But I have come to learn about China's plans for building dams. It's not as easy as I thought. Three great rivers—the Salween, the Mekong and the Yangzi—come roaring out of the Tibetan plateau and tumble down through northern Yunnan in steep parallel gorges, each a mountain ridge apart. Further south they start to go their different ways before reaching the sea in very different places: the Salween in Myanmar, the Mekong in Vietnam and the Yangzi near Shanghai.
China has hugely ambitious plans for hydropower. Just above Xishuangbanna the new Jinghong dam has just started working. Further up the Mekong, Xiaowan dam is being built. When complete, it will be the highest arch dam in the world, and China's biggest hydropower project after the giant Three Gorges dam. The reservoir behind it is already filling up. At least a dozen other projects are either planned or under construction.
More than that, however, little is known. The government puts out next to no information. Even Chinese academics in favour of hydropower complain that nearly all information to do with these rivers, even the amount of rain that reaches them, is treated as a state secret.
Those who oppose the dam-building on environmental grounds, or out of concern for perhaps 500,000 locals, mainly ethnic minorities, who are being displaced and forcibly resettled, ask that their names not be published. The Chinese media rarely touch the subject. The downstream countries of Thailand, Laos, Cambodia and Vietnam, which have seen a sharp drop in Mekong levels in recent years, complain that China neither consults nor informs about what it's up to. For all that it preaches harmony and good neighbourliness, China comes across as a regional bully.
China denies the critics' charge that it is responsible for reducing the Mekong's flow downriver. It blames the drought instead. The truth lies somewhere in between. For while it is true that less than one-sixth of the total Mekong water catchment is in China, that flow is critical to neighbours during the dry season. China has certainly held back some of the dry-season flow.
The past month's monsoon rains will draw some of the criticism's sting. So too, perhaps, will a possible easing of Chinese secrecy. In an unprecedented gesture of openness, last month China invited diplomats from Thailand, Cambodia, Laos and Vietnam to view both Xiaowan and Jinghong dams. I had less luck. Near Jinghong nervous policemen ordered me to leg it before I got so much as a glimpse of the structure.