1. What's it all about?

All dams and reservoirs as many other human activities, become a part of their environment which they influence and transform to a degree and within a range that vary from project to project. Frequently seeming to be in opposition, but not necessarily irreconcilable, dams and their environment interrelate with a degree of complexity that makes the task of the dam engineer particularly difficult. The solution must be to find the golden mean by striking a balance between divergent, and sometimes contradictory goals.

We need dams and the many benefits which their reservoirs offer all over the world, by storing water in times of surplus and dispensing it in times of scarcity. Dams prevent or mitigate devastating floods and catastrophic droughts. They adjust natural runoff with its seasonal variations and climatic irregularities to meet the pattern of demand for irrigated agriculture, power generation, domestic and industrial supply and navigation. They provide recreation, attract tourism, promote aquaculture and fisheries, and can enhance environmental conditions. Thus, dams and reservoirs have become an integral part of our engineered infrastructure, of our man-made basis of survival. Still more dams will be needed in the future for the adequate management of the world's limited, unevenly distributed and in many places acutely scarce water resources (see also Annex A ). But more and more we also recognize an urgent need to protect and conserve our natural environment as the endangered basis of all life. And there is also a social side to the comprehensive conception of environment: the people, their land and settlements, their economy and traditions. The impact of dams and reservoirs on this environment is inevitable and undeniable; land is flooded, people are resettled, the continuity of aquatic life along a river is interrupted, and its runoff modified and often reduced by diversions.

Thus, dam engineers find themselves confronted with the basic problems inherent in the transformation of the natural world into a human environment. In our never ending quest to provide a growing number of people with a better life, the need to develop natural resources, including water, means that the natural environment cannot be preserved completely unchanged. But great care must be taken to protect the environment from all avoidable harm or interference. We must cooperate conscientiously with nature's inherent fragility as well as its dynamism without ever overtaxing its powers of regeneration, its ability to adapt to a new but ecologically equivalent equilibrium. And we must ensure that the people directly affected by a dam project are better off than before.

The contribution of dam engineers to the development of water resources is based on proven technology, as our profession's track record of over 39 000 [According to the criteria of the ICOLD World Register, dams higher than 15 m (or higher than 10 m but with more than 500 m crest length, or more than 1 million m 3 storage capacity, or more than 2 000 m 3 /s spilling capacity)] large dams clearly shows. This technology continues to benefit from ongoing refinement and a steady growth of knowledge and experience, in particular with regard to its social and environmental consequences. Guided by the concept of sustainable development, ICOLD will make every effort to make the contribution expected of a leading professional organization to the further improvement of dam engineering. This contribution will reflect increased environmental sensitivity as well as the traditional technical excellence.