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Where does groundwater come from, and where does it go? March 11, 2011

Posted by WaterWise Consulting in water conservation, Water Pollution.
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Simply put, groundwater is water that is stored underground in aquifers—dirt, sand, and rock. This water is stored between the particles of matter underground. These moist areas can be found close to the Earth’s surface or as many as thousands of feet underground.

Then you discover a spring or other form of water seemingly coming from nowhere, the source is often groundwater. This underground water makes its way into natural lakes and rivers and is often pumped out by wells for drinking and irrigation supply.

Over half of U.S. residents get their drinking water from groundwater.

As more residents populate the United States, more water is pumped out of underground aquifers. One of the problems arise when runoff from agricultural and industrial waste infiltrates and pollutes our groundwater. However, the biggest and most dangerous threat is over-drawing this limited resource.

Over-drawing our groundwater is such a dangerous problem because farmers are given subsidized water at low prices. This in turn negates the push to conserve water and save water. As a result, many farmers use inefficient irrigation techniques simply because they are easier and cheaper than retrofitting their equipment and saving money.
Brian O’Neill
boneill@waterwise-consulting.com
http://www.waterwise-consulting.com

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1. David Isaacson - March 16, 2011

One of the most serious cases of groundwater “overdrafting” (withdrawing more water from an underground aquifer than can be naturally replenished by rain) is the Ogallala Aquifer. This huge underground body of water sits beneath much of the Great Plains of the United States, including the states of South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas.

Farmers have been tapping into this groundwater with wells and pumping out water to irrigate their crops for decades, and in large part this has made possible the huge agricultural yields our grain belt is famous for. Unfortunately, the Ogallala is what is known as a “fossil aquifer”, meaning that the water has been accumulating there for millions of years. Recharge is mostly from rainfall, and varies between fractions of an inch to 5 or 6 inches per year, varying in different parts of the area.

We are steadily drawing down the level of the aquifer faster than it can recharge. Deeper wells and more powerful pumps over the years have allowed farmers to continue this unsustainable “mining” of ancient water. But water levels keep dropping, and in some areas it is no longer accessible (parts of Texas), leading to dustbowl-type conditions.

Although the USGS estimated in 2005 that only about 9% of the volume of the aquifer has been depleted since pumping began (253 million acre-feet of water), what remains will continue to get more difficult and expensive to access. The deeper the well, the more power it takes to pump it to the surface, and we know that energy costs are going up and supplies oil and natural gas are limited.

No one knows when we will reach the point when the water level has dropped so low that we can no longer reach it with existing pump technology, or too expensive to use for large-scale irrigation, leading to huge increases in food costs for the U.S. at best.

According to David Brauer of the US Agriculture Department agency, the Ogallala Research Service ‘The Ogallala supply is going to run out and the Plains will become uneconomical to farm,’ Brauer says. ‘That is beyond reasonable argument. Our goal now is to engineer a soft landing. That’s all we can do.’ [http://www.telegraph.co.uk/earth/8359076/US-farmers-fear-the-return-of-the-Dust-Bowl.html]

This situation is not unique to the Ogallala, or to the United States. Aquifers around the world are facing similar or worse strains, especially China and India with their huge populations.

Preventing future catastrophe means learning to live within our means, water-wise. This will require sustainable management of our water supplies, especially groundwater (meaning using no more than can be naturally recharged). Agricultural water efficiency must be improved, and urban water use will also need continued efficiency improvement.

2. Bruce Hage Irrigation - May 5, 2011

It always seems as if money is the incentive! Eventually, this motive isn’t going to cut it anymore once we start running into more environmental problems, which we are already starting to see now (ie, availability of clean drinking water, pollution in our water supply)


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