Our Oversized Groundwater Footprint

We don’t see it, smell it or hear it, but the tragedy unfolding underground is nonetheless real – and it spells big trouble.



I’m talking about the depletion of groundwater, the stores of H2O contained in geologic formations called aquifers, which billions of people depend upon to supply their drinking water and grow their food.

For a long time, we had only a vague sense of the scale of this depletion, mostly through anecdotal evidence and selected country studies. While researching my 1999 book Pillar of Sand, I gathered the best data I could find at the time, and with all the necessary caveats, estimated that about 8-10 percent of the world’s food supply depended upon the draining of underground aquifers.

About a decade later, modeling work by Marc Bierkens of Utrecht University in the Netherlands and his colleagues arrived at a global depletion estimate that produced a similar figure: their estimated 283 billion cubic meters of groundwater depleted in 2000 is sufficient to produce 188.6 million tons of grain, equal to 10 percent of that year’s global grain production. While not all groundwater pumped from the earth is used to produce grain, the vast majority of it is.

In recent years a number of other studies, along with NASA’s GRACE (Gravity Recovery and Climate Experiment) mission, have corroborated the dangerous trend. From the Arabian deserts to the North China Plain, and from the breadbasket of India to the fruit and vegetable bowl of the United States, we are increasingly dependent on the unsustainable use of groundwater.

In effect, we’re robbing the Peters of the future to feed the Pauls of today.

Now a new study, led by Tom Gleeson of McGill University in Montreal and published last week in the journal Nature, provides perhaps the most compelling and informative assessment to date of what’s happening with groundwater globally.

Gleeson and his team build upon the concept of our “ecological footprint,” which expresses humanity’s consumption as the area of biomass needed to support that consumption sustainably. Today, according to the Global Footprint Network, humanity uses the equivalent of 1.5 planet Earths. In other words, we’ve overshot sustainable levels by half an Earth.

In a creative adaptation, Gleeson’s team applied a similar approach to assessing humanity’s groundwater footprint. They estimate that the size of the global groundwater footprint – defined as the area required to sustain groundwater use and groundwater-dependent ecosystem services — is about 3.5 times the actual area of aquifers tapped for water supplies. More

Wasting [water] Resources

New study cites Pakistan among seven countries dangerously exploiting groundwater aquifers.

Heavily populated regions of Asia, the arid Middle East and parts of the U.S. corn-belt are dangerously over-exploiting their underground water supplies, according to a study published on Wednesday in scientific journal Nature.

 

“The countries that are overusing groundwater most significantly are the United States, India, China, Pakistan, Iran, Saudi Arabia and Mexico, and the highest number of people that are impacted by this live in India and China,” Canadian hydrologist Tom Gleeson told AFP.

 

“Over a quarter of the world’s population live in these regions where groundwater is being overused,” he said in a phone interview. Many places are rapidly pumping out “fossil” water, or water that was laid down sometimes thousands of years ago and cannot be replaced on a human timescale.

 

Seeking a yardstick of sustainability, the study creates a measure called the groundwater footprint. It calculates the area of land sustained by extracted water and compares this to the size of the aquifer beneath. The global groundwater footprint is a whopping 3.5 times the size of the world’s aquifers, the study found.

 

However, this stress is accounted for by a small number of countries. For instance, in the South Caspian region of northern Iran, the footprint is 98 times the size of the aquifer; in the Upper Ganges in India and Pakistan, it is 54; while in the U.S. High Plains, the figure is nine.

 

“Humans are over-exploiting groundwater in many large aquifers that are crucial to agriculture, especially in North America and Asia,” said Gleeson. “Irrigation for agriculture is largely causing the problem but it is already impacting in some regions the ability to use groundwater for irrigation, so it is almost like a self-reinforcing problem.”

 

The study aims at adding a new analytical tool to help policymakers cope with the world’s intensifying water problems. In March, the U.N. warned in its Fourth World Water Report that water problems in many parts of the world were chronic, and without a crackdown on wastage would worsen as demand for food rises and climate change intensifies.

 

By 2050, agricultural use of water will rise by nearly 20 percent, on the basis of current farming methods, to meet food demands from a population set to rise from seven billion today to more than nine billion.

 

Gleeson, a specialist at McGill University in Montreal, Canada, used a computer model in collaboration with scientists at Utrecht University in the Netherlands and crunched national statistics on water use. The next step will be to use satellite data, which should be a more reliable source, he said. More