China is bafflingly silent about strange, record-breaking changes that have been wreaking havoc on the mighty Mekong River in recent months ... The dams China has built hundreds of miles upstream from Kroolong’s home are what brought me to the Mekong, one of the world’s mightiest waterways. The river is so long that if it were in the US, it would stretch all the way from Los Angeles across to New York. It starts off high in the snowy peaks of the Tibetan plateau before plunging down through the mountains of China’s southern Yunnan province towards Myanmar, Thailand, Laos, Cambodia and finally Vietnam, where it pours into the South China Sea. Just under half the river’s length is in China, which first started damming it in Yunnan more than 20 years ago. ... The early dams were large but nothing like two enormous, newer ones. The Xiaowan, completed nearly four years ago, is one of China’s biggest hydropower projects after Three Gorges on the Yangtze River, with a wall almost as high as the Eiffel Tower and a reservoir that can hold 15 billion cubic metres of water. It is dwarfed in volume, though not quite height, by the newer Nuozhadu dam, which can store 22.7 billion cubic metres of water. Together, the pair can hold enough to drown an area the size of London in water 24 metres deep. ... There have long been odd stories about the impact these two dams might be having on the countries further south, where people have blamed them for everything from drought to a drop-off in fish catches. But what emerged from my visit to the Mekong, as I followed the story of the floods that took Den Kroolong’s boat, was even stranger – a cautionary tale about the world’s newest superpower, and about water, a resource under mounting pressure.