Powder and Tongue River Basins (6)
February 1999

Snow
The Powder River basin snow water equivalent (SWE), in Wyoming, is now 87 percent of average (103 percent of last year at this time). The Upper Tongue River drainage is 87 percent of normal (91 percent of last year). Goose Creek drainage is 70 percent of average (73 percent of last year). Clear Creek drainage is 92 percent of normal (97 percent of last year). Crazy Woman Drainage is 87 percent of normal (112 percent of last year). The Upper Powder River is 83 percent of normal (109 percent of last year). The Powder River in Wyoming is 87 percent of normal and 103 percent of what it was last year. For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
January precipitation was 113 percent of average for the 11 reporting stations (107 percent of last year). Monthly percentages range from 33 to 204 percent. Precipitation for the year ranges from 85 to 167 percent of average. Year-to-date precipitation is 118 percent of average in the basin; this is 117 percent of last year at this time.

Reservoir
Tongue River Reservoir did not report this month. 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 21,200 acre-feet (108 percent of normal). The North Fork of the Powder near Hazelton should yield about 12,700 acre-feet (126 percent of normal). The estimated yield for Clear Creek near Buffalo is 45,000 acre-feet (115 percent of average). Rock Creek near Buffalo will yield about 23,000 acre-feet (96 percent of normal), and Piney Creek at Kearny should yield about 44,000 acre feet (86 percent of average). 

==================================================================================================================================
                                                   POWDER & TONGUE RIVER BASINS
                                               Streamflow Forecasts - February 1, 1999
==================================================================================================================================
                                              |  <<====== 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 nr Dayton (2)           APR-SEP        67        85    |       97        84    |       109       127            115
                                                                    |                       |
MIDDLE FORK POWDER nr Barnum         APR-SEP      13.6      18.1    |       21       108    |        24        29           19.7
                                                                    |                       |
NORTH FORK POWDER nr Hazelton        APR-SEP      10.1      11.6    |     12.7       126    |      13.8      15.3           10.1
                                                                    |                       |
CLEAR CREEK nr Buffalo               APR-SEP        37        42    |       45       115    |        48        53             39
                                                                    |                       |
ROCK CREEK nr Buffalo                APR-SEP      17.7        21    |       23        96    |        25        28             24
                                                                    |                       |
PINEY CREEK at Kearny                APR-SEP      17.6        33    |       44        86    |        55        70             51
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of January               |        Watershed Snowpack Analysis - February 1, 1999
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
TONGUE RIVER                                    NO REPORT               |   UPPER TONGUE RIVER          9        91        87
                                                                        |
                                                                        |   GOOSE CREEK                 3        73        70
                                                                        |
                                                                        |   CLEAR CREEK                 4        97        92
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           3       112        87
                                                                        |
                                                                        |   UPPER POWDER RIVER          4       109        83
                                                                        |
                                                                        |   POWDER RIVER in WY          8       103        87
                                                                        |
==================================================================================================================================
 * 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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