Managing China’s thousands of dams is trickier in the era of climate change
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China has about 98,000 dams, most of them small-scale and constructed before the 1970s. In addition to flood control, these dams play an important role in hydroelectric power generation, and ensuring water security. But flooding in recent years due to unusually heavy downpours has drawn more attention to the challenges of managing dams in an era of climate change, when extreme rainfall poses new risks for surrounding communities.
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“Because of climate change there could be higher and higher precipitation, that’s something that may have not been considered during the process of designing the dam,” said Wen Wang, a professor of hydrology at Hohai University in Nanjing, adding that it’s a major issue engineers are paying attention to now, yet one that’s hard to construct for given the difficult of accurately forecasting volumes of extreme rain.
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Zhengzhou city, in central China’s Henan province, for example, recorded what is typically nearly a year’s worth of rain on a single day. Torrential rain on July 20 caused floods that left more than 300 dead, including many who were trapped in car parks or in the inundated subway system.
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One of the dams that collapsed this year, the Xinfa dam in Inner Mongolia, was “well constructed and prepared very well (for floods)” said Mohammad Heiderzahad, an associate professor of civil engineering at Brunel University in London. Heiderzahad, who is a dam engineer himself, explained that even so the dam collapsed quickly despite having two spillways and an emergency bottom outlet, which allows for water to be released safely when a dam is in danger of overflowing.
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