http://news.bbc.co.uk/2/hi/science/nature/1926667.stm
Tuesday, 16 April,
2002, 15:46 GMT 16:46 UK
Himalayan warming 'may trigger floods'
By Alex Kirby
BBC News Online environment correspondent
CAPTION:
"The Himalayas' temperature has shown a marked recent rise"
Scientists say more than 40 Himalayan lakes could soon overflow,
imperilling tens of thousands of people.
They say the lakes
are filling up because rising temperatures
are melting the surrounding glaciers and snowfields that feed
them.
Regional air temperatures
are 1C higher than they were in the 1970s.
Work has started to
lower the water level in one lake in Nepal.
The scientists work
for the United Nations Environment Programme
(Unep) and the International Centre for Integrated Mountain
Development (Icimod).
Surendra Shrestha of
Unep said: "Our findings indicate that
20 glacial lakes in Nepal and 24 in Bhutan have become
potentially dangerous as a result of climate change.
"We have evidence
that any one of these could, unless
urgent action is taken, burst its banks in five to
ten years' time.
"These are the
ones we know about. Who knows how many others,
elsewhere in the Himalayas and across the world, are in a
similar critical state?"
Warning system
The lake where remedial
work has begun is Tsho Rolpa, which
researchers say is six times larger now than in the late 1950s.
It was identified as critical by ground surveys and satellite
images.
Pradeep Mool of Icimod
said: "A flood from this lake could
cause serious damage down to the village of Tribeni, which
is 108 km (67 miles) downstream, threatening about 10,000
people, thousands of livestock, agricultural land, bridges
and other infrastructure."
A network of sensors
and sirens has been built to link the
lake to threatened villages. Engineers hope to lower the lake
level by 30 m (95 feet).
Mr Shrestha said his
team was working to help Nepal and Bhutan
to identify potentially dangerous lakes, develop early warning
systems and reduce the threats.
He said: "Some
donor country governments are backing our efforts,
but much more aid is needed. Solving this problem is going to
be
costly, because glacial lakes are situated in remote areas which
are difficult to reach."
The UN has declared
2002 the International Year of the Mountains.
Dr Klaus Toepfer, executive
director of Unep, said: "Mountains
were once considered indomitable, unchanging and impregnable.
But we are learning that they are as vulnerable as the world's
oceans, grasslands and forests.
Dryer future
"It is not just
the risk to human lives, agriculture and
property that should worry us. Mountains are the world's
water towers, feeding the rivers and lakes upon which all
life depends.
"If the glaciers
continue to retreat at the rates being seen
in places like the Himalayas, many rivers and freshwater systems
could run dry."
Unep says there is
evidence that glacial lake outburst floods
(glofs, as they are known) have been happening more often over
the last thirty years.
It says data from 49
Nepalese monitoring stations shows
temperatures in the high Himalayas have been rising over
that period by an average of 0.06C annually.
Rapid melting
The research into lakes
at risk began in 1999, and is based
on topographic maps, aerial photographs and images from Landsat,
Spot and IRS satellites.
The scientists say
that glaciers in Bhutan are retreating
at 30-40m annually. One glacier, Tradkarding, which feeds
the Tsho Rolpa lake, retreated 100m last year.
Scientists from Bhutan
and Nepal worked with Unep and Icimod
on the survey. An international conference on protecting the
world's mountains is being held in late October in Bishkek,
the capital of Kyrgyzstan.
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