Underground water is being pumped
so aggressively around the globe that land is sinking, civil wars are being
waged, and agriculture is being transformed. In some neighborhoods, the ground
is giving way at a rate of four inches a year as water in the giant aquifer
below it is pumped.
The groundwater has been so
depleted that China’s capital city, home to more than 20 million people, could
face serious disruptions in its rail system, roadways, and building
foundations, an international team of scientists concluded earlier this year.
Beijing, despite tapping into the gigantic North China Plain aquifer, is the
world’s fifth most water-stressed city and its water problems are likely to get
even worse.
Beijing isn’t the only place
experiencing subsidence, or sinking, as soil collapses into space created as
groundwater is depleted. Parts of Shanghai, Mexico City, and other cities are
sinking, too. Sections of California’s Central Valley have dropped by a foot,
and in some localized areas, by as much as 28 feet.
Around the world, alarms are
being sounded about the depletion of underground water supplies. The United
Nations predicts a global shortfall in water by 2030. About 30 percent of the
planet’s available freshwater is in the aquifers that underlie every continent.
More than two-thirds of the
groundwater consumed around the world irrigates agriculture, while the rest
supplies drinking water to cities. These aquifers long have served as a backup
to carry regions and countries through droughts and warm winters lacking enough
snowmelt to replenish rivers and streams. Now, the world’s largest underground
water reserves in Africa, Eurasia, and the Americas are under stress. Many of
them are being drawn down at unsustainable rates. Nearly two billion people
rely on groundwater that is considered under threat.
Richard Damania, a lead economist
at the World Bank, predicts that without adequate water supplies, economic growth
in the most stressed parts of the world could decline by six percent of GDP.
His findings conclude that the most severe impacts of climate change will
deplete water supplies.
“If you are in a dry area, you
are going to get a lot less rainfall. Run-off is declining,” he says. “People
are turning to groundwater in a very, very big way.”
But few things are more difficult
to control than groundwater pumping, Damania says. In the United States,
farmers are withdrawing water at unsustainable rates from the High Plains, or
Ogallala Aquifer, even though they have been aware of the threat for six
decades.
“What you have in developing
countries is a large number of small farmers pumping. Given that these guys are
earning so little, there is very little you can do to control it,” Damania
says. “And you are, literally, in a race to the bottom.”Over the past three
decades, Saudi Arabia has been drilling for a resource more precious than oil.
Engineers and farmers have tapped hidden reserves of water to grow grains,
fruits, and vegetables in the one of the driest places in the world. They are
tapping into the aquifer at unsustainable rates. On these NASA satellite images
of the Wadi As-Sirhan Basin, green indicates crops, contrasting with the pink
and yellow of dry, barren land.
As regions and nations run short
of water, Damania says, economic growth will decline and food prices will
spike, raising the risk of violent conflict and waves of large migrations.
Unrest in Yemen, which heavily taps into groundwater and which experienced
water riots in 2009, is rooted in a water crisis. Experts say water scarcity
also helped destabilize Syria and launch its civil war. Jordan, which relies on
aquifers as its only source of water, is even more water-stressed now that more
than a half-million Syrian refugees arrived.
Jay Famiglietti, lead scientist
on a 2015 study using NASA satellites to record changes in the world’s 37
largest aquifers, says that the ones under the greatest threat are in the most
heavily populated areas.
"Without sustainable
groundwater reserves, global security is at far greater risk,” he says. “As the
dry parts are getting drier, we will rely on groundwater even more heavily. The
implications are just staggering and really need to be discussed at the international
level.”
Below are answers to your key
questions.
Where is groundwater the most
threatened?
The most over-stressed is the
Arabian Aquifer System, which supplies water to 60 million people in Saudi
Arabia and Yemen. The Indus Basin aquifer in northwest India and Pakistan is
the second-most threatened, and the Murzuk-Djado Basin in northern Africa the
third.
How did these giant basins become
so depleted?
Drought, bad management of
pumping, leaky pipes in big-city municipal water systems, aging infrastructure,
inadequate technology, population growth, and the demand for more food
production all put increasing demand on pumping more groundwater. Flood
irrigation, which is inefficient, remains the dominant irrigation method
worldwide. In India, the world’s largest consumer of groundwater, the
government subsidizes electricity – an incentive to farmers to keep pumping.
How has irrigation changed
farming?
Irrigation has enabled
water-intensive crops to be grown in dry places, which in turn created local
economies that are now difficult to undo. These include sugar cane and rice in
India, winter wheat in China, and corn in the southern High Plains of North
America. Aquaculture has boomed in the land-locked Ararat Basin, which lies
along the border between Armenia and Turkey. Groundwater is cold enough to
raise cold-water fish, such as trout and sturgeon. In less than two decades,
the aquifer there has been drawn down so severely for fish ponds that municipal
water supplies in more than two dozen communities are now threatened.
How much water remains?
More is known about oil reserves
than water. Calculating what remains in aquifers is extraordinarily difficult.
In 2015, scientists at the University of Victoria in British Columbia, Canada
concluded that less than six percent of groundwater above one-and-a-half miles
(two kilometers) in the Earth’s landmass is renewable within a human lifetime.
But other hydrologists caution that measurements of stores can mislead. More
important is how the water is distributed throughout the aquifer. When water
levels drop below to 50 feet or less, it is often not economically practical to
pump water to the surface, and much of that water is brackish or contains so
many minerals that it is unusable.
Is there any good news?
Depleted groundwater is a
slow-speed crisis, scientists say, so there's time to develop new technologies
and water efficiencies. In Western Australia, desalinated water has been
injected to recharge the large aquifer that Perth, Australia's driest city,
taps for drinking water. China is working to regulate pumping. In west Texas,
the city of Abernathy is drilling into a deeper aquifer that lies beneath the
High Plains aquifer and mixing the two to supplement the municipal water
supply. Source:
National Geographic
