Chinese environmental protection experts warn that a dam under discussion may introduce a massive algae outbreak in the country's largest freshwater lake, and they suggested that the project be delayed until there is sufficient data to demonstrate its need.
During the weekend, a thick layer of blue-green algae was seen in Poyang Lake in Jiangxi province - an area adjacent to the Yangtze River.
Cheng Huiying, deputy director of the environmental protection bureau of Duchang county, where the algae outbreak was reported, said floodwaters following heavy rains upstream had pushed the algae into the lake.
"Our monitoring data showed no signs of excessive richness of nutrients or high levels of nitrogen or phosphorus in the water," Cheng said. "That proves the algae was not produced in the lake but was flooded into it. We'll arrange for workers to clear the algae."
According to Zhou Qiong, deputy director of the provincial water management office, water can easily be exchanged by the lake and river in either direction.
"When the river lacks water, the lake's water runs into it," said Zhou. "When the river swells with a downpour, its water level surpasses the lake's, and water begins to flood into the lake."
"The construction of a dam to control the water has been under discussion for years," Zhou said. "People's opinions vary about whether to control the flooding by intervention or to adapt to the natural environmental conditions."
Chen Jiakuan, a professor at Fudan University's Institute of Biodiversity Science, said the dam would prevent the lake from exchanging water with the river, so algae would break out massively in the relatively still water.
"Algae broke out in Chaohu Lake and Taihu Lake once they were disconnected from the Yangtze," Chen was quoted as saying by The Paper, a news outlet in Shanghai. "Poyang Lake would be disconnected also, once the dam is constructed. Today's Chaohu and Taihu lakes will be tomorrow's Poyang Lake."
According to a report by Jiangxi Information Daily in December, the construction of the dam has been listed as one of the country's major water conservation projects.
Zhou said it is possible that the construction of the dam will introduce more algae outbreaks, but that the situation will be manageable if the water that runs into the lake is clean.
"Insisting that the dam will worsen the algae outbreak may oversimplify the problem," said Zhou. "We need to do more research before drawing a conclusion.
"It's not a decision that Jiangxi province can make alone. It's a job for the State Council and the National Development and Reform Commission."
"I used to support the theory that people should take the initiative to control nature," Zhou said.
"But after years of research and experience, now I prefer that we don't control nature through man-made means. At minimum, the dam should not be constructed until more research is done to establish that no severe consequences will result."
