Warming Will Depleat Summer Hydro Reservoirs
- Study: Warming Will Depleat Water
By ANDREW BRIDGES, AP Science Writer
LOS ANGELES (AP) - Global warming (news - web sites) will have a
devastating effect on water availability in the western United
States, a new climate forecast predicts.
The report, released Thursday, involved more than two dozen
scientists and engineers from around the country who undertook the
study as a test of a national climate forecasting effort.
What they found doesn't bode well for the West.
Even the report's best-case scenario predicted water supplies would
fall far short of future demands by cities, farms and wildlife,
generating critical water-rights' issues that have already surfaced
during the West's current drought.
"You'd like there to be some good news in there somewhere, but
unfortunately there is not," said Scripps Institution of Oceanography
research marine physicist Tim Barnett.
The study predicts overall precipitation levels are likely to remain
constant, but warmer temperatures mean what would have fallen as snow
will instead come down as rain.
Currently, the snowpack acts a natural reservoir, storing water
through the winter so it will melt and be released during the spring
and summer when demand spikes. If that precipitation falls as winter
rain, however, it will fill rivers and streams at a time of year when
demand is low.
To create the forecasts, scientists began two years ago with current
observations of the state of the world's oceans those vast
reservoirs of heat that drive climate and worked to translate that
into real effects on precipitation and temperature on the West's
three most important river systems: the Columbia, Sacramento and
Colorado river basins.
According to some research, global warming is due to an increase in
atmospheric greenhouse gases, principally carbon dioxide from the
burning of oil, gas and coal. Global temperatures are thought to have
risen by about 1.1 degrees over the last century, with the top few
thousand feet of ocean waters increasing by about one-tenth of a
Among the new study's forecasts for the next 25 to 50 years:
_ Reservoir levels along the Colorado River will drop by more than a
third, and releases by 17 percent. The lower levels and flows will
cut hydropower generation by as much as 40 percent.
_ The Sacramento River will see reduced reliability in the volumes of
water available for irrigation, cities and hydropower. With less
fresh water, the Sacramento Delta will increase in salinity,
disrupting the ecosystem.
_ Along the Columbia River system, there will be either water in the
summer and fall to generate electricity, or in the spring and summer
for salmon runs but not both.
"The problem is you basically can't resolve that trade-off," said
Dennis Lettenmaier, a professor of civil and environmental
engineering at the University of Washington.
The continued growth in the population of the West will exacerbate
the problem. Indeed, that alone makes for a crisis, said Bill
Patzert, a National Aeronautics and Space Administration research
oceanographer who was not connected with the new research.
"The problem in the West is not climate change, it's too many ...
people using too much water," Patzert said. "If nothing happens,
we're in trouble. If something happens, it's worse."
The study included researchers from institutions including Scripps,
the University of Washington, the Energy Department and the U.S.
Geological Survey (news - web sites). The results are expected to
appear in a future issue of the journal Climatic Change.