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Dams: What They Are and What They Do
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Frequently Asked Questions About Dams

Q: Why is there so much opposition to large dams?

Large dams have provoked opposition for social, environmental and economic reasons. The main reason for opposition worldwide is the forced eviction of huge numbers of people from their homes to make way for reservoirs created by dams.

Millions of people around the world also suffer from the downstream impacts of dams, which can include loss of fisheries, decreased water quality and a decline in the fertility of farmlands and forests due to the loss of natural fertilizers and seasonal floods that healthy rivers provide. Dams also spread waterborne diseases such as malaria and schistosomiasis.

The benefits of dams are also frequently exaggerated, and their costs underestimated by dam promoters. This has prevented more efficient and sustainable alternatives from being implemented.

Q: How many people have been displaced by dams?

An estimated 40 to 80 million people have been displaced by dams. At present perhaps 2 million people are displaced every year by large dams. This does not take into account people whose livelihoods are impacted by dams

Q: Don’t people displaced by dams share in the benefits, and get compensated for their losses?

In nearly every case, the majority of people evicted by dams end up further impoverished, and rarely share in the benefits. They suffer cultural decline, high rates of sickness and great psychological stress. The ones who suffer are typically those most marginalized in society – poor farmers and indigenous people. In some cases, people receive no or negligible compensation for their losses. Where compensation is given, cash payments are rarely enough to compensate for the loss of land, homes, jobs and businesses.

Dam–affected communities are often promised great improvements such as electricity, new clinics and improved schools. Such promises are often broken.

Q: How big is the peoples’ movement against large dams?

The movement against large dams is comprised of thousands of environmental, human rights, and dam–affected peoples’ groups across the world. The movement does not just try to stop destructive dam projects, it also advocates for affordable, community–based methods of providing water and energy to the millions of people currently without access to these essential needs.

The movement is particularly strong in developing countries with large numbers of dams and poor records of forcible resettlement. Brazil and India boast large national organizations devoted to helping dam–affected communities and pressing for better alternatives. Even in China, where it is often a criminal offense to oppose the government in any way, massive demonstrations to protest large dam projects have taken place, and a growing environmental movement is becoming increasingly vocal about the impacts of large dams.

Q: Surely we need dams to produce cheap electricity?

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. Actual costs for hydropower dams are almost always far higher than estimated costs; in a number of cases, the actual cost was more than double the estimated cost. The Itaipu Dam in South America cost $20 billion and took 18 years to build. This was 488% higher than originally estimated.

Dams often produce less power than promised. Dam promoters frequently overestimate how much power their dams will produce and fail to take into account the impacts of droughts. In addition, the transmission lines needed to distribute the power generated by the dam are often inefficient and expensive. When these factors are taken into account, hydropower is actually a very costly form of power generation.

Where hydropower is indeed cost–effective then it certainly should be one of the energy options to be considered, but only through a comprehensive and transparent planning process that takes into account the social and environmental impacts of the project.

Q: But don’t dams produce "clean energy?"

Dams cannot be considered to be clean sources of electricity because of their serious social and environmental impacts. In addition, studies reveal that rotting organic matter in dam reservoirs produce greenhouse gases. In some cases, especially in the tropics, reservoirs can produce more greenhouse gases than even the dirtiest fossil fuel power plants. The Balbina Dam in the Brazilian Amazon is estimated to produce 20–40 times the amount of carbon dioxide produced by coal fired power plants.

Q: How can we reduce poverty in developing countries unless we exploit all available power sources, including hydro?

Like other investments, funding for the power sector in developing countries will always be limited. It should therefore be directed toward uses that are most beneficial. Better processes for selecting energy projects can help avoid the political favoritism (and even bribery) that now often influences the decision–making process, and too often leads to white–elephant dams being built.

The World Commission on Dams, an international panel that provided the first independent and comprehensive assessment of dams, devised an approach to dam–planning that would ensure affected communities are able to negotiate their own compensation packages, and would be primary beneficiaries of dam projects’ benefits.

Dams planned using the commission’s recommendations and guidelines are more likely to have been chosen only after carefully analyzing all available options, and through a fair and transparent planning process. Some countries – for example, South Africa – have taken steps to incorporate the WCD’s recommendations into their planning processes for water and energy projects.

Q: What forms of power generation do large dam critics support?

No energy source is a panacea to the world’s growing energy needs. The key is an open assessment of needs and the costs and benefits (and the distribution of these costs and benefits) of the various options for providing them. But one of the first "sources" of energy we need to address is in reducing waste of electricity. 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. Energy losses through inefficient systems are huge even in developing countries with low production of electricity. As an example, almost 50% of power generated in India is lost before reaching the consumer. Indian energy analysts have estimated that improved efficiency could provide the entire increase in energy supply supposed to be needed over the next decade, at a fraction of the cost of new supply.

When new power plants are clearly needed, most environmentalists favor the use of renewable energy sources such as wind, solar, and geothermal power. Biofuels and turning agricultural waste into power are also advancing. Small dams can be a sustainable and economic source of electricity, especially in rural areas. All of these options can help bring electricity to the parts of the world that need it most: rural communities far from national electricity grids.

Q: What about the jobs produced by dams?

A: In developing countries (where most dams are being built today), most jobs to design and build dams go to highly trained engineers and contractors who are brought in to build the project, not local people and often not even citizens of that country. Maintaining dams provides many fewer jobs, so the long–term jobs benefit is often minimal. Wind power creates 4–10 times more jobs per unit of output than large hydro (and biomass and solar power can create many more jobs than wind).

Q: Are dams an effective method of stopping flood damage?

Dams can stop regular annual floods but often fail to hold back exceptionally large floods. Because they give people a false sense of security, dams can lead to increased development of floodplains. When large floods do occur, damages caused are often greater than they would have been otherwise.

Q: Are dams a safety concern?

The global stock of dams as a whole is ageing, and as dams get old they become increasingly more expensive to maintain. Around the world, 5,000 large dams are at least 50 years old; the average US dam is in its forties. Worldwide, as in the US, there is systematic underfunding of dam maintenance. It would cost billions of dollars to bring the world’s dams to safety.

Today, the biggest dam–safety challenge is climate change. The world’s more than 45,000 existing large dams have not been built to allow for a rapidly intensifying hydrological cycle. In this sense, all dams should now be considered unsafe. While the climatic future is filled with uncertainties, climatologists almost universally agree is that we will see (and indeed are already seeing) more extreme storms and increasingly severe floods – which will have major implications for dam safety.

Q: Are there other ways of supplying water to farmers and cities?

Most water from large dams goes to large agriculture plantations – 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.

In addition, the benefits of irrigated agriculture have 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.

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