CHINA will have seen nothing like it since the building of the Great Wall. Last month, premier Li Peng inaugurated work on the world’s largest hydroelectric dam project, the Three Gorges scheme on the Yangtze river. Its dam will be nearly 2 kilometres long and some 100 metres high, and it will consume enough material to build 44 Great Pyramids (see Map).
More than a million people will have to move to make way for the reservoir, which will stretch 600 kilometres upstream, longer than any other. Its water will drive turbines with a generating capacity of almost 18 000 megawatts, eight times that of the Aswan Dam on the Nile, four times greater than any power station in Europe, and 50 per cent more than the world’s largest existing hydroelectric dam, the Itaipu Dam in Paraguay.
Itaipu powers Brazil’s two great megacities, São Paulo and Rio de Janeiro. Three Gorges will supply power to Shanghai, the world’s fifth largest city, and fuel a $175 billion programme of economic development of the upper Yangtze River basin around Chongqing, a city of three million people, with airports and heavy industry. A consortium of international investors, headed by the American merchant bank Merrill Lynch, has been given access to markets in the region in return for its help in arranging loans for the project.
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The dam, sited at Sandouping, will take between 15 and 20 years to build, but nobody is sure how much it will cost. The Chinese government estimates $12 billion at 1990 prices. But independent estimates range from $22 to 70 billion, including interest charges and inflation. China expects to raise 90 per cent of the money itself, and has already levied a 2 per cent tax on electricity to help fund the project.
Besides powering China’s industrialisation, the Three Gorges project is designed to protect some 10 million people downstream from floods that have killed 300 000 people this century, and to open the river above the gorges to shipping. The Qutang, Wu and Xiling gorges form 180 kilometres of rapids and whirlpools, bounded by sheer cliffs rising into fog-shrouded mountains. The dam will plug the Xiling Gorge, raise water levels in all three gorges by around 90 metres and turn the churning waters into a placid slow-moving lake.
The Yangtze pours from Tibet, through the mountains of southwest China and the gorges, onto a wide floodplain and to the sea at Shanghai. It drains 1.8 million square kilometres of China and discharges 700 cubic kilometres of water to the sea each year. The floodplain provides two-thirds of China’s rice, and is home to 400 million people, or one person in 13 on the planet. Any flood is therefore disastrous. To hold back the waters, Chinese peasants under both Imperial and Communist rule, have built and raised dykes that stretch for thousands of kilometres and rise up to 16 metres above the fields. But their leaders have increasingly looked to augment the dykes with large dams to control floods before they reach the floodplain.
Sun Yat-Sen, leader of the 1911 Chinese revolution, first proposed damming the Yangtze at Three Gorges in 1919. Later, after floods killed 200 000 people in 1931 and 1935, nationalist leaders surveyed the area with American engineers. After floods in 1954, which left 30 000 dead, Mao Tse-tung called in Soviet engineers to design a dam that would combine flood protection and power generation. Over the next three decades, Three Gorges went in and out of favour, until Li Peng, a former hydroengineer, forced the project onto the current 10-year plan.
China’s engineers calculate that the country has a theoretical hydroelectric capacity of 380 000 megawatts, the world’s largest, but that only 10 per cent of this is so far tapped. They regard Sandouping as one of the best sites in engineering terms, and note that the dam will flood out only half as many people per megawatt of generating capacity as the average for Chinese dams (fewer than 70 people compared with 140).
Sandouping is also in a good position. Most of the mountain gorges that can generate large amounts of electricity are in the west of China, while the large factories that consume three-quarters of the electricity are in the east. Three Gorges is the most easterly gorge site in China. The dam will help China hold back from burning its vast coal reserves, thus reducing the country’s chronic smogs and its contribution to the greenhouse effect, which has doubled in the past 15 years.
But critics say China uses its power inefficiently. Its heavy industries typically consume twice as much energy for every tonne of output as their Western rivals. If China brought its industrial efficiency up to existing Western levels, it could cut demand by a third, making Three Gorges redundant.
And if these measures failed to end the country’s long blackouts and power rationing, they say smaller hydroelectric dams on the tributaries of the Yangtze could be brought on stream much more quickly than one giant scheme.
One of the big questions to be answered about the Three Gorges project, as with other large multipurpose dams, is what the “normal” operating level of the reservoir should be. Should it be kept as full as possible to maximise hydroelectric power? Or should it be empty in readiness for capturing floods? The situation is complicated by the need to prevent the reservoir from filling with silt brought down by the river during the annual flood. To do this, the water level should be kept low during the flood season, to allow the silty floodwaters to flow through as quickly as possible. However, if heavy floods occur, requiring downstream regions to be protected, then the reservoir would have to be filled.
Power struggle
The debate about water levels has rumbled on for many years. In 1990, the plan was to maintain the reservoir level at 160 metres above sea level, which is some 25 metres below the maximum safe height. This was to have been reduced to 140 metres during the flood season when the reservoir might suddenly have to store floodwaters. The arrangement was a compromise between flood prevention managers, who wanted a normal level of 150 metres throughout the year, and power and navigation authorities who wanted a higher level – they complained that a level of 140 metres would reduce power production substantially, and that several rapids would reappear at the top end of the reservoir near Chongqing.
In 1992 Li Peng ordered that the normal level be raised to 175 metres. As power and navigation authorities rejoiced, flood prevention managers warned that more people would need to be resettled and the risk of flooding would rise.
But even if the dam were operated primarily for flood protection, it could only shield a relatively short stretch of the river immediately downstream. This is because most floodwaters in recent disasters have come from tributaries that enter the Yangtze below the gorges. That was the case in both 1954 and, most recently, in 1991 when more than 2000 people died. Indeed the Yangtze could well become more dangerous with the dam in place. With part of its burden of silt left behind on the bottom of the reservoir, the river would be able to pick up more material and thus its current would have greater power to destroy dykes. A detailed evaluation of the scheme, the Three Gorges Water Control Project Feasibility Study funded in the late 1980s by the Canadian government’s international aid agency and the World Bank at a cost of $14 million, warned that the silt-free river would tend to alter its course, eating at banks and dykes and increasing the risk of disastrous floods. The likely death toll from a major breach of the main JingJiang dyke is put by Chinese officials at 100 000.
There are other fears. The region of the Three Gorges is seismically active and landslides are frequent. An earthquake or a landslide overtopping or breaking the dam could submerge downstream cities such as Wuhan, with a population of 4 million. And dams do fail. In 1975 the Banqiao dam in Hunan province, which held just half of a cubic kilometre of water compared with the 40 cubic kilometres to be impounded by the Three Gorges dam, failed killing an estimated 10 000 people.
American engineers who visited the Three Gorges site in the early 1980s concluded that the project would not prevent flooding. According to one, John Morris, former chief of the US Army Corps of Engineers, landslides, earthquakes or military attack could all breach the dam. They backed alternative plans drawn up by Chinese engineers for a series of smaller dams on the river’s tributaries. Philip Williams, an hydrologist and partner of the Californian consultant, Philip Williams Associates, argues that large flood-protection dams have an inbuilt tendency to create the disasters that they are designed to prevent. Williams, who is also president of the International Rivers Network, a nongovernmental organisation that often campaigns against large dams, says that large dams encourage undue confidence downstream and building in flood prone areas. If the dam were unable to hold back a future flood, “the loss of life would be greater than if the dam had never been built”, he notes. And he believes that “the consequences of failure at Three Gorges would rank as history’s worst man-made disaster”, on a par with the estimated loss of between 300 000 and more than one million people when Chinese generals deliberately broke dykes on the Yellow River to halt an enemy advance at the height of the Sino-Japanese War in 1938.
The dam should allow large ships unimpeded passage up the Yangtze, through ship locks at the dam and along the tranquil reservoir as far as Chongqing. The Ministry of Communications predicts that shipping traffic will increase fivefold to 50 million tonnes per year once the dam is built. But again there are complications. At the 140-metre operating level, rapids would reappear and, during the two decades of construction, existing boat traffic would be severely disrupted.
And there are doubts about whether Chongqing port, the intended destination for the shipping, can survive the creation of the reservoir which will have its head close by. As river waters enter the reservoir and the speed of flow drops, much of its silt will settle onto the reservoir floor, forming a fan of sediment that may destroy the city’s port, without massive dredging. And it may also increase the risk of flooding in the city.
Against the problematic benefits of the dam are some all-too-tangible disbenefits. Up to 1.2 million people will have to move to make way for the dam and reservoir. The precise number depends on final decisions about the normal water level in the reservoir. The reservoir will inundate dozens of towns including the city of Wanxian, an unlovely industrial town of 140 000 people, and Fuling, with a population of 80 000 people. And it will lap at the banks of the homes of Chongqing’s 3 million people. Building new houses for these people will be the largest dam resettlement programme ever attempted anywhere in the world. Already tens of thousands of people have been moved.
The Chinese government says it will spend up to $4 billion on resettlement, mostly on rebuilding towns on higher ground. The original idea was for the 300 000 farmers who will lose their land to move farther up the hillsides. But, says the Canadian study, more than half the land available for resettling farmers is more than 800 metres above sea level. These remote hillsides are colder with poorer soils and will grow many fewer crops. A study by soil scientists in 1991 at the Chinese Academy of Sciences concluded that five times as much new land would be needed to replace the fields in the valley bottom than would be lost to the reservoir.
How long will the reservoir so expensively created actually last? Engineers round the world are increasingly worried about the accumulation of silt in large reservoirs, with many lasting only a few decades (“A dammed fine mess”, New Scientist, 4 May 1991). On the Yellow River in China, the reservoir behind the Sanmenxia Dam filled with silt within four years of opening in 1960, and was emptied, dredged and rebuilt. The reservoir today has less than half of its original capacity.
The Yangtze is not as yellow as the Yellow River, but it carries 530 million tonnes of silt through the gorges each year. The first dam on the river, the Gezhouba Dam, regarded as a test run for the Three Gorges, lost more than a third of its capacity within seven years of opening. Lin Bingan, a silt expert on the project, warned earlier this year that to avoid a similar fate at Three Gorges: “During the high-water season the reservoir should be kept at a lower level, allowing water and silt to flow into the lower reaches of the river as much as possible.” If operated in this way, with water levels kept to 140 metres during the flood, Chinese government engineers estimate that only 10 per cent of the reservoir’s capacity will be lost.
Nevertheless, there are considerable uncertainties in these calculations. They assume the river will erode many of the sand bars it creates during the flood season, a process known as retrogressive scouring. But Shiu-hung Luk, a Chinese soil scientist now at the University of Toronto, says retrogressive scouring occurs only near the dam. It will not occur 600 kilometres away at the head of the reservoir, where the majority of the silt at Three Gorges will accumulate. If it does not, the risks of flooding in Chongqing would increase greatly, he says.
To reduce the river’s silt load, China’s Ministry of Forestry announced in 1993 that it plans to double the upper Yangtze valley’s tree cover to 40 per cent within 40 years in order to bind the soil and reduce erosion. But there are no examples anywhere in the world of reforestation projects having an effect on the flow of river silt on this scale. Moreover, other factors could increase the silt load. The thousands of people forced to farm steep hillsides above the flooded river valley are likely to increase soil erosion. And Shiu-hung Luk warns that the Yangtze’s silt load is currently reduced by small dams in tributaries upstream that collect silt. “Within a few decades, these reservoirs will become clogged. They will have to be flushed out, causing a significant increase in the river’s total sediment load.”
Naturally, the full impact of the dam on the environment is as yet unknown. Some warnings may be exaggerated. The dam will undoubtedly interrupt fish swimming upstream. However, their way is already blocked by the much smaller Gezhouba Dam downstream, says Philip Fearnside of Brazil’s National Institute for Research in the Amazon, who has investigated the impact of large dam projects worldwide. Existing disruption to the river’s hydrology and silt flows will be drastically worsened by the Three Gorges Dam, however. Much of the floodplain of the lower Yangtze is farmed using traditional methods that are dependent on the seasonal fluctuation of the river to provide free irrigation and wetland grazing for animals. But with the Three Gorges dam in place, the flood regime will drastically change.
Among endangered species downstream of the dam are the 300 surviving White Flag dolphin and the 500 surviving Chinese alligator, as well as Chinese sturgeon and finless porpoise. Most of these species are in serious decline. But the dam could be the final straw. Most of the world’s Siberian white cranes winter on Poyang Lake, where they eat weeds rooted to the lake bottom. Changes to water levels in the lake during that season could eliminate this food source, and threaten the species’ survival. But China is unlikely to abandon its plans to save a few species that are, arguably, already doomed.
Browned relics
Internationally, there may be greater concern about the destruction of archaeological treasures in the Yangtze valley. More than a hundred major cultural and historic sites will be inundated. Already there are calls for an effort to save the best of them, along the lines of the efforts in Egypt during construction of the Aswan Dam. China’s National Bureau of Cultural Relics says it will move several major temples, such as Zhang Fei, to higher ground. But the ancient city of Fengdu (the City of Ghosts), one of the capitals of the Ba Kingdom, will be largely lost, as will much of the 2000-year-old plank road through Wuhan and Wuqi and hundreds of lesser archaeological sites, many not yet explored.
China’s decision to go ahead with Three Gorges is a major shot in the arm for the world’s dam builders. After the investment of hundreds of billions of dollars over the past five decades or so in one of the great postwar engineering enterprises, dam-building has seemed to founder in the past five years. A history of cost overruns and corruption scandals, growing concern about the environmental impact, civil unrest arising from failed resettlement programmes and the campaigning of an international network of anti-dam protesters, have all undermined the case for giant dams.
Last May, Daniel Beard, the commissioner of the US government’s Bureau of Reclamation, which built the Hoover and Grand Coulee dams and dozens of others, said that “the dam-building era in the US is over”. He told delegates to a meeting of the International Commission on Irrigation and Drainage that most projects cost 50 per cent more than predicted and that “often, project benefits were never realised”. In Canada, the grand and controversial James Bay hydroelectric project was halted last year. And in Australia last year, scientists were pushing a plan to drain the giant reservoir created 20 years ago when Lake Pedder in Tasmania was converted into a huge hydroelectric reservoir.
In Africa, the money for giant dams has run out as Western aid agencies withdraw funds. The World Bank, which had lent $60 billion for dams over 50 years, has got cold feet, with funding more than halved in the 1990s. Britain’s Overseas Development Administration stopped funding large dams even before the Pergau Dam scandal broke, concluding they were usually bad value for money and had hidden environmental and social costs.
Only in Asia are governments determined to continue to build dams, with or without international aid. Within days of the public inauguration of Three Gorges, the countries along the Mekong, which include Vietnam, Thailand, Laos and Cambodia, announced the formation of a new organisation to begin dam-building on the river. India has persisted with the controversial Sardar Sarovar Dam on the Narmada river, despite losing World Bank support. And late last year, it resumed construction of the 250-metre high Tehri Dam in the headwaters of the Ganges. Malaysia, fresh from its battles with Britain over aid funding for the Pergau Dam, announced the go-ahead for a 230-metre high dam in the rainforest of Borneo.
Now the Three Gorges project has created a honey pot that few construction companies or governments can resist. At the height of environmental concern about large dams at the end of the 1980s, Canada’s Liberal Party said the project would “impoverish and dislocate millions of people, spread debilitating diseases [and] endanger rare species”. But last November, Jean Chretian, the country’s premier and Liberal Party member, urged Canadian companies to capitalise on the detailed feasibility study completed earlier. The US government, which two years ago expressed concern about the project’s impact and refused to get involved, is now also considering renewing its backing to help ensure American companies win contracts. The signs are that, with environmental concerns on the retreat worldwide, the drive to build large dams may be resuming.
Today, there are more than 100 “super-dams” with heights greater than 150 metres. Their reservoirs cover 600 000 square kilometres, an area greater than the North Sea, and have a capacity of 6000 cubic kilometres, equivalent to 15 per cent of the annual runoff of the world’s rivers.
Of the world’s 30 largest rivers, apart from those flowing into the Arctic, most have dams across them, holding back substantial parts of their flow. They include the Ganges, Parana, Tocantins (a major tributary of the Amazon), Columbia, Zambezi, Niger, Danube, Nile and Indus. After the Yangtze has been dammed, engineers will be left with only two major rivers to plug: the Zaire and the main stem of the Amazon.