Wind River Basin (3)
April 1999

Snow
The Wind River basin has above average snow water equivalent (SWE) for this time of the year. The Wind River above Dubois is 114 percent of average (127 percent of last year). The Little Wind is 107 percent of average water content (96 percent of last year), and the Popo Agie drainage is about 94 percent of average (102 percent of last year). The Wind River basin, above Boysen Reservoir, SWE is about 104 percent of average (About 113 percent of last year). See the Basin Summary of Snow Course Data at the front of this report for details.

Precipitation
March precipitation in the basin varied from 9 to 92 percent of average. March precipitation for the basin was about 60 percent of average for the 11 reporting stations; that is about 42 percent of last March's amount. Water year-to-date precipitation is 108 percent of normal. The current water-year-to-date average is about 107 percent of last year at this time. Year to date figures range from 98 to 152 percent of average for the 11 reporting stations.

Reservoirs
Current storage varies from 90 to 117 percent of average. Bull Lake is currently storing about 97,500 acre feet (117 percent of average). Boysen Reservoir is storing about 473,800 acre feet (90 percent of average). Pilot Butte is storing 22,200 acre feet (103 percent of average). Bull Lake is about 103 percent of last year's storage amount, while Boysen is 93 percent of last year, and Pilot Butte is 102 percent of last year at this time.

Streamflow
Water supply is estimated to be above normal this year. The following values reflect the 50 percent chance yields for the April through September runoff period. In the upper portion of the drainage, Wind River near Dubois is expected to yield about 120,000 acre feet (about 118 percent of average). The Wind River above Bull Lake Creek is expected to yield 610,000 acre feet (113 percent of average). Wind River at Riverton will yield about 740,000 acre feet (114 percent of average). Boysen Reservoir inflow will yield about 940,000 acre feet (116 percent of normal). Bull Lake Creek near Lenore is expected to yield about 195,000 acre feet (107 percent of average). Little Popo Agie River near Lander is expected to yield about 57,000 acre feet (110 percent of average). South Fork of Little Wind near Fort Washakie will yield about 92,000 acre feet (114 percent of average). Little Wind River near Riverton will yield about 370,000 acre feet (114 percent of average). 

==================================================================================================================================
                                                         WIND RIVER BASIN
                                               Streamflow Forecasts - April 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)
====================================================================|=======================|=====================================
WIND RIVER near Dubois (D)           APR-SEP       104       113    |      120       118    |       127       136            102
                                                                    |                       |
WIND RIVER abv Bull Lake Cr (2)      APR-SEP       517       572    |      610       113    |       648       703            538
                                                                    |                       |
WIND RIVER at Riverton (2)           APR-SEP       536       657    |      740       114    |       823       944            648
                                                                    |                       |
BOYSEN Reservoir Inflow (2)          APR-SEP       644       820    |      940       116    |      1060      1236            809
                                                                    |                       |
BULL LAKE CR near Lenore (2)         APR-SEP       157       180    |      195       107    |       210       233            183
                                                                    |                       |
LT POPO AGIE RIVER nr Lander         APR-SEP        40        50    |       57       110    |        64        74             52
                                                                    |                       |
SF LT WIND nr Fort Washakie          APR-SEP        66        81    |       92       114    |       103       118             81
                                                                    |                       |
LT WIND RIVER nr Riverton            APR-SEP       222       310    |      370       114    |       430       518            324
                                                                    |                       |
==================================================================================================================================
                            WIND RIVER BASIN                            |                    WIND RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1999
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
BULL LAKE                              151.8     97.5     94.7     83.4 |   WIND RIVER above Dubios     7       127       114
                                                                        |
BOYSEN                                 596.0    473.8    509.8    529.3 |   LITTLE WIND                 2        96       107
                                                                        |
PILOT BUTTE                             31.6     22.2     21.8     21.5 |   POPO AGIE                   6       102        94
                                                                        |
                                                                        |   WIND above Boysen Resv     14       113       104
                                                                        |
==================================================================================================================================
 * 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.
(D) - The operational measurement of flow at this point has been discountinued.
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