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Dams and Development E-Paper Contents

p. -1 of 74 BACK | NEXT Home Page of Dams and Development Foreword I. Why an e-paper on dams and development? II. Assessing options III. Participatory processes IV. Social impacts V. Environmental impacts VI. Benefit distribution VII. Dam safety and sustainability VIII. Existing projects IX. Improving governance X. What other organizations say XI. ADB, Dams, and Development XII. References Contact Us

International Energy Agency - on Cumulative Impacts

As part of the its Implementing Agreement for Hydropower Technologies and Programmes, the International Energy Agency (IEA) has prepared a series of Technical Reports including Hydropower and the Environment (Annex III). Appendix G deals with cumulative impacts. The following are extracts from this appendix:

'One major challenge in the CIA [cumulative impact assessment] is determining impact significance. Even if legal frameworks usually establish who will decide whether an impact is significant or not, the matter about how to do so is less obvious, as it involves probabilities, such as the probability of occurrence as well as the degree of scientific certitude that can be associated to the assessment results. In order to state about potential cumulative impacts the following factors may provide indications about significance:

• exceeding a threshold
• the efficiency of mitigation measures
• the size of the investigation area / study zone
• the rarity of a species
• the importance of local effects
• the magnitude of change in relation to the variability of the natural environment
• the engendering of inducted effects. (page G3)

Finally, some useful questions to ask in assessing Cis are:

• What are the valued environmental components2 that might be affected?
• How does the proposed project combined with other existing and planned activities affect the condition of these valued environmental components?
• What is the probability that these effects may occur?
• Are the resulting effects unacceptable?
• Are these effects permanent ? If not, how long will it take before recovery?
• What is the probable extent as well as the probable duration of these effect?
• What additional accumulation of effects the valued environmental components can tolerate before they may undergo an irreversible alteration of their conditions?
• What degree of certitude can be related to the estimates concerning the occurrence and the magnitude of these anticipated effects?
• And finally, what are the cumulative impacts of the next best alternative to the project? (page G4)

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