As China’s Largest Freshwater Lake Shrinks, Solution Faces Criticism

Hundreds of thousands of migratory birds, including the endangered Siberian crane, gathering for the winter at Poyang, China’s largest freshwater lake, in Jiangxi Province. Credit Visual China Group, via Getty Images

HONG KONG — Long celebrated as China’s largest freshwater lake, Poyang reaches more than three times the expanse of Los Angeles in the summer wet season. It is home to the rare Yangtze finless porpoise, and its mud flats are the primary winter feeding grounds for thousands of birds that fly south each autumn to escape Siberia’s chill, including the critically endangered Siberian crane.

Now it is Poyang itself that is at risk.

In recent years, the average expanse of the lake, in the southeastern province of Jiangxi, has been shrinking, and winter water levels have declined sharply.

The local government has a proposed solution, but it faces a chorus of opposition from scientists and environmental groups in China and beyond who argue that it could have disastrous effects on the lake’s fragile ecosystem and drive the Siberian crane and other migratory birds further toward extinction.

Water levels in the lake have always fluctuated radically between the summer rains and winter dryness, but there is now concern that the levels are off balance. Culprits include the Three Gorges Dam, which stores water upstream on the Yangtze for winter electricity generation, lowering a nearby river channel and sucking water from the lake. Dredging to collect sand for construction projects has also lowered the lake’s bed and caused more runoff. This year, drought turned much of the lake into grassy plains.

The local government has proposed building a sluice gate to keep more water inside the lake in the winter, but critics say the gate would essentially be a dam, and it could cause bigger problems.

“I think you’re proposing a solution without understanding the causes of the problem,” said David Shankman, a professor emeritus of geography at the University of Alabama who has studied the lake’s hydrology.

“The whole idea of the dam is that there would be some economic benefit, but there may be potential long-term ecological problems,” he added.

The primary feature of the $1.9 billion Poyang Lake Water Conservancy Project would be a 10,000-foot sluice gate across a natural channel that connects the lake’s northern edge to the Yangtze, according to a November report by the Jiangxi provincial government.

Fallen Star Boulder, a scenic spot in Poyang, was exposed on the dry lake bed on Jan. 2, 2015. Water levels have historically dropped in the winter months, but in recent years drought, dams and dredging have contributed to sections of the lake drying up. Credit Imaginechina, via Associated Press

Among other benefits, the report said, the sluice gate would help to stabilize the drinking water supply and promote shipping on the lake. The report described the project as an ideal way to create “first-class water quality, first-class air, first-class ecology and a first-class environmental standard for residents.”

The National Development and Reform Commission, the government agency that helps oversee economic planning, has been reviewing the proposal since 2009, and the Ministry of Environmental Protection began its environmental impact assessment in November. The proposal could still be derailed if senior officials turn against it.

Scientists said in interviews that the project could irreparably alter the lake’s seasonal flood pulse, which causes water to rise and fall by up to 30 feet between the wet and dry seasons and has carried sediment into Poyang from as far away as the Tibetan plateau.

The project would also allow water to rush in from the Yangtze during the winter dry season, the scientists said, drowning vegetation that grows in Poyang’s mud flats and provides a crucial food source for hundreds of species of migratory birds.

“Whatever’s built is going to be able to drown that entire system during the winter,” said James Burnham, a doctoral candidate at the University of Wisconsin-Madison who has researched how changes in China’s wetlands affect endangered water birds.

The Siberian crane, whose estimated 4,000 remaining individuals winter almost exclusively at Poyang because it is the closest lake to Siberia that does not freeze, is among Jiangxi’s best-known birds. But more than a dozen other threatened or endangered bird species depend on Poyang as a wintering site and would be threatened by the project, Mr. Burnham said.

Several prominent environmental groups have also criticized the project.

WWF, which has been working to protect the endangered Yangtze finless porpoises that live in Poyang, has said that the project would “irreversibly and unpredictably” affect water quality and species diversity.

Zhang Yunbo, who heads Let Birds Fly, an environmental group based in Beijing, said that he was not categorically opposed to reasonable engineering solutions at Poyang, but that the complexity of the hydrological problems there made him wary of a large-scale engineering solution.

“Just because the water level is going down doesn’t mean we have to engineer the water levels,” Mr. Zhang said.

Cargo boats on Poyang Lake in 2012. Credit Imaginechina, via Associated Press

Some experts say that an alternative would be to stop the sand mining that appears to be lowering the lake bed and causing more water to escape from the water channels that appear in Poyang’s mud flats during the winter. Much of the sand is used for construction in Shanghai, about 400 miles east, and other Chinese cities along the lower Yangtze River basin.

Officials at the Jiangxi Provincial Water Bureau declined a request for an interview and referred inquiries to the government’s report on the project.

Separately, local officials released some details in November from its environmental impact assessment of the project. But critics, including Greenpeace, the international environmental organization, said that the details did not allow for a full assessment by outsiders of the project’s likely ecological consequences.

A 2014 study in the journal Scientific Reports found that reservoirs covering a total area equivalent to the size of Vermont had been constructed across China over the previous six decades, and that most of China’s large freshwater lakes — not including Poyang and Dongting, another freshwater lake in the Yangtze River basin — were regulated for irrigation, flood protection and other uses.

Lu Xixi, one of the study’s authors and a geography professor at the National University of Singapore, said the Chinese government’s approach to hydrological challenges was often driven by an “engineering mentality.” As a result, he said, the consequences of engineering projects — such as erosion — were often addressed with further engineering, even when less-intensive solutions might be more effective or less harmful to the watershed.

“We think the mentality must be changed,” Mr. Lu said in an interview.

Mr. Burnham said that stabilizing Poyang’s flood pulse would make its seasonal variations more predictable, potentially allowing for economic activities in places near the lake that were once at risk of flooding during the summer.

But he said it was unlikely that the migratory birds that feed at the lake during the winter dry season would see any benefits from the proposed sluice gate.

One of Mr. Burnham’s latest studies shows that when Poyang’s water levels were high during an unusually wet winter in 2011, Siberian cranes fled to nearby grasslands but did not absorb as many calories there as they normally do from vegetation in the lake’s mud flats. The study also says that grassland feeding could potentially slow the birds’ reproduction over the long term.

“There aren’t many other places for these birds to go: Poyang is the last, best place around,” Mr. Burnham said. “And if that’s no longer available, or if it gets altered to the point where it can’t be used anymore, you’re going to see a collapse of these species in the wild.”

Source: NYTimes