26/08/2014 12:45 BST | Updated 26/10/2014 05:59 GMT

Why I'm Not Participating in the ALS Ice-Bucket Challenge

No, I'm not being churlish or reactionary. I think the ALS Ice-Bucket Challenge is a fantastic idea. It's a simple concept that has been shared globally and allows everyone from presidents to children to share in the same activity that spreads awareness of ALS (also known as Motor Neurone Disorder) and raises funds for research.

I have now been nominated three times, by a friend in London, another in Scotland, and my nephew in Hampshire. I couldn't respond immediately when I was initially nominated as I was travelling home after a holiday - ironically from the largest wetland in the world.

I started thinking about where I could film my own ice bucket dunking. The small town where I live has the second largest statue of Christ in Brazil - only the famous one at Rio is bigger - so I thought this might make a suitably dramatic backdrop. But after I talked to my wife about it my own attitude changed.

She thought that the obvious waste of an ice-bucket dunking is in poor taste given that São Paulo is suffering a severe drought at present. In parts of the state, the reservoirs are dry and cracked and all non-essential water use is banned. Where I live things are not quite so bad, but the local papers warn week after week that we are also on the cusp of extreme rationing.

We haven't been rationed in our town yet, so in theory there is nothing wrong in arranging an ice dunking in front of the tourists visiting the Christ statue, but as I started reading more about the issues faced in São Paulo I started feeling more guilty about any water that I'm wasting right now - not just the water I would need to film my ALS challenge.

Meteorologists cannot see when the present dry spell will end. Being British, I love these endless days of sun and 30c temperatures (in the middle of winter), but I live close to a reservoir and I can see that what once looked like an enormous lake now resembles a mud pit. The reservoirs are now so low that only an enormous - and unlikely - amount of spring rain will replenish them. The reality is that they will probably not be restocked at all this year so this area of Brazil is facing a water crisis that will go on until at least 2016. And maybe longer if changes in water use don't happen fast.

Critics in the media are arguing that the local water company, Sabesp, has not done enough to discourage waste. Left-wing commentators are using this opportunity to argue that you can't have a private - or even a public/private - water company because if they profit from sales, why would they ever encourage people to stop wasting water?

Regardless of the politics there is an acceptance that the cities are getting bigger, water demand is on the rise, yet nature is offering less to the reservoirs. Managing waste and improving the supply are enormous priorities right now in São Paulo - and Brazil in general. Don't forget that this is the wealthiest state in the country and we are struggling to cope here - think what it must be like in Amazonia, where scientists predict that average temperatures will rise by 8c over the next decade.

This is not just a problem for Brazil. California is suffering the toughest drought on record - ever. It's great for wine production, but farmers producing other crops are considering new careers that don't depend on rainfall. Perhaps an additional positive outcome from the ALS challenge will be that people start talking in more detail about how valuable water is today - and how it will become even more important in future. All those sci-fi authors who talked about water as a valuable commodity really were on to something.

So I will make a donation to ALS. I think the challenge is a great idea that has been wonderfully spread using social channels. Every charity and medical research organization across the world will surely be trying to think of the next 'challenge' that can grab our attention.

But I'd feel a bit guilty to go and chuck a bucket of water over my head today, given the current situation where I live in São Paulo. The sun is blazing today, so a bucket of water would be welcome right now, but then that's really the problem we have.

In São Paulo right now we just need some rain, not ice buckets.