"Water is life. It is the heart of a green economy. That's why we must talk about water efficiency," stressed Kenza Robinson, the secretary of UN-Water who also works at the United Nations Department of Economics and Social Affairs.

Water is used in nearly every undertaking. Within the energy sector, power culled from water is considered environmentally friendly. Industry needs enormous quantities of water to manufacture products. In creating a single computer microchip, manufacturers use around 32 liters of water. Building a car requires an average of 400,000 liters of the liquid.

One big cycle

But agriculture is the biggest water consumer, currently using around 70 percent of global water resources. The agriculture industry doesn't just provide people with food these days. It also uses water in raising crops for biofuels and for feeding livestock. The world's water resources are all part of an enormous water cycle. They are recycled, but new water resources are not added into the mix. The quantity always remains the same.

So the issue at stake is how well water is being used, said Benedikt Haerlin of the German environmental group Foundation for the Future of Agriculture.

"The decisive point is actually how we maintain the water in the ground and in plants throughout the ecosystem before it evaporates, and the cycle starts all over again," said the journalist and agriculture expert, who is also a member of the International Commission on the Future of Food.

The virtual dimension

Haerlin supports developing sustainable agriculture as a way of feeding the world's growing population in a healthy fashion. For him, sustainability means that so-called virtual water also enters into the equation. Virtual water is the amount of water behind any given product and which is an often invisible part of the export process in agriculture. For example, in a dry country like Somalia, it takes 18,000 liters of water to grow one kilogram of wheat. But in Slovakia, it takes just 465 liters for the same product. So Benedikt Haerlin argues that the entire food production process needs to be adapted to available water quantities.

"Germany imports water from regions in which water is much scarcer than it is here at home - for instance in the form of soy," said Haerlin, who noted that soy production requires immense quantities of water.

"Trade with virtual water would have to take into account where water is scarce rather than simply trading based on where the most money is," Haerlin added.

Changing agriculture

Haerlin believes that including virtual water in trade calculations would lead people away from the agricultural practice known as monoculture in which a single crop is grown year after year in the same place. Little water is preserved in the ground by farming in this way, Haerlin said, which has a negative effect on the global water cycle. Often, farms of this sort also use artificial watering systems. The key, Haerlin stresses, is for food producers around the world to account better for the amount of water available to them and adapt their practices accordingly.

Robinson adds that we must think much further in advance when it comes to water than with other resources, like fossil fuels.

"Water is a human right. It stands above all other resources," she said. "Because of its special significance, we must view it in a comprehensive way."