Friday, October 29, 2010
The latest concerns have been its effect on the Earth's rotation, as the water level at the world's largest hydropower project reached its designed highest mark of 175 meters on Tuesday.
Typing the key words "three gorges earth rotation," Google's search engine showed 3,280 results, many with such sensational headings as "China's Monster Three Gorges Dam Will Slow The Rotation of The Earth."
"This is just an updated version of earlier criticism claiming the project would trigger earthquakes due to its mass," said Chen Houqun, a member of the Chinese Academy of Engineering.
He said the Three Gorges is the world's largest hydro-power project, in terms of its installed power generating capacity and dam construction, not its maximum water holding capacity of 39.3 billion cubic meters, which only ranks 22nd in the world.
Prior to the 1960s, there had already been six reservoirs on Earth, each with a water holding capacity larger than the Three Gorges. The largest one is in Zimbabwe, and the smallest in Canada.
"Compared with them, the effect of the Three Gorges on the Earth's rotation can be ignored," said the academician.
Cao Guangjing, chairman of China Three Gorges Project Corporation (CTGPC), developer of the project, said since the dam began "trial operations" at high water levels of close to 175 meters this year, the largest earth tremor detected near the reservoir area was measured at 2.3 on the Richter scale and located in Badong County, Chongqing Municipality.
"Both intensity and frequency of the quakes were even lower than that recorded in 2008 and 2009, when the water level was kept at 135 meters and 156 meters, respectively, " he said.
Cao said Tuesday that the water level would be maintained at 175 meters for about two months for surveillance and then be allowed to drop. In the future, the water level would be kept at between 145 meters and 175 meters, depending on flood control needs.
Pan Jiazheng, a member of both the Chinese Academy of Sciences and the Chinese Academy of Engineering, said the gigantic hydro-power project has been controversial from the beginning, but criticism has helped prompt authorities to take extra measures, ensuring the project's efficiency and safety.
"I was one of the opponents of the project," he said.
Pan added that he was opposed to the dam for three reasons: The project would cause sediment build-up problems, it caused the unprecedented relocation of millions of people, and huge investments were allocated that might overburden the government's finances.
The Chinese government launched its feasibility study of the Three Gorges Project in 1984 after 30 years of reconnaissance and preparation work. Two years later, when the State Council invited 412 experts to review the feasibility reports, Pan, then chief engineer of the hydro-power department of the Ministry of Energy, was appointed as deputy director of the expert group.
"As an opponent, I was aware that the government was ready to hear different opinions and trusted expertise in the reasoning of the feasibility," said Pan.
In the ensuing three years, dozens of subsidiary panels were set up to tackle the key problems raised by critics, including possibilities of geological and ecological disasters, hydrological problems, sediment, budgets, relocation, flood-control, navigation on the Yangtze River, comprehensive economic benefits and other issues.
The final conclusion drawn by Pan's group was that the project could bring more merits than negative effects.
"Looking back, we have seen many doubts and questions were invalid. But the opposing views have prompted the authorities to be prudent in their decision-making and continuously improve its management, construction standards and boost the technological renovation," Pan said.
According to CTGPC, the total investment on the project reached 185 billion yuan (27 billion U.S. dollars), including money spent for relocating residents, by the end of 2009.
This amount is within the predicted budget in the 1989 feasibility report proposed by Pan's group.
Regarding the sediment problem, the latest monitoring results suggested the reservoir could maintain 90 percent of its water holding capacity after operating for 100 years at the current speed of silting.
The results were even more optimistic than the previous design for avoiding sediment pile-up at the dam, which was aimed to maintain the capacity at 85 percent 100 years later.
Cao said the resolution of the sediment problem should be attributed to "opponents" led by Huang Wanli, who warned that the danger of sediment piling up could ruin the project.
"Silting has been listed by the developers of the Three Gorges Project as one of the major technical problems that they faced. A lot of investment has gone into resolving the problem," said Prof. Wang Jun, a Chinese water control specialist with the Yangtze River Water Resources Committee.
Further, CTGPC chairman Cao said storing water at the dam's full capacity does not mean complete success for the project. It does, however, allow for testing of various public concerns and doubts raised since the very beginning, such as the functioning of key equipment, geological disasters and water quality.