Virtual water is the total volume of freshwater used to produce a commodity, good, or service. The concept reveals the hidden water embedded in traded products and helps explain global water resource transfers.
Virtual water, a concept introduced by Professor Tony Allan in the early 1990s, represents the total volume of freshwater consumed or polluted throughout the full production chain of a commodity, product, or service. For example, producing one kilogram of beef requires approximately 15,400 liters of virtual water (including water for growing feed crops, drinking water for the animal, and processing), while one kilogram of wheat requires about 1,800 liters. Virtual water has three components: green water (rainwater consumed through crop evapotranspiration), blue water (surface and groundwater consumed), and grey water (freshwater needed to dilute pollutants to acceptable levels). International trade in agricultural products involves massive virtual water flows between countries; water-scarce nations can effectively import water by purchasing food produced in water-abundant regions, a strategy that eases pressure on domestic water resources. The global virtual water trade amounts to approximately 2,320 billion cubic meters per year, with agricultural products accounting for over 90 percent of the total. The concept has been instrumental in raising awareness about the true water costs of consumption patterns and has influenced discussions about food security, trade policy, and water resource management. Critics note that virtual water calculations do not distinguish between green and blue water or consider the opportunity cost and local impacts of water use in exporting regions.