Impacts of Large Dams: A Global Assessment

The clue to the contents of this book is in the title. The book contains a collection of objective case studies on the impacts of large dams. A number of leading and respected specialists were selected to prepare case studies on the impacts of large dams –both positive and negative. These case studies were discussed at several workshops and then the analyses were modified before publication.

Until the 1970s, dams were assumed to benefit society; but then, through to the publication of the Report of the World Commission on Dams ‘Dams and Development: a new framework for decision making’, the debates became increasingly emotional, dogmatic and confrontational.

In the late 1990s, the anti-dam lobby seemed to reach its peak, but at the same time many of the developing countries started to unite behind the fact that large water infrastructure projects are essential for economic development, but also recognizing that social and environmental issues have to be at least considered.

Chapters in this book look at a number of specific sites including the Sobradinho dam in Brazil, the Atatürk dam in Southeast Anatolia, Turkey, the King River Power Development in Australia, the Kangsabati, Bhakra-Nangal and Koyna dam projects in India, and the High Aswan dam in Egypt.

The Sobradinho dam was built as a multipurpose structure, and has achieved benefits in terms of hydro generation, social improvements, navigation, flood control and irrigation. Negative effects include sedimentation (although in this case there are benefits in some places as regards deposition), and also areas where erosion is taking place, possible salt water intrusion into coastal aquifers and reduction in fish stocks.

However, it is reported that work is now in hand to mitigate some of these effects.

The GAP project, which included the construction of the Atatürk dam, was established to improve one of the less developed regions of Turkey. The main direct benefits of the dam are seen to be hydro generation and irrigation, but it is also clear that the dam has played a major role in improving economic growth and regional development.

The King River Power Development in Tasmania was developed at a time when the controversy associated with large dams was raging, and hence the scheme was changed to incorporate concerns from the local communities regarding the environmental changes which could result from the construction. The scheme led to the development of a formalized environmental management system by Hydro Tasmania. An organization has been created which understands and promotes the concepts of sustainability, based on an understanding of the wishes of the country at large.

Another case study looks at the impacts of the Kangsabati project, and gives a significant amount of data, which enable the reader to assess the benefits and disbenefits of the scheme as built.

Many positive effects are demonstrated, including: enhanced crop production; increased irrigation; flood alleviation; water supply; social improvements in terms of health, education and literacy; and, improved road and transport infrastructure. Negative effects have included loss of forest, and some effects on wildlife, flora and fauna as a result of submergence.

The case study on the Aswan dam illustrates that the cost of construction was recovered in only two years! The dam has made a significant contribution to the economic survival of Egypt having protected the country from both droughts and floods.

The case study shows that the assessment and analyses of a large dam project are extremely complex and challenging, and suggests that many people have come to completely erroneous conclusions as a result of conducting simplistic analyses. The chapter on Aswan presents a significant amount of information and concludes by suggesting that the High Aswan dam is one of the ‘most successful hydraulic structures of the world’.

The book also presents a review of dams in Switzerland, a country where the dams are seen to be a significant contributor to the production of electricity and to the provision of flood protection.

There are a number of chapters which deal with the sensitive issue of resettlement, with chapters from China, Argentina, as well as one which deals more generally with large dams around the world and includes a significant amount of useful analytical data.

Greenhouse gas emissions and indirect economic inputs are also discussed in detail.

In conclusion, this is a very readable book with a number of well balanced analyses of schemes, as well as some detailed chapters on the wider issues associated with large dams.

The authors, many of whom are eminent specialists in their field, seem to have achieved a sensible balance as they consider the benefits and disbenefits of dams. For the first time we seem to have a coherent and balanced treatise on a number of large dams.

The final edited version provides a comprehensive compilation of useful material, while demonstrating the multiple benefits of large water infrastructure schemes. At the same time, readers are warned that the disbenefits and concerns of the past must be taken into account, and measures taken to try to reduce the negative impacts which could arise in the schemes.

Overall, this is an extremely helpful book for those who are planning, promoting and engineering large dam schemes.

Andy Hughes
Honorary Vice-President, ICOLD Director of Dams & Water Resources Atkins Ltd, UK
Published in Hydropower and Dams