IT is assumed that an individual consumes about 2 litres of water every day for drinking. But have you ever wondered how much water is consumed when we eat an apple or a slice of bread? The food we consume contains calories. A medium-sized apple has approximately 95 calories, a slice of bread has 66 calories and a cup of black tea has about 3 calories. To produce these items, we need a certain volume of water. An apple requires 70 litres, a slice of bread requires 42 litres and a cup of black tea requires 28 litres of water. So, when we eat these food products we are also consuming water in its indirect form. This indirect water incorporated and used by humans is called ‘virtual water’. It is defined as the volume of water used to produce the goods as well as services that we consume and use. We call it ‘virtual water’ as the water is no longer physically contained in the product. This applies not only to food products but also to other goods such as jeans, pencils, smartphones, etc. So, virtual water is the largest volume of water we consume every day, larger than the water we use for drinking, washing, bathing, sanitation, etc.

This concept was first introduced by Prof. Tony Allan from the King’s College London in 1993. He proposed this concept when he was researching on ‘how countries with water scarcity can meet their water needs?’ Countries in North Africa and the Middle East have less water resources and hence cannot produce all the food products that they need. They import the food that cannot be produced in the home country.

Q-1: what is an assumption of individual water consumption for a day?                        

Q-2: How many calories contained a medium sized apple and a slice of bread ? Q-3: What is ‘ virtual water’ ?                        

Q-4: Why we called virtual water as indirect water ?                                                   

Q-5 : Who first introduced the concept of virtual water?