Little Snake River Basin (10)
May 1999

Snow
Snowfall has been near average across the basin this year. Currently, snow water equivalent (SWE) in the Little Snake River drainage is 98 percent of average (109 percent of last year at this time). For more information see Basin Summary of Snow Courses at beginning of this report.

Precipitation
Precipitation across the basin was above average this past month. April precipitation was 134 percent of average (215 percent of last year) for the 5 reporting stations. The Little Snake River basin water-year-to-date precipitation is currently 112 percent of average (117 percent of last year). Year-to-date percentages range from 104 to 122 percent of average.

Streamflow
Runoff yield in the Little Snake River drainage is expected to be just below normal this year. Stream yield is based on the 50 percent probability for the April through July forecast period. The Little Snake River near Slater should yield about 140,000 acre-feet (90 percent of normal). Little Snake River near Dixon is estimated to yield 290,000 acre-feet (88 percent of normal). 


==================================================================================================================================
                                                     LITTLE SNAKE RIVER BASIN
                                               Streamflow Forecasts - May 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)
====================================================================|=======================|=====================================
Little Snake River nr Slater         APR-JUL        98       122    |      140        90    |       159       189            155
                                                                    |                       |
LITTLE SNAKE R nr Dixon              APR-JUL       184       247    |      290        88    |       333       396            329
                                                                    |                       |
==================================================================================================================================
                        LITTLE SNAKE RIVER BASIN                        |                LITTLE SNAKE RIVER BASIN
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 1, 1999
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
                                                                        |   LITTLE SNAKE RIVER          8       109        98
                                                                        |
==================================================================================================================================
 * 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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