January 2000 Water Supply Outlook - Wind River Basin (3)

Wind River Basin (3)
January 2000

Snow
The Wind River basin has well below average snow water equivalent (SWE) for this time of the year. The Wind River above Dubois is 55 percent of average (48 percent of last year). The Little Wind is 35 percent of average water content (32 percent of last year), and the Popo Agie drainage is about 38 percent of average (39 percent of last year). The Wind River basin, above Boysen Reservoir, SWE is about 47 percent of average (about 42 percent of last year). See the Basin Summary of Snow Course Data at the front of this report for details.

Precipitation
December precipitation in the basin varied from 4 to 75 percent of average. December precipitation for the basin was about 51 percent of average for the 10 reporting stations; that is about 57 percent of last year's amount. Water year-to-date precipitation is 44 percent of normal. The current water-year-to-date average is about 40 percent of last year at this time. Year to date figures range from 13 to 54 percent of average for the 10 reporting stations.

Reservoirs
Current storage varies from 63 to 92 percent of average. Bull Lake is currently storing about 95,700 acre feet (63 percent of capacity) -- normally the reservoir is at 58 percent of capacity at this time of the year. Boysen Reservoir is storing about 92 percent of capacity (547,000 acre feet) -- normally the reservoir is at 103 percent of capacity at this time of the year. Pilot Butte is storing 73 percent of capacity (23,000 acre feet) -- normally the reservoir is at 49 percent of capacity at this time of the year.

Streamflow
Water supply is estimated to be 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 385,000 acre feet (72 percent of average). Wind River at Riverton will yield about 395,000 acre feet (61 percent of average). Boysen Reservoir inflow will yield about 525,000 acre feet (65 percent of normal). Bull Lake Creek near Lenore is expected to yield about 125,000 acre feet (68 percent of average). Little Popo Agie River near Lander is expected to yield about 31,000 acre feet (60 percent of average). South Fork of Little Wind near Fort Washakie will yield about 54,000 acre feet (67 percent of average). Little Wind River near Riverton will yield about 155,000 acre feet (48 percent of average).

==================================================================================================================================
                                                         WIND RIVER BASIN
                                               Streamflow Forecasts - January 1, 2000
==================================================================================================================================
                                              |  <<====== 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)      APR-SEP       226       321    |      385        72    |       449       544            538
                                                                    |                       |
WIND RIVER at Riverton (2)           APR-SEP       108       279    |      395        61    |       511       682            648
                                                                    |                       |
BOYSEN RESERVOIR Inflow (2)          APR-SEP       173       383    |      525        65    |       667       877            809
                                                                    |                       |
BULL LAKE CR near Lenore (2)         APR-SEP        70       103    |      125        68    |       147       180            183
                                                                    |                       |
LT POPO AGIE RIVER nr Lander         APR-SEP       4.2      18.0    |       31        60    |        44        63             52
                                                                    |                       |
SF LT WIND nr Fort Washakie          APR-SEP        24        42    |       54        67    |        66        84             81
                                                                    |                       |
LT WIND RIVER nr Riverton            APR-SEP      16.0        86    |      155        48    |       224       326            324
                                                                    |                       |
==================================================================================================================================
                            WIND RIVER BASIN                            |                    WIND RIVER BASIN
             Reservoir Storage (1000 AF) - End of December              |        Watershed Snowpack Analysis - January 1, 2000
==================================================================================================================================
                                      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     95.7     98.1     88.8 |   WIND RIVER above Dubios     3        47        55
                                                                        |
BOYSEN                                 596.0    547.0    593.1    613.5 |   LITTLE WIND                 2        32        35
                                                                        |
PILOT BUTTE                             31.6     23.0     22.7     15.5 |   POPO AGIE                   3        39        38
                                                                        |
                                                                        |   WIND above Boysen Resv      7        43        46
                                                                        |
==================================================================================================================================
 * 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.
(3) - Forecasts produced in cooperation with Alberta Forecasting Staff Canada

To January 2000 Basin Outlook Report Content Page

Wind River Basin (3) January 2000

Wind River Basin (3)
January 2000