Virtual water (also known as embodied water) refers to the water needed to produce food and other goods. One hamburger (125g) requires a staggering 2400 litres of water to produce it!
People consume water not only when they drink it or take a shower. In 1993, Professor John Allan (2008 Stockholm Water Prize Laureate), strikingly demonstrated this by introducing the “virtual water” concept, which measures how water is embedded in the production and trade of food and other products.
Behind that morning cup of coffee are 140 litres of water used to grow, produce, package and ship the beans. That is roughly the same amount of water used by an average person daily in New Zealand for drinking and household needs. A hamburger needs a whopping 2,400 litres of water. Per capita, Americans consume around 6,800 litres of virtual water every day, over triple that of a Chinese person.
Virtual water has major impacts on global trade policy and research, especially in water-scarce regions, and has redefined discourse in water policy and management. By explaining how and why nations such as the US, Argentina and Brazil ‘export’ billions of litres of water each year, while others like Japan, Egypt and Italy ‘import’ billions, the virtual water concept has opened the door to more productive water use.
The following table shows the amount of virtual water ’embedded’ in a selection of goods.
1 glass of beer (250 ml)
1 glass of milk (200 ml)
1 cup of coffee (125 ml)
1 cup of tea (250 ml)
1 slice of bread (30 g)
1 slice of bread (30 g) with cheese (10 g)
1 potato (100 g)
1 apple (100 g)
1 cotton T-shirt (250 g)
1 sheet of A4-paper (80 g/m2 )
1 glass of wine (125 ml)
1 glass of apple juice (200 ml)
1 glass of orange juice (200 ml)
1 bag of potato crisps (200 g)
1 egg (40 g)
1 hamburger (150 g)
1 tomato (70 g)
1 orange (100 g)
1 pair of shoes (bovine leather)
1 microchip (2 g)