WUHAN, Nov. 4 (Xinhua) -- China's second largest freshwater lake, Dongting, has shrunk in area by almost two thirds in just a month, a local meteorologist said Wednesday.

    The water area of the lake, which spans the central provinces of Hubei and Hunan, measured 537.84 square kilometers by mid October, only 40 percent of its size recorded in September, said Liu Jinghui, of the Wuhan regional climate center of Hubei Provincial Meteorological Bureau.

    Satellite monitoring indicated the water area measured 1,338.57sq km in September, Liu said, quoting results of a survey conducted last month.

    Liu attributed the drastic shrinkage to a lingering drought in the lake region due to lack of rainfall since August. The average precipitation dropped by about 50 percent and in some areas, up to90 percent.

    Southern and central China suffered a rare drought over the past month, cutting down water input to Dongting and many other lakes, said Shen Xiaoli, general engineer with the Institute of Environmental Sciences of Hubei.

    "The latest monthly shrinkage was the worst anyone can recall in a century," said Liu.

    In addition to the climate change, water storage at the Yangtze Three Gorges project in the upper reaches of the lake basin may also have affected the lake, the report said.

    "It requires further analysis to find out the real causes," Liu said.

    However, the monthly figure does not reflect the long-term change in the lake as meteorological and other factors could fluctuate drastically in a short period, Liu pointed out.

    Since 2001, the year the monitoring began, the water area of the lake has been shrinking by more than 1 percent, or about 16 square km, each year, he said.

    China's largest freshwater lake, Poyang, even shrank to less than 50 square km in 2007 from the maximum area of 4,350 square kmdue to a severe drought.

    GLOBAL CHALLENGE

    The shrinkage of water area, water pollution and the degradation of ecological functions are the major problems threatening worldwide lakes and bringing direct impact to people's lives and production activities.

    Lakes, a key element in sustaining ecological balance, remained fragile in the face of global warming and rapid industrial and agricultural growth.

    Hubei Province, once known as "a province with 1,000 lakes," has 2,438 square kilometers of lake areas, or about 34 percent of the figure in the 1950s.

    China has more than 24,800 natural lakes, but they are disappearing at a rate of about 20 every year.

    In addition, many lakes suffer eutrophication, a result of excessive waste discharge amid increasing human activities.

    A number of key lakes across China have suffered outbreaks of blue algae over the past decade, forcing local authorities to launch expensive emergency treatment campaigns.

    "Global warming speeded up the vaporization process and magnifies human influences," said Erik Jeppeson, a professor from the Freshwater Ecology Department at the University of Aarhus in Denmark.

    The situation is serious, not only in China but also across the world, said David Garman, president of International Water Association.

    Large amount of discharge from industrial, agricultural facilities and household wastes beyond the carrying capacity of lakes has triggered frequent outbreaks of blue algae, damaging the ecological functions of lakes and finally affecting people's live.

    "Water stays in a lake much longer than in a river, so it can take 100 years to tackle a polluted lake," said Masahisa Nakamura, scientific committee chairman of the International Lake Environment Committee.

    Degradation of Biwa Lake forced the Japanese government to launch pollution control projects in the 1970s, which involved limiting waste discharge, higher discharge and environment assessment standards, and strict requirements for the treatment of household sewage.

    China has been trying hard to cure lake and river problems amidrapid economic and social development. However, a survey in 2007 showed 27 of the 43 lakes tested suffered from eutrophication, and12 of them seriously.

    Another survey by the National Audit Office last week showed water quality in three major rivers and lakes in the country had improved only slightly despite continued pollution control effortsbetween 2001 to 2007 at a cost of 91 billion yuan (13.3 billion U.S. dollars).

    LAKE REHABILITATION

    People used to just focus pollution treatment on the lake itself rather than pursuing the root causes, that's why the results were not satisfactory, Wang Hao, an academician of the Chinese Academy of Engineering, told Xinhua at the ongoing World Lake Conference held in Wuhan, capital of Hubei.

    "For a long time, China has not paid enough attention to land pollution sources while curing lake contamination," he said. "Lakes don't produce pollutants themselves, they receive everything left by human activities on land and drainage areas."

    Lakes were vulnerable to pollution from activities such as fish breeding, the release of sediment contaminants, and the growth of invasive species in lake waters. They also faced pollution from domestic sewage and industrial waste water discharges, agricultural fertilizers, soil erosion and over-extraction, he said.

    To allow lakes to rehabilitate, he proposed an integrated lake-land treatment mechanism, which combined comprehensive land pollution control measures, including higher waste discharge standards, stringent punishments by economic and administrative means, and greater public awareness through education.

    "You should make sure pollutants don't go to the sewage system. you can assist by reducing litter, replanting bank side vegetation and help with wetland restoration. And there are just so many things that people can do at local level," said Garman.

    "Tackling lake contamination needs a long-term plan which can span as long as 20 years and needs consistent efforts," said Jin Xiangcan, a leading expert on water environment at the Chinese Research Academy of Environmental Science.

    Chen Zhili, vice chairwoman of the Standing Committee of the National People's Congress, China's top legislature, called for greater legislative powers to stop lake water pollution and prevent lakes from disappearing.

    She urged establishment of special lake protection laws and regulations and implementation of strict judicial and administrative means in the management and supervision of industrial, agricultural and household waste, especially that of highly- contaminating facilities such as paper mills and chemical plants.

    Chen Lei, Chinese Minister of Water Resources, proposed to clean and renew the lakes by ways including waste prevention and treatment, connecting lakes with rivers, clearing silt, bio-tech management and comprehensive treatment of estuaries.

    The minister also urged tougher management of industrial development, while maintaining strict supervision and punishment over illegal activities.

    Raising the awareness of reducing waste discharge in daily life among children and local residents is also a pressing task for the government, said Jeffrey A. Thornton, managing director of the International Environmental Management Services Limited based in the United States.

    "Cleaning up the lake is not the sole responsibility of researchers and scientists. The local residents' participation is the key to tackle lake contamination. The less water they produce and fewer energies they consume, the cleaner the lakes will be," Dr. Vishwas Yerale, a representative from Mumbai, India, said at the conference.

    Governments of those countries suffering from similar lake problems should impose systematic pollution control measures based on the situation of each lake basin while taking into consideration the factors of climate change, the emergence of new types of pollutants amid expanding human activities, and establish effective risk assessment and prevention mechanisms, Jin Xiangcan said.