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 1,338.57 sq 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 to 90 percent.

The water area of the lake has been shrinking by less than 1 percent, or about 16 square km, annually since 2001, the year monitoring began.

"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.

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

China has more than 24,800 natural lakes, but an average of 20 disappear every year.

Lakes, a key element in sustaining ecological balance, remained fragile in the face of rapid industrial growth and increasing human activities, "while global warming speeded up the vaporization process and magnified human influences," said Professor Erik Jeppeson, of the Department of Freshwater Ecology at the University of Aarhus in Denmark.