Home' Technology Review : May June 2007 Contents 66 FEATURE STORY
TECHNOLOGY REVIEW /
But such studies are just the rst academic pass at plan-
ning. The scenarios they envision are still relatively vague.
And while suggested remedies abound, they re ect more
imagination than engineering. Physical oceanographer
Malcolm Bowman of the State University of New York
at Stony Brook, for one, would place a tidal-surge barrier
at the Verrazano Narrows (between Brooklyn and Staten
Island); another near the Throgs Neck Bridge, where the
East River meets Long Island Sound; another between
Perth Amboy, NJ, and Staten Island; and a fourth across
Rockaway Inlet at the entrance to Jamaica Bay. The bar-
riers---more ambitious versions of the stor m-surge barrier
at the mouth of the Thames River outside London---could
theoretically prevent tens of billions of dollars in damage.
With the models and computational power available now,
however, it s hard to determine whether and when such
ideas need to be acted on. "If you look at European expe-
rience," says Bowman, "it takes a major ood and a major
loss of life to get the bureaucracy to do anything."
The Dry West
Colorado Springs, CO, is a boomtown in an arid region---just
one of many cities that rely for water on the melting snow-
pack of the nearby mountains, delivered via the Colorado
River and Arkansas River watersheds. Many other cities get
their water similarly from the Sierra Nevada Mountains of
California. But right now, the wester n United States is fac-
ing a slow-motion water-supply catastrophe wrought by
climate changes that will inexorably reduce the snowpack.
"The wester n U.S. is really not in good shape at this point,"
says Linda Mearns, a climatologist at the National Center
for Atmospheric Research (NCAR) in Boulder, CO, where
she is director of the Institute for the Study of Society and
Environment. This has become fairly clear "even without
the regional detail" in climate models, she adds.
But the regional detail is still important for deciding how,
where, and when to respond. Consider the Homestake Res-
er voir. High in the Rocky Mountains, not far from Vail, CO,
it is part of a network of reservoirs and pipelines that feed
water to Colorado Springs. In June 2006, the reservoir lled
at the unprecedented average rate of nearly two feet per day.
Because of higher temperatures earlier in the season, the
snowpack was melting more quickly than usual.
The unprecedented may become routine as global warm-
ing makes more precipitation fall as rain, while what snow
there is melts ever faster. That s worrisome: a reser voir
that lls more quickly than expected can stress a dry levee.
And there are other concerns. At what point will earlier
snowmelt translate into summer water shortages? Will
early spring tor rents raise the risk of downstream ood-
ing? Will more-intense spring rainfalls increase sediment,
over whelming ltration systems and washing more pol-
lutants into the water supply? And these climate-related
questions arise at a time when rapid population growth is
already stressing water resources.
Planners need to understand as precisely as possible the
amount, timing, and form---rain or snow---of future precipi-
tation. Only then can they determine when and where to
build new water-storage, ood-control, and ltration sys-
tems and how to guide future residential or commercial
development in watershed areas. So last winter, in a win-
dowless conference room in an industrial area of Colorado
Springs, engineers from Colorado Springs Utilities met
with David Yates, an NCAR hydrologist, to start revising
their water-supply management plans in light of climate-
change projections. "Plans are typically made based on
historical 20- to 40-year stream- ow averages," Yates said.
"That mode of planning is no longer relevant."
Concrete local projections are especially important in
this region, where politics constrain the way scienti c nd-
ings can be discussed. Colorado Springs is a politically con-
ser vative city and home to a powerful Christian evangelical
organization that is skeptical of concerns about global warm-
ing. Toward the end of the meeting, the utilities manager
of water-supply resources, Wayne Vanderschuere, entered
the room. He was already thinking about how any new
climate-change-related ndings might be framed. "All the
talk about climate change and CO2---we don t want to go
there. We don t want to talk about Kyoto, all the postur-
ing," he said, refer ring to the Kyoto Protocol, the U.S.-
rejected treaty that mandates limits on greenhouse-gas
emissions. "We just want the analytic risk to supplying
water that this poses."
Brett Gracely, the utilities planning super visor, said Colo-
rado Springs was at a turning point. "We re trying to get a
handle on what this all means for us," he said. He---and his
city, and the rest of the country---just aren t sure exactly when
and to what extent global trends will in uence regional trends
and make existing hydrology models obsolete. "If it comes
down to literally building a model, how do we do that?" Yates
asked during the meeting. "What needs to be done---what
resources are needed to do that?" Colorado Springs e ort
to build a model of how climate will a ect local hydrology
has just begun and could take two years.
One strategy the model is likely to use is to break down
mountainous regions into elevation bands rather than small,
uniform grid boxes. Mountain areas, with their myriad
microclimates, are particularly di cult to model. Mountains
can cause winds to shift and clouds to form; snow-covered
north faces, war m south faces, and cold valleys can give rise
to strikingly di erent conditions. L. Ruby Leung and Steve
Ghan, climate physicists at the Paci c Northwest National
Laboratory in Richland, WA, are pioneers in the elevation-
band approach, which they say can be as accurate as nesting
Links Archive March April 2007 July August 2007 Navigation Previous Page Next Page