Wyoming Water Supply Outlook Report
April 2001

General
Generally, snow water equivalent (SWE) across the state is much below normal for this time of the year. SWE averages for the State are about 67 percent of normal for this time of the year. Northwest portion of the State is 56 of percent normal. Northeast Wyoming is 71 of percent of normal, and the southeast part of the State is 75 percent of average. Southwestern Wyoming is 65 percent of average for this time of the year.

Precipitation for March was generally much below average for the State. Year-to- date precipitation is below average for the State - the Belle Fourche drainage is still feeling the effects of the heavy snow last fall and is currently 99 percent of average. Reservoir levels vary from about 30 percent of average to 159 percent of average, the exception being Eden Reservoir which is too low to measure. Generally, the larger capacity reservoirs are above average storage. Forecast runoff varies from 20 to 77 percent of average. The mean of all the forecast points in the State is about 53 percent of average (47 percent below average).

Snowpack
SWE is below to much below average for the entire State. SWE in the northwestern portion of the State is about 54 percent of average (63 percent of last year). Northeast Wyoming SWE is currently about 73 percent of average (92 percent of last year). The southeast portion is currently about 75 percent of average SWE (85 percent of last year). And the southwest is about 65 percent of average (74 percent of last year).

Precipitation
March precipitation was much below normal over the State. Most of the basins in the state received less than 70 percent of normal precipitation. The Wind River and Lower North Platte received less than half of the usual precipitation. The following table displays the major river basins and their departure from normal for this month.

BasinDeparture
from normal
BasinDeparture
from normal
Snake River -39%Upper North Platte River-31%
Yellowstone & Madison -15%Lower North Platte River-55%
Wind River -57%Little Snake River -31%
Bighorn -29%Upper Green River -36%
Shoshone & Clarks Fork -26%Lower Green River -39%
Powder & Tongue River -31%Upper Bear River -35%
Belle Fourche & Cheyenne-21%

Streams
Stream flow yield is expected to be below average across the State, and well below average in the northern half of the State. Most probable yield for the State is forecast to be about 52 percent of average (varies from 20 to 77 percent of average). The northwest part of the State is expected to yield about 50 percent of normal -- yield estimates vary from 21 to 69 percent of normal through the northwest region of the State. Yield from the northeast portion of Wyoming will be below average (about 52 percent of average) -- yield estimates vary from 41 to 60 percent of average for the various forecast points. The southeast portion of the state will be about 57 percent of normal -- yield estimates range from 30 to 71 percent of normal. The southwest portion of Wyoming yield will be much below normal (about 53 percent of average), and estimates vary from 20 to 77 percent of average.

Reservoirs
The following reservoir data is based on the usable capacity of each reservoir. Although several reservoirs did not report, reservoir storage for those reporting is generally near 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  MARCH   2001


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

  ALCOVA                    85          85          88          97         100
  ANGOSTURA                 89          99          90          99          90
  BELLE FOURCHE             99         101          73         135          98
  BIG SANDY                 20          55          52          39          36
  BIGHORN LAKE              63          67          59         107          94
  BOYSEN                    75          88          89          84          85
  BUFFALO BILL              55          67          56         100          82
  BULL LAKE                 41          63          55          75          65
  DEERFIELD                 99          99          89         112         101
  EDEN                                      NO REPORT
  ENNIS LAKE                73          71          81          90         102
  FLAMING GORGE                       AVERAGE NOT ESTABLISHED
  FONTENELLE                32          30          46          70         105
  GLENDO                    78          92          83          94          85
  GRASSY LAKE               85          84          74         115         102
  GUERNSEY                  41          41          47          86         100
  HEBGEN LAKE               72          81          65         110          89
  JACKSON LAKE              76          78          56         136          98
  KEYHOLE                   87          90          56         156          96
  PACTOLA                   99          98          85         116         100
  PALISADES                 55          85          72          76          65
  PATHFINDER                76          98          61         125          77
  PILOT BUTTE               74          71          68         108         104
  SEMINOE                   64          73          36         176          87
  SHADEHILL                102          69          78         131         147
  VIVA NAUGHTON RES         76          79          64         119          96
  WHEATLAND #2              46          75          49          92          61
  WOODRUFF NARROWS                          NO REPORT
  GLENDO PROJECT USERS      83          85          69         120          98
  KENDRICK PROJECT          81          82          68         119          98
  NORTH PLATTE PROJ         65         100          64         103          65



To April 2001 Basin Outlook Report Contents Page