Are Yangtze River Basin lakes doomed?

(Ecns.cn) – A total of 243 lakes have perished in China over the past three decades. About 42 percent have fallen victim to land reclamation, according to Southern Weekend, and the surface areas of these lost lakes cover more than one square kilometer each.

By contrast, the number of lakes near the source of the Yangtze River on the Tibetan Plateau is increasing and their surface areas widening. This is hardly good news, since the increases result mainly from glacial melt under the effect of global warming.

Early this month, the surface area of Poyang Lake, China's largest freshwater lake and one which connects to the Yangtze River, shrunk to less than 200 square kilometers following the country's worst drought in 50 years, according to the Jiangxi Provincial Hydrographic Bureau.

Though the lake's shrinkage has been largely due to dry weather, many water resource projects have added to the problem. Among them, the Three Gorges Dam is undeniably to blame for negative impacts on the ecological environment of the middle and lower reaches of the Yangtze River.

As the Year of the Dragon dawned, Chinese maritime authorities closed the Yangtze River above the port of Wuhan, more than 960 kilometers upriver from Shanghai.

Lake expansion bad news

On January 6, 2012, the Yangtze Conservation and Development Report 2011 was released by the Nanjing Institute of Geography and Limnology (NIGL), in which lower water levels, rapid urbanization and large water infrastructure projects across the Yangtze Basin are shown to be compromising the overall health of many lakes along the 6,300-kilometer river. The Yangtze provides livelihoods for nearly one-third of China's population.

The report is based on a study conducted by 30 experts from NIGL, China Development Bank, the World Wildlife Fund and an assortment of NGOs. Starting in 2007, the report has been released every two years and has carried extensive data on the amount, coverage and locations of all China's lakes with surface areas beyond 10 square kilometers.

It escapes no one's notice that the latest report has focused on lakes along the Yangtze River, and the reason is obvious: these lakes are in an abnormal state.

According to the report, in the last three decades 60 new lakes have formed with surface areas that measure more than one square kilometer each. They are scattered mainly around glaciers, intermountain depressions, marshes and river valleys.

The abnormality amounts to glacial melt that is picking up speed, resulting in increased rainfall that pours into the new lakes, said Wu Qinglong, a researcher with NIGL.

Meteorological data for the past 50 years shows that temperatures at the source of the Yangtze River have been on the rise, especially after the 1990s. With a warming climate, glacial retreat has become a serious problem in urgent need of solutions.

Such a trend as these changes to lakes in the Tibetan Plateau and in the southwest Yunnan-Guizhou Plateau will have unexpected impacts on the overall ecosystem comprising all lakes in China, noted Wu, who added the report has cast a shadow on prospects for the future of the Yangtze River.

Water eutrophication a common phenomenon

Apart from land reclamation, pollution from industrial runoff is also accelerating the demise of many lakes. According to Chen Yuwei, a colleague of Wu Qinglong, the water quality and bio-diversity of Poyang Lake have been in decline for years.

It appears the types of water plants that live only in fresh water are decreasing, while at the same time a kind of pondweed that resists pollution is growing at a maddening rate. Chen said it signals a heavy degree of mineral and organic nutrients that promote algae, which in turn reduce the dissolved oxygen content of water and often cause the extinction of other organisms.

To take the Dianchi Lake in Yunnan Province as an example, scientists there find only 19 species of water plants today, while in the 1950s more than 100 types made the lake home, according to China Daily.

It calls to mind the serious ecological disaster of 2007, when large blooms of blue-green algae in Taihu Lake caused severe deterioration of water quality and affected the water supply in Wuxi, East China's Jiangsu Province.

At that time, despite the local water department's attempts at mitigating the crisis, the water supply to a great number of households was contaminated, putrid and very unpleasant to drink. Local residents flocked to buy clean bottled water at supermarkets.

Measures needed

If measures are not taken in time to mitigate the impacts of climate change, increased industrialization, and urbanization along China's longest river, many dramatically shrinking Yangtze River Basin lakes could dry up completely in the end, the report warned.

The primary consideration is that these lakes are all connected to the Yangtze and form the one and only mega-system of lakes and river in the world; the role the system plays in sustaining bio-diversity and water quality is crucuial, said NIGL director Yang Guishan. Now even lakes in the north and northwest are suffering from dropping water levels, while those in the east are succumbing to such problems such as water eutrophication, added Yang.

China's two largest freshwater lakes, Poyang and Dongting, have obviously been affected by the Three Gorges Dam. The lake ecosystems in the Yangtze River Basin have undergone dramatic changes, and the results go beyond an insufficient water supply; add to that a decline in their flood retention capacity and their ability to even undergo a purification process, Yang points out.

This time, the Yangtze Conservation and Development Report 2011 takes the stand that a comprehensive action plan is an absolute necessity to ensure the future health of the Yangtze River. Land reclamation should be stopped immediately, and restoration of already reclaimed land back to lakebed is advised. Meanwhile, large infrastructure projects such as the Three Gorges Dam and the South to North Water Transfer Project on the Yangtze River should be given some sober second thought rather than automatically going to the next step.