New Delhi, July 22 -- India is keeping a close watch on China's construction of what is set to be the world's largest hydropower dam on the upper reaches of the Brahmaputra river and could fast-track a multipurpose dam in Arunachal Pradesh to act as a buffer against sudden changes in water flows, people familiar with the matter said on Monday. Chinese Premier Li Qiang presided over a ceremony on Saturday marking the start of construction on the $167-billion dam on Yarlung Tsangpo river in Tibet, according to reports in China's state-run media. The Motuo hydropower station is set to overtake the Three Gorges dam as the world's largest. There was no reaction from Indian officials to the development, though people familiar with the matter said...