RAIN along the middle and lower Yangzi River this week has helped alleviate the region's worst drought in 50 years. But it has not doused a storm of criticism of the Three Gorges dam upriver, including allegations that it contributed to the disaster. Opponents of the colossal edifice have been emboldened by rare government admissions of environmental and other “urgent” problems caused by the dam.

In private, officials have worried about the project for some time and occasionally their doubts have surfaced in the official media. But the government itself has refused to acknowledge them. When the project was approved by the rubber-stamp parliament in 1992, debate was stifled by the oppressive political atmosphere of the time, following the Tiananmen Square massacre three years earlier. Last July, with the dam facing its biggest flood crest since completion in 2006, officials hinted that they might have overstated its ability to control flooding. On May 18th, with the dam again in the spotlight because of the drought, a cabinet meeting chaired by the prime minister, Wen Jiabao, went further in acknowledging drawbacks.

Having called the dam “hugely beneficial overall”, the cabinet's statement said there were problems relating to the resettlement of 1.4m people, to the environment and to the “prevention of geological disasters” that urgently needed addressing. The dam, it said, had had “a certain impact” on navigation, irrigation and water-supply downstream. Some of these problems had been forecast at the design stage or spotted during construction. But they had been “difficult to resolve effectively because of limitations imposed by conditions at the time.” It did not elaborate.

The confession has triggered a flurry of articles in official newspapers about the dam's deficiencies. Some recalled a warning given by one of China's most famous critics, Huang Wanli, before his death ten years ago that the dam would silt up the reservoir basin and sooner or later have to be blown up. The Oriental Morning Post even filled its front page with a picture of Mr Huang, who was persecuted by Mao Zedong for his criticism of the Sanmenxia dam on the Yellow River. Sanmenxia was the nation's pride until its reservoir silted up. On June 7th Shanghai Daily, an English-language paper, called the Three Gorges “that monstrous damming project”.

Its effect on the drought is difficult to prove. Officials deny assertions that the dam and its more than 600-km (370-mile) reservoir might have affected the regional climate. But one official, Wang Jingquan of the Yangzi's Water Resources Committee, conceded that the dam had lowered water levels in two of the country's biggest freshwater lakes, making the impact worse. The rapid lowering of the reservoir's level has also raised fears of landslides and earthquakes. Probe International, a Canadian NGO, published a report on June 1st by Chinese government experts saying the dam had caused “significantly increased” seismic activity.

This debate has erupted at a time of heightened political uncertainty as the Communist Party prepares for sweeping leadership changes next year. The government's decision to be open about doubts that had previously been harboured in private could reflect struggles between outgoing leaders and their still-influential predecessors. The earlier generation had been responsible for getting the project started in the 1990s. But President Hu Jintao and Mr Wen did not attend the dam's completion ceremony in May 2006.

For liberal intellectuals, the furore has provided an opportunity to push back against hardliners (who tend to favour grandiose displays of state power). One liberal newspaper published an interview with Mao Yushi, a prominent economist who has been fiercely denounced recently by hardliners because of an article he wrote attacking Mao Zedong. Mr Mao (the economist rather than the Helmsman) contributed to a book criticising the Three Gorges dam which was published in 1989, shortly before the Tiananmen protests. It was later banned.

In the interview Mr Mao accused the government of shuffling off responsibility for the dam 20 years ago by ignoring anti-dam experts and then getting the legislature to approve the project. “If there are any problems in future, you won't be able to find anyone. There is nobody taking real responsibility,” he said.