Simeon Brody
Many people now understand the concept of embodied energy, ie the amout of fuel resources it has taken to make or grow something and to get it to the consumer. However, the concept of embodied water is just becoming known. This may be called 'virtual' or 'embedded' water and it is the amount of fresh water used to grow or manufacture something. Water is just as important to us as fuel and energy, if not more so, and to understand our true use of this much under-rated resource can help us behave more ethically.
How much water do you use?
A fair amount of research has been done on this in the past 10 years, including the United Nations Education, Scientific and Cultural Organisation (UNESCO) Institute of Water Education which has looked at the impact of virtual water on different nations trading goods internationally, most recently holding a symposium on virtual water and biofuels. This research suggests that many countries, some of them with few water resources and problems of drought and poverty, are in effect 'exporting' water in the form of cut flowers, fruit and vegetables.
The amount of water 'contained' within various products is quite amazing... a cup of coffee has a water footprint of 140 litres, a kilo of wheat 1350 litres, a kilo of rice 3000 litres, a kilo of beef 16000 litres. Even a sheet of A4 paper has 10 litres! The Institute of Water Education has a brilliant and easy to use website, www.waterfootprint.org which allows you to estimate your personal water footprint. This is made up of the water you use directly plus that embodied in the food you eat. Like the carbon calculators I have explained about, this is just a 'rough and ready' attempt at giving us some information. My measured water use, via the water meter we had fitted, is 84 cubic metres annually for a family of four, therefore my share is 21 m3, or 21000 litres. However, the waterfootprint calculator suggests that my total footprint is between 650 and 700 cubic metres, and as a vegetarian who doesn't use much sugar or wash a car, this is lower than the national average.
So if you want to reduce your direct potable (drinkable) water use you can do a number of easy things. Lavatories use the most water, so these should be fitted with a dual flush or interflush retro-fit or a 'hippo' equivalent... see waterwise for more products and ideas. In the garden a water butt can replace a hose, and there are now many other ways in which rainwater can be harvested. When using tapwater to brush your teeth, don't leave the tap running. I've found that filling a mug half full and using that to wash my mouth out saves such a lot of water.
All these are direct water use. For virtual water savings, try to buy local, in season produce. As I keep saying with regards to carbon emissions, meat is also a no-no when it comes to embodied water. Visit waterfootprint for some other products with high and low embedded water and try to choose a diet and lifestyle which treats this resource with respect.
I have been harvesting rainwater since 1999. I use it to flush my toilets with, since fitting a dual flush toilet I have gone for almost two years on rainwater only. This system is constructed from readily available components and has saved a fortune (~£200 pa) economically and saved wasting drinking-quality water (which needs a fair bit of energy to treat) by contaminating it with poo. No limescale in the bowl either.