Wyoming Water Supply Outlook Report
March 1997

General
Water conditions across Wyoming are very good. February precipitation varied from much below normal to much above normal. Snowpack in all the basins is above average for this time of year. Nearly half of the state is approaching maximum snow water equivalent levels for the year. Precipitation for the year is good across the state with all areas above average. Reservoir storage is looking very good across the state also. There should be no water shortages this year, if the current trend continues.

Snowpack
Snowpack over the State is above normal for this time of the year. Snow Water Equivalent (SWE) ranges from 40 to 60 percent above normal across most of the State. The Powder-Tongue River drainage currently has the lowest percentage of average SWE (119 percent); all the other basins go up from there with a high of 165 percent of average in the upper Yellowstone and Madison drainage. SWE is well ahead of last year at this time. February (SWE), compared to last year, varies from 8 to 76 percent more than last year.

Precipitation
Basins in the state received above average precipitation during the month. The higher altitude sites have generally received above normal precipitation. The Powder and Tongue River basin has received the lowest precipitation in the state so far this water year (Oct - Sep). The entire State has above normal year-to-date precipitation. The extremes are Powder - Tongue (20% above average) and Shoshone and Belle Fourche Basins (96% above normal). 

Basin                      Departure      Basin                    Departure
                           from normal                             from normal
Snake River                   +37%        Upper North Platte River    +33%
Yellowstone & Madison         +61%        Lower North Platte          +36%
Wind River                    +32%        Little Snake River          +32%
Big Horn                      +27%        Upper Green River           +22%
Shoshone & Clarks Fork        +71%        Lower Green River           +33%
Powder & Tongue River         +20%        Upper Bear River            +44%
Belle Fourche & Cheyenne      +96%
Streams
Even though February was generally below average precipitation, all basins in the state should see average or above average runoff -- in some cases there will be much above average yield if the present trend continues. Record SWE is being recorded in some portions of the state (generally the northwest and southwest portion); high runoff might be expected in those portions of Wyoming. Under the right conditions exceptionally high flows could occur in the areas with record snow levels. Water users should not expect any shortages during the irrigation season. The only basin that might expect flows close to average is the Powder-Tongue River basin.

Reservoirs
Generally speaking, reservoir storage is above average in the state with almost all reservoirs holding more than average amounts. Most reservoirs should fill to capacity this year. Some reservoirs are currently being drawn down in anticipation of excessive flows during the runoff season. See following table for further information about reservoir storage.

Major Reservoirs in Wyoming

BARE - DATA CURRENT AS OF:03/06/97 06:33:58


                             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 FEBRUARY 1997


 BASIN AREA         CURRENT AS  LAST YR AS  AVERAGE AS  CURRENT AS  CURRENT AS
  RESERVOIR         % CAPACITY  % CAPACITY  % CAPACITY   % AVERAGE   % LAST YR
--------------------------------------------------------------------------------
  ALCOVA                    86          85          85         101         101
  ANGOSTURA                 99          80          83         119         124
  BELLE FOURCHE             96         100          63         151          96
  BIG SANDY                 42          75          48          88          56
  BIGHORN LAKE              56          61          60          94          93
  BOYSEN                    88          93          93          94          95
  BUFFALO BILL              75          78          61         124          96
  BULL LAKE                 53          65          56          95          82
  DEERFIELD                 96          98          87         111          98
  EDEN                      31          52          35          88          59
  ENNIS LAKE                69          66          83          83         104
  FONTENELLE                35          35          50          69          98
  GLENDO                    74          62          76          97         118
  GRASSY LAKE               87          88          72         120          99
  GUERNSEY                  39          47          30         132          84
  HEBGEN LAKE               65          67          66          99          97
  JACKSON LAKE              77          80          57         136          97
  KEYHOLE                   84          62          53         160         137
  PACTOLA                   96         103          84         115          94
  PALISADES                 61          85          76          80          72
  PATHFINDER                87          77          58         151         113
  PILOT BUTTE               74          70          56         133         106
  SEMINOE                   66          72          40         164          92
  SHADEHILL                 51          73          61          84          71
  WHEATLAND #2              56          66          44         127          85
  VIVA NAUGHTON RES                         NO REPORT
  GLENDO PROJECT USERS      87          90          69         126          97
  KENDRICK PROJECT          82          54          68         120         150
  NORTH PLATTE PROJ         76          97          60         128          79
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