Thursday, 29 March 2012

Impact on River Hydrology in Tibet and Sustenance of Lower Riparian Countries

Snow peaks and glaciers enable Tibet to be the source of major rivers that flow into Asia and meet its water demand. Rivers such as Machu (Yellow), Drichu (Yangtze), Zachu (Mekong), Gyalmo Nyulchu (Salween), Yarlung Tsangpo (Brahmaputra), Macha Khabab (Karnali), Langchen Khabab (Sutlej), Sengey Khabab (Indus), Bhumchu (Arun) and Lhodrak Sharchu (Manas) have their sources in the Tibetan Plateau.

Drainage Basin of major rivers originating from the Tibetan Plateau (Image copyright: Environment and Development Desk, CTA)

According to some estimate, approximately 1.3 billion people in Asia are directly dependent on the watersheds of these major rivers. For instance, YarlungTsangpo originates from the glaciers of Mt. Kailash range in Tibet and drains an area of 651,335 sq. km connecting Tibet (50.5%), India (33.6%), Bangladesh (8.1%) and Bhutan (7.8%). Beyond the populations residing in the watersheds of these rivers are the additional hundreds of millions who depend on monsoon rains drawn inland by the Tibetan Plateau.

Unfortunately, the flow regimes of the rivers in Tibet are changing due to climate change and human interventions. In 2007, the WWF (World Wide Fund For Nature) identified that four out of the world’s top ten rivers, which are at greatest risk (from six important threats including dams and infrastructure, excessive water extraction, climate change, invasive species, over-fishing, and pollution), originate from the Tibetan Plateau. This includes Sengye Khabab affected by climate change, Drichu confronting a pollution crisis, Gyalmo Ngyulchu threatened by dam construction and Zachu threatened by overfishing.

According to the World Commission on Dams, the Chinese government increased the number of large dams from 22 in 1950 to 22,000 in 2000. Although the plans to divert water from the Drichu and Yarlung Tsangpo rivers to the fast-drying Machu River will improve its flow through the most populated areas of China, it will deprive water to the millions of people in the lower riparian (downstream) regions.

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