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is increasing, and that this has altered the hydrological
cycle, vegetation composition, and carbon dioxide and
methane fl uxes which appear to be linked to permafrost
degradation.
The Himalayas have many lakes with an enormous
capacity for water storage. For example, the Tibetan
Plateau alone has more than 1000 lakes, with a total
area of approximately 45,000 sq.km. The major
sources of lakewater are rainfall, and glacial, snow, and
permafrost melting. In addition, many glacial lakes have
formed associated with the retreat of valley glaciers.
According to ICIMOD’s inventory, there are 8790
glacial lakes in Bhutan, Nepal, and selected areas
of China, India, and Pakistan. These lakes also offer
a certain storage capacity, but a number of them are
also potentially dangerous, that is they could burst out
and cause catastrophic fl oods downstream (GLOFs) at
any time. There have been at least 35 GLOF events in
Bhutan, China, and Nepal in the past.
High altitude wetlands account for around 16% of the
total area of the Hindu Kush-Himalayas Himalayas and
play an important role in water storage and regulating
water regimes (Trisal and Kumar 2008). They maintain
water quality, regulate water fl ow (fl oods and droughts),
and support biodiversity. They also play an important
role in mitigating the impacts of climate change by
Himalayan mountain stream
acting as carbon sinks. The peatlands in the Tibetan
Plateau are one of the most important stores of carbon in
in the mean annual temperature for High Asia of 1.0°C
the mountain region, storing 1500-4000 tonnes per ha
to 6.0°C by 2100 is likely to result in an extensive
(Trisal and Kumar 2008). The Himalayan wetlands are
diminishing of glacial coverage. Continued deglaciation
under pressure from drainage for agriculture, tourism-
could have profound impacts on the hydrological
related pollution, overgrazing, and climate changes.
regimes of the ten river basins originating in the
Some areas, such as the Ruoergai Marshes of the
Himalayas. It is suggested that river discharges are likely
Tibetan Plateau, have been severely degraded over
to increase for some time due to accelerated melting,
the past decades due to drainage, overgrazing, and
but as the glaciers’ water storage capacity is reduced,
climate change.
the fl ow is likely to decline. Indications of shifting in
the hydrographs of some rivers in Nepal have already Groundwater aquifers are important for water storage in
been observed. The hydrological implications of such the Himalayan region, but there is little data available
deglaciation are expected to be most severe in the arid to allow assessment of the change and uses of
parts of the Himalayan region. groundwater on a regional scale.
Areas in the high mountains and on the high plateaus Offi cial statistics on dams higher than 15 metres from the
not covered in perennial snow and ice are underlain World Register of Large Dams show that India has 4300
by permafrost. The areas covered by permafrost are dams and China 1855, compared to 6600 in the USA
much larger than those covered by glaciers or perennial and 2700 in Japan. There are also a large number of
snow, especially in the Tibetan Plateau, China. The non-registered dams in China. Researchers have tried
Tibetan Plateau has approximately 1,360,000 cu.km to explain the viability and cost of dam construction at
of perennial permafrost (Xin Li and Cheng Guodong a location in terms of its geographical features such as
1999). But recent studies show that the extent of average land gradient and river gradient. They have
permafrost is shrinking, that the thickness of the active also concluded that rivers fl owing at a gradient of over
layer (the upper portion of soil that thaws each summer) 6% increase the suitability for dam construction. To this
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