Construction of large dams has been a controversial issue in recent years. Proponents of large dams claim that they deliver many benefits, among which are increased water availability for domestic and industrial purposes; increased agricultural production because of the availability of reliable water for irrigation; protection from floods and droughts; generation of hydroelectric power; navigation; and overall regional development which improves the quality of life of the people, including women. They argue that like any other large infrastructure development or national policy, dams have both benefits and costs. However, the overall benefits of dams far outweigh their total costs, and thus society as a whole is far better off with dams.

In contrast, opponents argue that dams bring catastrophic losses to the society, and that these societal and environmental costs far outweigh any benefits to which they may contribute. They claim that dams accentuate unequal income distributions since benefits go exclusively to the rich, while the poor slide further down the economic ladder. Further, they argue that the main beneficiaries of dams are construction companies, consulting engineers, corrupt politicians and government officials, who work in tandem to promote these structures. The poor do not benefit from the dam 'gravy train': they mostly suffer because of it.

The sweeping generalizations of the two groups mostly do not survive careful and objective scrutiny. In the cacophony of arguments and counter-arguments, what is often forgotten is that the issues involved are complex, and there is no single answer that could cover all the dams of the world, constructed or proposed, irrespective of their locations and qualities. Nor can one view be everlasting in any country: it could, and often does, change with time.

A major reason as to why the current non-productive debate on dams has thrived is because of the absence of objective and in-depth ex-post analyses of the physical, economic, social and environmental impacts of large dams, 5, 10 or 15 years after their construction. At present, thousands of studies exist on environmental impact assessments (EIAs) of large dams, some of which are very good but others are not even worth the paper on which they are printed. It should be realized that all EIAs are invariably predictions, and until the dams become operational, their impacts (types, magnitudes and spatial and temporal distributions) are not certain, and thus remain in the realm of hypotheses.

While countless studies are now available on EIAs of large dams, which were prepared prior to their construction, assessment of actual impacts of large dams, say a decade after their construction, from anywhere in the world, can be counted on the fingers of one’s hands, and still have some fingers left over. Some have now claimed that the World Commission on Dams (WCD) prepared numerous such assessments of large dams from different parts of the world. Regrettably, most of these analyses are somewhat superficial and often skewed to prove the dogmatic and one-sided views of the authors who prepared these studies. They can be considered to be neither objective nor comprehensive and definitive. It is possible that among these assessments, there are a few good case studies. Most unfortunately, however, no rigorous peer reviews of these case studies were ever carried out. Consequently, if there are some 'wheat' among the mostly 'chaff', they remain indeed very well-hidden. Thus, the so-called WCD knowledge-base of the assessments of the real impacts of large dams from different parts of the world are of very limited use to the water and development professionals, irrespective of the current rhetoric of the WCD supporters.

Because of the current undesirable situation, the Third World Centre for Water Management initiated comprehensive impact assessments (positive and negative) of three large dams that have been operational for at least 10 years. These are the High Aswan Dam in Egypt, Atatürk Dam in Turkey, and the Bhakra Nangal Project in India. The results of the Bhakra-Nangal Project have been published by Oxford University Press. More information in Publications of the Centre.

The details of the impacts analyses of the High Aswan Dam and the Atatürk Dam are being published by Springer at the end of 2010, together with the case studies of 15 more dams in different parts of the world.

Finally, the book Water as a Focus for Regional Development by Oxford University Press, examines in-depth global experiences on the roles water has played as an engine for regional development. For more information visit our Publications of the Centre.