My immediate thought is at what point does desalination tech + clean energy reach the crossover where building a 60 mile tunnel over 60 years not make sense?
It feels like very soon, and coastal cities can stop relying on hinterland reservoirs for water.
Capital vs operating is a big factor here. The tunnels operations & maintenance cost is probably far lower than a desalinization plant that could produce an equivalent volume of potable water.
Desalination will be a West Coast thing. The East Coast has abundant fresh water.
It’s probably more likely AI will become sentient and kill us than it is desalination and clean energy are cheaper than this.
This was only a 60 year project because of politics.
Probably never. The tunnels cost a lot to build but, once built run almost for free - they're powered by gravity and will keep running for close to a century before major maintained is needed.