No evidence that dam causes drought: experts

English.news.cn   2011-05-25 12:32:47 FeedbackPrintRSS

WUHAN, May 25 (Xinhua) -- Chinese specialists said Wednesday that there is no evidence to support the hypothesis that the Three Gorges Dam, the world's largest water conservation project, is to blame for the severe drought currently plaguing central China.

"According to data we currently have available, we have found no evidence that the drought was caused by the dam," said Liu Min, a meteorological specialist with the Hubei Provincial Weather Bureau.

According to data collected before and after the dam was built, Liu said the dam has had "very little" impact on regional temperature, humidity, wind velocity and other climate conditions.

"We believe the ongoing drought is more a periodical phenomenon than a result of improper water conservation," Liu said.

He said the "La Nina" weather phenomenon, which occurred last year, disrupted normal atmospheric circulation and prevented warm, humid air currents from reaching the Yangtze River's middle and lower regions. "This caused a lack of rain in these regions since November," he said.

As a result, the worst drought to hit the region in 50 years has affected 9.89 million people in four of China's central provinces, including Hunan, Hubei, Jiangxi and Anhui.

Some Internet users still believe the dam is at fault for the devastating dry spell.

"The dam has blocked water from flowing downstream, that certainly can cause climate changes," said a Beijinger using the screenname "Bull village head."

Extreme weather conditions in recent years, including last year's prolonged drought in southwest China and torrential rainfall in the central provinces, have occasionally retriggered public uproar over the dam.

Zheng Shouren, an academic with the Chinese Academy of Engineering and one of the dam's chief designers, dismissed the accusations as being groundless and unfair.

"Had the dam not been built, the drought would have been even worse in the middle and lower reaches of the Yangtze," Zheng said.

The dam, he said, was designed to store water toward the end of the Yangtze's flood season and supply water to the middle and lower reaches in the dry season.

"During this year's January-May dry season, water supplies from the dam's reservoir increased the Yangtze's downstream flow by 2,000 cubic meters," Zheng said.

This year, the dam's reservoir has supplied a total of 1.7 million cubic meters of water to the downstream provinces of Hubei, Hunan, Jiangxi and Anhui, he said.

The current drought has led authorities to discharge even more water from the dam. Water discharges were increased to 10,000 cubic meters per second from May 20 this year, increasing the water flow by 3,000 cubic meters per second.

Hydrological data from Tuesday indicated that water levels in two major downstream hydrological stations located in the Dongting and Poyang lakes had risen by 1.56 and 1.16 meters, respectively.

Even greater discharges will be put into effect starting from Wednesday this week, according to the China Three Gorges Corporation, the company in charge of operating the dam.

Water discharges will increase to 11,000 or 12,000 cubic meters per second until the flood season begins on June 10, according to Zhao Yunfa, a water conservancy engineer from the China Three Gorges Corporation. Zhao said the dam reservoir is expected to be closed up during the flood season in order to store more water for possible future droughts.

Pan Kejian, an official from the town of Bianhe, which is located in the middle reaches of the Yangtze, said the dam's role in fighting the drought has been "significant."

"Water levels rose by at least 1 meter after the dam's reservoir accelerated its discharges. If it rises another meter, we won't have to rely on pumps for irrigation," Pan said.

When a massive flood hit the town in 1998, the dam was still incomplete, and the town suffered as a result.

"We had another major flood last summer, but it was far less devastating, as the dam blocked some of the water," Pan said.

Cao Guangjing, chairman of the China Three Gorges Corporation, said the dam's role in drought prevention should not be denied, but his company is also open to criticism and constructive suggestions.

"Since the dam began storing water, we have taken measures to minimize any potential impact on the local environment", he said.

Cao said his company has carried out joint experiments with the Chinese Academy of Sciences to monitor water quality and contain the spread of algae that has plagued some of the Yangtze's tributaries.

The algae is another problem for which many people believe the Dam is to blame, he said.

"We've been trying to remove the algae with specialized equipment and chemicals. We've also raised algae-eating fish to try and solve the problem in a more environmentally friendly way," he said.

Since some fish are known to spawn in great numbers during floods, Cao said his company is planning to create "artificial flood crests" at the end of this month by increasing water discharges in order to increase the number of fish in the region.

The Three Gorges Dam project was launched in 1993 with a budget of 180 billion yuan (22.5 billion U.S. dollars).

Located on the middle reaches of the Yangtze River in Hubei Province, the total project consists of a 185-meter-high dam, which was completed in early 2006, a five-tier ship lock, a reservoir and 26 hydropower generators.

The project generates electricity, controls flooding by storing excess water and helps to regulate the river's shipping capacity.

Editor: Mo Hong'e
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