Thomas Sutcliffe: Sorry, but this is just a drop in the ocean...

Here's a downturn with a silver lining. According to a retail analyst, sales of bottled water in Britain have fallen for the first time, dropping nine per cent in the year to March. This may be because of general belt-tightening, or it could be that people are getting less comfortable about the ecological costs of bottling and shipping the stuff.

But, either way, it's clear that the bottled water companies aren't just going to sit on their hands and let their oasis of profit simply evaporate. In the same Sunday paper that I learn about the drop in sales, I come across an advert for a new Volvic promotion. Buy one litre of "1L=10L" branded Volvic, the company promises, and it will supply 10 litres of drinkable water in Africa through a partnership with the charity World Vision. This water, the advert implies, comes with a special additive. It's got philanthropy dissolved in it.

On the face of it, nobody loses. Volvic gets to polish its corporate credentials, World Vision gets extra funding and the British consumer can re-hydrate in the knowledge that he or she is doing their bit. But since Volvic has presented its initiative in arithmetical form, I found myself provoked into doing some sums myself.

Ten litres of water is roughly the daily consumption for one person in the developing world, so anyone who does their duty and sinks a litre of Volvic a day will be covering the water needs of one African villager. Buy in bulk and it will cost you less than 50p a day, which sounds pretty good. But if you genuinely want to spend your money on slaking African thirst, rather than easing your own conscience, there are immeasurably more efficient ways of doing it.

The charity WaterAid, for example, which specialises in water projects, reckons that a £15 donation will cover the per capita cost of providing safe water, sanitation and hygiene education for years and years. Spend the same sum on Volvic and the cup will run dry after 45 days.

Here's another sum. WaterAid calculates that the cost of water for Tanzanians who buy their supplies from street vendors is about £4 per cubic metre, compared to about 80p per cubic metre for British tap water. If my maths is right, a cubic metre of Volvic, at current supermarket prices, will cost you a staggering £355 (and would supply drinking water for just ten people for a little over three months). So, if you were to stop buying Volvic and drink tap water instead, you would have enough cash spare to permanently supply a small village with clean water.

And there are more piecemeal ways of doing it. A while ago, Juliet Banner, a restaurateur in Crouch End, north London, came up with the idea of applying a voluntary charge of 15p for diners who asked for tap water, with the money going to safe drinking water projects. After three years, with very few customer refusals, that one restaurant had raised nearly £10,000 and the scheme is now being rolled out to other restaurants.

None of these sums, it should be noted, takes any account of the ecological downsides of bottled water in terms of energy costs – a contribution to global warming which may be playing its own part in desertification and water shortages.

And, when you add those in, it should be clear that while the "1L=10L" scheme might be good marketing it is less than efficient charity. Whether it is on a restaurant table in London or bubbling out of a standpipe in Africa, Volvic's water may be unsustainably expensive.

Oh for a gentler Gladiator

Connoisseurs of silly bombast had a treat this weekend with the unveiling of a new roster of Gladiators, in anticipation of Sky's revival of the steroid abuser's favourite TV show. We'll soon be able to enjoy the muscle-bound pugnacity of Destroyer ("Angry and unstoppable"), Predator ("Hunts down prey and takes no prisoners") and – my favourite – Battleaxe, left, who looks like a Waffen SS pin-up and is described as "aggressive and indomitable". But isn't there room for a champion for the gentler viewer? What about Conciliator ("Always ready to see the other person's point of view") or just Meek ("Expects to inherit the earth, but won't shove to the front of the queue"). It would be nice if modesty triumphed just once.

* Alicia Keys is reported to believe that gangsta rap was invented by the US Government as a way of promoting internecine strife and preventing the rise of a new generation of black leaders. I suppose it might offer an explanation for the lethally self-defeating nature of the more violent rap songs – but I find I stumble when I try to imagine the government office in which this dastardly plan was conceived and prosecuted.

Located in Foggy Bottom or at the CIA headquarters in Langley, it would presumably have contained earnest young Ivy League types in button-down collars. In one corner a zealous young intern would be thumbing through a rhyming dictionary looking for words that go with "Glock" and "Uzi" and "ho", while in another some bright spark would be on the phone to Snoop Dogg, offering him Federally-crafted insults to sling at East Coast rappers. I just can't see it myself. Gangsta rap was a self-inflicted wound.

t.sutcliffe@independent.co.uk