A water potable water supply that is say for three or four suburbs in a city together, and there'll be a standalone system. So if that system needs maintenance and goes down for a bit, the systems around it keep going. Whereas at the moment, if you have one problem in a water plant, the whole city goes down.

So it's not just water. We need water that's not polluted. And so that there are drinking water standards that need to be adhered to. So traditionally we just get that out of a stream or a pond. But now we've got so much population in areas which the climate doesn't lend itself to supplying such a lot of water for so many people. So we need to seriously think about how do we actually provide clean drinking water. 00:52:16 And if we don't, and this is the problem with the next one, which is sanitation. If we don't have proper drinking water, we start having disease rippling through our society, which will cripple us, our ability to do certain things. And so we have to have the ability to filter water. And so we might move into a society where water will have to be filtered through, you can make a filter with things like charcoal and rock and gravel. 00:52:42 And water might have to go through that to remove its bacteria load. See at the moment, our water is purified in water purification plants, but they're done centrally and their water's pushed out along all these pipes all over the city. So what if that is no longer practical? For example, we can't maintain such a large network of pipes anymore easily. So we might have to go to a more localized way of managing water.