nurek dam, in tajikistan, is the world’s tallest: as tall as a building STORIES HIGH 65 1980 1940 1900 over the last 50 years, humans have built more than LARGE DAMS around the world 47,000 more than of the world’s rivers have been dammed or diverted PERCENT 60 Dam after Dam In the northwestern U.S., more than 19 big dams, including the Dalles Dam, block the Columbia River. So on a river 2,000 kilometers (1,240 miles) long, only about 70 kilometers (43 miles) flows freely. The majority of the world’s large dams are in the United States or Europe. But Asia and South America are building the most dams today. Will future generations regret the social and environmental costs? Map courtesy of Jun Magome, Hydrology and Water Resources Laboratory, University of Yamanashi DAMMING THE WORLD’S RIVERS La Plata River Basin More than 40 dams have been proposed for the La Plata River basin, South America’s second largest. The river supports dozens of bird and fish species found nowhere else. Blue Danube The Danube River basin, spread over 17 countries, is already fragmented by several dams. Eight new dams are planned, under construction, or recently built. Disputed Waters The Nile River basin spans 10 African countries, but a 1959 treaty grants Egypt rights to use the largest share of Nile water. In recent years, some upstream countries have been challenging that treaty, arguing that they deserve a greater share of the Nile’s water. These maps show the world’s “large” dams— those taller than 15 meters (49 feet). Global Dams ©2009 American Museum of Natural History | Seminars on Science | learn.amnh.org