Problems With Big Dams

By 2015, the dam industry had choked more than half of the Earth's major rivers with some 57,000 large dams. The consequences of this massive engineering program have been devastating. The world's large dams have wiped out species; flooded huge areas of wetlands, forests and farmlands; and displaced tens of millions of people.

 Courtesy of James Syvitski at Colorado University, who produced the video with Bob Stallard of the USGS and Albert Kettner at CSDMS. Data from Alex de Sherbinin (CIESIN, University of Colorado), and Bernhard Lehner (Department of Geography, McGill University).

The "one-size-fits-all" approach to meeting the world's water and energy needs is also outdated: better solutions exist. While not every dam causes huge problems, cumulatively the world's large dams have replumbed rivers in a massive experiment that has left the planet's freshwaters in far worse shape than any other major ecosystem type, including tropical rainforests. In response, dam-affected communities in many parts of the world are working to resolve the legacies of poorly planned dams. Elsewhere (and especially in North America), communities are starting to take down dams that have outlived their usefulness, as part of a broader river restoration movement.

Impacts of Dams

Dam Basics

Fact sheets: