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A New Force of Nature, an excerpt from Keepers of the Spring: Our Water in an Age of Globalization

There are today some 800,000 dams around the world. Some 45,000 of them are more than 50 feet high; more than a hundred tower 500 feet or higher above the rivers they are intended to tame. If all the water in all the reservoirs behind all the dams in the world were collected together, it would measure 8 billion acre-feet. It would cover half of California to a height of 130 feet. If it were all released into the oceans, it would raise the sea level on every beach around the world by some 8 inches.

... Since 1900, the world has on average completed one large dam every day. Their turbines generate a fifth of the world's electricity, and their waters irrigate a sixth of the world's crops. They barricade 61 percent of the world's river flows.

These dams have even changed the shape and rotation of planet Earth. The water in their reservoirs is so heavy that it deforms the Earth's crust and unleashes periodic earthquakes. And by shifting water away from the equator, where ocean water is concentrated, they have altered the speed of the Earth's rotation in much the same way as ice skaters speed up by pulling their arms in close to the body. The "reservoir effect" has so far shortened the length of the day by about a thousandth of a second. The asymmetrical distribution of reservoirs round the Earth has even tilted the Earth's axis. The North and South Poles and every line of latitude and longitude are now 2 feet from where they would otherwise have been.

Dams are more than an earth-shaping technology. They have great power as totems of modernism and as symbols of a very mechanistic notion of how mankind can "tame nature."

Keepers of the Spring: Reclaiming Our Water in an Age of Globalization
Fred Pearce
Island Press, $26

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