Billion-dollar dams are making water shortages, not solving them

By Fred Pearce

Dams are supposed to collect water from rivers and redistribute it to alleviate water shortages, right? Not so fast. It turns out that in most cases they actually create water scarcity, especially for people living downstream.

Almost a quarter of the global population experiences significant decreases in water availability through human interventions on rivers, says Ted Veldkamp at Vrije University in Amsterdam, the Netherlands. Those interventions primarily involve dams that take water for irrigation or cities, or to generate hydroelectricity.

Winners and losers

To investigate the impact of dams on communities, Veldkamp and her colleagues created a detailed modelling study that divided the world into 50-kilometre squares. They used this to assess water scarcity between 1971 and 2010, so they could identify the hydrological winners and losers from dam interventions.

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1 COMMENT

  1. The issue of over-extraction of water from rivers – especially in dry climates, has been known for decades.

    http://www.smithsonianmag.com/science-nature/the-colorado-river-runs-dry-61427169/

    Then, beginning in the 1920s, Western states began divvying up the Colorado’s water, building dams and diverting the flow hundreds of miles, to Los Angeles, San Diego, Phoenix and other fast-growing cities. The river now serves 30 million people in seven U.S. states and Mexico, with 70 percent or more of its water siphoned off to irrigate 3.5 million acres of cropland.

    In 1922, conservationist Aldo Leopold paddled a canoe through the great delta at the mouth of the Colorado River. He wrote about a “wealth of fowl and fish” and “still waters…of a deep emerald hue.” In Leopold’s time, the delta stretched over nearly 3,000 square miles; today, it covers fewer than 250, and the only water flowing through it, except after heavy rains, is the runoff from alfalfa, lettuce and melon fields and pecan orchards.

    The river has become a perfect symbol of what happens when we ask too much of a limited resource: it disappears. In fact, the Colorado no longer regularly reaches the sea.

    Invasive plants, such as salt cedar and cattails, now dominate the delta, a landscape of seemingly endless mud flats where forests used to stand. And in the Gulf of California itself, shellfish, shrimp and waterfowl have declined dramatically as fresh water has dried up.

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