Alterations of Riparian Ecosystems Caused by River Regulation

A n estimated two-thirds of the fresh water flowing to the oceans is obstructed by approximately 40,000 large dams (defined as more than 15 m in height) and more than 800,000 smaller ones Many additional rivers are constrained by artificial levees or dikes. These hydrological alterations-to ensure water for agricultural, industrial, and domestic purposes; for hydroelectricity; or for flood protection-have changed ecosystem structures and processes in running waters and associated environments the world over. In this article, we discuss the global-scale ecological changes in riparian ecosystems resulting from dam operations.