1. The water footprint of a person, family, community, nation is the total volume of fresh water used to produce the goods (including food) and services consumed, in other words, the water footprint is the volume of water required to sustain a personal or family lifestyle or indeed a global population;
2. The virtual water content of a food is the volume of water it has taken to grow, process and prepare the food rather than the actual nutritional content and it is the virtual water content we consider when we talk about the water footprint of a food for example an apple has a virtual water content of 70 Litres of water, a 100g orange 50L; 100g of chicken meat 390L and 100g of beef 1600L;
3. The water footprint of a food or product can increase significantly if the production process gives rise to waste water that has to be treated or waste products that have to be diluted before they are disposed of;
4. Water is called blue when it is surface water or is abstracted from groundwater and is called green when it is infiltrated rainfall;
5. A food can have a different footprint depending on where it is produced. For example if cotton product is produced in China it has a virtual water content of 5404 m3/ton, but if it is produced in India it will have a virtual water content of 21563 m3/ton. The variation will depend on the amount of rainfall, the water available in the soil and the amount of water needed for irrigation and the water required to dilute processing by-products before disposal.
6. Virtual water consumption varies between countries dependent on the level of personal consumption in terms of food, goods and services. In the UK it is 1245 m3/person/yr, in the US 2483 m3/person/yr which is three times the level in China.
7. The per capita consumption of virtual water contained in our diets varies according to the type of diet, from 1 m3/day for a survival diet, to 2.6 m3/day for a vegetarian diet and over 5 m3 for a US style meat based diet.
8. The water footprint of a food is often not in the country where the food is being consumed;
9. A nation’s water footprint can be described by location either as internal, where the nation’s footprint is within its national boundaries or external when goods are imported and the water used to produce those goods is external to the country;
10. The UK has a relatively high water import dependency of 70%. This compares with other European countries such as Switzerland (79%), Belgium-Lux (80%), Netherlands (72%) but much higher than France (37%).