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| The Big Dam Debate
Case Study: Three Gorges Dam, China |
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Quick Start |
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Large (or mega-) dams (over 100 m high) have been used all over the world for flood protection and water resource management. The construction of the colossal Hoover Dam in the 1930s heralded the start of an economic and political craze for large dams that continues to the present day. They were believed to be the solution to water supply or flood problems, or as a 'green' source of power. However, the environmental (and in some cases socio-economic) problems soon became apparent. The environmental impacts of large dams on river systems are well documented. These impacts include:
Socio-economic impacts of large dams include:
As a result of environmnetal considerations, fluvial geomorphologists and some dam engineers have switched to constructing strategically-placed small dams. However, some countries and dam engineers have failed to heed these lessons and have continued to pursue the construction of large dams. So are Big Dams (over 100 m high) still the way forward in terms of flood protection and water resource management? |
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2. Introducing the Case Study: Three Gorges Dam, China The most topical and controversial large dam scheme is undoubtedly the Three Gorges Dam on the Yangtze River, China. It will be the largest man-made structure in the world. It has been constructed not only for flood protection, navigation and hydroelectric power generation purposes, but as a political statement to the world. The impact on the local populations has been immense, involving relocation of over a million people, the abandonment (and eventual inundation under dam waters) of entire cities, the drowning of archaeological sites, and destruction of the wildlife and habitats during construction. The
Three Gorges refers to towering limestone cliffs of the Qutang, Wu and
Xiling gorges, which stretch for about 200 km from Fengjie (Sichun
province) to Yichang (Hubei province) along the middle reaches of the
Yangtze. Along with the Yellow River in the north, the Yangtze is of
fundamental importance to the culture and psyche of the Chinese as well
as the economic well-being of the country. At
6 300 km long, the Yangtze (Chang Yiang, meaning Long River) ranks as
the third largest in the world and the largest in China. More than 700
tributaries drain 1.8 million km2, approximately 20% of
China's land. The river drains from the Tibetan Plateau in the east,
flows through China's largest and heavily polluted city, Chongqing, and
enters the sea in the west near Shanghai. The catchment of the Yangtze
represents 25% of entire crop land, 350 million people (33% of China's
population), 40% of grain, 70% of rice, 40% of agricultural and
industrial output in China. The
idea of a giant dam on the Yangtze at the Three Gorges was first
proposed in 1919 by Dr Sun Yet-Sen, founder of the first Chinese
republic. After floods in the 1930s killed 200 000 people, the area was
surveyed with engineers from the US Bureau of Reclamation. Following 30
000 deaths as a result of floods in 1954, the new Communist ruler Mao
Tse Tung entertained plans to design a large dam on the Three Gorges,
but after 1960 it was dropped in favour of other irrigation and drainage
projects. Over the next three decades of turbulent politics the project
fell in and out of favour. Strong citizen opposition, and scientific and
media objections, also forced the People's Congress to suspend plans.
However, the ascent of Premier Li Peng and the Communist clamp-down in
the late 1980s led to the project going ahead and construction commenced
in 1994. The Gezhouba Dam upstream was initiated as a trial run for the
project. When
completed, the Three Gorges Dam will be the largest, most expensive dam
and the largest hydroelectric power plant ever constructed, generating
eight times more power than the High Aswan Dam. The Three Gorges Dam
Project will involve a 185 m (600 feet) dam containing a reservoir 632
km (375 miles) long, 1100 m (3 600 feet) wide, maximum depth of 175 m
(575 feet), approximately 39.3 billion m3 of water and
inundating 30 000 hectares of arable land. 19 cities and 326 towns will
also be drowned. In October 1997 a diversion canal was open for
navigation and the following month the main channel was dammed. It will
take 18 years to build, and it is due for completion by 2009 AD and
fully operational in 2013 AD. Many
international funders (e.g. the World Bank and the US Export-Import
Bank) and construction firms have refused to participate in the project
boycotting because of the economic and environmental controversy
surrounding the project. Foreign financing has come from export credit
agencies, which are not restricted by environmental or human rights
regulations (unlike development agencies such as the World Bank), in
Canada, Germany, Switzerland and Japan. The projected cost is US$ 10.7
billion, but opponents claim that total costs (including the dam, new
housing, infrastructure) could amount to US$ 75 billion. Benefits
include flood control, power generation, improved navigation, economic
growth and development, and water supply. However, such a large project
inevitably has environmental, social and economic impacts. Environmental
concerns include siltation of the reservoir, and detrimental effects on
aquatic and terrestrial ecosystem through increases low flows, the
release of cold water, and clear-water erosion for a considerable
distance below the dam. It is also argued that industrial and
agricultural toxins will become concentrated because they are not
dispersed downstream, resulting in increased water pollution. It is also
envisaged that there will be increased suffering from infectious
diseases. Landslides are also a concern, not only during construction,
but also due to local tectonic disturbance possibly induced by the
crustal loading by the mass of reservoir water and the dam structure
itself. The principal social impacts include resettlement and the
drowning of archaeological sites. Economic concerns include pressures on
agriculture, forced onto higher and less fertile slopes, and disruption
of fisheries. The project has been controversial, both in China and
abroad. Repeated environmental and engineering concerns, with human
rights issues at the fore. Some Chinese dissidents, such as Dai Qing,
have been out-spoken despite political dangers. |
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This module provides a synopsis of the topic and issues, suggests useful web sites, and suggests ways of incorporating these into teaching and learning using question sheets on introductory and advanced themes, role-play and debate. The variety of web resources on the Three Gorges Dam caters for the range of learning objectives and educational levels, from GCSE to A-level and undergraduate levels. The notes for teachers contains further pedagogic information and ideas, supported by web links and references lists that comprises both pupil and teacher texts and articles. |
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The materials contained in this module are adapted from:
Regularly consult the The Geography Association website for further educational resources and range of services. |
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© British Society for Geomorphology (Education and Outreach). Author: Dave Simm, Bath Spa University College (2004). |
