Wyoming Water Supply Outlook Report
June 2001

General
Generally, snow water equivalent (SWE) across the state is much below normal for this time of the year. Most of the snow has melted out below 10,000 feet. Northwest portion of the State has only 3 percent of normal snowpack left. Northeast Wyoming is 2 percent of normal, and the southeast part of the State is 23 percent of average. Southwestern Wyoming is 11 percent of average for this time of the year.

Precipitation for May was much below normal across the State. Year-to-date precipitation is generally well below average for the State. Precipitation ranged from 15 to 42 percent below average, with all of the basins receiving below average. Reservoir levels vary from about 58 percent of average to 150 percent of average. Generally, the larger capacity reservoirs are above average storage. Forecast runoff varies from 9 to 73 percent of average. The mean of all the forecast points in the State is about 55 percent of average.

Snowpack
SWE is much below average for the entire State. Nearly all the SNOTEL sites have melted out.

Precipitation
May precipitation was much below average across the State. Nearly half of the State reported near 50 percent of average or less for the month. The southwest portion of the State received the least precipitation in percent of average, along with the Big Horn Basin in north central Wyoming. The following table displays the major river basins and their departure from normal for this month.

BasinDeparture
from normal
BasinDeparture
from normal
Snake River -37%Upper North Platte River-33%
Yellowstone & Madison -26%Lower North Platte River-15%
Wind River -36%Little Snake River -62%
Bighorn -61%Upper Green River -47%
Shoshone & Clarks Fork -39%Lower Green River -67%
Powder & Tongue River -49%Upper Bear River -68%
Belle Fourche & Cheyenne-48%

Streams
Stream flow yield is expected to be below average across most of the State, and well below average in the northern half of the State. Most probable yield for the State is forecast to be about 41 percent of average (varies from 9 to 73 percent of average). The northwest part of the State is expected to yield about 40 percent of normal -- yield estimates vary from 18 to 53 percent of normal through the northwest region of the State. Yield from the northeast portion of Wyoming will be below average (about 26 percent of average) -- yield estimates vary from 9 to 42 percent of average for the various forecast points. The southeast portion of the state will be about 50 percent of normal -- yield estimates range from 34 to 73 percent of normal. The southwest portion of Wyoming yield will be much below normal (about 42 percent of average), and estimates vary from 19 to 66 percent of average.

Reservoirs

                             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   MAY    2001


 BASIN AREA         CURRENT AS  LAST YR AS  AVERAGE AS  CURRENT AS  CURRENT AS
  RESERVIOR         % CAPACITY  % CAPACITY  % CAPACITY   % AVERAGE   % LAST YR
--------------------------------------------------------------------------------
  ALCOVA                    98          98          98         100         100
  ANGOSTURA                 94          98          96          98          96
  BELLE FOURCHE            103         107          85         121          97
  BIG SANDY                 51          86          74          69          59
  BIGHORN LAKE              62          70          63          98          89
  BOYSEN                    69          91          92          76          76
  BUFFALO BILL              63          78          58         108          81
  BULL LAKE                 52          74          61          86          70
  DEERFIELD                 99          99          89         111         100
  EDEN                      24          45          66          36          53
  ENNIS LAKE                89          78          87         102         114
  FLAMING GORGE                             NO REPORT
  FONTENELLE                46          54          57          81          85
  GLENDO                    88         100          99          89          88
  GRASSY LAKE               97          94          89         108         103
  GUERNSEY                  78          79          76         103          99
  HEBGEN LAKE               92          94          82         113          98
  JACKSON LAKE              90         100          64         140          90
  KEYHOLE                   88          91          59         150          97
  PACTOLA                   99          99          88         112          99
  PALISADES                 60          95          75          80          64
  PATHFINDER                78          98          63         125          80
  PILOT BUTTE               47          78          81          58          60
  SEMINOE                   74          90          54         136          82
  SHADEHILL                 96          69          84         113         138
  VIVA NAUGHTON RES        101         107          80         126          95
  WHEATLAND #2              62          82          55         112          75
  WOODRUFF NARROWS                          NO REPORT
  GLENDO PROJECT USERS      94          94          82         115         100
  KENDRICK PROJECT          78          87          70         112          75
  NORTH PLATTE PROJ         84         100          86          99          85

To June 2001 Basin Outlook Report Contents Page