* Through the Gorges the river drops at an average rate of 16 inches for every mile of distance travelled. Once out into the coastal plains, the Yangtze takes 940 miles to drop the remaining 134 feet, at an average of 1.6 inches drifting downward in each mile. When Chairman Mao was warned about the fierce currents and turbulences of Wuhan, it was the sheer volume of water, not the very modest gradient of the river, that concerned his aides.

* In what most of the world's dam engineers consider a moment of supreme folly, the Chinese had in 1981 considered building a dam with a pool level of no less than 660 feet. American engineers, horrified by the likely dangers inherent in so gargantuan a structure, told their Chinese counterparts that if there was going to be any American help forthcoming, a significantly smaller dam with a lower-level reservoir would have to be designed. Eventually, realizing the effect of the pressure, the Chinese side complied.

* Miss Dai dislikes being lumped together with the political dissidents of the time – deed, she went to Tiananmen Square in a vain effort to persuade the protesting students to go back to their homes, and is as a result somewhat ill regarded by many of the diehards in the opposition camp. But she spent ten months in the Qinchen high-security prison reserved for political prisoners and was threatened with execution. The Chinese government has never explained why she was arrested, though Miss Dai insists it was for her anti-dam writings. Meanwhile the woman who published her book, and who had had a record of printing and distributing controversial and polemical literature and journalism, remains active. Miss Dai, after stints in New York and Canberra, is now back in Beijing, as tireless a campaigner as ever.

* All of the sewage produced in Chongqing and the scores of other cities above the dam will also end up in the new lake, stagnating and making the waters additionally foul.

* In 1938 Chiang Kai-shek ordered his troops to blow up the dykes protecting the Yellow River, in an effort to frustrate the Japanese southerly advance towards Wuhan. The resulting floods killed tens of thousands of Chinese peasants – but held up the Japanese vehicles for little more than three months.

* A brand-new airport was being built outside town: it would have an international terminal, the better to serve would-be investors in the dam.

* Canada, having been among the first countries to show official interest in the project, felt it deserved prominent participation in the dam. Its highly experienced hydro-engineers were disappointed when Ottawa backed away from the scheme, and a number of big firms promptly formed ‘Team Canada' to exploit what they could in the Chinese market. But there was still a good deal of opposition at home: the British Columbian government, for example, forbade any formal provincial involvement whatsoever in the Three Gorges project.

* These will be as nothing compared to 180-foot-tall illuminated billboards with which the authorities say they are planning to decorate the spectacularly lovely cliffs of the Xiling Gorge, advertising local wines and spirits. Their illumination, of course, comes courtesy of the hydroelectric power made by the dams, so at one fell swoop they will be advertising two aspects of the country's modernization.