In a rare revelation, Beijing has admitted that its 2.4-kilometer Three Gorges Dam spanning the Yangtze River in Hubei province “deformed slightly” after record flooding.
The official Xinhua News Agency quoted the operator of the the world’s largest hydroelectric gravity dam as saying that some nonstructural, peripheral parts of the dam had buckled.
The dam was a pet project of the late Premier Li Peng and a monumental pride of the nation when it blocked and diverted Asia’s largest river in 1997.
The deformation occurred last Saturday when the flood from western provinces including Sichuan and Chongqing along the upper reaches of the Yangtze River peaked at a record-setting 61,000 cubic meters per second, according to China Three Gorges Corporation, a state-owned enterprise that manages the dam and the sprawling power plant underneath it.
The company noted that parts of the dam had “deformed slightly,” displacing some external structures, and seepage into the main outlet walls had also been reported throughout the 18 hours on Saturday and Sunday when water was discharged though its outlets.
But the problem of water seeping out did not last long, as the dam reportedly deployed floodgates to hold as much water as possible in its 39.3 billion-cubic-meter reservoir to shield the cities downstream from the biggest Yangtze deluge so far this year.
It is believed that the dam’s operator must protect the central megacity of Wuhan, whose 10 million residents are still reeling from the coronavirus pandemic that erupted there in December.
Xinhua also stressed in its report that all metrics were still up to standard and all the variables being monitored fell within the design parameters.
Meanwhile, Wang Hao, a member of the Chinese Academy of Engineering and an authority on hydraulics who sits on the Ministry of Water Resources’ Yangtze River Administration Commission, has also assured that the dam is sound enough to withstand the impact from floods twice the mass flow rate recorded on Saturday.
Still, Wang’s remarks stoked a volley of mockery after he said the flooding could be a good thing as the dam would only become more rigid the longer it was steeped up to its top.
Zhang Shuguang, director of the Three Gorges Corp’s Hub Management Bureau, echoed Wang’s judgement, saying nothing could topple the dam in the next 500 years and that not one of the 12,000 sensors fitted throughout the humongous concrete barrier had ever flashed red on the central control panel.
Zhang added that the dam was constructed from concrete, whose cement reacts with the water to form a hard matrix binding blocks together into a durable form. Also, as a gravity dam, it was designed to hold back water by using the weight of the material alone to resist the horizontal pressure of water pushing against it, with ample structural redundancy built in. He said each section of the dam would remain stable and independent of any other section, even if the structural integrity of one portion was compromised.
Still, he warned that flood control measures for the entire Yangtze River Basin could not rely on the Three Gorges Dam to control flooding as his paramount task would be to ensure its own safety.
Flood control was one of the key merits touted by Li when he rammed the 95.5 billion yuan (US$13.5 billion) project through the National People’s Congress in 1994, although almost a third of its deputies abstained or voted against the project.
Proponents of the mammoth project to harness the Yangtze stressed back then that the dam was designed to discharge and regulate floods of “cataclysmic” proportions that might only strike once in ten centuries, when concerns over the dam’s own safety during flooding almost scuppered the plan during deliberations by the Chinese parliament.
China is in another all-out mobilization following the Covid-19 plague as virtually all southern provinces have been drenched by rainstorms unseen in decades, with many rivers overflowing within the dam’s catchment area.
About 95,000 residents have been evacuated before a 180 square kilometer floodwater diversion zone in Anhui province was used to regulate storm water runoff since Monday.