World over-using underground water reserves for agriculture

LONDON Fri Aug 10, 2012 4:50pm EDT

A general view shows an artificial lake with depleted levels of water in Qaraoun, West Bekaa, December 2, 2010. REUTERS/ Mohamed Azakir

A general view shows an artificial lake with depleted levels of water in Qaraoun, West Bekaa, December 2, 2010.

Credit: Reuters/ Mohamed Azakir

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LONDON (Reuters) - The world is depleting underground water reserves faster than they can be replenished due to over-exploitation, according to scientists in Canada and the Netherlands.

The researchers, from McGill University in Montreal and Utrecht University in the Netherlands, combined groundwater usage data from around the globe with computer models of underground water resources to come up with a measure of water usage relative to supply.

That measure shows the groundwater footprint - the area above ground that relies on water from underground sources - is about 3.5 times bigger than the aquifers themselves.

The research suggests about 1.7 billion people, mostly in Asia, are living in areas where underground water reserves and the ecosystems that rely on them are under threat, they said.

Tom Gleeson from McGill, who led the study, said the results are "sobering", showing that people are over-using groundwater in a number of regions in Asia and North America.

Over 99 percent of the world's fresh and unfrozen water sits underground, and he suggests this huge reservoir that could be crucial for the world's growing population, if managed properly.

The study, published in the journal Nature, found that 80 percent of the world's aquifers are being used sustainably but this is offset by heavy over-exploitation in a few key areas.

Those areas included western Mexico, the High Plains and California's Central Valley in the United States, Saudi Arabia, Iran, northern India and parts of northern China.


"The relatively few aquifers that are being heavily exploited are unfortunately critical to agriculture in a number of different countries," Gleeson told Reuters. "So even though the number is relatively small, these are critical resources that need better management."

Previous research has shown that it takes about 140 liters of water to grow the beans that go into one cup of coffee, whether they are cultivated in arid Ethiopia or the Colombian rain forest.

"The effect of this water use on the supply of available water will be very different," the researchers wrote. "Until now, there has been no way of quantifying the impact of such agricultural groundwater use in any consistent, global way."

Gleeson said limits on water extraction, more efficient irrigation and the promotion of different diets, with less or no meat, could make these water resources more sustainable.

Water sitting in underground aquifers was the subject of research by British researchers published in April that mapped huge reserves sitting under large parts of Africa that could provide a buffer against the effects of climate change, if used sustainably.

A team from the British Geological Survey and University College London estimated that reserves of groundwater across Africa are about 100 times the amount found on the continent's surface.

Some of the largest reserves are under the driest North African countries like Libya, Algeria, Egypt and Sudan, but some schemes to exploit them are not sustainable.

The biggest is Libya's $25 billion Great Manmade River project, built by the regime of slain dictator Muammar Gaddafi to supply cities including Tripoli, Benghazi and Sirte with an estimated 6.5 million cubic meters of water a day.

The network of pipes and boreholes is sucking water out of the ground that was deposited in the rocks under the Sahara an estimated 40,000 years ago, but is not being replenished.

It is unclear how long this water source will last, with estimates ranging between 60 and 100 years.

(Editing by Mark Heinrich)

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Comments (20)
HippoP wrote:
The water footprint isn’t an accurate messurement given that the ground is flat yet the aquifer may be miles deep, if you actually read the report it says that most of the world is running very sustainably with a few small exceptions like the California desert and parts of mainland china. There is no water shortage. The biggest concern here is why people keep insisting on using desert lands for agricultural purposes even though this has been proven again and again throughout history to be dibilitating to the polulations that depend on them. Use more fertile land and you would end up using less water on your crops.

八月 12, 2012 1:08am EDT  --  Report as abuse
AZWarrior wrote:
The second and third world is reproducing to absorb all gains in energy and food. As long as that is allowed to continue, shortages will continue until a great world catastrophe occurs and “thins the herd”. This will happen because no world leaders can face the politically incorrect stance that China has with their one child policy, which although in some cases cruel to a few, may save the many.

八月 12, 2012 3:23am EDT  --  Report as abuse
microman wrote:
Old enough to remember how easy, clean and predictable life was in the 50s and 60s, when the world population was less than a third of what it is now.

We were guaranteed decent education, good employment and affordable housing. We were able to plan for our future, old age and retirement with a sense of confidence and security.

Look at the state of our world today. There is not enough to go round yet we are breeding at a frightening rate and are encouraged to do so by every government, private institution, the UN and the entire Media network.

We can dig deeper for oil and water, can recycle our bath and toilet water and can squeeze more people to live in tins and underground too, but is this the future we wish for our children and grandchildren?

八月 12, 2012 4:10am EDT  --  Report as abuse
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