Virtual water is a measure of indirect consumption of water resources in the form of agricultural products, silicon chips and other goods requiring significant quantities of clean water in their production.

Daniel Zimmer, Director of the World Water Council, in his presentation at the session on "virtual water trade and geopolitics" at the 2003 World Water Forum in Kyoto:

"When you consume one kilogram of grain, you are also consuming 1,000 litres of water needed to grow that grain; when you consume a kilogram of beef you are consuming 13,000 litres of water needed to produce that amount of meat, and this is the hidden or virtual water. It is this unconscious behaviour that causes humans to consume so much water. [...]
"The contrast in water use can be noticed between continents. In Asia, people consume an average of 1,400 litres of virtual water a day, while in Europe and North America, people consume about 4,000 litres. About 70 per cent of all water used by humans goes into food production. [...]
"Among the biggest net exporter countries of virtual water are the U.S, Canada, Thailand, Argentina, India, Vietnam, France and Brazil. Some of the largest net import countries are Sri Lanka, Japan, the Netherlands, South Korea, China, Spain, Egypt, Germany and Italy."