Powder and Tongue River Basins (6)
March 1999

Snow
The Powder River basin snow water equivalent (SWE), in Wyoming, is now 85 percent of average (85 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 68 percent of average (67 percent of last year). Clear Creek drainage is 83 percent of normal (79 percent of last year). Crazy Woman Drainage is 92 percent of normal (97 percent of last year). The Upper Powder River is 94 percent of normal (107 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
February precipitation was 113 percent of average for the 12 reporting stations (93 percent of last year). Monthly percentages range from 66 to 164 percent. Precipitation for the year ranges from 90 to 170 percent of average. Year-to-date precipitation is 118 percent of average in the basin; this is 113 percent of last year at this time.

Reservoir
Tongue River Reservoir is currently at 26 percent of average (111 percent of last year), and 11 percent of the total capacity). About 7,800 acre feet are presently being stored, compared to 7,000 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 22,000 acre-feet (112 percent of normal). The North Fork of the Powder near Hazelton should yield about 12,000 acre-feet (119 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 - March 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        68        85    |       97        84    |       109       126            115
                                                                    |                       |
MIDDLE FORK POWDER nr Barnum         APR-SEP      14.8      19.1    |       22       112    |        25        29           19.7
                                                                    |                       |
NORTH FORK POWDER nr Hazelton        APR-SEP       9.4      11.0    |     12.0       119    |      13.0      14.6           10.1
                                                                    |                       |
CLEAR CREEK nr Buffalo               APR-SEP        33        40    |       45       115    |        50        57             39
                                                                    |                       |
ROCK CREEK nr Buffalo                APR-SEP      17.4        21    |       23        96    |        25        29             24
                                                                    |                       |
PINEY CREEK at Kearny                APR-SEP      17.2        33    |       44        86    |        55        71             51
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of February              |        Watershed Snowpack Analysis - March 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      7.8      7.0     30.1 |   UPPER TONGUE RIVER          9        86        85
                                                                        |
                                                                        |   GOOSE CREEK                 3        69        69
                                                                        |
                                                                        |   CLEAR CREEK                 4        81        85
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           3       100        95
                                                                        |
                                                                        |   UPPER POWDER RIVER          4       109        96
                                                                        |
                                                                        |   POWDER RIVER in WY          8        95        91
                                                                        |
==================================================================================================================================
 * 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 March 1999 Basin Outlook Report Contents Page