Global Warming & Water Problems In The West
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WARMING STUDY INDICATES WATER PROBLEMS IN THE WEST
DOE/Pacific Northwest National Laboratory / EurekAlert!
November 21, 2002
Contact: Geoff Harvey
DOE/Pacific Northwest National Laboratory
Accelerated Climate Prediction Initiative
"Water may be the resource that defines the limits of sustainable
development," states a 2001 United Nations Population Fund report, which
noted that water use has grown six-fold over the past 70 years.
Nowhere is that more true than in the western United States, where existing
water resources already are stretched to their limits. There is little or no
leeway for changes in current water allocations. But there is every reason
to expect that climate change, such as that associated with greenhouse
warming, could dramatically alter the availability of water in the West. In
the most rigorous study to date of potential greenhouse impacts, leading
scientists detail how major water problems could evolve over the next 50
years throughout the West as a result of climate change already underway.
Many people have heard about the impacts of global warming, but the general
public typically doesn't grasp the ramifications of such changes. A degree
or so change in global mean temperature seems harmless enough. What most
people do not know is that the regional or local climate changes associated
with global warming will be far more significant than apparently small
average changes might imply.
New simulations by a group of leading global warming and climate change
researchers suggest the effects of rising temperatures will exacerbate
problems we are beginning to see. In the West, the effects of global warming
already have begun to emerge in earlier melting of mountain snow packs and
spring flooding dates. Scientific studies show that these, and other
expected climate changes, could have a devastating impact on water resources
in some parts of the West over the next half century.
- In the Columbia River System of Washington State, residents and
industries likely will be faced with the choice of water for summer and fall
hydroelectric power or spring and summer releases for salmon runs, but not
both. Accelerated Climate Prediction Initiative research, or ACPI, shows
that with climate change, the river cannot be managed to accommodate both.
In fact, the window for successful salmon reproduction in the Pacific
Northwest may become so compressed by climate change that some species could
cease to exist regardless of any current or future water policies.
- The Colorado River Reservoir System will not be able to meet all of the
demands placed on it -- including water supply for Southern California and
the inland Southwest -- because reservoir levels will be reduced by more
than one-third and releases by as much as 17 percent. The greatest effects
will be on lower Colorado River Basin states. All users of Colorado River
hydroelectric power will be affected by lower reservoir levels and flows,
which will result in reductions in hydropower generation by as much as 40
- In the Central Valley of California, it will be impossible to meet
current water system performance levels so that impacts will be felt in
reduced reliability of water supply deliveries, hydropower production and
instream flows. With less fresh water available, the Sacramento Delta could
experience a dramatic increase in salinity and subsequent ecosystem
"Population and economic growth already are placing severe pressure on water
resources in the West. Climate change is one more very important factor that
has to be taken into account when thinking about the future," said Bill
Pennell, director of the Atmospheric Science and Global Change Division at
Pacific Northwest National Laboratory.
"It also is important to point out," said Dennis Lettenmaier, Professor of
Civil Engineering at the University of Washington, "that these predictions
are based on one of the most conservative climate models. Other models show
a much larger warming effect. However, even this conservative model
indicates substantial changes. For example, by mid-century the yearly
average snow pack in the Washington and Oregon Cascades may be reduced on
the order of 50 percent and because most of our water storage is in this
snow pack, such a reduction will result in big changes in flows and water
temperatures in Cascade rivers and streams."
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