Though the Chinese authorities have made much progress in evaluating the social and environmental impact of dams, the emphasis is still on building them, even when mitigating the damage would be hard. Critics have called it the “hydro-industrial complex”: China has armies of water engineers (including Hu Jintao, the former president) and at least 300 gigawatts of untapped hydroelectric potential. China’s total generating capacity in 2012 was 1,145GW, of which 758GW came from coal-burning plants.

An important motive for China to pursue hydropower is, ironically, the environment. China desperately needs to expand its energy supply while reducing its dependence on carbon-based fuels, especially coal. The government wants 15% of power consumption to come from clean or renewable sources by 2020, up from 9% now. Hydropower is essential for achieving that goal, as is nuclear power. “Hydro, including large hydro in China, is seen as green,” says Darrin Magee, an expert on Chinese dams at Hobart and William Smith Colleges in New York state.

There is also a political reason why large hydro schemes continue to go ahead. Dambuilders and local governments have almost unlimited power to plan and approve projects, whereas environmental officials have almost no power to stop them.

The problems begin with the planning for China’s rivers, which are divided into fiefs by the state-owned power companies that build dams in much the same way as the Corps of Engineers and the Bureau of Reclamation divided up American rivers in the early 20th century. Though the staff of the water-resources ministry in Beijing know a lot about the environment, they have no say. “Big hydro projects are designed and approved by everybody but the ministry of water resources,” says Mr Magee.

Local governments, meanwhile, view dams as enticing economic development projects. The dambuilders, which have special privileges to borrow, put up the financing. The extra electricity supports industrial expansion and brings in revenues. Local officials are promoted for meeting economic performance targets and some collude for personal gain with the dambuilders. Because of the decentralised nature of the industry, local officials try to include dams in their plans. Once they have done so, they can expect the environmental impact assessments that follow to be a formality—if only because the consultants who undertake them are paid by the hydropower companies.

Environmental officials who have not been financially captured by the dambuilding economy find themselves as scarce as some of the fish they are charged to protect. Environmental activists, meanwhile, can request access to public records and demand public hearings, both required by law. But they say that these avenues are barred when they are most needed—on controversial projects that face vocal opposition. For example, the authorities have rejected requests for public records on Xiaonanhai and they have not granted a public hearing.

If environmental regulators and activists want any hope of halting a project, they must go outside normal bureaucratic channels to lobby powerful Politburo members or the national media. Although that may not always work, it did in 2004, when Wen Jiabao, then prime minister, halted construction of a cascade of 13 dams on the Nu River in south-west China in order to protect the environment. Even then some work on the projects still proceeded. Meanwhile, smaller schemes race ahead unchecked. Promoted by dambuilders and local governments, nearly 100 smaller hydroelectric projects in the Nu river region went forward without needing permission from higher up. Some began before they had even received the final approval.

China’s new leaders in recent months have signalled that they want yet more dams, approving several ambitious new projects, including what would be the highest dam in the world, on the Dadu river. After Mr Wen stepped down from his posts in the party and the government, the dams on the Nu river that he blocked received the go-ahead again.

Chinese leaders have for millennia sought to tame the country’s great rivers, which have sustained and destroyed countless lives with cycles of abundance, famine and floods. Indeed their legitimacy as rulers has long been linked to their ability to do so. The Communist Party has built thousands of large dams since 1949. China is also the world’s leading builder of big dams abroad; International Rivers, a pressure group, says that Chinese companies and financiers are involved in about 300 dam projects in 66 countries.

The politics of dam-building: Opening the floodgates, Economist, Sept. 21, 2013, at 47