Eos, Transactions American Geophysical Union

Report on large dams calls for balanced assessment of projects and revised decision-making process


  • Randy Showstack


Some 45,000 large dams were built around the world during the last century, which averages out to more than one new impoundment per day These structures have come with substantial development benefits—including irrigation, flood control, water supply and hydroelectric power—for millions of people. But they have also brought controversy The social costs include tens of millions of people displaced and numerous complaints that the benefits of dams are distributed inequitably Dams often have also caused dramatic changes in water flow and water quality, in aquatic biodiversity and ecosystems, and, in some cases, have led to possible excess greenhouse gas emissions from rotting vegetation in reservoirs and carbon inflows from catchments.