Thursday April 12, 6:04 AM     Reuters

*Warming could spark N. American water scramble*

By Timothy Gardner

NEW YORK (Reuters) - Climate change could diminish North American water
supplies and trigger disputes between the United States and Canada over
water reserves already stressed by industry and agriculture, U.N.
experts said on Wednesday.

More heat waves like those that killed more than 100 people in the
United States in 2006, storms like the killer hurricanes that struck the
Gulf of Mexico in 2005 and wildfires are likely in North America as
temperatures rise, according to a new report that provided regional
details on a U.N. climate panel study on global warming issued in
Brussels on April 6.

Severe weather already costs North America tens of billions of dollars
annually in productivity and damaged property, and those costs are
expected to rise, the U.N. report said.

The broadest effects of climate change will be water problems across the
entire continent -- including more frequent droughts, urban flooding and
a scramble for water from the Great Lakes, which border both the United
States and Canada.

"Water was an issue in every region ... but in very different ways and
very different places," Michael MacCracken, a review editor of the
report, said in a telephone interview.

Unlike many continents, North America has no east to west mountain
ranges that limit droughts by forcing rapidly moving wet air to release
rain, said MacCracken, also chief scientist for climate change at the
Climate Institute, a Washington-based nonprofit group.

Cities will also be threatened as glacial melt leads to higher ocean
levels. Late in the 21st century, severe flooding that occurs in New
York once every 500 years could happen as often as once in 50 years,
putting at risk much of the infrastructure in the New York region, the
report said.

Droughts would also occur more often in the U.S. Midwest and Southwest
as warmer temperatures evaporate soil moisture.

Those droughts could diminish underground supplies like the Edwards
Aquifer in Texas, which supplies 2 million people with water, by up to
40 percent, and cut levels of the Ogallala aquifer which underlies eight
U.S. states, the report said.

During droughts like the Dust Bowl of the 1930s, U.S. farmers pumped
water from underground aquifers to save their fields through irrigation.
"Much of that water is now gone," said MacCracken. "We've used up our
savings bank."

Tight underground water supplies could kick off a scramble for large
above-ground supplies in the Great Lakes, the report said. Spats have
already occurred over diversion of the lakes' water for distant cities
and farms, while calls have increased for channelling water to the
Mississippi River to supply U.S. cities during hot summers.

Problems are also expected to intensify as warmer temperatures lower
water levels through evaporation. "Climate change will exacerbate these
issues and create new challenges for binational cooperation," the report
said.

The tension could be heightened by the fact that a majority of the
Canadian population lives close to the Great Lakes, while only a small
fraction of the U.S. population reside nearby, MacCracken said.