Powder and Tongue River Basins (6)
April 1998

Snow
The Powder River basin snow water equivalent (SWE), in Wyoming, is now 94 percent of average (80 percent of last year at this time). The Upper Tongue River drainage is 90 percent of normal (81 percent of last year). Goose Creek drainage is 85 percent of normal (81 percent of last year). Clear Creek drainage is 100 percent of normal (90 percent of last year). Crazy Woman Drainage is 95 percent of normal (79 percent of last year), and the Upper Powder is 90 percent of average (74 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
March precipitation was 89 percent of average for the 12 reporting stations (100 percent of last year). Precipitation for the year ranges from 55 percent of average at Burgess Junction-SCS to 199 percent of average at Bruneau. Year-to-date precipitation is 101 percent of average in the basin; this is 92 percent of last year at this time.

Reservoir
Storage in the Tongue River Reservoir this month is 9,500 acre feet (26 percent of average). Normally, Tongue River reservoir stores 36,100 acre feet of water (53 percent of capacity)

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 110,000 acre feet (96 percent of normal). Water users on the Middle Fork near Barnum should have a yield near 18,000 acre feet (91 percent of normal). The North Fork of the Powder near Hazelton should yield about 9,600 acre feet (95 percent of normal). The estimated yield for Clear Creek near Buffalo is 36,000 acre feet (92 percent of average). Rock Creek near Buffalo will yield about 21,000 acre feet (88 percent of normal), and Piney Creek at Kearny should yield about 45,000 acre feet (88 percent of average). 

==================================================================================================================================
                                                   POWDER & TONGUE RIVER BASINS
                                               Streamflow Forecasts - April 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        87       101    |      110        96    |       119       133            115
                                                                    |                       |
MIDDLE FORK POWDER near Barnum       APR-SEP      11.1      15.2    |     18.0        91    |        21        25           19.7
                                                                    |                       |
NORTH FORK POWDER near Hazelton      APR-SEP       6.4       8.3    |      9.6        95    |      10.9      12.8           10.1
                                                                    |                       |
CLEAR CREEK near Buffalo             APR-SEP        30        34    |       36        93    |        39        42             39
                                                                    |                       |
ROCK CREEK near Buffalo              APR-SEP      15.7      19.0    |       21        88    |        23        27             24
                                                                    |                       |
PINEY CREEK at Kearny                APR-SEP        22        36    |       45        88    |        54        68             51
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 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      9.5     25.5     36.1 |   UPPER TONGUE RIVER          9        81        90
                                                                        |
                                                                        |   GOOSE CREEK                 3        81        85
                                                                        |
                                                                        |   CLEAR CREEK                 4        90       100
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           3        79        95
                                                                        |
                                                                        |   UPPER POWDER RIVER          5        74        90
                                                                        |
                                                                        |   POWDER RIVER in WY          9        80        94
                                                                        |
==================================================================================================================================
 * 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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