An article that I read today on BBC News summarizes a report by Engineering the Future alliance of professional engineering bodies which discusses a potential problem of Britain's import of water by proxy. Through the import of crops and good manufactured in developing countries, two-thirds of the water used to make UK imports is used outside its borders. The concept of "embedded water" is developed to account for all the water input into various goods.
Embedded in a pint of beer, for example, is about 130 pints (74 litres) of water - the total amount needed to grow the ingredients and run all the processes that make the pint of beer.
A cup of coffee embeds about 140 litres (246 pints) of water, a cotton T-shirt about 2,000 litres, and a kilogram of steak 15,000 litres.
This isn't a new concept, but I don't recall seeing firm figures attached to so many different foods before: 10 liters for a sheet of paper, 140 liters for a cup of coffee, up to jeans at 10,850 liters per pair, and so forth.
The article suggests that the fresh understanding of where water is used in the manufacture or consumption of imported goods may affect public policy.