The China Meteorological Administration has claimed the Three Gorges Dam, the world's largest hydropower project, did not trigger the severe drought along the Yangtze River earlier this year.

The project influences temperatures and precipitation only within 20 km of the dam, according to a report released by the national climate center under the China Meteorological Administration in July.

The major droughts of recent years were mainly caused by abnormal atmospheric circulation and unbalanced heat distribution, the report said.

"The water area of the Three Gorges Dam is not that large compared with the Yangtze River, which causes little impact on the local climate," said Zhang Boting, deputy secretary general of the China Society for Hydropower Engineering.

Although some experts are determined to prove hydropower stations have little effect on environmental and meteorological conditions, the frequent extreme weather, such as flooding and drought along the Yangtze River, has prompted other experts and the public to criticize the construction of the Three Gorges Dam.

In May, Poyang Lake, at the south bank of the Yangtze River, shrank to 1,326 square kilometers from its normal area of 3,914 sq km, the smallest size it has been recorded at, according to the satellite monitor image released by the China Meteorological Administration.

Ma Jun, director of the Institute of Public and Environmental Affairs, said the meteorological administration should analyze the dam's impact, because "the dam cannot change the climate, but it can adjust the flooding or drought with its control of the water flowing in and out".

"In drought season, the dam will store water to generate electricity with less water discharging downstream, which makes the drought worse," Ma explained.

Authorities have been aware of the environmental impact of the dam for some time. In mid-May, the State Council, China's Cabinet, issued a statement saying urgent issues, such as ecological protection, water transport and geological disaster prevention, must be addressed. The council vowed to establish a disaster alert system.

Since 2003, when the dam was partially constructed, earthquakes, flooding and droughts in the region have occurred frequently and may become more frequent in the next 20 years, the report said.

In the next 20 years, the temperature along the Yangtze River may climb by 0.8 C at most and precipitation downstream decrease by 10 percent, while increasing by 10 percent upstream, the report said.

The risks of flooding and drought are increasing along the Yangtze River, it added.

By May 29, the drought earlier this year had affected more than 7 million hectares of farmland. The downstream area of the Yangtze River was the place that had been the worst hit, according to statistics from the State Flood Control and Drought Relief Headquarters.