Wyoming Water Supply Outlook Report
January 1998

General
Genreally, snow water equivalent (SWE) across the state is below normal. Early "El Nino" forecasts indicated that the nothwest portion of Wyoming would have less than normal snow; that seems to be the case for most of the state. Most of the precipitation did occur as snow. Because of carry-over storage, most of the reservoir levels are above average. Except for some irrigated areas that rely on direct diversion, irrigation water supplies should be adequate this year.

Snowpack
Snowpack over the State varied from normal to well below average. Only a few smaller drainages and individual sites record near normal snow water equivalent. Generally, SWE is in the 75 to 85 percent of normal across the State. Notable exceptions are the Upper Green and Little Snake River drainages that appear to be in the 55-65 percent of average range.

Precipitation Basins across Wyoming received a mixed bag as far as December precipitation is concerned. The Lower Green received only 66 percent of average during the month. Nine of the 13 basins were below average for the month of December. The following table displays the major river basins and their departure from normal.

Basin Departure from
normal		 Basin Departure from
normal
Snake River -57% Upper North Platte River -42%
Yellowstone & Madison -45% Lower North Platte -11%
Wind River +02% Little Snake River -46%
Big Horn +09% Upper Green River -68%
Shoshone & Clarks Fork -28% Lower Green River -55%
Powder & Tongue River +06% Upper Bear River -51%
Belle Fourche & Cheyenne +26%

Streams
Runoff is expected to vary from average to well below average across the state. The northwestern part of the state is expected to have yields 15 to 20 percent below normal. In most cases, the southeast portion of the state will be about 20 - 30 percent below normal -- some of the smaller drainages will approach 55 percent below normal. The northeast portion of Wyoming varies from 60 percent of average (in the Belle Fourche) to 80 percent of average (in the Powder River drainage). The southwest varies from 55 to 70 percent of average; the Green River drainage can expect only about 55-60 percent of normal, while the Bear River will probably yield in the 60-70 percent of normal range.

Reservoirs
Reservoir storage varies from well below to well above average, however, the majority are above average for this time of the year. Even a below average runoff should fill most reservoirs. 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 1997

 BASIN AREA         CURRENT AS  LAST YR AS  AVERAGE AS  CURRENT AS  CURRENT AS
  RESERVOIR         % CAPACITY  % CAPACITY  % CAPACITY   % AVERAGE   % LAST YR
------------------------------------------------------------------------------

  ALCOVA                    85          84          83         102         101
  ANGOSTURA                 92          73          79         117         126
  BELLE FOURCHE             92          77          51         181         120
  BIG SANDY                 55          41          45         122         134
  BIGHORN LAKE              71          66          66         108         108
  BOYSEN                    95          93         103          93         102
  BUFFALO BILL              84          79          68         125         106
  BULL LAKE                 64          52          58         109         123
  DEERFIELD                101         101          81         124          99
  EDEN                      30          31          36          83          97
  ENNIS LAKE                73          78          82          89          93
  FLAMING GORGE                             NO REPORT
  FONTENELLE                65          54          60         107         120
  GLENDO                    72          51          55         132         142
  GRASSY LAKE               54          84          69          78          65
  GUERNSEY                  28          26          12         233         109
  HEBGEN LAKE               76          70          65         116         108
  JACKSON LAKE              76          80          56         137          95
  KEYHOLE                   89          73          51         176         122
  PACTOLA                   95          99          83         114          97
  PALISADES                 93          89          74         126         105
  PATHFINDER                91          82          50         182         111
  PILOT BUTTE               71          75          49         144          94
  SEMINOE                   86          73          53         162         118
  SHADEHILL                 51          54          62          81          93
  TONGUE RIVER               9          25          38          23          35
  GLENDO PROJECT USERS      84          82          63         133         103
  KENDRICK PROJECT          84          82          68         123         102
  NORTH PLATTE PROJ         89          67          54         167         134
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