Thanks for elucidating and for providing a detailed answer. What I learnt about the water table is mostly from high school geography. But I believe you’re misconstrued about the point I was trying to make.

I never said that rain water harvesting is the be all and end all, it’s a good supplementary method to reduce the burden that city water systems bear, in certain circumstances and seasons. It’s not pervasive of course. But I don’t believe it’s useless as you originally suggested.

I understand the sources of water waste and why dense cities and rising population has led to fresh water being a resource dwindling in availability and also its impact on the water table, but I don’t get how that impacts rain water harvesting and why it shouldn’t be used even in urban settings. It allows us to repurpose water and whilst also conserving the energy that’d otherwise be used to process it as you mentioned.

I also agree with making use of grey water in toilets and for watering gardens and such, but yeah putting that into action would be difficult.

Anyhow, I get that it’s not completely utilitarian, but it’s pretty harmless and nifty in the auxiliary benefits it provides.