You don't miss your water 'til your well runs dry: GLOBAL WATER TABLES PLUNGING

Dems Will Win

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Tue Jul-31-07 09:48 AM
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You don't miss your water 'til your well runs dry: GLOBAL WATER TABLES PLUNGING

Edited on Tue Jul-31-07 09:51 AM by Dems Will Win

Hello drip irrigation. Time to conserve water as well as energy. And stop having so many babies!!!

C'mon Earth - WAKE UP!

This is written by the esteemed Lester Brown:

WATER TABLES FALLING AND RIVERS RUNNING DRY

Lester R. Brown

As the world�s demand for water has tripled over the last half-century and as the demand for hydroelectric power has grown even faster, dams and diversions of river water have drained many rivers dry. As water tables fall, the springs that feed rivers go dry, reducing river flows.

Scores of countries are overpumping aquifers as they struggle to satisfy their growing water needs, including each of the big three grain producers�China, India, and the United States. More than half the world�s people live in countries where water tables are falling.

There are two types of aquifers: replenishable and nonreplenishable (or fossil) aquifers. Most of the aquifers in India and the shallow aquifer under the North China Plain are replenishable. When these are depleted, the maximum rate of pumping is automatically reduced to the rate of recharge.

For fossil aquifers, such as the vast U.S. Ogallala aquifer, the deep aquifer under the North China Plain, or the Saudi aquifer, depletion brings pumping to an end. Farmers who lose their irrigation water have the option of returning to lower-yield dryland farming if rainfall permits. In more arid regions, however, such as in the southwestern United States or the Middle East, the loss of irrigation water means the end of agriculture.

The U.S. embassy in Beijing reports that Chinese wheat farmers in some areas are now pumping from a depth of 300 meters, or nearly 1,000 feet. Pumping water from this far down raises pumping costs so high that farmers are often forced to abandon irrigation and return to less productive dryland farming. A World Bank study indicates that China is overpumping three river basins in the north�the Hai, which flows through Beijing and Tianjin; the Yellow; and the Huai, the next river south of the Yellow. Since it takes 1,000 tons of water to produce one ton of grain, the shortfall in the Hai basin of nearly 40 billion tons of water per year (1 ton equals 1 cubic meter) means that when the aquifer is depleted, the grain harvest will drop by 40 million tons�enough to feed 120 million Chinese.

In India, water shortages are particularly serious simply because the margin between actual food consumption and survival is so precarious. In a survey of India�s water situation, Fred Pearce reported in New Scientist that the 21 million wells drilled are lowering water tables in most of the country. In North Gujarat, the water table is falling by 6 meters (20 feet) per year. In Tamil Nadu, a state with more than 62 million people in southern India, wells are going dry almost everywhere and falling water tables have dried up 95 percent of the wells owned by small farmers, reducing the irrigated area in the state by half over the last decade.

As water tables fall, well drillers are using modified oil-drilling technology to reach water, going as deep as 1,000 meters in some locations. In communities where underground water sources have dried up entirely, all agriculture is rain-fed and drinking water is trucked in. Tushaar Shah, who heads the International Water Management Institute�s groundwater station in Gujarat, says of India�s water situation, �When the balloon bursts, untold anarchy will be the lot of rural India.�

In the United States, the U.S. Department of Agriculture reports that in parts of Texas, Oklahoma, and Kansas�three leading grain-producing states�the underground water table has dropped by more than 30 meters (100 feet). As a result, wells have gone dry on thousands of farms in the southern Great Plains. Although this mining of underground water is taking a toll on U.S. grain production, irrigated land accounts for only one fifth of the U.S. grain harvest, compared with close to three fifths of the harvest in India and four fifths in China.

MORE: http://www.earth-policy.org/Books/Seg/PB2ch03_ss2.htm

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