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. The dam, which will be located in the lower reaches of the Yarlung Zangbo River, could produce 300 billion kilowatt-hours of electricity annually, according to an estimate provided by the Power Construction Corp of China in 2020. That would more than triple the 88.2 billion kWh designed capacity of the Three Gorges Dam, currently the world's largest, in central China.