Crisis at Poyang Lake

Dam projects, pollution and climate change threaten the future of China’s largest freshwater lake. Li Taige reports from Jiangxi province.

China’s last remaining expanse of clean water, Poyang Lake, faces a crisis. Not only is the lake drying up, but the little water left behind is polluted.

Once known as Pengli, Poyang Lake is in the northern part of east China’s Jiangxi province. During the wet season, the lake covers over 4,000 square kilometres.Water feeds in to the lake from the Gan, Fu, Xin, Rao and Xiushui rivers and flows out again into the Yangtze River. The river basins of these waterways cover 97% of the province’s land area.

Jiangxi is one of the poorer provinces in eastern China, and this may explain why the lake has escaped major industrial pollution so far. Of China’s four major freshwater lakes – the others are Dongting Lake, Taihu Lake and Hongze Lake – it is the only one not to suffer eutrophication.

Every year Poyang Lake sees extreme variation – of 10 metres or more – in its water levels. It is known for its wide expanse of clear water in times of flood, but it shrinks dramatically in the dry season, becoming little more than a river.

Varying water levels are nothing new, but recent years have seen a succession of new lows. The dry season is also getting longer. The water level used to reach its lowest point in January or February; now this happens in December or even earlier.

Jiangxi is a water-rich province. However, the areas around Poyang Lake are starting to suffer from water shortages. In October 2006, the drinking water inlet for Duchang county was left dry by the retreating lake.

The province’s drying rivers and lakes are like an illness, said Tan Huiru, a researcher at the Mountain-River-Lake Development Office for Jiangxi province. “Floods are rapid and violent like an acute sickness,” he said, “but the shortage of water in an ecosystem is more like a chronic disease. The damage it causes to wetlands will take a long time to repair.”

Experts point to a number of factors that are driving the increased water shortages, including climate change and decreased flows from upstream rivers.

The Three Gorges Dam (see “The Three Gorges: a wiser approach”) is also a major factor affecting Poyang Lake and the ecology of its water basin. Speaking at the Second Yangtze Forum in April 2007, deputy governor of Jiangxi, Xiong Shengwen, said that the dam had caused a “historical change in the relationship between the Yangtze and Poyang Lake.”

Some experts also say that as the Three Gorges Dam reduces water levels along the Yangtze River, the volume of water flowing out of Poyang Lake and into the river will increase. In September last year, the Three Gorges Dam started storing water at the end of the flood season. Several days later the Jiangxi Water Bureau found that 6,000 cubic metres of water per second were flowing out of the lake and into the Yangtze. At the same time, only 1,000 cubic meters per second were feeding into the lake from its tributaries.

Caijing magazine reported a retired senior water engineer from Jiangxi, Xiong Dakan, saying the erosion of upstream riverbeds and siltation at the lake’s mouth due to the Three Gorges Dam could have disastrous consequences for flood prevention efforts in the next 30 years.

The impact of the Three Gorges Dam on water shortages and flood prevention needs further research. The Jiangxi Water Sciences Institute took the lead in December last year by launching an assessment of the impact of the Three Gorges Dam on Poyang Lake and its tributaries. The conclusions of that report are eagerly awaited. 

But it is not just the quantity of water that is a problem; quality is also an issue.

Seven years ago Poyang Lake had clear waters. In 2001, the water was classed as Category I or II on 80% of tests; it was Category III in the remaining 20%. These are the top three classes in China’s scale of water quality. This meant the water in Poyang Lake was suitable to drink all year round.

By September 2007, however, a provincial monitoring centre found no Category I or II water in 10 locations in the lake. (The water was at its normal level for the time of year and covered 3,000 square kilometres). The water was Category III in 60% of tests. The remaining 40% was Category IV: lightly polluted water. In December 2007 and January 2008 – when the water level was at a record low and the lake covered only 40 square kilometres – monitors found the water flowing from the lake in to the Yangtze was Category V: heavily polluted water.

In the last few years county towns in Jiangxi have stepped up efforts to attract investment. Many new industrial zones have been established and heavy polluters from richer provinces, such as Jiangsu and Zhejiang, have also started to relocate to Jiangxi. Rules on pollution are often breached. In many locations, the construction of water treatment plants is only just beginning. Poyang Lake has become the cesspit of the entire province.

Additionally, sand-dredging and the over-planting of trees are damaging the ecology of the region. Since 2003, many towns in the area have started large-scale planting of poplar trees. This fast-growing wood creates an income for both planters and the local government.

However, the poplars suck water out of the soil and leave other plants thirsty, threatening the survival of the lake’s wetlands. Large single-species forests are more susceptible to pests and disease. Experts are worried about the rash of poplar planting on the shores of the lake.

For years people have exploited the lake; it has been left wounded and exhausted. Tang dynasty poet Wang Bo reflected on the songs of returning fisherman, which drifted along the banks of the lake in the evening. But you won’t hear them today: there are few fish and the fishing industry has suffered.

Thankfully, awareness of the situation is improving. Chinese premier Wen Jiabao ordered improvements in the water quality of the lake in April last year. The provincial government held a telephone conference later that month to launch the cleanup operation and help end destructive practices such as over-planting trees. Poplars planted in the Poyang Nature Reserve have been removed.

But uprooting trees isn’t enough. Now is the time to save the country’s last remaining expanse of clean water. Jiangxi’s problem is the same the whole of China faces: how to encourage economic growth, without damaging the environment.

Li Taige is a Beijing-based journalist. He obtained a master’s degree in engineering from Sichuan University in 1997, and studied as a Knight Science Journalism Fellow at the Massachusetts Institute of Technology (MIT) in 2003-2004.