Bang goes another illusion. I thought that if I stopped the tap running while I brushed my teeth, thus saving 9 litres of water, and showered instead of bathing in a tub, I could consider myself a good water saver. Having done my little bit to save this precious global resource, I rewarded my virtue with a cup of coffee – which just used up one cupful of water. Didn’t it? Afraid not. 

Fred Pearce’s compelling book, When the Rivers Run Dry: What happens when our water runs out? (Eden Project Books, 2006), has punctured this comforting fantasy. Making a cup of coffee in fact uses up an astonishing 1,120 cupfuls of water, just to produce the coffee itself. A teaspoonful of sugar adds another 50 cupfuls of water. So my one cup of coffee actually uses up 1,170 cupfuls of water. Oh, and that doesn’t include the milk, which uses up an eye-popping 1,000 litres per glass. (Yes, that’s 1,000 litres, not 1,000 cupfuls.) 

And I still haven’t included that cupful of water I poured from the kettle into the coffee cup… which I hadn’t realized was only the last of many, many cups in a long and water-heavy process. 

Pearce is a science journalist who is also a wonderful storyteller. It’s time for a blue revolution, he says – though, unlike most revolutionaries, he writes without haranguing: more in sorrow than in anger. But you can sense the depth of his passion, which quietly powers this elegy to our beautiful blue water planet.  If you want one serious book to read this spring break, this could be the one.

For the water-extravagance of my one cup of coffee is as nothing compared to the amount of water sucked out of the planet by the production of some other everyday foods. A solitary cheeseburger consumes a staggering 3,000 litres! Sound unbelievable? Tot it up and see. 

It takes 24,000 litres of water ‘to grow the feed for enough cow to make a kilo of beef’ (Pearce). So producing 100 grams of beef - about the size of a quarter-pounder - will have consumed 2,400 litres of water. Producing a kilo of Cheddar uses around 5,000 litres, so even 50 grams of cheese will have used up 250 litres. Two slices of bread consume 300 litres (a hamburger bap is plumper than slices of bread, but let that pass).  So far, my burger has already cost the planet 2,950 litres of water – and we haven’t yet counted in the water-cost of producing the onions, the cooking fat, the mayonnaise or the mustard, so I reckon 3,000 litres is a pretty conservative estimate. 

Since the water-costliest item in the cheeseburger list was the meat, would a vegetarian diet be less extravagant? Probably, though the vegetarian meals that require cows or other ruminants to produce milk are a lot more costly than others. For example, if I were to inflict that pallid, sticky blob of cholesterol known as cheese risotto on my poor family, who have done nothing to deserve it, that would mean using 2,500 litres to grow a half kilo of rice, another 2,000 litres for the cheese, and at least the same again for the cream. That’s 6,500 litres of water for a plain lunch for four. 

Would a vegan lunch, avoiding animals altogether, be less water-expensive? Possibly, though I don’t know for sure. A pound of potatoes could feed four people and use up just (just?) 250 litres of water, with a mixed salad adding another 2,000 litres. It sounds like a better proposition, but I have no idea how much adding tofu, say, or chick peas would add to the water bill.  It seems to me that we all need a lot more education about the water-costs of food production. 

And we also need a good name that sums up the issue in a phrase - like ‘food miles’ brilliantly summed up the environmental costs of transporting food around the country or around the world. Any ideas? 

But doesn’t bathing and washing clothes use up at least as much water as lunch? No, nothing like as much. Pearce reckons that typical northern citizens use around 150 litres a day for washing and flushing the loo - even Americans typically consume no more than 400 litres a day for household use, he says. It’s peanuts compared with producing …er, peanuts. 

So how about adding water costs to food labels? Maybe someone could start a campaign for this – do write in and tell us, if you know someone who is doing this already. 

For unless we all start to count the water cost of what we eat and what we drink, we will soon suck our planet dry, with no idea about how we did it. After all, we switched to showers, didn’t we, and turned the taps off when we brushed our teeth?