From The Desert Sun:
|Farmer Jay Garetson surveys drying-out land on his property in SW Kansas. Source: Steve Elfers, The Desert Sun.|
Pumped beyond limits, many U.S. aquifers in decline.
by Ian James and Steve Reilly, The Desert Sun(in cooperation with USA Today)
10 December 2015
Time is running out for portions of the High Plains Aquifer, which lies beneath eight states from South Dakota to Texas and is the lifeblood of one of the world’s most productive farming economies. The aquifer, also known as the Ogallala, makes possible about one-fifth of the country’s output of corn, wheat and cattle. But its levels have been rapidly declining, and with each passing year more wells are going dry.
As less water pours from wells, some farmers are adapting by switching to different crops. Others are shutting down their drained wells and trying to scratch out a living as dryland farmers, relying only on the rains.
In parts of western Kansas, the groundwater has already been exhausted and very little can be extracted for irrigation. In other areas, the remaining water could be mostly used up within a decade.
The severe depletion of the Ogallala Aquifer is symptomatic of a larger crisis in the United States and many parts of the world. Much more water is being pumped from the ground than can be naturally replenished, and groundwater levels are plummeting. It’s happening not only in the High Plains and drought-ravaged California but also in places from the Gulf Coastal Plain to the farmland of the Mississippi River Valley, and from the dry Southwest to the green Southeast....
Aquifers are being drawn down in many areas by pumping for agriculture, which accounts for nearly two-thirds of the nation’s use of fresh groundwater. Water is also being drained for cities, expanding development and industries. Across much of the country, overpumping has become a widespread habit. And while the symptoms have long remained largely invisible to most people, the problem is analogous to gradually squandering the balance of a collective bank account. As the balance drops, there’s less of that resource to draw on when it’s needed.
At the same time, falling groundwater levels are bringing increasing costs for well owners, water utilities and society as a whole. As water levels drop, more energy is required to lift water from wells, and those pumping bills are rising. In areas where aquifers are being severely depleted, new wells are being drilled hundreds of feet into the earth at enormous cost. That trend of going deeper and deeper can only go on so long....
In places, water that seeped underground over tens of thousands of years is being pumped out before many fully appreciate the value of what’s lost. The declines in groundwater in the United States mirror similar decreases in many parts of the world.
NASA satellites have allowed scientists to map the changes underground on a global scale for the first time, putting into stark relief a drawdown that has long remained largely out of sight. The latest satellite data, together with measurements of water levels in wells, reveal widespread declines in places from Europe to India, and from the Middle East to China.
“Groundwater depletion is this incredible global phenomenon,” said Jay Famiglietti, a professor of earth system science at the University of California, Irvine, and the senior water scientist at NASA's Jet Propulsion Laboratory. “We never really understood it the way we understand it now. It’s pervasive and it’s happening at a rapid clip.”
Famiglietti and his colleagues have found that more than half of the world’s largest aquifers are declining. Those large-scale losses of groundwater are being monitored from space by two satellites as part of the GRACE mission, which stands for Gravity Recovery and Climate Experiment.
Since 2002, the orbiting satellites have been taking detailed measurements of Earth’s gravity field and recording changes in the total amounts of water, both aboveground and underground. Using that data, the researchers have created a global map showing areas of disappearing water as patches of yellow, orange and red. Those “hotspots” mark regions where there is overpumping of water or where drought has taken a toll.And by experience, when it becomes more and more difficult and expensive to extract water from a groundwater well, eventually one will encounter diminishing returns -- first it costs more both in terms of energy and money, and later on no matter what the well owner does, he is finding that he can pump out less and less water over time, until the water runs out. And then he has to either find a new watersource, or just depend on rainfall, like some farmers in Kansas are now doing.
The map shows that, just as scientists have been predicting due to climate change, some areas in the tropics and the higher latitudes have been growing wetter, Famiglietti said, while many dry and semi-arid regions in the mid-latitudes have been growing drier. In those same dry regions, intensive agriculture is drawing heavily on groundwater.
More at the link: http://www.desertsun.com/story/news/environment/2015/12/10/pumped-beyond-limits-many-us-aquifers-decline/76570380/