Powder and Tongue River Basins (6)
April 1999

Snow
The Powder River basin snow water equivalent (SWE), in Wyoming, is now 83 percent of average (87 percent of last year at this time). The Upper Tongue River drainage is 84 percent of normal (92 percent of last year). Goose Creek drainage is 77 percent of average (86 percent of last year). Clear Creek drainage is 80 percent of normal (80 percent of last year). Crazy Woman Drainage is 83 percent of normal (87 percent of last year). The Upper Powder River is 85 percent of normal (93 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
March precipitation was 76 percent of average for the 11 reporting stations (86 percent of last year). Monthly percentages range from 4 to 103 percent of average. Precipitation for the year ranges from 93 to 149 percent of average. Year-to-date precipitation is 109 percent of average in the basin; this is 108 percent of last year at this time.

Reservoir
Tongue River Reservoir is currently at 34 percent of average (129 percent of last year), and 18 percent of the total capacity). About 12,300 acre feet are presently being stored, compared to 9,500 acre feet last year. The total reservoir capacity is about 68,000 acre feet 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 16,800 acre-feet (85 percent of normal). The North Fork of the Powder near Hazelton should yield about 9,300 acre-feet (92 percent of normal). The estimated yield for Clear Creek near Buffalo is 34,000 acre-feet (87 percent of average). Rock Creek near Buffalo will yield about 19,000 acre-feet (79 percent of normal), and Piney Creek at Kearny should yield about 43,000 acre-feet (84 percent of average). 

==================================================================================================================================
                                                   POWDER & TONGUE RIVER BASINS
                                               Streamflow Forecasts - April 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        69        86    |       97        84    |       108       125            115
                                                                    |                       |
MIDDLE FORK POWDER nr Barnum         APR-SEP       9.7      13.9    |     16.8        85    |      19.7        24           19.7
                                                                    |                       |
NORTH FORK POWDER nr Hazelton        APR-SEP       6.7       8.2    |      9.3        92    |      10.4      11.9           10.1
                                                                    |                       |
CLEAR CREEK nr Buffalo               APR-SEP        25        31    |       34        87    |        38        43             39
                                                                    |                       |
ROCK CREEK nr Buffalo                APR-SEP      12.2      16.2    |     19.0        79    |        22        26             24
                                                                    |                       |
PINEY CREEK at Kearny                APR-SEP      17.3        33    |       43        84    |        53        69             51
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 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                            68.0     12.3      9.5     36.1 |   UPPER TONGUE RIVER          9        92        84
                                                                        |
                                                                        |   GOOSE CREEK                 3        86        77
                                                                        |
                                                                        |   CLEAR CREEK                 4        80        80
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           3        87        83
                                                                        |
                                                                        |   UPPER POWDER RIVER          4        93        85
                                                                        |
                                                                        |   POWDER RIVER in WY          8        87        83
                                                                        |
==================================================================================================================================
 * 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.
(D) - The operational measurement of flow at this point has been discountinued.
To April 1999 Basin Outlook Report Contents Page