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Satellite Studies Reveal Groundwater Depletion around the World

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Access to freshwater resources has always been a critical need for human and all forms of life on Earth. With a world population estimated at just shy of 7 billion and growing, the UN Food and Agriculture Organization says agricultural production will need to increase 70% by 2050. As agriculture takes up most of human water use, that’s going to put vastly greater demands and strains on our water resources at a time when climate change is changing temperature and precipitation levels and patterns in ways that cannot be predicted at local levels but are likely to make this even more difficult to achieve.

One thing that has been determined is that groundwater levels have dropped in many places around the world in the past nine years, including across key agricultural areas, such as southern Argentina, western Australia and the western US, according to a pair of studies of satellite gravity monitoring data conducted by researchers at the University of California Center for Hydrologic Modeling in Irvine, Science News reports.

The GRACE Project

Groundwater depletion is especially pronounced beneath parts of California, India, the Middle East and China. Besides showing that water is being pumped out of underground groundwater aquifers faster than it’s being replenished, the results raise concerns that farming in particular is the primary cause, according to the Science News report.

“Groundwater is being depleted at a rapid clip in virtually of all of the major aquifers in the world’s arid and semiarid regions,” cautioned UC Center hydrologist Jay Famiglietti, whose team presented the results at a Dec. 6 meeting of the American Geophysical Union.

The Gravity Recovery and Climate Experiment (GRACE), conducted jointly by NASA and the German Aerospace Center, has been taking monthly snapshots of global groundwater used in the two studies since 2002. GRACE data is especially useful in accumulating data across countries where governments do not maintain extensive networks of groundwater monitoring wells. While the US maintains an extensive nationwide network of such wells, countries, such as China, do not.

Nicknamed Tom and Jerry, GRACE’s two satellites are pulled apart and pushed together by variations in the gravitational pull of the areas of the earth they pass over. While mountains and other large concentrations of mass have large, steady impacts on earth’s gravitational pull on the areas where they’re found, water moves over time and creates small fluctuations that the two satellites sense.

Isolating groundwater changes

To isolate the effects of groundwater in particular, researchers have to subtract the effects of snow pack, rivers, lakes and soil moisture, the Science Times article explains. Doing so, they can detect changes in groundwater levels greater than one centimeter (~0.4 inches) over an area about the size of Illinois.

Results of analyzing the data obtained in the two UC Center studies shows that China’s been underestimating groundwater use. GRACE’s measurements indicate that water levels have been dropping 6 or 7 centimeters per year beneath the country’s northeast plains.

Short-term variability in climate is also taking its toll on groundwater levels. having suffered recent droughts, aquifers in Patagonia and the southeastern US now store less groundwater than they did in 2002.

Farming is almost certainly the largest contributing factor, however. Booming agriculture in northern India, takes some 18 cubic kilometers of water out of the ground every year, more than enough to fill 7 million Olympic-size swimming pools, according to Science News.

Farmers in California’s Central Valley, which accounts for nearly 1/6 of irrigated land in the entire country, pump nearly 4 cubic kilometers of water per year out from underground. The valley has been sinking for decades as more wells have been drilled and water pumped out, land subsidence that’s also been occurring and causing increasing concerns, and costly remediation efforts, in Mexico City.

Aquifers in arid and desert areas with fast-growing populations, such as the Middle East, are also being depleted. The “fossil water” that fell millions of years ago and is now stored in the Arabian aquifer beneath Saudi Arabia and neighboring countries is being pumped out faster than it’s being replenished.

Just how much water is there?

Climate change only makes the problem more acute, according to UC Center’s Famiglietti. Precipitation patterns are becoming more extreme, with the severity of droughts increasing. Wet areas are becoming wetters and dry areas drier, Science News reports, and that may accelerate groundwater depletion in some areas.

A big question remains unanswered, however, as hydrologists don’t really know just how large these aquifers are and just how much water is left in them. That’s because GRACE can only show changes in aquifer levels, not their total volume.

Yet while they lack reliable estimates for the total amount of groundwater stored in the world’s aquifers, it’s become clear to hydrologists studying them that water use has become unsustainable in many areas. Better irrigation systems would help reduce water usage, as could channeling water runoff into aquifers during wet periods.

“There are too many areas in the world where groundwater development far exceeds a sustainable level,” US Geological Survey hydrogeologist Leonard Konikow, was quoted as saying. “Something will have to change.”

Image credit: GRACE
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Comments

  1. man is his own greatest enemy and the enemy of all life on Mother Earth.

    About the food shortages, it is not possible to agree with FAO, because if we can stop the cultivation of all unwanted and harmful food crops (tobacco, sugar cane, tea and coffee) it would release so much arable land for cultivation of essential food crops and also make the best os available ground water.

    • Not only that but methodology could be slowly changed over time to more organic and sustainable methods. Dumping all the ammonia nitrate into the ground isn’t working either.

      We’re not the enemies of nature or ourselves. The greed inside us has deluded us into thinking man is incapable of doing the right thing.

      We just don’t know better, collectively, at any given time and the many default to the judgement of the few to often.

      • As an afterthought, if we stopped consuming beef, which has an awful water/energy to produce ratio it would also leave us much better off.

        Chicken would be a much better alternative as they can be free ranged easier, eat insects and their shit makes excellent fertilizer.

  2. Water was better managed 2000 yrs. ago with rooftop rain catching cistines & channeling water like the beavers do. Today, we have destroyed the aqua filters with manmade dams & destroyed rivers with levys & bulkheads.
    Elites, are “white shoe boys” they walk on concrete & not one has worked on a farm, nor lived in a tree house. They boost about the conjested cities they build & now they complain about water ? When yesterday they built all those dams, built all the levys around their cities, something tells me they need to be put to bed & let the people spread out. This is what happens when a group of wealthy power brokers feel free to pollute, shape & destroy the Earth for a short term profit without thinking about the future & learning how the Earth works.

  3. There is a virus, developed in Australia ‘by accident’ at a bio-warfare lab ,
    hybrid of human H5N1 flu virus, and Mousepox.

    The result is 100% contagious and 100 fatal.

    They found the developed frozen to death, ‘by accident’ in his lab.

    All that’s needed is enough of this material to be aerosoled into every major airport in the world at approximately the same time.

    End of water problem.

    • Thats the most uneducated response I’ve ever read from someone who feigned to have a degree.

      What makes you believe that there wasn’t already deadly viruses developed in bio labs that you aren’t even aware exist.

      Even in jest what you’re saying is enough for me to wonder if you should bring that degree back and get a refund, they obviously did something wrong during your edification.

  4. At what point does the human population stop growing, what is your suggestion? I suggest you take a video break and watch the 8 part series on exponential grown at:
    http://www.youtube.com/watch?v=VoiiVnQadwE
    I am hoping for education but it is regrettably the poor that need to slow down as far as numbers go, while the rich need to wean themselves out of unbridled consumerism.

  5. hmm? grazing cattle eat dry grass that otherwise means massive fires.
    Ban CAFOS for ALL animals.
    damn rivers in India and Pak, and store the water.
    ban automatic washing machines that use heaps for one load.
    people need to use water wisely in the 1st world and 3rd world needs education and storage.
    the texas drought, now snow, then floods, why not save the snow in dams for later?
    its stupidity thats the problem, not the amount of humans.

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