During the twentieth century, governments and private utilities have transformed their relationship with rivers and their tributaries by building as many as 45,000 large hydroelectric dams. Proponents argued that with electricity usage projected to nearly double by 2035 from 5.2 terawatts to 9.3 terawatts, big projects such as large hydroelectric dams offered many benefits. In addition to meeting electrical needs, the benefits, according to proponents, included a reduction in fossil fuel consumption, flood control, irrigation, improved water transportation and employment for the construction industry. After 1945, developing countries, with aid from the World Bank and the International Monetary Fund, dams producing electricity became fixtures on nearly all of the world’s largest rivers. On the negative side, as many as 60 percent of the dams and reservoirs financed in this way removed between 30 and 60 million people from their homes.1

In recent years, the momentum to build more large dams to produce electricity has slowed in the developed world as evidence accumulates suggesting that large dams as sources of clean energy do not leave a light footprint on the land. There now exists extensive documentation of the ecological damage done to the land and to aquatic life by large dams. For example, governments and utilities removed 538 dams in the 90 years before 2005. In eight years, from 2006 and 2014, they removed 548 dams, many of them considered unsafe or replaceable by more efficient means for producing electricity.