Guwahati, April 9 -- Mehebub Sahana, University of Manchester

China recently approved the construction of the world's largest hydropower dam, across the Yarlung Tsangpo river in Tibet. When fully up and running, it will be the world's largest power plant - by some distance.

Yet many are worried the dam will displace local people and cause huge environmental disruption. This is particularly the case in the downstream nations of India and Bangladesh, where that same river is known as the Brahmaputra.

The proposed dam highlights some of the geopolitical issues raised by rivers that cross international borders. Who owns the river itself, and who has the right to use its water? Do countries have obligations not to pollute shared rivers, or ...