Bureau:
March Shows Declines in Western Basins' Snowpack
Columbia
Basin
Bulletin
April 27, 2007
The Bureau of Reclamation
today released an update on the water supply in the western
United States
.
After hoping for a wet
and cool March, the opposite occurred instead – unseasonably dry with
near-record warmth – and nearly every Western basin registered a
decline in snow packs with significant meltouts.
According to the Natural
Resource Conservation Service's April 1 Western Snowpack Conditions and
Water Supply Forecasts, the losses were greatest in the Southwest and
central
Oregon
, where snow packs declined
more than 30 percent.
As a result, snow packs
are extremely low in
Arizona
,
Utah
,
Nevada
,
California
, and eastern
Oregon
.
Some sites in central
Arizona
,
Utah
, northern
Nevada
, and eastern
Oregon
had already melted out.
This was also true in
California
's
Sierra Nevada
, and should result in a
very poor spring and summer stream flow and runoff.
Fortunately, April 1
reservoir storages are above seasonal averages in
California
,
Colorado
,
Idaho
,
Nevada
and
Washington
, and only slightly
below-normal in
Oregon
and
Utah
, providing some cushion
from the expected poor 2007 streamflow and runoff forecast.
In contrast,
Arizona
,
Montana
,
New Mexico
and
Wyoming
reservoirs are at
below-normal capacities.
"In many areas of
the West we continue to face a drought that has had impacts for the past
several years," said Reclamation Commissioner Robert Johnson.
"The continuation of the drought is cause for concern. Our saving
grace is the water storage system we have across the West that has
allowed us to efficiently manage water deliveries in times of drought as
well as in times of plenty. The system is working but water managers and
the public need to continue prudent use of our limited water
supplies."
Johnson indicated that
one exception can be found in the Great Plains Region where he says,
"Initial signs indicate a spring that is more normal and wetter
than what the region has faced in past years. The state of
Oklahoma
is drought free for the
first time since 2005 and although the drought is far from over in the
region, it provides some much-needed short-term relief."
The ramifications of a
warm and dry March continue to be felt in some parts of the West.
All states in the West
are gearing up for a potentially early and long fire season as a result
of the drought and early snowmelt combination.
Following are current
conditions in the major basins in the western
United States
:
-- Pacific Northwest
Region (
Idaho
,
Oregon
, Washington, western
Wyoming
and western
Montana
). The first half of April
has brought typical spring weather to the Pacific Northwest Region: a
little bit of everything. The unseasonably warm March has been replaced
with more normal temps along with occasional blustery winds and showers.
A strong winter-like storm is currently impacting much of the interior
of the region with cold temperatures and moderate snow in the mountains.
The current weather helps to reduce irrigation demands and/or maintain
them at normal levels, but a continuation of wet weather into May would
be needed to materially affect the water supply. Most reservoirs will
fill this year, with the primary exception of several in eastern
Oregon
.
-- Mid-Pacific Region
(northern
California
, southern
Oregon
, northern
Nevada
).
Klamath
Basin
--
Upper Klamath Lake
's projected runoff (Water
Year Type) remains classified below average for the irrigation season
projected at 70 percent of average inflow. The
Lost
River Basin
also remains considerably
drier with a spring runoff forecast at 41 percent of average. This
year's projected water supply projection continues to meet the water
requirements of fish, wildlife, and irrigation. CVP -- reservoir storage
levels compared to the 15-year average are: Trinity -- 100 percent and
Shasta -- 99 percent.
--
Great Plains
Region (
Colorado
,
Montana
,
Wyoming
, North
Dakoka
,
South Dakota
,
Nebraska
,
Kansas
,
Oklahoma
and
Texas
). Weather conditions across
the northern portion of the Great Plains Region are more reminiscent of
springs once past. Several days of cool temperatures and precipitation
are followed by warmer and dry conditions. Precipitation has ranged from
wet, heavy snow to light misty rainfall. Temperatures have ranged from
the low 30s to the upper 60s. Spring crops are beginning to emerge
across the Region. Although the drought is far from over, the initial
signs are for a more normal and wetter spring than what the Region has
faced in past years.
-- Upper Colorado Region
(
New Mexico
,
Utah
, western
Colorado
and southern
Wyoming
). Colder temperatures
descended over much of this region and slowed the snowmelt. While the
significant decrease in both snowpack and projected runoff has slowed,
the deficit in snow accumulation and deceased snowmelt at an earlier
than average time frame cannot be recaptured. Colder temperatures and
above average precipitation is predicted for this region over the next
two weeks. The runoff into
Lake
Powell
is currently projected at
53 percent of normal.
-- Lower Colorado Region
(southern
Nevada
,
Arizona
, and southern
California
)
Lake Mead
is currently at 53 percent
of capacity. Its elevation is currently 1122.17feet (97.4 feet below
full pool). Based on our daily reservoir operations
Lake Mead
's elevation is projected to be approximately 1120.58 feet by the
end of April. The Salt River Project reservoirs on the Salt and
Verde
Rivers
in central
Arizona
are currently at 63 percent
of capacity, and runoff is at 30 percent of normal. The current snowpack
in the
Gila
Basin
is only 15 percent of
average, while flows on the
Little Colorado River
and
Virgin River
are currently less than 10
percent and less than 50 percent, respectively. The 15 day outlook for
the Lower Colorado Region depicts above average temperature conditions
and below average conditions for precipitation.
For the most recent U.S.
Drought Monitor Map access the following website: http://drought.unl.edu/dm/monitor.html
For more information on
water supply, please visit Reclamation's Water Operations page, http://www.usbr.gov/main/water/
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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Source:
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