Altering the Natural Flow

Abstract

Abstract The natural flow of the vast majority of rivers in the northern hemisphere has been altered, and such alterations are now ongoing on a massive scale in South America, Africa, and Southeast Asia. Dams greatly change historical flow regimes used by native fishes, block anadromous fish migrations, change water chemistry, and alter the riparian vegetation community and wildlife usage by blocking the flood pulse. Interbasin transfer of water from a river to a different watershed has occurred on large scales, such as in the Colorado River; such water diversions have strong impacts on fisheries, aquatic-based economics, and even international relations. Deciding what to do regarding water use in a given river requires stakeholder contributions, data gathering, and adaptive management approaches. With the availability of water in some regions now imperilled, advances in water conservation techniques and even wastewater recycling are now becoming critical to maintaining liveable cities in arid regions of even the wealthiest nations.