Earlier quoted context omitted.
It takes energy, not time. It takes a long time if you passively wait for random environmental processes to slowly replace the water, and a very short amount of time if you actively apply energy to the problem.
That actually highlights the problem perfectly. Energy is the metric that matters. With current knowledge and level of technology humanity has, we can make almost anything by applying energy to shuffling dirt. Need gasoline? We can synthesize it. Need gold? We can recycle it out of stuff. Need drinking water? We can make it out of almost anything. All that's needed is energy, which is something we don't have much of…
One key questions for rulers and governments from antiquity is how to allow the population to gather energy to survive. It could be farming, or building oil wells and then hand out the profits or build a service economy around the oil.
I couldn't figure out how to maintain a modern population without oil (more people same amount of land) until I saw this on HN the other day https://medium.com/invironment/an-army-of-ocean-farmers-on-t...
Zero input food. Can be used to generate ethanol. All you need is open ocean.
Food for thought.