What is virtual water ?
Virtual water is an estimate of how much water a food-importing consumer country would need if it were to produce the food it imports domestically.
For example, it takes about 2,600 liters of agricultural water to produce 1 kg of barley. Also, because cows consume large amounts of barley and other feed as they grow, it takes as much as 20,600 liters of agricultural water to produce 1 kg of beef.
In other words, by importing food from overseas, Japan is able to avoid using the amount of water required for its production. In other words, food imports can be thought of as importing water in a different form.
One could say that Japanese people depend on water from overseas for their survival. In other words, Japan is connected to the rest of the world through the import of virtual water, and water problems overseas, such as water shortages and water pollution, are not unrelated to Japan.