Powder and Tongue River Basins (6)
April 2000

Snow
Snow water equivalent (SWE) in the Upper Tongue River drainage is 90 percent of normal (106 percent of last year). Goose Creek drainage SWE is 83 percent of average (104 percent of last year). Clear Creek drainage is 85 percent of normal SWE (106 percent of last year). Crazy Woman Drainage is 81 percent of normal (98 percent of last year). The Upper Powder River is 85 percent of normal (100 percent of last year). The Powder River basin snow water equivalent (SWE), in Wyoming, is about 85 percent of average (103 percent of last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
March precipitation was 81 percent of average for the 10 reporting stations (107 percent of last year). Monthly percentages range from 42 to 123 percent of average. Precipitation for the year ranges from 68 to 108 percent of average. Year-to-date precipitation is about 92 percent of average in the basin; this is 85 percent of last year at this time.

Reservoir
Tongue River Reservoir is currently at 102 percent of average storage for this time of year (that is 36,900 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 April through September forecast period. The estimated yield for Tongue River near Dayton is 100,000 acre-feet (87 percent of normal). Water users on the Middle Fork near Barnum should have a yield near 9,000 acre-feet (46 percent of normal). The North Fork of the Powder near Hazelton should yield about 6,900 acre-feet (68 percent of normal). The estimated yield for Clear Creek near Buffalo is 27,000 acre-feet (69 percent of average). Rock Creek near Buffalo will yield about 29,500 acre-feet (81 percent of normal), and Piney Creek at Kearny should yield about 42,500 acre-feet (83 percent of average). 

==================================================================================================================================
                                                   POWDER & TONGUE RIVER BASINS
                                               Streamflow Forecasts - April 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)           APR-SEP        72        89    |      100        87    |       111       128            115
                                                                    |                       |
MIDDLE FORK POWDER nr Barnum         APR-SEP       1.9       6.1    |      9.0        46    |      11.9      16.1           19.7
                                                                    |                       |
NORTH FORK POWDER nr Hazelton        APR-SEP       4.3       5.8    |      6.9        68    |       8.0       9.5           10.1
                                                                    |                       |
CLEAR CREEK nr Buffalo               APR-SEP      18.3        24    |       27        69    |        31        36             39
                                                                    |                       |
ROCK CREEK nr Buffalo                APR-SEP      12.7      16.7    |     19.5        81    |        22        26             24
                                                                    |                       |
PINEY CREEK at Kearny                APR-SEP      16.8        32    |       43        83    |        53        68             51
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 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     36.9     12.3     36.1 |   UPPER TONGUE RIVER          8       111        90
                                                                        |
                                                                        |   GOOSE CREEK                 2       109        83
                                                                        |
                                                                        |   CLEAR CREEK                 4       106        85
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           3        98        81
                                                                        |
                                                                        |   UPPER POWDER RIVER          4       100        85
                                                                        |
                                                                        |   POWDER RIVER in WY          8       103        85
                                                                        |
==================================================================================================================================
 * 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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