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 built today?
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 1000 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 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 original holdings.
Q: What happens when people refuse to move to make way for dams?
A: In many cases people have been forced out of their homes at gunpoint,
in others they have simply been flooded out when the dam authorities
started to fill the reservoir. In Guatemala in 1982, 369 Mayan Indians,
mainly women and children, were murdered after their community refused to
accept the inadequate compensation offered for the loss of their homes to
the Chixoy Dam.
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 per cent 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 earthquakes caused by Koyna Dam in India in 1967 killed
around 180 people.
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 above benefits.
Q: Surely we need dams to produce cheap and clean electricity?
Hydroelectricity is cheap to produce -- once dams are built. The problem
is the huge costs of building dams and the long time it takes to build
them. Itaip� 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 per cent 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. Itaip� generates around 20 per cent
less electricity than predicted.
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 areas.
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 dam.
Q: Are there other ways of supplying water to farmers and cities?
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 with
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.
For further information, please contact:
Day of Action Coordinator
International Rivers
1847 Berkeley Way
Berkeley, CA 94703 USA
tel: +1 510 848 1155
fax: +1 510 848 1008
e-mail: dayofaction [at] internationalrivers [dot] org
