Powder and Tongue River Basins (6)
January 1999

Snow
The Powder River basin snow water equivalent (SWE), in Wyoming, is now 89 percent of average (108 percent of last year at this time). The Upper Tongue River drainage is 81 percent of normal (83 percent of last year). Goose Creek drainage is 62 percent of average (64 percent of last year). Clear Creek drainage is 109 percent of normal (110 percent of last year). Crazy Woman Drainage is 94 percent of normal (112 percent of last year). The Upper Powder River is 77 percent of normal (106 percent of last year). The Powder River in Wyoming is 89 percent of normal and 108 percent of what it was last year. For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
December precipitation was 102 percent of average for the 13 reporting stations (100 percent of last year). Monthly percentages range from 12 to 200 percent. Precipitation for the year ranges from 74 to 223 percent of average. Year-to-date precipitation is 122 percent of average in the basin; this is 125 percent of last year at this time.

Reservoir
Storage in the Tongue River Reservoir is currently 5800 acre feet (22 percent of average). This is 97 percent of last year's volume on January 1. Detailed reservoir data is shown on the following page and on the reservoir storage summary at the beginning of this report.

Streamflow
The following runoff values are for the 50 percent probability during the April through September forecast period. The estimated yield for Tongue River near Dayton is 97,000 acre feet (84 percent of normal). Water users on the Middle Fork near Barnum should have a yield near 20,000 acre feet (104 percent of normal). The North Fork of the Powder near Hazelton should yield about 12,500 acre feet (124 percent of normal). The estimated yield for Clear Creek near Buffalo is 45,000 acre feet (114 percent of average). Rock Creek near Buffalo will yield about 22,000 acre feet (93 percent of normal), and Piney Creek at Kearny should yield about 43,000 acre feet (84 percent of average). 

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                                                   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
                                                                    |                       |
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                      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
                                                                        |
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 * 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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