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considerable feedbacks to global environmental changes, while at the same
time sensitive to current fl uctuations. It is also infl uencing downstream
hydrological systems, the alpine ecosystems and their services are affected
by human activities and exacerbating the degradation.
Glaciers in the region are undergoing accelerated retreat, though the
extent differs according to location. All glaciers are showing negative
mass balance and are tipping which is refl ected in increased discharges in
melt water streams. Recent studies recognize the impact of black carbon
or soot on glacial melt on the southern Tibetan Plateau, which receives
black soot via the Indian monsoon during summer and from the west via
winter westerly's. Black soot quantitative modeling on glacier dynamics is
a current challenge. Nevertheless, some recent studies indicate that black
soot is the important factor accelerating the HKH-Tibetan glacial melting
(Ramanathan et al. 2007).
If irregular challenges caused by climate change go unchecked,
they could lead to large scale regional confl icts as countries compete for
dwindling water resources. Emerging global cooperation on the climate
system and the Himalaya/Tibetan plateau adds complications as to how
South Asian countries shape their own national strategies.
During the recent years, population dynamics, new economic growth
and climate change in South Asia and China have occurred so intensely and
so rapidly that traditional and balanced sustainable growth is fast losing
their effi cacy. The vast ice reserves of mountains are in peril. Accelerated
glacial melting and environmental degradation threaten the traditional
role that mountain regions have played as water reservoir for millions of
its people.
The Tibetan plateau and surrounding mountain system of the Himalaya,
Karakorum and Hindu Kush are often referred to as the 'Water towers of
Asia' because they are the source of 10 of the largest rivers and contributes
more than 40% of the world's freshwater. The major river basins of the
region are the Amu Darya, Indus, Ganga, Brahmaputra, Irrawaddy, Salween,
Mekong, Yangtze, Yellow and Tarim as shown in Fig. 13.1.
Unchecked global warming via greenhouse gases and enhanced heating
by black carbon aerosols threaten to substantially reduce the Himalayan
glaciers that nourish the region's major rivers. Nevertheless, what makes
glacial melt so critical, even though in some it is a relatively small percentage
of a river's annual fl ow, is the timing at which it occurs—melt drives fl ows
during the dry spring and fall months, the so-called 'shoulder months'
just before and after the monsoon rains (Orville 2010). As de-glaciations
continue, however, melt water fl ows will wane. According to Immerzeel et
al. (2010), receding glaciers could trim the water supply by 2050 in the Indus
(-8.4%), Ganges (-17.6%), Brahmaputra (-19.6%), and Yangtze (-5.2%).
Rivers, implying considerable shifts in stream fl ows that are expected to
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