Powder and Tongue River Basins (6)
June 1998

Snow
The Powder River basin snow water equivalent (SWE), in Wyoming, is now 5 percent of average (4 percent of last year at this time). The Upper Tongue River drainage is 17 percent of normal (16 percent of last year). Goose Creek drainage is melted out as of June 1. Clear Creek drainage is 8 percent of normal (6 percent of last year). Crazy Woman Drainage and the Upper Powder are also melted out. For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
May precipitation was 34 percent of average for the 11 reporting stations (38 percent of last year). Precipitation for the year ranges from 81 percent of average at Sucker Creek SNOTEL to 114 percent of average at Hansen Sawmill SNOTEL. Year-to-date precipitation is 93 percent of average in the basin; this is 87 percent of last year at this time.

Reservoir
Storage in the Tongue River Reservoir was not reported this month.

Streamflow
The following runoff values are for the 50 percent probability during the June through September forecast period. The estimated yield for Tongue River near Dayton is 55,000 acre feet (71 percent of normal). Water users on the Middle Fork near Barnum should have a yield near 4,000 acre feet (51 percent of normal). The North Fork of the Powder near Hazelton should yield about 4,600 acre feet (77 percent of normal). The estimated yield for Clear Creek near Buffalo is 22,000 acre feet (79 percent of average). Rock Creek near Buffalo will yield about 13,500 acre feet (80 percent of normal), and Piney Creek at Kearny should yield about 26,000 acre feet (81 percent of average). 


==================================================================================================================================
                                                   POWDER & TONGUE RIVER BASINS
                                               Streamflow Forecasts - June 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)         JUN-SEP        41        50    |       55        71    |        61        69             77
                                                                    |                       |
MIDDLE FORK POWDER near Barnum       JUN-SEP      1.04      2.80    |     4.00        51    |      5.20      6.96           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       9.6      11.9    |     13.5        80    |      15.1      17.4           16.8
                                                                    |                       |
PINEY CREEK at Kearny                JUN-SEP      14.0        21    |       26        81    |        31        38             32
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 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     26.8     31.2     48.2 |   UPPER TONGUE RIVER          5        16        17
                                                                        |
                                                                        |   GOOSE CREEK                 1         0         0
                                                                        |
                                                                        |   CLEAR CREEK                 2         6         8
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           1         0         0
                                                                        |
                                                                        |   UPPER POWDER RIVER          3         0         0
                                                                        |
                                                                        |   POWDER RIVER in WY          5         4         5
                                                                        |
==================================================================================================================================
 * 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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