Note: In general these figures have been derived from work done by Waterfootprint.org and represent gallons of water consumed per pound of food (except for beverages, whose volumes are listed). They represent global averages, not specific conditions in any one place.
Fruits, Vegetables & Grains
If you want to really reduce the water footprint of your food then eating a diet where fruits, veggies and grains for the vast majority of your calories is clearly the way to go—it also happens to be healthier, cheaper and better for carbon emissions, by the way. But even here there are some big variations:
Lettuce -- 15 gallons;
Tomatoes -- 22 gallons;
Cabbage -- 24 gallons;
Cucumber -- 28 gallons;
Potatoes -- 30 gallons;
Oranges -- 55 gallons;
Apples -- 83 gallons;
Bananas -- 102 gallons;
Corn -- 107 gallons;
Peaches or Nectarines -- 142 gallons;
Wheat Bread -- 154 gallons;
Mango -- 190 gallons;
Avocado -- 220 gallons;
Tofu -- 244 gallons;
Groundnuts -- 368 gallons;
Rice -- 403 gallons;
Olives -- 522 gallons;
Chocolate -- 2847 gallons;
Meat & Dairy
This is where water intensity really starts increasing. If you want to reduce the water footprint of your diet, this is where you want to really cut back:
Eggs -- 573 gallons;
Chicken -- 815 gallons;
Cheese -- 896 gallons;
Pork -- 1630 gallons;
Butter -- 2044 gallons;
Beef -- 2500-5000 gallons; (Global figures for the water intensity of beef vary so significantly that an average isn't particularly informative, so a range of figures is given)
Beverages
You want something to drink and keep your water footprint as low as possible? Tap water is probably the best thing, but even the most hair-shirt person wants some variety, so here is how the water footprint of some beverages breaks down:
Tea (8oz) -- 7 gallons;
Beer, barley (8oz) -- 36 gallons;
Coffee (8oz) -- 29 gallons;
Wine (8oz) -- 58 gallons;
Via : http://www.treehugger.com/files/2009/06/from-lettuce-to-beef-whats-water-footprint-of-your-food.php