Special report: Three Gorges Project

Explosions to dismantle the last cofferdam protecting the just-completed Three Gorges Dam created huge waves Tuesday afternoon in the reservoir, with its aftereffect on water creatures to last for another two to three hours, said biologists here.

Professor Tan Xichang from the Water Biological Engineering Institute under the Chinese Academy of Sciences took in charge of a fish dispelling operation three hours before the demolition that occurred at 4:00 p.m.

He said that the two dispelling vessels succeeded in driving 90 percent of fish within a reach of 600 meters from the cofferdam an hour before the explosion of the protective dam, according to ultrasonic monitoring result in the reservoir.

Tan said that based on fish behavior study, the startled fish will not be able to banish the fear until two to three hours later.

"It was the first time that we have used electric devises to create high-pressure electric pulse in water to dispel fish schools in such a large scale," said Tan, adding that the operation helped control the negative effect of the blast on water creatures to the minimum level.

Tan said that the dispelling method is China's patented scientific breakthrough, which proved effective in driving away creatures in water without hurting them.

The electric pulse can disturb creatures 35 meters deep underwater. The two vessels created the electric effect for disturbance in an area of 700 square meters close to the cofferdam before the designated explosion, said Tan.

The Three Gorges reservoir has become a natural habitat for many endangered freshwater species, such as river dolphins, Chinese sturgeon and Chinese paddlefish, since the cofferdam exerted its role to store water in the middle reaches of China's longest river of Yangtze in 2003.

A report from the Ministry of Agriculture has revealed that the creation of the vast Three Gorges dam might bring significant changes to the river's speed, temperature and even water quality in the upper and down streams of the dam, which might negatively affect the lives of the endangered species.

After years of researches, scientists studying on the project’s environmental issues believed that the hydropower project would affect water lives, water quality, cause silt accumulation and maybe slightly modify local climate through years in the dam's surrounding areas.

The fish dispelling has been seen as part of the country's efforts to offset negative impacts posed by the construction of the world's largest hydropower project.

In addition, Chinese experts have developed artificial breeding of endangered water species and put the rare aquatic species' fries in the river. About five million artificially bred sturgeon fries have been freed into the Yangtze River for restocking the oldest species in the river. Meanwhile, fishing ban on the Yangtze River is introduced in the spring and summer seasons every year.

Cao Guangjing, deputy general manager of the China Yangtze River Three Gorges Project Development Corporation said that the company has made a great endeavor in dealing with various environmental problems concerning the project.

A great deal of sewage was produced in the concrete manufacturing for the project. Only after it had been decontaminated, could it be discharged, he stressed, adding that half of the sewage has been processed for recycling.

"The negative effects of industrial sewage and dust produced in the project's construction process on environment is under control," Cao said.

The construction of the mammoth Three Gorges project started in 1994, and its major structure, the 185-meter-high main dam, was completed on May 20, which involved concrete placement of approximately 16 million cubic meters.