Wind River Basin (3)
April 1998

Snow
The Wind River basin has above average snow water equivalent (SWE) for this time of the year; measured snow depths ranged from 26 to 49 inches. Above Dubois, SWE is 92 percent average for this time of the year (59 percent of last year). The Little Wind is 111 percent of average water content (97 percent of last year), and the Popo Agie drainage is about 92 percent of average (76 percent of last year). The Wind River basin, above Boysen Reservoir, SWE is about 99 percent of average (About 73 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 99 percent of average, at Togwotee Pass SNOTEL, to 691 percent of average for Riverton. March's average precipitation for the basin was about 147 percent of average for the 13 reporting stations; that is about 161 percent of last year's amount. Water year-to-date precipitation is 101 percent of normal. The current water-year-to-date average is about 79 percent of last year at this time.

Reservoirs
Current storage varies from 96 to 114 percent of average. Bull Lake is currently storing about 94,700 acre feet (114 percent of average). Boysen Reservoir is storing about 509,800 acre feet (96 percent of average). Pilot Butte is storing 21,800 acre feet (101 percent of average). Bull Lake is about 116 percent of last year's storage amount, while Boysen is 112 percent of last year, and Pilot Butte is 93 percent of last year at this time.

Streamflow
Water supply is estimated to be near 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 94,000 acre feet (about 92 percent of average). The Wind River above Bull Lake Creek is expected to yield 515,000 acre feet (96 percent of average). Wind River at Riverton will yield about 615,000 acre feet (95 percent of average). Wind River below Boysen will yield about 755,000 acre feet (93 percent of normal). Bull Lake Creek near Lenore is expected to yield about 175,000 acre feet (96 percent of average). Little Popo Agie River near Lander is expected to yield about 48,000 acre feet (92 percent of average). South Fork of Little Wind near Fort Washakie will yield about 75,000 acre feet (93 percent of average). Little Wind River near Riverton will yield about 290,000 acre feet (90 percent of average).

==================================================================================================================================
                                                         WIND RIVER BASIN
                                               Streamflow Forecasts - April 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)
====================================================================|=======================|=====================================
WIND RIVER near Dubois               APR-SEP        75        86    |       94        92    |       102       113            102
                                                                    |                       |
WIND RIVER abv Bull Lake Cr (2)      APR-SEP       428       480    |      515        96    |       550       602            538
                                                                    |                       |
WIND RIVER at Riverton (2)           APR-SEP       462       553    |      615        95    |       677       768            648
                                                                    |                       |
WIND RIVER below Boysen (2)          APR-SEP       459       635    |      755        93    |       875      1051            809
                                                                    |                       |
BULL LAKE CREEK near Lenore (2)      APR-SEP       138       160    |      175        96    |       190       212            183
                                                                    |                       |
LITTLE POPO AGIE RIVER near Lander   APR-SEP        33        42    |       48        92    |        54        64             52
                                                                    |                       |
SF LITTLE WIND RIVER nr Fort Washaki APR-SEP        58        68    |       75        93    |        82        92             81
                                                                    |                       |
LITTLE WIND RIVER near Riverton      APR-SEP       163       239    |      290        90    |       341       417            324
                                                                    |                       |
==================================================================================================================================
                            WIND RIVER BASIN                            |                    WIND RIVER BASIN
             Reservoir Storage (1000 AF) - End of March                 |        Watershed Snowpack Analysis - April 1, 1998
==================================================================================================================================
                                      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     94.7     81.4     83.4 |   WIND RIVER above Dubios     7        59        92
                                                                        |
BOYSEN                                 596.0    509.8    456.2    529.3 |   LITTLE WIND                 2        97       111
                                                                        |
PILOT BUTTE                             31.6     21.8     23.5     21.5 |   POPO AGIE                   7        76        92
                                                                        |
                                                                        |   WIND above Boysen Resv     15        69        94
                                                                        |
==================================================================================================================================
 * 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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