I'm curious what you mean about the nature of the population?

Age? Ethnic makeup? Urbanisation?

The population is older, less white, more in cities, fewer kids, but I'm not sure what any of that has to do with our water consumption or ability to build for it - other than maybe older people, especially the ones that moved out of the cities to live some LOTR-inspired faux-rural lifestyle, tend to be more NIMBY?

But equally though our appliances and lifestyles aren't the same as 1960. Showers are massively more efficient than baths, but we use them daily instead of once a week. Industry has mostly disappeared, and thermal power stations are on the way out (both extremely heavy water users), but agriculture has become more intensive.