QUESTIONS AND ANSWERS
the international movement against large dams...
Q. What is a large
dam? How many large dams are there?
A: A large dam is defined by the dam
industry as one higher than 15 metres (taller than a four-story
building). There are more than 40,000 large dams worldwide. There are
more than 300 major dams - giants which meet one of a number of criteria
on height (at least 150 metres), dam volume and reservoir volume.
Q: Which countries
have the most large dams?
A: China has around 19,000 large dams.
The US is the second most dammed country with some 5,500 large dams,
followed by the ex-USSR, Japan and India. Brazil is in tenth place with
around 516 large dams. The US has the most major dams - 50 - followed by
the ex-USSR, Canada and then Brazil with 16.
Q: How many are being
A: The rate at which large dams are
completed has declined from around 1,000 a year from the 1950s to the
mid-1970s to around 260 a year during the early 1990s. More than 1,000
large dams were under construction at the beginning of 1994. The
countries with the most large dams under construction are currently
China, Turkey, South Korea and Japan.
Q: Why is there so
much opposition to large dams?
A: Large dams have provoked opposition
for numerous social, environmental, economic and safety reasons. The
main reason for opposition worldwide are the huge numbers of people
evicted from their lands and homes to make way for reservoirs. The
livelihoods of many millions of people also suffer because of the
downstream effects of dams: the loss of fisheries, contaminated water,
decreased amounts of water, and a reduction in the fertility of
farmlands and forests due to the loss of natural fertilizers and
irrigation in seasonal floods. Dams also spread waterborne diseases such
as malaria, leishmaniasis and schistosomiasis. Opponents also believe
that the benefits of dams have frequently been deliberately exaggerated
and that the services they provide could be provided by other more
efficient and sustainable means.
Q: How many people
have been displaced by dams?
A: Between 30 and 60 million, the
majority of them in China and India. At present perhaps 2 million people
are displaced every year by large dams.
Q: Aren't people
displaced by dams fairly compensated?
A: In nearly every case which has been
studied, the majority of people evicted - usually poor farmers and
indigenous people - are further impoverished economically and suffer
cultural decline, high rates of sickness and death, and great
psychological stress. In some cases people receive no or negligible
compensation for their losses. Where compensation is given, cash
payments are very rarely enough to compensate for the loss of land,
homes, jobs and businesses and replacement land for farmers is usually
of poorer quality and smaller than the original holdings.
Q: How much land has
been flooded under reservoirs?
A: More than 400,000 square kilometres -
the area of California - have been inundated by reservoirs worldwide.
This represents 0.3 percent of the world's land area, but the
significance of the loss is greater than the figure suggests as river
valley land provides the world's most fertile farmland, and most diverse
forests and wetland ecosystems.
Q: Have many people
been killed in dam collapses?
A: More than 13,500 people have been
swept to their deaths by the roughly 200 dams outside China which have
collapsed or been overtopped during the 20th century. Two large dams
which burst when a massive typhoon hit the Chinese province of Henan in
August 1975 left an estimated 80,000 to 230,000 dead. This disaster was
kept secret by the Chinese government and was only revealed to the
outside world in 1995. People have also died in earthquakes caused by
the great weight of water in large reservoirs. A magnitude 6.3
earthquake caused by Koyna Dam in India in 1967 killed around 180
Q: What are the benefits
provided by large dams?
A: The majority of large dams are built
for irrigation; almost all major dams are built for hydropower. Nearly
one-fifth of the world's electricity is generated by dams. Dams also
provide flood control, supply water to cities, and can assist river
navigation. Many dams are multipurpose, providing two or more of the
Q: Surely we need dams
to produce cheap and clean electricity?
A: Hydroelectricity is cheap to produce -
once the dams are built. The problem is the huge costs of building dams
and the long time it takes to build them. The Itaipu Dam, for example,
cost $20 billion and took 18 years to build. Actual costs for hydropower
dams are also almost always far higher than estimated costs - on average
around 30 percent higher. Dam designers are often very optimistic about
how much power their dams will produce and often fail to account for the
impacts of droughts, meaning that dams often produce less power than
promised. Itaipu generates around 20 percent less electricity than
When these high costs, delays and risks
of low river flows are factored into calculations of the costs of
electricity it can be seen that hydropower is now an expensive form of
power generation. Hydropower should not be considered as clean power
because of the destruction of river ecosystems and its many social
impacts. Internationally, private investors in power projects are
largely avoiding large dams and prefer to invest in cheaper and less
risky gas-fired power plants.
Q: What forms of power
generation do large dam critics support?
A: Electricity use in most parts of the
world is extremely wasteful. The priority before building new power
plants should always be to improve the efficiency of existing energy
supply and use. When new power plants are clearly needed, most
environmentalists favor the use of solar and wind power, which are now
on the verge of becoming commercially viable. Until these renewables are
viable, gas-fired generation is cost-effective and has a far lower
environmental impact than coal or oil-generation. Small dams can be a
sustainable and economic source of electricity, especially in rural
Q: Are dams an
effective method of stopping flood damage?
A: Dams can stop regular annual floods
but often fail to hold back exceptionally large floods. Because dams
lead people to believe that floods are controlled, they lead to
increased development of floodplains. When a large flood does come,
damages caused are often greater than they would have been without the
Q: Are there other
ways of supplying water to farmers and cities?
A: Most water from large dams goes to
farmers - only a very small percentage goes to cities. Irrigation
systems around the world are in general very wasteful of water. The
cheapest and most effective way of providing more water to cities is
therefore to increase the efficiency of irrigated agriculture. The
benefits of irrigated agriculture have in any case been seriously
overstated - many large irrigation schemes have displaced huge numbers
of small landholders and replaced traditional farming systems wih
agribusiness plantations producing expensive crops for cities and for
export, increasing landlessness and rural hunger. Improving leakage and
waste in urban water supply systems is also important.
Q: Do critics of large
dams oppose all dams?
In general, opponents of large dams do
not believe that no dam should ever be constructed. They do believe that
dams (and other development projects) should only be built after all
relevant project information has been made public; the claims of project
promoters of the economic, environmental and social benefits and costs
of projects are verified by independent experts; and when affected
people agree that the project should be built.
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