buffalo              APR-SEP      14.5      17.8    |       20        83    |        22        26             24
                                                                    |                       |
PINEY CREEK at Kearny                APR-SEP        25        39    |       48        94    |        57        71             51
                                                                    |                       |
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                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 1, 1998
==================================================================================================================================
                                      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      5.1     18.4     27.1 |   UPPER TONGUE RIVER          9        77        94
                                                                        |
                                                                        |   GOOSE CREEK                 3        78        90
                                                                        |
                                                                        |   CLEAR CREEK                 4        73        93
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           3        66        77
                                                                        |
                                                                        |   UPPER POWDER RIVER          4        60        76
                                                                        |
                                                                        |   POWDER RIVER in WY          8        66        83
                                                                        |
==================================================================================================================================
 * 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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