Snowpack
May conditions varied across the State. Cool weather has resulted in
a slower than normal runoff, which in turn causes a higher than normal
comparison to average. The western portion of Wyoming remains well
above average. Northwest Wyoming is about 70 percent above average,
mostly because of the Wind River drainage -- the Wind River drainage
is about 280 percent of normal. Northeast Wyoming is about 60 percent
above normal -- snow in the Belle Fourche drainage has nearly all
melted out. The Southeast portion of the State is about 25 percent
above normal and the Southwest portion is about 50 percent above
normal.
Precipitation
May precipitation was near average to a little above average across
the state. The only basin to receive below average precipitation was
the Shoshone and Clarks Fork. The following table displays the major
river basins and their departure from normal for May 1999.
| Basin | Departure from normal | Basin | Departure from normal |
| Snake River | +22% | Upper North Platte River | +28% |
| Yellowstone & Madison | +19% | Lower North Platte River | +03% |
| Wind River | +03% | Little Snake River | +17% |
| Bighorn | +23% | Upper Green River | +11% |
| Shoshone & Clarks Fork | -18% | Lower Green River | +29% |
| Powder & Tongue River | +05% | Upper Bear River | +10% |
| Belle Fourche & Cheyenne | -01% |
Streams
Runoff is expected to vary greatly across the state. Yield from the
northeast portion of Wyoming should be just above average -- yield
estimates vary from 91 to 122 percent of average (mean is 107%). In
most cases, the southeast portion of the state will be about 20
percent above normal -- yield estimates range from 81 to 181 percent
of normal. The southwest portion of Wyoming varies from 93 to 130
percent of average -- mean estimated yield for southeast Wyoming is
110 percent of average. The northwest part of the State is expected
to yield about 24 percent more than normal -- yields vary from 107 to
138 percent of normal.
Reservoirs
Reservoir storage is generally above average for this time of the
year. See following table for further information about reservoir
storage.
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 1999
BASIN AREA CURRENT AS LAST YR AS AVERAGE AS CURRENT AS CURRENT AS
RESERVOIR % CAPACITY % CAPACITY % CAPACITY % AVERAGE % LAST YR
------------------------------------------------------------------------------
ALCOVA 97 98 98 99 99
ANGOSTURA 99 98 96 103 101
BELLE FOURCHE 105 96 85 123 109
BIG SANDY 105 81 74 142 130
BIGHORN LAKE 67 63 63 107 106
BOYSEN 82 75 92 90 110
BUFFALO BILL 61 77 58 104 79
BULL LAKE 62 77 61 102 81
DEERFIELD 100 100 89 112 100
EDEN 72 48 66 109 149
ENNIS LAKE 84 89 87 97 95
FLAMING GORGE NO REPORT
FONTENELLE 60 52 57 105 114
GLENDO 109 92 99 110 118
GRASSY LAKE 89 98 89 100 91
GUERNSEY 74 75 76 98 99
HEBGEN LAKE 79 93 82 96 85
JACKSON LAKE 76 89 64 120 85
KEYHOLE 93 92 59 158 101
PACTOLA 100 100 88 113 100
PALISADES 52 80 75 69 65
PATHFINDER 98 96 63 156 102
PILOT BUTTE 53 57 81 65 92
SEMINOE 83 76 54 153 108
SHADEHILL 96 87 84 114 110
TONGUE RIVER 96 39 71 135 243
VIVA NAUGHTON RES 81 0 80 101 0
WHEATLAND #2 91 72 55 165 127
WOODRUFF NARROWS NO REPORT
GLENDO PROJECT USERS 94 91 82 115 103
KENDRICK PROJECT 87 86 70 124 101
NORTH PLATTE PROJ 100 100 86 117 100
To June 1999 Basin Outlook Report Contents Page