Snowpack
Much of the snow across the State has melted. The northwest
portion of the State is generally average to below average with
some individual locations well below normal. The Wind River
drainage is about 15 percent normal, while the remaining
portions of the northwest part of Wyoming are 10-30 percent
below normal. Snow water equivalent ( SWE ) in the northeast
part of Wyoming is well below normal -- Powder River drainage
is about 80 percent below -- and the Belle Fourche and Cheyenne
River drainages have already melted out. The southeast portion
of the State is below normal, generally 25-60 percent below
normal; the exception is the Encampment River-Brush Creek area,
which is only about 10 percent below normal. Portions of the
southeast are 60-70 percent below normal. Generally, the
southwest part of the State is average to below average; the
upper Green River basin is about 31 percent below normal. The
Bear River drainage SWE appears to be 15-25 percent below
normal.
Precipitation
Most basins across Wyoming received below average precipitation
for the month of May. Nine of the 13 basins were below average
for the month of May. The following table displays the major
river basins and their departure from normal.
| Basin | Departure from normal | Basin | Departure from normal |
| Snake River | +13% | Upper North Platte River | -17% |
| Yellowstone & Madison | -16% | Lower North Platte River | -31% |
| Wind River | -31% | Little Snake River | -30% |
| Bighorn | -62% | Upper Green River | +15% |
| Shoshone & Clarks Fork | -41% | Lower Green River | +10% |
| Powder & Tongue River | -66% | Upper Bear River | +75% |
| Belle Fourche & Cheyenne | -64% |
Streams
Runoff is expected to vary from average to below average across
the state. The northwestern part of the state is expected to
have yields varying from average to as much as 31 percent below
average, generally runoff will be 15-20 percent below normal.
The northeast portion of Wyoming varies from 20 to 39 percent
below average (most of the area will be about 20 percent below
normal). In most cases, the southeast portion of the state
will vary from 15 to 30 percent below normal (as much as 89
percent below normal in the Deer Creek drainage). The southwest
portion of Wyoming varies from near average to 15 percent below
average on the Green River drainage, while the Bear River will
produce 10-20 percent below average yields.
Reservoirs
Reservoir storage varies from well below to well above average,
however, the majority are average to 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
R E S E R V O I R S U M M A R Y
FOR THE END OF MAY 1998
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 98 99 96 102 99
BELLE FOURCHE 96 105 85 113 92
BIG SANDY 81 105 74 109 77
BIGHORN LAKE 63 62 63 100 102
BOYSEN 75 71 92 82 106
BUFFALO BILL 77 52 58 132 148
BULL LAKE 77 64 61 125 119
DEERFIELD 100 99 89 112 101
EDEN 48 103 66 73 47
ENNIS LAKE 89 80 87 102 112
FLAMING GORGE NO REPORT
FONTENELLE 52 62 57 92 85
GLENDO 92 100 99 93 92
GRASSY LAKE 98 99 89 110 99
GUERNSEY 75 77 76 99 97
HEBGEN LAKE 93 88 82 113 106
JACKSON LAKE 89 85 64 140 106
KEYHOLE 92 95 59 157 97
PACTOLA 100 101 88 113 99
PALISADES 80 66 75 106 122
PATHFINDER 96 94 63 152 102
PILOT BUTTE 57 70 81 71 82
SEMINOE 76 77 54 141 99
SHADEHILL 87 82 84 103 106
TONGUE RIVER 39 46 71 56 86
VIVA NAUGHTON RES NO REPORT
WHEATLAND #2 72 64 55 130 113
WOODRUFF NARROWS NO REPORT
GLENDO PROJECT USERS 91 90 82 112 102
KENDRICK PROJECT 86 85 70 123 102
NORTH PLATTE PROJ 100 99 86 116 100
To June 1998 Basin Outlook Report Contents Page