Wind River Basin
April 1997

Snow
The Wind River basin has well above average snow water equivalent (SWE) for this time of the year. The Wind River basin above Boysen Reservoir averages about 34 percent above normal (SWE) for April 1. Above Dubois, the water content is about 54% above normal for this time of the year, while the Popo Agie drainage is about 12 percent and the Little Wind is about 14% above normal. Nearly all drainages are well above last year at this time. See the Basin Summary Of Snow Course Data at the front of this report for details.

Precipitation
March precipitation in the basin, varied from 50 percent of average at Hobbs Park and St. Lawrence R.S. to 265 percent of average for South Pass. March's average precipitation for the basin was near normal (99 percent of average for the 12 reporting stations); that is about 11 percent less than last years amount. Water year-to-date precipitation is 28 percent more than normal. The current water-year-to-date average is about 10 percent more than last year at this time.

Reservoirs
Current storage varies from 94 to 133 percent of average. Current storage, compared to average for the three storage reservoirs in the basin, is as follows; Bull Lake 54% (81,400 acre feet), Boysen 77% (456,000 acre feet), and Pilot Butte 77% (31,600 acre feet). Bull Lake is about 17 percent below last year's storage amount, while Boysen is 15 percent less and Pilot Butte is 5 percent more than last year at this time.

Streamflow
There should be an adequate water supply this year. If the present trend continues, some excessive flows can be expected this spring. In the upper portion of the drainage, Wind River near Dubois is expected to yield about 140,000 acre feet (about 37 percent above normal) during the April to September period. Other forecast points on the Wind River drainage include Wind River above Bull Lake 740,000 acre feet (38% above normal), Wind River at Riverton 885,000 acre feet (37% above average), and below Boysen 1,130,000 acre feet (40 % above normal). Bull Lake Creek near Lenore is expected to yield about 220,000 acre feet (20% above normal), Little Popo Agie River near Lander about 75,000 acre feet (44% above normal), South Fork of Little Wind near Fort Washakie about 105,000 acre feet (30% above normal), and Little Wind River near Riverton about 445,000 acre feet (37 percent more than normal). All forecasts are for the April to September period. 

==================================================================================================================================
                                                         WIND RIVER BASIN
                                               Streamflow Forecasts - April 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)
====================================================================|=======================|=====================================
WIND RIVER near Dubois               APR-SEP       121       132    |      140       137    |       148       159            102
                                                                    |                       |
WIND RIVER abv Bull Lake Cr (2)      APR-SEP       653       705    |      740       138    |       775       827            538
                                                                    |                       |
WIND RIVER at Riverton (2)           APR-SEP       732       823    |      885       137    |       947      1038            648
                                                                    |                       |
WIND RIVER below Boysen (2)          APR-SEP       834      1010    |     1130       140    |      1250      1426            809
                                                                    |                       |
BULL LAKE CREEK near Lenore (2)      APR-SEP       183       205    |      220       120    |       235       257            183
                                                                    |                       |
LITTLE POPO AGIE RIVER near Lander   APR-SEP        60        69    |       75       144    |        81        91             52
                                                                    |                       |
SF LITTLE WIND RIVER nr Fort Washaki APR-SEP        88        98    |      105       130    |       112       122             81
                                                                    |                       |
LITTLE WIND RIVER near Riverton      APR-SEP       318       394    |      445       137    |       496       572            324
                                                                    |                       |
==================================================================================================================================
                            WIND RIVER BASIN                            |                    WIND RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1997
==================================================================================================================================
                                      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     81.4     98.1     83.4 |   WIND RIVER above Dubios     7       116       154
                                                                        |
BOYSEN                                 596.0    456.2    534.3    529.3 |   LITTLE WIND                 2        96       114
                                                                        |
PILOT BUTTE                             31.6     23.5     22.3     21.5 |   POPO AGIE                   7       105       112
                                                                        |
                                                                        |   WIND above Boysen Resv     15       110       131
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual flow 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 flow - actual flow may be affected by upstream water management.
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