One
of the
frustrations we
have in the science
field is that we
don’t know the
processes well
enough on how
the precipitation
is made, on cloud
physics, to say that
if you do this, this
will happen.”
– Paul Try,
Science Consultant |
|
Oh
say can you seed? Basin states looking to make rain
ARIZONA - Needing more water to keep up with growth, seven
Colorado River Basin states are looking to the sky.
In three years, officials hope to launch the first phase of
a regional cloud seeding program to create more snowfall in
the Upper Rockies to feed the Colorado River and its tributaries.
The seven states plan to hire a consultant this spring to
evaluate the practice and make recommendations for whether,
where and how to pursue it.
Seeding-which injects chemicals such as silver iodide into
clouds to allow water droplets or ice crystals to form more
easily-is just one of many water enhancing technologies that
the consultant will review. Others include desalinization,
treating water from coal bed methane in Wyoming and Utah,
removing water sucking salt cedar trees from rivers and cleaning
up brackish groundwater near Yuma. |
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But
seeding is considered a prime candidate because several Western
states do it on a smaller scale. It's not very expensive, costing
from $1 to $20 per acre foot of water.
"We're going to seed the clouds," said Herb Guenther,
director of the Arizona Department of Water Resources. "To
what degree and how we do it and how we fund it is yet to be determined."
Today, cloud seeding is a popular but still controversial practice.
Utah, Wyoming, Colorado and Nevada have major programs, but 60 years
after seeding experiments began, many experts are divided about
its effectiveness.
In 2003, a National Academy of Sciences panel said there hasn't
been much research to prove cloud seeding successes that have been
reported didn't occur by chance.
"One of the frustrations we have in the science field is that
we don't know the processes well enough on how the precipitation
is made, on cloud physics, to say that if you do this, this will
happen," said Paul Try, who worked on the academy report and
runs a science technology consulting firm in the Washington, D.C.
area.
The Weather Modification Association, a national group that promotes
research and development of cloud seeding, has fired back with a
report that says that there have been statistically proven seeding
success stories. The academy's standards are unrealistically strict,
the group said.
Utah experiments found a 10 percent snowfall increase from seeded
compared with nonseeded clouds. In Nevada, the Desert Research Institute
has traced the presence of chemicals from cloud seeding in snowpack.
Wyoming is undertaking a five year, $8.8 million cloud seeding project
that seeks to provide definitive science on the effects of cloud
seeding.
Kelly Redmond, a federal climatologist in Nevada, said seeding seems
to work when done properly in the right situations, and because
of its low cost it need not be wildly successful to pay for itself.
But he's skeptical that seeding could boost regional snowpack by
more than a few percent.
"It would have to be practiced on a pretty large scale,"
he said. "Can you produce it in a lot of places at once?"
If seeding worked, it could nourish an over allocated Colorado River.
The U.S. Bureau of Reclamation estimated this month that seeding
could produce up to 67 percent of the water each year that the Central
Arizona Project annually delivers to Arizona, including Tucson,
where it is used for drinking water.
Arizona and the other six states aren't sure how big a program they
want, said a spokesman for the Southern Nevada Water Authority,
which is overseeing hiring the consultant. Answering that question
will be the consultant's job.
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