Little Snake River Basin (10)
May 1998

Snow
Snowfall has been near average across the basin this year. Currently, snow water equivalent (SWE) in the Little Snake River drainage is 90 percent of average (69 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 has been below average this month. The Little Snake River basin water-year-to-date precipitation is currently 95 percent of average (78 percent of last year). April precipitation was 62 percent of average (58 percent of last year) for the 5 reporting stations. Sandstone Ranger Station SNOTEL had the lowest percentage of average (49 percent) and Old Battle SNOTEL had the highest percentage of average (88 percent).

Streamflow
Runoff yield in the Little Snake River drainage should be near 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 155,000 acre feet (100 percent of normal). Little Snake River near Dixon is estimated to yield 325,000 acre feet (99 percent of normal). 

==================================================================================================================================
                                                     LITTLE SNAKE RIVER BASIN
                                               Streamflow Forecasts - May 1, 1998
==================================================================================================================================
                                              |  <<====== 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 R nr Slater             APR-JUL       124       142    |      155       100    |       168       186            155
                                                                    |                       |
LITTLE SNAKE R nr Dixon              APR-JUL       219       282    |      325        99    |       368       431            329
                                                                    |                       |
==================================================================================================================================
                        LITTLE SNAKE RIVER BASIN                        |                LITTLE SNAKE RIVER BASIN
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 1, 1998
==================================================================================================================================
                                      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        69        90
                                                                        |
==================================================================================================================================
 * 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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