Upper Bear River Basin
May 1997

Snow
Snow water equivalent (SWE) at data sites in the Bear River above the Idaho State Line is 55 percent above average (16 percent less than last year). The Bear River in Utah measured about 55 percent more SWE than average; that is about 10 percent less than last year at this time. SWE In the Wyoming portion of the Bear River drainage (Smiths and Thomas Forks) is estimated to be about 50 percent of average (about 23 percent more than last year). See the Basin Summary of Snow Course Data at the beginning of this report for more detailed information.

Precipitation
Precipitation for the month of April was about 58 percent above average for the two reporting stations; this is about 56 percent more than April of last year. The year-to-date precipitation figure for the basin is 141 percent of average; this is about 24 percent more than last year.

Reservoir
Woodruff Narrows Reservoir presently contains about 57,300 acre feet of water; that is compared to 53,000 acre feet at this time last year. The maximum capacity of the reservoir is 57,300 acre feet.

Streamflow
The 50 percent chance stream flow yields are expected to be much above average in the Bear River drainage. The Bear River near the Utah State Line is expected to yield 160,000 acre feet; that is about 33 percent more than average. The Thomas Fork drainage is estimated to yield 42,000 acre feet or 40 percent more than normal for the May-September period. The 50 percent chance yield for Smiths Fork near Border is about 160,000 acre feet (47 percent more than normal) for the May-September period. The Bear River near Woodruff is expected to yield about 205,000 acre feet, about 38 percent more than normal for the April-July period and about 175,000 acre feet (39 percent above average) for the May-September period.

==================================================================================================================================
                                                      UPPER BEAR RIVER BASIN
                                               Streamflow Forecasts - May 1, 1997
==================================================================================================================================
                                              |  <<====== 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)
====================================================================|=======================|=====================================
SMITHS FORK nr Border, WY            MAY-SEP       140       152    |      160       147    |       168       180            109
                                                                    |                       |
THOMAS FK nr WY-ID State Line        MAY-SEP        27        35    |       42       140    |        50        64             30
                                                                    |                       |
BEAR R nr UT-WY State Line           MAY-SEP       131       147    |      160       133    |       174       196            120
                                                                    |                       |
BEAR R nr Woodruff (2)               APR-JUL       111       167    |      205       138    |       243       299            149
                                                                    |                       |
BEAR R nr Woodruff                   MAY-JUL        96       143    |      175       139    |       207       254            126
                                                                    |                       |
==================================================================================================================================
                         UPPER BEAR RIVER BASIN                         |                 UPPER BEAR RIVER BASIN
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 1, 1997
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
WOODRUFF NARROWS                        57.3     57.3     57.3      --- |   UPPER BEAR RIVER in Utah    5        90       155
                                                                        |
                                                                        |   SMITHS & THOMAS FORKS       4       123       150
                                                                        |
                                                                        |   BEAR RIVER abv ID line      9       116       155
                                                                        |
==================================================================================================================================
 * 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.
To May 1997 Basin Outlook Report Contents Page