Canadian Consulting Engineer

Three Gorges Dam

Since December 2002 until this June, cruise ships and freight barges travelling down China's Yangtze River have been docking just upstream from the massive Three Gorges Dam. From there, freight and pa...

July 1, 2003  By Ted Davis

Since December 2002 until this June, cruise ships and freight barges travelling down China’s Yangtze River have been docking just upstream from the massive Three Gorges Dam. From there, freight and passengers had to embark on short overland trips to skirt the massive dam project.

Mid-June was the date that marked the end of the second phase of construction on the controversial project and the beginning of the third and final phase. The Yangtze was allowed to start flowing into the basin behind the dam, forming a vast reservoir for hundreds of miles in the valley. As the water levels started rising in the system of gorges and rivers that flow into the Yangtze, the landscape began taking its final bow before being submerged for good. This marks the biggest single jump in water level for the whole 17-year project — from 66 to 135 metres. The water will rise again to 175 metres in 2009, marking the project’s completion.

Critics of the Three Gorges project were not looking forward to this June. Damming the Yangtze, they say, will cause drastic alterations to the landscape, wreak havoc on the environment and increase pollution levels in the river. The very reasoning for the dam has also been assailed, as critics charge that there will be no demand for the levels of electricity that it can generate. Also being scrutinized are the costs in terms of human dislocation, as 22 towns near the Yangtze are demolished and their populations relocated. Then there is the loss of many important historic and archeaological sites to the newly formed manmade lake that will inundate the Three Gorges.

Proponents deny those predictions, saying that pollution will be controlled and that there will be demand for the electricity as the newly-tamed river fosters industrial growth. According to projections, about 10 per cent of China’s electricity is to be generated by the dam, which will reduce the country’s reliance on fossil fuels. The Chinese proponents also say that the immense benefits of controlling the disastrous Yangtze River floods will foster economic growth in the region. And while the new water levels will shrink the height of the gorges, they will open up new, wider waterways for tourist exploration.

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No-one can argue with the sheer proportions of the project. At 185 metres in height and 2,335 metres in length, the structure is the largest dam ever built. It is located in the midst of the Xiling Gorge, the furthest downstream of the Three Gorges or “Sanxia” in Hubei Province. Xiling Gorge is also the longest and most hazardous passage to navigate, with many hidden shoals, reefs and whirlpools. The dam is being built on a wide section of the river, at the town site of Sandouping, and is anchored by a small, mid-stream island. The raised water levels are expected not only to make shipping safer through here, but will improve access by allowing two lanes — upstream and downstream — of water traffic.

The construction involves two power plants, ship navigation facilities and the dam itself. The dam is a concrete gravity type. Amounting to a total of 26.43 million cubic metres of concrete work, it has a maximum water height of 175 metres. On either side of the central spillway are water intakes for spinning the hydroelectric turbines. At its maximum the dam can discharge 116,000 cubic metres of water per second.

Behind the dam is the massive water reservoir, 630 kilometres long and a kilometre wide. Within it are almost 40 billion cubic metres of water. Starting in June, some of that water was to start churning through the two power stations, in which are located 26 turbine generators — 14 in the powerhouse on the left side of the dam, and 12 on the right. The turbines are each designed to generate 700 MW, totalling 18,200 MW in installed capacity. Five turbines are to start producing electricity by the end of 2003, and by completion the Three Gorges project is expected to generate 84.68 billion kWh of electricity annually.

A number of Canadian companies and engineering firms have contributed to the massive project. Teshmont Consultants of Winnipeg has an ongoing contract with the China Power Grid Development Company to work on the 500 kV, 3000 MW HVDC transmission system. “This has gone quite well for us, even though it has been a very complicated job,” says Teshmont’s business development manager David Fletcher, P.Eng.. Teshmont works on nearly all China’s DC systems, he says. Teshmont’s parent companies are Stantec of Edmonton, Manitoba Hydro and AMEC of Toronto. AMEC — then AGRA — also provided project management resources in the 1990s. In the early stages of the project SNC-Lavalin of Montreal and Acres International of Toronto were involved in feasibility studies.

Starting in mid-June, when cruise ships and barges arrive at the dam they will take an extraordinary ride. Adjacent sets of ship locks allow traffic to proceed upstream and downstream at the same time. Five massive steps make up the locks, and each lock chamber has the capacity to handle a 10,000 ton freight barge. As well, a ship elevator is located next to the locks. It can raise and lower vessels weighing up to 3,000 tons.

In response to the many criticisms levelled at the Three Gorges Dam project, a Chinese official recently said, “Everything has a positive and negative act, and the Three Gorges is no exception. We must achieve a balance between both.” The test of whether the dam satisfies that criteria is about to begin.

Ted Davis is a freelance writer living in Vancouver.

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