Construction of a large-scale dam in Tibet is prompting familiar fears downstream on the Brahmaputra. Joydeep Gupta reports on India's concerns.
Only five rivers in the world carry more water than the Yarlung Zangbo, or Brahmaputra as it is known when it reaches India. Only one carries more silt. Rising at a height of 5,300 metres in the Kailash range of the Middle Himalayas – an area holy to both Hindus and Buddhists – the river flows east through Tibet for 1,625 kilometres before taking a horseshoe bend, changing its name and flowing as the Brahmaputra into north-eastern India.
There, for 918 kilometres, it is both a lifeline due to the water it carries and a scourge because of the floods it causes almost every year. It then takes a southward turn and flows into Bangladesh for 363 kilometres before it merges with the Ganges, together forming south Asia’s largest river, the Meghna, and flowing into the Bay of Bengal. This huge river, with its 25 large tributaries in Tibet and 105 in India, drains much of the eastern Himalayas.
As the world’s youngest mountain range, the Himalayas are particularly unstable – and so is the river. It has changed its course significantly at least once in the last 200 years, following a major earthquake. Smaller changes in course are common, wiping out farms and homes on one bank while depositing fertile silt on the other. Now humans are changing the course of this river: Chinese engineers have started to build the Zangmu hydroelectric power station in Lhoka prefecture, 325 kilometres from Lhasa, Tibet’s capital. The development has led to serious expressions of concern, particularly in India but also in China.