Managing the environmental impact of dams

In its final report, published in November 2000, the World Commission on Dams concluded that the benefits derived from large dams have made a significant contribution to human development. However, in many cases the environmental and social costs have been unnecessary and, by present standards, unacceptable. Often negative impacts arise as a consequence of lack of foresight and because dams are planned and managed in isolation from other developments occurring in a catchment. Given the huge number of existing dams and the large number that may be built in the future, it is clear that humankind must live with the environmental and social impacts for many decades to come. Consequently, there is a need to improve environmental practices in the operation of both existing and new dams. This paper provides a brief review of the consequences for ecosystems and biodiversity resulting directly from the presence of dams on rivers. Strategies to protect the environment are described. A prerequisite for successful environmental protection is that dams are managed within the specific environmental, social and economic context of the catchment in which they are situated.