Wednesday, July 7, 2010

Water -- will there be enough?

Sandra Postel in Energy Bulletin, via Yes! magazine: For at least three decades, Americans have had some inkling that we face an uncertain energy future, but we’ve ignored a much more worrisome crisis—water. Cheap and seemingly abundant, water is so common that it’s hard to believe we could ever run out. Ever since the Apollo astronauts photographed Earth from space, we’ve had the image of our home as a strikingly blue planet, a place of great water wealth. But of all the water on Earth, only about 2.5 percent is freshwater—and two-thirds of that is locked up in glaciers and ice caps. Less than one hundredth of one percent of Earth’s water is fresh and renewed each year by the solar-powered hydrologic cycle.

Across the United States and around the world, we’re already reaching or overshooting the limits of that cycle. The Colorado and Rio Grande Rivers are now so overtapped that they discharge little or no water to the sea for months at a time. In the West, we’re growing food and supplying water to our communities by overpumping groundwater. This creates a bubble in the food economy far more serious than the recent housing, credit, or dot-com bubbles: We are meeting some of today’s food needs with tomorrow’s water.

The massive Ogallala Aquifer, which spans parts of eight states from southern South Dakota to northwest Texas, and provides 30 percent of the groundwater used for irrigation in the country, is steadily being depleted. As of 2005, a volume equivalent to two-thirds of the water in Lake Erie had been pumped out of this water reserve. Most farmers will stop irrigating when the wells run dry or the water drops so far down that it’s too expensive to pump.

At the same time, climate change is rewriting the rules about how much water we’ll have available and when. Climate scientists warn of more extreme droughts and floods, and of changing precipitation patterns that will make weather, storms, and natural disasters more severe and less predictable. The historical data and statistical tools used to plan billions of dollars worth of annual global investments in dams, flood control structures, diversion projects, and other big pieces of water infrastructure are no longer reliable….

Image from NASA

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