BEIJING - A total of 243 lakes covering more than one square kilometer each have disappeared in China over the past 50 years, reported Sunday's Science and Technology Daily.

The daily cited a survey conducted by the Nanjing Institute of Geography and Limnology (NIGL), adding that bio-diversity has also been affected by the changes of the country's lakes.

Scientists conducted the survey in the past almost five years starting from 2007, employing remote sensing to check the amount, coverage and locations of the lakes beyond the coverage of 10 square kilometers around the country.

Lakes in the north and northwest have suffered from dropping water levels, while those in the east have been affected by problems such as water eutrophication, Yang Guishan, director of NIGL, was quoted as saying.

Water capacity of the lakes in the Tibetan Plateau have fluctuated violently and lakes in southwestern Yunnan-Guizhou Plateau have witnessed decreasing water quality and bio-diversity, due to overfishing, disconnection between lakes and rivers, as well as invasive alien species, he added.

Take the Dianchi Lake in Yunnan Province for example, scientists have found only 19 species of water plants according to the recent survey, while in the 1950s more than 100 water plants lived in the lake.

In another recent report on protection and development of the Yangtze River, the number of the lakes in the river basin has also keep diminishing.

Ninety-six lakes covering over one square kilometer each along the Yangtze River Valley disappeared in the past 30 years, according to a report jointly issued by the World Wide Fund for Nature (WWF), NIGL and China Development Bank.

The WWF hopes the report can offer suggestions and examples for the utilization and protection of lakes and the Yangtze River as well as to increase public awareness of the need to protect the river and lakes, said WWF China CEO Jim Gradoville.