How much water is required in a meal?

It used to be once said that clean water and security are free in Japan. However, the myth is on the verge of collapse. I have read an article in the Nikkei newspaper on 11.05.2008 about Japanese water consumption. What I found really interesting is how much water requires in our meal. To make the explanation clear, the concept of "Virtual Water" is introduced in the article. Virtual water is the amount of water that is used in the production of food. For example, a cup of milk requires 110 liters of water in the production process. A kilogram of beef costs 2 tons of water. I was astonished that a huge amount of water is required if we convert our meal into virtual water.
Japanese annual rainfall is 1,718 mm, which is double the world average. However, if we look at the amount per capita, it is only one third of the world average. An expert explains in the article that one of the reasons we do not feel seriously water shortage in Japan is that we import plenty of food from abroad. Japanese self-sufficiency rate of food is only 39%, which is the lowest rate among the developed countries. If Japan tries to produce all the amount of food we need in Japan, it will costs 62.7 billion tons of water. It is quite difficult to achieve it, according to the university of Tokyo. The nobel prizewinning organisation IPCC reported that water resource in the globe will be dwindling to 10% to 30 % by 2050 in the face of global warming. I think food shortage results in water shortage. It seems to me that all the problems in the world are linked to water shortage. I have no idea how to find the solution, but I have to keep in mind, our days of plenty are numbered. It is time to live with frugality, which is a phrase I was taught by my grandfather.