Vertical city farming on a large scale is fucking stupid. Rip the local water table. It's bad enough with flat farms taking water a little bit from a large area because that still rapes your water table. Now imagine that condensed into a city.
Unless you find somewhere you don't give a shit about turning into a desert and piping it from there and rinse repeating the process every few decades.
What is rainwater harvesting?
nice runway
Rainwater harvesting denies the local table much of the water it needs to replenish itself. Also you would need fucking huge catchment systems for the kind of city wide systems proposed here. Having a big barrel fed off the roof will be nowhere near enough.
wut? Rainwater is currently sent away as fast as possible. And best storage is in the ground. Vertical farming is gay as fuck but rainwater harvesting is not a problem.
You have to think though, about the fertilizer.
There is literally no reason for "urban farming". The land isn't suitable. It's a retarded idea entertained only by dumbshit hipsters who aren't grounded in reality.
The point of permaculture is you don't need fertilizer.
"Vertical farming" is a meme for idiots who never leave the city and earnestly thing we're constrained for horizontal space.
Cities themselves, below a certain size, aren't bad, in fact they are pretty comfy.
But New York City style nonsense is cancer.