But politicians in India, sitting downstream, have voiced fears the dam could be a “water bomb” exacerbating floods in monsoons, or that it could steal water in dry seasons.
Since Beijing approved the project in December last year, there have been lots of discussions, but little proof.
Now a joint study by Hohai University and China’s Ministry of Water Resources suggested the dam’s impact on the Yarlung Tsangpo could be opposite to India’s fears.
The study draws data from two large dams already working upstream: Zangmu and Jiacha. Measured since 2014 at hydrological downstream, the results are clear: dry seasons get wetter.
Low flows were up more than 50 per cent in February. Water rose significantly throughout the dry season. India feared drought – the dams brought more water instead.