Wind River Basin (3)
May 2001

Snow
The Wind River basin has much below average snow water equivalent (SWE) for this time of the year. SWE in the Wind River above Dubois is 58 percent of average (84 percent of last year). The Little Wind SWE is 27 percent of average water content (67 percent of last year), and the Popo Agie drainage SWE is about 37 percent of average (72 percent of last year). The Wind River basin, above Boysen Reservoir, SWE is about 45 percent of average (about 78 percent of last year). See the Basin Summary of Snow Course Data at the front of this report for details.

Precipitation
April precipitation in the basin varied from 28 to 109 percent of average. April precipitation for the basin was about 60 percent of average for the 9 reporting stations; that is about 53 percent of last year's amount. Water year-to-date precipitation is 57 percent of normal. The current water-year- to-date average is about 73 percent of last year at this time. Year to date figures range from 46 to 108 percent of average.

Reservoirs
Current usable storage varies from 77 to 82 percent of average. Bull Lake is currently storing about 61,700 acre feet (41 percent of capacity) -- the reservoir is at 77 percent of average at this time of the year. Boysen Reservoir is storing about 73 percent of capacity (437,300 acre feet) -- the reservoir is at 87 percent of average for this time of the year. Pilot Butte is storing 78 percent of capacity (24,700 acre feet) -- the reservoir is at 82 percent of average for this time of the year.

Streamflow
Water supply is estimated to be much below normal this year. The following values reflect the 50 percent chance yields for the April through September runoff period. The Wind River above Bull Lake Creek is expected to yield 315,000 acre feet (62 percent of average). Wind River at Riverton will yield about 312,000 acre feet (51 percent of average). Boysen Reservoir inflow will yield about 320,000 acre feet (42 percent of normal). Bull Lake Creek near Lenore is expected to yield about 100,000 acre feet (56 percent of average). Little Popo Agie River near Lander is expected to yield about 22,500 acre feet (46 percent of average). South Fork of Little Wind near Fort Washakie will yield about 51,000 acre feet (65 percent of average). Little Wind River near Riverton will yield about 145,000 acre feet (48 percent of average). 

==================================================================================================================================
                                                         WIND RIVER BASIN
                                               Streamflow Forecasts - May 1, 2001
==================================================================================================================================
                                              |  <<====== 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 abv Bull Lake Cr (2)      MAY-SEP       254       290    |      315        62    |       355       414            511
                                                                    |                       |
WIND RIVER at Riverton (2)           MAY-SEP       243       284    |      312        51    |       384       490            609
                                                                    |                       |
BOYSEN RESERVOIR Inflow (2)          MAY-SEP       211       276    |      320        42    |       425       579            758
                                                                    |                       |
BULL LAKE CR near Lenore (2)         MAY-SEP        82        93    |      100        56    |       113       132            179
                                                                    |                       |
LT POPO AGIE RIVER nr Lander         MAY-SEP      16.2      19.9    |       23        46    |        28        36             49
                                                                    |                       |
SF LT WIND nr Fort Washakie          MAY-SEP        38        46    |       51        65    |        59        71             78
                                                                    |                       |
LT WIND RIVER nr Riverton            MAY-SEP        88       122    |      145        48    |       193       263            303
                                                                    |                       |
==================================================================================================================================
                            WIND RIVER BASIN                            |                    WIND RIVER BASIN
             Reservoir Storage (1000 AF) - End of April                 |        Watershed Snowpack Analysis - May 1, 2001
==================================================================================================================================
                                      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     61.7     93.5     79.9 |   WIND RIVER above Dubios     7        84        58
                                                                        |
BOYSEN                                 596.0    437.3    501.4    502.6 |   LITTLE WIND                 2        67        27
                                                                        |
PILOT BUTTE                                     NO REPORT               |   POPO AGIE                   6        72        37
                                                                        |
                                                                        |   WIND above Boysen Resv     14        78        45
                                                                        |
==================================================================================================================================
 * 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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