© Hoekstra and Mekonnen/PNAS 2012
It's no secret that water scarcity is a serious and growing problem. But where exactly does it all go? A new study out of the Netherlands' University of Twente seeks to answer just that question, and has been referred to as the most comprehensive analysis of global water use to date.
The researchers analyzed the quantity and distribution of global water use from 1996 to 2005, and produced three major findings:
1. Agriculture accounts for 92 percent of all freshwater use globally. Specifically, water-intensive cereal grains like wheat, rice and corn account for 27 percent; meat production 22 percent; and dairy 7 percent.
2. Arid countries are relying more and more on water from other countries without even realizing—consuming what the researchers call "virtual water."
3. Three countries are responsible for nearly 38 percent of global water consumption: China, India, and the United States. But the U.S., which has a much smaller population than China or India, led the world in per capita consumption: 2842 cubic meters each year, compared with the global average of 1385 cubic meters per year.
Virtual WaterThe overall picture put forth by this study is more complex than looking at which countries are running their household taps dry, a point made clear by the tremendous water footprint of agriculture. ScienceNOW continues:
The study also tracked the flow of "virtual water." For example, a previous analysis found that it takes about 5300 liters of water to grow and process a dollar’s worth of grain—an immense volume of water that’s not apparent when you consider a sack of flour sitting on a store shelf. Many nations are water-poor, and they, in essence, outsource their consumption by importing water-intensive commodities, such as grain or electronics, that are produced elsewhere, Hoekstra says. “This flow of ‘virtual water’ is a large part of global economics,” he adds. In all, about 22% of the water consumed worldwide is “virtual water” imported across international borders.
For example, from Science News:
China took only 10 percent of its virtual water from abroad. Yet the researchers note that the economically flourishing country as a matter of policy is now leasing and buying land in Africa to secure its food — and virtual water supply.
And, The New York Times explains, "On average, exported goods were found to consume and to pollute surface and groundwater more than domestically consumed goods do."
Where Meat Fits InWhile meat production accounted for 22 percent of consumption, that's likely a lowball estimate. Science News explains more:
A worldwide trend toward eating more animal products and processed foods could increase demands for water. Producing a gram of protein in milk, eggs and chicken meat typically requires at least half again as much water as providing a gram of legume protein, Hoekstra and Twente colleague Mesfin Mekonnen reported online January 24 in Ecosystems.
ScienceNOW has more on meat and explains why there's hope for agriculture generally:
Agriculture’s huge water usage offers hope that humans can reduce overall water consumption, Hoekstra says. Improving the efficiency of irrigation, for example, will allow enhanced use of surface water derived from precipitation and reduce dependence on unsustainable withdrawals of groundwater. Each cubic meter of water that’s drawn from surface sources, which are generally renewable, is a cubic meter that doesn’t have to be pumped from aquifers. Such underground sources of water typically aren’t considered renewable at timescales relevant for humans, he notes.
Another way to shrink our water footprint is to change our eating habits, Postel says. In particular, people can opt to eat less meat or to switch from grain-fed beef—which, again, requires about 5300 liters of water for each dollar’s worth of grain fed to a cow—to grass-fed beef, which typically requires only the rainwater falling on a pasture.
It's important to note, however, that while grass-fed beef may be better than grain-fed, it can't stand up to the choice of not eating either. Grist made this point well a couple weeks ago:
Eating truly sustainable meat, in modest quantities, is a fine thing. But it’s not better than eating no meat — certainly not when we’ve got more than 7 billion people on a fast-heating planet competing to feed themselves via shrinking, oversubscribed cropland and increasingly limited, degraded freshwater supplies.