Virtual water cannot remedy freshwater shortage

June 7, 2011

The implementation of virtual water into trading deals has been suggested as a realistic solution to solving the global inequality of renewable freshwater, but new research suggests that it may not be as revolutionary as first thought.

In a study published today, Tuesday 7 June, in IOP Publishing's journal Environmental Research Letters, researchers have claimed that virtual water is unlikely to increase water use , primarily because the existing amount of virtual water is not large enough to overcome the inequalities that exist.

Lead author David Seekell, of the University of Virginia, said, "Virtual water is unlikely to overcome these constraints because there just isn't enough to go around."

80 per cent of humanity currently lives in regions where is threatened, meaning that as the grows against a finite volume of freshwater, a more equal distribution of water use between countries will be needed.

Virtual water—the amount of water it takes to produce goods or a service—has been suggested as a possible solution to this growing problem by using virtual water values to inform international trade deals.

Most goods carry a virtual water value—for example, producing one kilogram of beef requires 15 thousand litres of water—which can act as a significant tool for addressing a country's input and output of water.

For example, a trade deal could be struck where products with a high virtual water value, such as oranges, could be exported from countries where there is an efficient and abundant water supply, into a country where the requirement of water to grow that particular product is more of a burden.

This would allow the receiving country to save on water, relieving the pressure on their limited water resources, and allowing the water to be used elsewhere in its infrastructure.

This study, performed by researchers at the University of Virginia, assessed the in water use between countries and examined how different uses, such as industrial, household, and for agricultural products consumed domestically, contributed to the overall inequality.

To do this, the authors compared United Nations statistics on both social and human development statuses with water usage statistics for a range of countries.

Their study concludes that virtual water transfers are not sufficient to equalise water use among nations because water used for agriculture consumed domestically dominates a nation's water needs and cannot be completely compensated by current volumes of virtual water transfers.

Seekell continued, "Even if it cannot completely equalise water use between countries, virtual water may stand to contribute to this effort if there is increased transfer from high water use to low water use countries, but the danger here is that these transfers effectively prop up populations above the carrying capacity of their natural resources and this could actually erode a population's long-term resilience to drought or other disasters.

"There are a myriad of political and economic barriers to trade, and because water is not usually a deciding factor in trade decisions, it is unlikely that global trade will ever be viewed as efficient from a point of view."

Explore further: Counting the cost of water

More information: Virtual water transfers unlikely to redress inequality in global water use, D A Seekell et al 2011 Environ. Res. Lett. 6 024017 doi: 10.1088/1748-9326/6/2/024017

The distribution of renewable freshwater resources between countries is highly unequal and 80% of humanity lives in regions where water security is threatened. The transfer of agricultural and industrial products to areas where water is limited through global trade may have potential for redressing water imbalances. These transfers represent 'virtual water' used in commodity production. We evaluated the current water-use inequality between countries and the potential of virtual water transfers to equalize water use among nations using multiple statistical measures of inequality. Overall, the actual use of renewable water resources is relatively equal even though the physical distribution of renewable water resources is highly unequal. Most inequality (76%) in water use is due to agricultural production and can be attributed to climate and arable land availability, not social development status. Virtual water use is highly unequal and is almost completely explained by social development status. Virtual water transfer is unlikely to increase water-use equality primarily because agricultural water use dominates national water needs and cannot be completely compensated by virtual water transfers.

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4 / 5 (1) Jun 07, 2011
"The distribution of renewable freshwater resources between countries is highly unequal and 80% of humanity lives in regions where water security is threatened."

Build fission power and desalination plants, or move. Problem solved.
not rated yet Jun 07, 2011
Either solution is cheaper than those proposed. Equalizing water supplies between countries. Reducing water use "inequality" between countries. Bah.
not rated yet Jun 07, 2011
Build fission power and desalination plants, or move. Problem solved.

I'm certainly not against building more nuclear power plants, but there is an elegant source of both power and fresh water that areas with desert near mountains can use. Evaporate salt, brackish, or "grey" water using solar power. The water vapor needs to be captured (thin plastic films are enough to cover evaporators. The water vapor is then routed up a mountain through a fairly wide tunnel. At the top of the tunnel the water is condensed, and now goes into a standpipe for a conventional (hydroelectric dam) turbine to create power.

And the fresh water coming out of the turbine can be routed directly into a municipal water supply. No, I didn't invent this idea. There are areas where it has been considered as a way to produce solar power that can be time shifted. (Put the water in a tank or behind a dam until the power is needed.)
5 / 5 (1) Jun 07, 2011
Yeah, stills are a non-technical way to achieve potable water.

I envision a string of nuke/de-sal plants along the Sea of Cortez in Mexico. Power and fresh water to be sold to the desert Southwest and stoopid California (who won't do anything to solve any of their problems - too many stupified idiots what think the world owes them a living.

I also envision pumping the now purified water back into depleted aquifers. Fill the aquifers until the artesian springs start flowing again.
not rated yet Jun 07, 2011
for example, producing one kilogram of beef requires 15 thousand litres of water
Hmmmmm.... Say, a feeder steer reaches 600 kg liveweight at 18 months of age. It then nets out 750 kg meat. A grown steer will drink perhaps 50 litres / day. So give it (and its mother) 2 yrs consumption at 50 litres / day to produce 750 kg meat.

2 x 365 x 50 / 750 = 48.6666 litres / kg meat. So that's not it...

Say the steer and its mother eats 25 kg grain corn / day for 2 x 365 days. Each sq meter of grain corn (if say rationally moderate irrigation used) requires 330 litres of water, and produces 160 kg corn. So a steer to full growth requires

(25 x 2 x 365) / (160) * 330 = 37,640 litres of water. Netting 750 kg meat, = 50.19 litres / kg meat.

Total = 48.6666 + 50.19 = 98.85 litres per kg meat. Say 100 litres / kg. Where the HECK did they get 15,000 litres?
not rated yet Jun 07, 2011
Sorry, that should be "netting 360 kg meat", not 750.

Result changes to 205.95 litres / kg meat.
3 / 5 (2) Jun 07, 2011
The error can be attributed to a missing bead on Dave's abacus. As a graduate student, Dave has saved up almost enough to replace the missing bead on his abacus.

Dave has continuously led the way in implementing the use of high-end, high tech abacuses. Dave uses a binary abacus, in a show of solidarity to the use of binary counting systems.

Nothing personal, Dave. All in jest.
not rated yet Jun 08, 2011

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