China has approved the construction of what will be the world's largest hydropower dam, kicking off an ambitious project on the eastern rim of the Tibetan plateau that could affect millions downstream in India and Bangladesh.

Beijing has approved plans to dam a gorge in the Himalayas that is three times as deep as the Grand Canyon, despite concerns about the impact on Tibet and India.

Beijing's approval of a controversial mega dam in the lower reaches of the Yarlung Tsangpo River, which flows from Tibet autonomous region into India, has sparked concerns about the environmental impact of the project,