China has begun building what it says will be the world’s largest hydropower complex on the lower reaches of the Yarlung Tsangpo River in Tibet, a stretch that becomes the Brahmaputra once it enters India and Bangladesh. Premier Li Qiang presided over a groundbreaking ceremony on 19 July, formally launching the project and unveiling a new central-state enterprise, China Yajiang Group, to oversee its construction and operation. The five-cascade dam will require about 1.2 trillion yuan ($167 billion) in investment and is designed to generate roughly 300 billion kilowatt-hours of electricity a year—more than triple the output of the Three Gorges facility on the Yangtze. Beijing says the project, slated to come online in stages during the 2030s, will underpin Tibet’s energy supply, advance national carbon-reduction goals and act as a cornerstone of an infrastructure-led economic stimulus programme. Neighbouring countries and environmental groups reacted with alarm. India’s Arunachal Pradesh Chief Minister Pema Khandu warned in a media interview that the structure could serve as a “ticking water bomb,” posing an existential threat to communities downstream. New Delhi and Dhaka have long sought more transparency on Chinese hydropower plans, arguing that large dams in the seismically active Himalayan region risk altering water flows, triggering flash floods or withholding crucial silt deposits. Beijing maintains that the project will have “no major effect” on downstream water availability and says ecological conservation will be prioritised. News of the construction sparked a rally in related Chinese assets. The CSI Construction & Engineering Index rose as much as 4 percent to a seven-month high, while shares in Power Construction Corporation of China and Arcplus Group hit their 10 percent daily limits. Iron-ore and steel prices also touched four-month peaks on expectations of stronger materials demand. Citi analysts estimate the build-out could add about 0.2 percentage point to China’s annual investment growth during peak construction years.