Virtual water value in food supply management

Virtual water is the fraction of water required to produce the good under consideration. A double definition of the value of virtual water for a food product can then be proposed. The value equals to the real water consumption at production site, or the value of water needed to produce the same quantity of the same product or the equivalent in terms on nutrient contents, on the consuming site of the product. This last value is inverse of water productivity on this site. The concept of virtual water feeds several complementary visions: strategic vision for food security, liberalism vision for developing water markets, ecological vision to alleviate pressure on natural resources, solidarity vision for food supply and environment. Virtual water is governed by at least three of the main principles ruling real water: principle of real water savings, principle of accountability of actors, principle of security of supply.