In our critical attempts to solve the pressing current problems of a limited water supply, it is essential that we act always with a global view to the future. Recognizing this, an international group of scholars—from the Soviet Union, Canada, Africa, and the United States—met to review together their experiences and research on the environmental effects of a number of large scale river management programs. This edited collection of their reports provides a balanced view of a vital element in the total ecosystem. Their analysis points out the urgent need to take account of long-term trends in climate, to consider all feasible management alternatives, and, especially, to manage demand (as opposed to simply increasing water supply) and to defer irreversible action until all environmental impacts are estimated.