Powder and Tongue River Basins (6)
May 2000

Snow
Snow water equivalent (SWE) in the Upper Tongue River drainage is 84 percent of normal (86 percent of last year). Goose Creek drainage SWE is 77 percent of average (85 percent of last year). Clear Creek drainage is 55 percent of normal SWE (52 percent of last year). Crazy Woman Drainage is 60 percent of normal (48 percent of last year). The Upper Powder River is 59 percent of normal (54 percent of last year). The Powder River basin snow water equivalent (SWE), in Wyoming, is about 57 percent of average (53 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
April precipitation was 100 percent of average for the 10 reporting stations (53 percent of last year). Monthly percentages range from 50 to 121 percent of average. Precipitation for the year ranges from 74 to 105 percent of average. Year-to-date precipitation is about 94 percent of average in the basin; this is 75 percent of last year at this time.

Reservoir
Tongue River Reservoir is currently at 112 percent of average storage for this time of year (that is 41,100 acre feet). 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 May through September forecast period. The estimated yield for Tongue River near Dayton is 93,000 acre-feet (85 percent of normal). Water users on the Middle Fork near Barnum should have a yield near 5,900 acre-feet (33 percent of normal). The North Fork of the Powder near Hazelton should yield about 6,500 acre-feet (68 percent of normal). The estimated yield for Clear Creek near Buffalo is 25,500 acre-feet (69 percent of average). Rock Creek near Buffalo will yield about 16,000 acre-feet (70 percent of normal), and Piney Creek at Kearny should yield about 37,500 acre-feet (80 percent of average). 

==================================================================================================================================
                                                   POWDER & TONGUE RIVER BASINS
                                               Streamflow Forecasts - May 1, 2000
==================================================================================================================================
                                              |  <<====== 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)           MAY-SEP        69        83    |       93        85    |       103       117            109
                                                                    |                       |
MIDDLE FORK POWDER nr Barnum         MAY-SEP       1.6       3.7    |      5.9        33    |       8.1      11.5           17.7
                                                                    |                       |
NORTH FORK POWDER nr Hazelton        MAY-SEP      4.00      5.49    |     6.50        68    |      7.51      9.00           9.50
                                                                    |                       |
CLEAR CREEK nr Buffalo               MAY-SEP      18.4        23    |       26        69    |        28        33             37
                                                                    |                       |
ROCK CREEK nr Buffalo                MAY-SEP      10.6      13.8    |     16.0        70    |      18.2        21             23
                                                                    |                       |
PINEY CREEK at Kearny                MAY-SEP      13.2        28    |       38        80    |        47        62             47
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 1, 2000
==================================================================================================================================
                                      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     41.1     27.3     36.6 |   UPPER TONGUE RIVER          8        82        84
                                                                        |
                                                                        |   GOOSE CREEK                 2        79        77
                                                                        |
                                                                        |   CLEAR CREEK                 2        59        72
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           1        53        66
                                                                        |
                                                                        |   UPPER POWDER RIVER          3        54        57
                                                                        |
                                                                        |   POWDER RIVER in WY          5        56        64
                                                                        |
==================================================================================================================================
 * 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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