China’s largest freshwater lake may be cut off from the Yangtze River during the dry season once the plan for building a dam on the lake is finally approved. Authorities in the eastern province of Jiangxi are soliciting public opinion over building a 3km (1.9 mile)-long and 23.4 metre (77 foot)-high sluice gate between Poyang Lake and the Yangtze River to control water levels and alleviate drought in winter. The lake is one of the two large bodies of water that naturally connect to the Yangtze River, but it has witnessed worsening winter droughts in recent years. Jiangxi authorities suggested building a series of sluice gates to raise water levels during the dry season, but it was opposed by environmentalists and the public. The water resources department of Jiangxi released a second environmental impact assessment last week. The deadline for the public to submit opinions about the project is Friday, it said. The project needs approval by the Ministry of Ecology and Environment before construction can begin. Poyang Lake is rich in biodiversity. The Ramsar Convention , an intergovernmental treaty, includes it on its “Wetlands of International Importance” list. The lake is home to the highly endangered Yangtze finless porpoise, whose population has declined to about 1,000, with about 450 living in the lake. Nearly 98 per cent of all Siberian cranes, which are critically endangered, spend winters at the lake, said Jiang Jiahu, a researcher with the Nanjing Institute of Geography and Limnology of the Chinese Academy of Sciences. “The environmental impact assessment is problematic. Its prerequisite is to build a dam and then to find the benefits but never mention the negative sides,” Jiang said. China puts total fishing ban on ailing Yellow River’s upper reaches According to the document, the sluice gates will be fully opened to connect the lake and the river in the flood season from April to August. In the dry season, from September to March, it will be closed to raise water levels and stop water flowing from the lake. The lake’s water level is expected to be returned to the levels before 2003 when the Three Gorges Dam was put into use. The document says this will be beneficial to plant growth in the wetlands and will expand the habitat area for migratory birds. The project’s impact on fish in the lake is not obvious, but it may further disturb the seasonal migration behaviour of the Yangtze finless porpoises in the river and lake, it added. The project would also aid irrigation, urban and rural water supply and shipping on the lake, it said. “The construction of the Poyang Lake water conservancy project is very necessary and its benefits outweigh the disadvantages,” the document concluded. Experts said the lake was drying up because of the dams built upstream of the Yangtze, which limited the flow of water downstream. Other factors include sand mining and the reservoirs on the rivers flowing to the lake. The project has been debated for about two decades and was shelved several times, primarily because of objections from environmentalists. The dam was first proposed by Jiangxi officials in 2002 but was shelved after meeting with opposition from the public. In 2009, the Jiangxi government sent the plan to the State Council for approval but it was knocked back over environmental impact concerns. In 2016, when the Jiangxi provincial government made the first environmental impact assessment public, multiple environmental NGOs opposed the building of a drought-mitigation sluice wall, expressing concerns that it would further damage the Yangtze River’s natural environment and the local ecology. Five years later, Jiangxi authorities released the location of the project for public feedback, again sparking opposition. China fears more devastating floods as Yangtze River’s levels rise again In an open letter to provincial authorities last week, the Hangzhou-based environmental group Let Birds Fly said it would be “extremely irresponsible” of the government to approve the project. “The impact of building a dam on Poyang Lake may be greater than the construction of the Three Gorges Dam because of the impact on the ecology and environment,” Jiang said. Fan Xiao, a geologist with the Sichuan Geology and Mineral Bureau, said Poyang Lake had dried up because of the lower water levels of the Yangtze and dams in the rivers flowing to Poyang Lake, resulting in less water moving to the lake. “Numerous dams are built up in the five main rivers flowing to Poyang Lake and they all need to reserve water during the dry season, resulting in lower water level in Poyang Lake,” he said. “It is not easy to solve the old problem by building a dam, which will bring new problems, especially for ecology.”