Old dam demolition protects marine ecology

HANGZHOU -- Before the demolition of the Xuanmen Dam in East China's Zhejiang province began, Liu Shijin, 75, who worked on the project as a technician 45 years ago, set foot on it one last time to bid farewell.

The 144-meter-long dam in Xuanmen Bay in the city of Yuhuan had served as an important passageway for the island residents to go outside since the 1970s.

"The populous island lacked fresh water and arable land. People traveled by ferry across the water, but the treacherous conditions made the short journey risky," Liu recalled.

As the country lacked the necessary technology to construct sea-crossing bridges at that time, building a dam that can help improve transportation looked like a viable solution to the problems of the island residents.

The dam was completed after three years of construction and opened to traffic in 1977.

For the past four decades, the 12-meter-wide dam played a significant role in boosting the development of the small island city, which later became one of the top 100 county-level cities in China, with regional GDP exceeding 70 billion yuan (about $9.77 billion) in 2021.

However, certain negative environmental effects of the dam have gradually become apparent. The dam blocked ocean currents, resulting in eutrophication in the surrounding water, and the shrinkage of fish resources.

In 2017, the local government decided to build a bridge and demolish the dam. Consequently, a six-lane bridge was constructed here after four years of work, paving the way for the demolition of the dam.

"I am a bus driver. I used to drive over the dam every day. The demolition of the old dam can make the city better, so I can understand the rationale behind this move," said Pan Jiaozhi, a local from Yuhuan.

In order to minimize the impact on the environment, a demolition timeline of three and a half months has been adopted instead of the quick blasting method, said Wu Hua'an, an official with the city's agriculture, rural affairs and water resources bureau.

A national wetland park has been built on the west side of the dam, and the demolition of the dam is expected to further improve the coastal ecology.

"The city has worked out a post-demolition ecosystem restoration plan, which will focus on the improvement of water quality and coastal environment, and the cultivation of aquatic life," said Xi Shengdong, deputy mayor of Yuhuan.

The story of Xuanmen Dam is not the only one. In an effort to restore the coastal ecosystem and enhance marine biodiversity, similar structures including dams and aquaculture farms that brought negative environmental effects in some coastal provinces have been removed in recent years.

According to the country's marine environment protection plan (2021-2025), China plans to carry out targeted pollution treatment with a focus on nearshore bays and estuaries while paying more attention to overall protection and systematic restoration.