Counting the carbon cost of bringing water to the desert

Abu Dhabi, UAE (CNN) -- During the summer months, in the arid, subtropical coastal plains of the United Arab Emirates, temperatures rise to 40 Celsius plus -- while average rainfall is a desolate four inches a year.

And yet, in the years since the discovery of vast oil reserves in the late 1950s, a forest of skyscrapers, luxury apartments, verdant green gardens and golf courses has risen from the sand.

It's been made possible only with recourse to unimaginably large amounts of water. Indeed, at 550 liters a day, Emiratis consume more per head of population than anyone else on earth.

"It just evaporates very, very quickly," explains Ivano Iannelli, CEO of the Dubai Carbon Center of Excellence. "Then when you add the lifestyle requirements -- the giant swimming pools; the cooling systems; the big gardens that need irrigating four times a day ... it goes some way to explain why the water consumption is so high."

With scarce native freshwater supplies, Iannelli says the oil-rich nation spends hundreds of million of dollars a year purifying coastal seawater. For a country that, according to OPEC, boasted over $74 billion crude-oil export revenue in 2010, the financial burden may seem relatively light. But the cost to the climate, says Iannelli, is certainly not.

"Desalination requires a lot of power ... we estimate that about four tonnes of carbon are emitted per million gallons of freshwater produced here," he says, with reference to the energy-intensive process of removing salt from seawater (see factbox).

To put that figure in context, Iannelli says that the energy required to pump freshwater from underground (which, he says, is the most common source of drinking water in the West) typically produces just over 1.5 tonnes of CO2 per million gallons.

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 The Fujairah desalination plant in Abu Dhabi has a freshwater generation capacity of 492 million liters a day, making it the biggest single producer on the planet, according to Iannelli, who notes that it "totally dwarfs anything found in the West."