Every year, on March 22, the United Nations invites all the world's citizens to celebrate water.

Here are some footprint calculators you might find interesting:

Products calculator: from apples to wine, see the water footprint of each: www.waterfootprint.org - sheep's meat looks to have the highest water footprint.

Here's an  extensive water calculator for your home use: wecalc.org, you do need to put in your e-mail address.

• The production of one kilogram of beef requires 22 thousand litres of water.
• To produce one cup of coffee we use 140 litres of water.