Every winter, Poyang Lake is a festival of sorts for bird lovers, environmentalists, and researchers: Tens of thousands of migratory waterbirds — oriental white storks, Siberian cranes, spotted redshanks, and many others — forage for food at the lake in eastern China’s Jiangxi province. While many of China’s wetlands have been destroyed to make way for industrial development, Poyang Lake, with its open connection to the Yangtze River, is still a haven for wildlife.

But now, environmentalists fear that plans to build a large floodgate at the site could further diminish the birds’ habitats and threaten endangered species in the area. With the release of the project’s environmental impact assessment on Nov. 23, opponents of the proposal only have until Dec. 6 to put a stop to the plans, according to Chinese law.

The 13 billion-yuan ($1.9 billion) project proposes building a floodgate at the narrowest part of the lake, where water flows in from the Yangtze River. According to the provincial government, the structure would help the lake retain water during the dry season, usually November to March, for shipping purposes and to ensure access to drinking water for the millions of people who live close to the lake.

Poyang Lake covers around 3,530 square kilometers during the rainy season and shrinks by a third in the dry season. The winter water level has begun hitting its lowest point of the year earlier and for a longer period of time in the past few decades — a phenomenon for which the provincial government has blamed the Three Gorges and other upriver dams.

Plans to regulate water flow in the area can be traced back to 1995, when the government announced its intention to build a dam on the lake. A few years later, however, due to concerns from the public that a dam would harm the lake’s fragile ecosystem, authorities changed the structure to a floodgate.

For birds, the lake’s seasonal shrinkage provides abundant food and helps maintain habitats. Li Fengshan, project manager at the International Crane Foundation, told Sixth Tone that the natural conditions at Poyang Lake are found nowhere else in Asia. According to a report by the foundation, over 250 bird species spend their winters at the lake, and for some endangered species the lake is a vital stopover along their migratory routes.

“A large number of [bird species] feed on plants on dry land or in shallow water instead of deep water,” said Li. “Maintaining the water at a high level will spell doom for them.”

The Jiangxi government says the floodgate will help maintain the wetlands, arguing that the recent drop in water levels has dried out many wetland areas and destroyed waterbird and fish habitats. But Li disagrees and says that further research is necessary. “A wetland is a complex ecosystem, and current studies aren’t enough for us to understand all the species,” he said.

Zhou Haixiang, director of the Ecology and Environment Research Office at Shenyang Ligong University, told Sixth Tone that under normal circumstances, increasing the water level in a lake will increase birds’ habitats, but that this is not true for Poyang Lake because it is surrounded by dikes to protect surrounding farmland. “Simply raising the water level won’t create more wetlands for birds,” he said.

Environmentalists also argue that it’s the large-scale sand excavation from the lake bed, not the Three Gorges Dam, that has caused drought in the past. According to research by scholars at Jiangxi Normal University, an average of over 200 million tons of sand is excavated from the lake every year — much more than the government-approved amount. The research concluded that the excavation causes the lake bed’s volume to grow by about 6.5 percent.

Some also worry that the new proposal will inspire other provincial governments to build their own floodgates to maintain water levels, thereby worsening conflicts for water between localities along the Yangtze River.

Millions of residents of Shanghai, which lies on the Yangtze Delta, have depended on water taken from the river. Now, water stored at the Three Gorges Dam during the dry season has worsened the drought in the eastern megacity. Zhou Jianjun, a professor of water conservation at Tsinghua University, said at a conference about the floodgate project on Thursday that the plans proposed for Poyang Lake are likely to cause more conflict.

In 2014, the drought in the Yangtze River Basin and water storage at the Three Gorges have resulted in the most severe influx of saltwater into the city on record. According to local media, the phenomenon salinized the water supply of some 2 million people.

(Header image: Waterfowl occupy the shore of Poyang Lake, Jiangxi province, December 2015. Zhou Haixiang for Sixth Tone)