Wyoming Water Supply Outlook Report
January 1999

General
Generally, snow water equivalent (SWE) across the state is below normal in the east and south portions of the state and normal to slightly above in the central and northwest areas. Precipitation for December was below normal, but precipitation in October and November was generally well above average. Most of the reservoir levels are above average. Forecast runoff varies from near normal to well below normal, but generally yields are expected to be near normal. Except for some irrigated areas that rely on direct diversion, irrigation water supplies should be adequate this year.

Snowpack
Conditions vary considerably across the State as of January 1. The northwest and western portions of the State are near average to a little above average. The southern and eastern areas of Wyoming are below to well below average in percent of normal snow water equivalent (SWE). The Shoshone and Upper Yellowstone Basins are well above average while the Belle Fourche, Little Snake, and Platte River basins are well below average for this time of year. The Bighorn River basin is a little above average, while on the other side of the Bighorn Mountains, the Powder-Tongue River basin is well below average.

Precipitation
Most basins across Wyoming received below average precipitation for the month of December. Ten of the 13 basins were below average for the month. The following table displays the major river basins and their departure from normal for December 1998.

BasinDeparture
from normal
BasinDeparture
from normal
Snake River -15%Upper North Platte River-38%
Yellowstone & Madison +03%Lower North Platte River-28%
Wind River -23%Little Snake River -35%
Bighorn -02%Upper Green River -17%
Shoshone & Clarks Fork +25%Lower Green River -29%
Powder & Tongue River +02%Upper Bear River -28%
Belle Fourche & Cheyenne-25%

Streams Runoff is expected to vary greatly across the state. The northwestern part of the state is expected to have yields varying from average to slightly above average. The northeast portion of Wyoming should be well above average. This is due to very high precipitation during the early part of the water year (Oct-Sep). In most cases, the southeast portion of the state will vary from 20 to 60 percent below normal (as much as 60 percent below normal in the LaPrele Creek drainage). The southwest portion of Wyoming varies from near average to 25 percent below average on the Green River drainage, while the Bear River will produce 15-30 percent below average yields.

Reservoirs
Reservoir storage is average to well above average for this time of the year. See following table for further information about reservoir storage.

Major Reservoirs in Wyoming

                             B A S I N    W I D E
                      R E S E R V O I R    S U M M A R Y

                        FOR THE END OF DECEMBER 1998


 BASIN AREA         CURRENT AS  LAST YR AS  AVERAGE AS  CURRENT AS  CURRENT AS
  RESERVIOR         % CAPACITY  % CAPACITY  % CAPACITY   % AVERAGE   % LAST YR
------------------------------------------------------------------------------
  ALCOVA                    85          85          83         102         100
  ANGOSTURA                 91          92          79         115          98
  BELLE FOURCHE             93          92          51         184         102
  BIG SANDY                 81          55          45         179         146
  BIGHORN LAKE              70          71          66         106          98
  BOYSEN                   100          95         103          97         104
  BUFFALO BILL              69          84          68         103          82
  BULL LAKE                 65          64          58         110         101
  DEERFIELD                 94         101          81         116          93
  EDEN                                      NO REPORT
  ENNIS LAKE                82          73          82         100         112
  FLAMING GORGE                       AVERAGE NOT ESTABLISHED
  FONTENELLE                66          65          60         109         102
  GLENDO                    69          72          55         126          95
  GRASSY LAKE               83          54          69         120         154
  GUERNSEY                  31          28          12         260         112
  HEBGEN LAKE               88          76          65         134         116
  JACKSON LAKE              70          76          56         125          92
  KEYHOLE                   91          89          51         180         102
  PACTOLA                   94          95          83         112          98
  PALISADES                 86          93          74         117          92
  PATHFINDER                86          91          50         172          95
  PILOT BUTTE               72          71          49         146         102
  SEMINOE                   74          86          53         140          86
  SHADEHILL                 71          68          62         114         104
  TONGUE RIVER               9           9          38          22          97
  VIVA NAUGHTON RES                         NO REPORT
  WHEATLAND #2                        AVERAGE NOT ESTABLISHED
  WOODRUFF NARROWS                    AVERAGE NOT ESTABLISHED
  GLENDO PROJECT USERS      85          84          63         135         101
  KENDRICK PROJECT          82          84          68         120          98
  NORTH PLATTE PROJ         76          89          54         142          85

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