Footprint

The basic idea of water footprint is simple: It is the amount of water used by a household or a country, or the amount used for a given task or for the production of a given quantity of some product or crop. For the latter, it means the total volume of freshwater used to produce a product, summed over the various steps of the production chain.

For example, the production of a cup of tea requires 32 litres of freshwater, a glass of milk means 200 litres, and one kilogram of beef is equivalent to 15,000 litres.

And, therefore, it goes without saying that for countries with limited water supply, it is far more cost effective (and more environmental friendly) to import a spoon of tea leave or a bottle of milk than to transport that gigantic volume of water to make the corresponding items locally. In fact, even if a country does not have to import water from other places to grow their own food (hardly any countries actually need so), there remains an opportunistic cost to pay. For example, do you really want to cut down the petroleum consumption slightly (by doing away with importing food from other countries) but, at the same time, cut down the freshwater available in a local river (with a number of ecological consequences to follow)?