Powder and Tongue River Basins (6)
June 1997

Snow
The entire basin, in Wyoming, is now 118 percent of average Snow Water Equivalent (SWE). The upper Tongue River drainage is about 2 percent above normal; the Goose Creek drainage is about 10 percent of normal; the Clear Creek drainage is 32 percent above normal; the Crazy Woman Drainage is 323 percent above normal. The Upper Powder is 5 percent above normal. These figures can appear skewed because of the early runoff and the above average snowpack. For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
Year-to-date precipitation is 6 percent above average in the basin; this is 6 percent less than it was last year at this time. May precipitation was 16 percent below average (79 percent of last year). Precipitation for the year ranges from 59 to 116 percent of average.

Reservoir
Storage in the Tongue River Reservoir this month is 31,200 acre feet (65 percent of average).

Streamflow
The following values are for the 50 percent probability during the June through September forecast period. The Tongue River near Dayton is estimated to yield 58,000 acre feet (75 percent of normal). Water users on the Middle Fork near Barnum should have a yield near 2,100 acre feet (27 percent of normal). The North Fork of the Powder near Hazelton should yield about 4,600 acre feet (77 percent of normal). Clear Creek near Buffalo is estimated to yield 22,000 acre feet (79 percent of average). Rock Creek near Buffalo will yield about 11,800 acre feet (70 percent of normal) and Piney Creek at Kearny should yield about 24,000 acre feet (75 percent above average). 

==================================================================================================================================
                                                   POWDER & TONGUE RIVER BASINS
                                               Streamflow Forecasts - June 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)         JUN-SEP        44        53    |       58        75    |        64        72             77
                                                                    |                       |
MIDDLE FORK POWDER near Barnum       JUN-SEP      0.40      0.90    |     2.10        27    |      3.30      5.06           7.90
                                                                    |                       |
NORTH FORK POWDER near Hazelton      JUN-SEP      2.51      3.76    |     4.60        77    |      5.44      6.69           6.00
                                                                    |                       |
CLEAR CREEK near Buffalo             JUN-SEP      15.1      19.2    |       22        79    |        25        29             28
                                                                    |                       |
ROCK CREEK near Buffalo              JUN-SEP       7.9      10.2    |     11.8        70    |      13.4      15.7           16.8
                                                                    |                       |
PINEY CREEK at Kearny                JUN-SEP      12.0      19.2    |       24        75    |        29        36             32
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 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     31.2     36.5     48.2 |   UPPER TONGUE RIVER          5        55       102
                                                                        |
                                                                        |   GOOSE CREEK                 1         9        10
                                                                        |
                                                                        |   CLEAR CREEK                 2        71       132
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           1        45       323
                                                                        |
                                                                        |   UPPER POWDER RIVER          4        41       105
                                                                        |
                                                                        |   POWDER RIVER in WY          6        53       118
                                                                        |
==================================================================================================================================
 * 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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