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I have been toying with the idea that all oceans are gone. Underground water still exists but the Earth has essentially turned into the planet from Dune.

My characters all live / survive out where the oceans once were as it's the closest source for water. The Earth is now just one big desert.

My question is, instead of 100% of all surface water gone, is 90% more feasible? I plan on having larger civilisations, mining towns etc. I want water to be a rare commodity, but not so rare that only 5 people can live off it.

As the majority of the story takes place out in these vast oceans of desert, there are going to be some large swathes of distance in-between continents / countries. Initially people were going to get around on horse back, but there's too much distance for a horse to travel, then I considered intercontinental railroads but that is taking technology in a direction I hadn't planned on going. So, if I leave a small portion of the ocean, travel by boat could seem plausible.

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    $\begingroup$ Given majority of trade is done by moving cargo across the water (be it ancient times or modern times), if 90% water vanishes, it is guaranteed there will be a global economic crisis of unprecedented levels. $\endgroup$ – Physicist137 Jan 21 at 3:57
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    $\begingroup$ Yeah we're well and truly past the point of global economic crisis at this part of the story ;) $\endgroup$ – Tomás Richardson Jan 21 at 4:02
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    $\begingroup$ Earth will survive just fine without water. Now, life on Earth is a different story... $\endgroup$ – John Dvorak Jan 21 at 4:32
  • $\begingroup$ The immediate problem is that with the oceans gone, the hydrological cycle slows to a crawl -- basically, there is no more rain, and all Earth is a fierce desert. What little water is left will naturally pool in the deepest parts of the ocean basins, where the high pressure will make for hellish temperatures. Plants will die, and with plants gone almost all oxygen will be consumed in less that a million years. $\endgroup$ – AlexP Jan 21 at 5:46
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    $\begingroup$ Mandatory XKCD. draining everything dry means all (or nearly all) the aquifers are dry, too. Everything dribbles to the lowest point. $\endgroup$ – JBH Jan 21 at 6:10
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There are a number of issues with eliminating our planet's oceans...

Our planet's gravity holds onto our water pretty tightly. The energies needed to evacuate several oceans worth of water out into space would probably also take our atmosphere along for the ride. You could send the water deeper into the planet's crust, but that leads to other issues...

50-85% of our oxygen comes from phytoplankton which live in the oceans near the surface. Eliminate the oceans (or even just poison them badly enough) and that oxygen goes bye-bye. Similarly, if the water submerges deeper into the crust, the percentage that remains near the surface will decrease greatly, leaving less room for the phytoplankton. So no matter where the water goes, oxygen will be in short supply after it is gone.

To combat the oxygen loss, you could evolve the phytoplankton to no longer require an aquatic environment. They could continue doing their job for us, living off of the nutrient rich silt and rotting fish corpses which cover the newly exposed ocean floor. That would give you a green and smelly desert, but at least your characters would still be able to breathe.

There would be other issues such as climate change and storm intensification. We might even discover that the former ocean waves served a hidden function, absorbing momentum from the winds which would otherwise rise to constant storm force everywhere. Your ocean-less planet is quickly transforming into a literal hell on Earth.

Earth would undoubtedly survive without its oceans, but its current infestation of organic life would probably not remain upon it for long.

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    $\begingroup$ +1 for the last paragraph - Earth'll be fine. We won't, but that's not the question being asked. ;) $\endgroup$ – jdunlop Jan 21 at 6:27
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    $\begingroup$ I'm also worried about the salinity of the remaining water. Maybe it's not an issue, but something to worry about. $\endgroup$ – rje Jan 21 at 15:21
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    $\begingroup$ Plankton loss is only a problem in the long term. Just because the water disappeared does not mean that the oxygen did as well. With virtually no civilization left, oxygen consumption goes way down, so the reduced replenishment rate is not the problem you think it is. In the short term. $\endgroup$ – WhatRoughBeast Jan 21 at 22:06
  • $\begingroup$ @WhatRoughBeast, valid point, but to support it, you would have to provide a method by which the de-oceaning of the planet instantly reduces population levels. Not a hard challenge given options like infrastructure collapse and crop loss, but for this particular answer, I was trying to save the extinction aspect of the event to punch up the last line. Thanks as always for keeping me honest! $\endgroup$ – Henry Taylor Jan 22 at 3:52
  • $\begingroup$ Population will not be a massive issue as a cataclysmic event has taken care of that, hence the situation of the oceans drying up. The narrative takes place a very long time after these events, purposely to try and give life a change to grow and evolve over time. Originally the idea was to completely remove the oceans, however going over XKCD posted above, I quite like the idea of shallower oceans, pooling in the deepest parts of the Earth. At least with that, I think I can solve quite a few of the issues without turning the planet into a literal hell on earth. $\endgroup$ – Tomás Richardson Jan 22 at 6:01
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The single biggest issue you'll face is the loss of thermal mass. One of the key reasons that deserts are so hot during the day, so cold at night is that there's no water that soaks up the heat and releases it slowly through the night. In your world, this is now the norm so your days will be extremely hot, and nights extremely cold.

Within the bounds of habitability? With underground homes, perhaps. I wouldn't want to be living on the surface though.

Water in such an environment is very precious, and your inhabitants will most likely have mechanisms similar to those described in Dune for rendering water from the dead and other biological material for re-use. Their Stillsuits would also be a likely invention as you wouldn't want to waste sweat or urine because of the water content.

Of bigger concern would be the impact on vegetation, both marine and land based. The real issue here is that trees (which you'll still need to generate oxygen, especially now the phytoplankton is gone) need lots of water to grow, and they expect to live in an environment where they regularly get rainfall. You've also got the food issue as crops need water. Meat is definitely out because you won't have enough water for grass, and the amount of water required to 'raise' a meal of red meat by comparison to a vegetable based meal is massive.

Even with 10% of the previous water levels, I don't see you rebuilding large cities of any kind because the amount of water required in most mining and industrial applications is prohibitive and the infrastructure required to do so requires seeding from an industrial complex probably from before the water loss.

I'd see society degenerating into small clans, fiercely protecting what water holdings and crops they have the manpower to defend. Clan structures don't scale well, the lack of water also makes trade next to impossible because of the increased cost of 'shipping' and as such, societies won't reach the critical mass of size where there is sufficient food and protection in place to support a small core of researchers or scientists tasked with making things better.

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Life would probably revert to some basic form. A large part of the phylogenic tree would disappear.

Bacterias, archeas, micro organisms and insects would probably survive.

Anything sophisticated like mamals would have a hard time and humans would probably disappear.

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If your goal is primarily water shortage, would it work if the water isn't actually gone, but has somehow become non-potable? It would need to be some means which would make reclaiming usable water either impossible or difficult to the point of being almost prohibitively expensive, so both water and the means to obtain it become precious. Some form of toxicity could also contribute towards desertification.

Not sure how you accomplish this. It's been years since I read it, but I've a vague memory of Gregory Benford's Timescape featuring some form of algal contamination that led to an ecosystem collapse. A lesser form of that might provide you with a lack of usable water without the issues associated with actually removing it. And you could still use it for industrial purposes which would resolve the issue @Tim B II raised,

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  • $\begingroup$ Absolutely. Based on some further readings, I've decided that shallower oceans might be the way to go, essentially just very large lakes. But yes, the idea was to for the water to be non-potable and it has to go through some kind of filtration process to be drinkable. I have planned for whole a society to be built around the mining / filtration process. I have actually been meaning to read Timescape for some time and you are not the first person who has recommended this to me in recent weeks. $\endgroup$ – Tomás Richardson Jan 22 at 6:10

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