The dayside of this arid, tidally locked world has no rain, but instead has glacier-fed endorheic rivers. Winds are unending, and vary from ~15kph to ~50kph depending on distance from the glaciers.

The renaissance-era society on this world is clustered around rivers, which provide water and food. Vegetation is only found near rivers, and the most useful is fast-growing bamboo (construction/fuel/food). Canals/flooding could be used for crop irrigation, but water is scarce and I'm not sure if this would be practical (and would there be salinity problems?).

There are no large wild animals because of the low vegetation cover, but some lizards, snakes, rabbits, weasels, etc. Few insects (humidity) and no birds (winds). Most rivers have enough fish to support major settlements.

The unending wind causes tornadoes, sandstorms, and snowstorms (near the glaciers), and has also eroded much of the terrain. I'm not sure where dirt comes from to replace the blown-away dirt... maybe from glacier erosion?

For protection, cities are built behind the remaining hills, down inside river valleys, or dug into glacier edges. Structures are built from bamboo, clay, and stone. Windmills are the main energy source.

Travel/trade between cities on the same river is accomplished by horse(?)-drawn barges, while travel between far-apart rivers is done by land sailing. I'm estimating ~100km per day for a car-sized yacht.

Is this natural and realistic? What pieces am I missing?

Edit: regarding the water cycle - this paper suggests nightside glaciers would be replenished indefinitely by snow from dayside evaporation (far far away from civilization).

Edit: title changed from "Planet" to "Hemisphere" to be more accurate

  • $\begingroup$ Fascinating. It sounds familiar. $\endgroup$
    – Slarty
    Nov 22, 2020 at 23:50
  • $\begingroup$ I guess there really is nothing new under the sun. What's it similar to? $\endgroup$
    – Dalas120
    Nov 22, 2020 at 23:53
  • $\begingroup$ With endorheic rivers and no rain there Will be a problem in refilled the glaciers especially on a tidally locked world. You might find some of my questions of interest as I have explored a number of similar scenarios: worldbuilding.stackexchange.com/users/42450/slarty $\endgroup$
    – Slarty
    Nov 23, 2020 at 0:05
  • $\begingroup$ Wouldn't they have unlimited energy through windmills? $\endgroup$
    – Joe Smith
    Nov 23, 2020 at 2:08
  • $\begingroup$ @JoeSmith good idea! Let me edit that into the original post. $\endgroup$
    – Dalas120
    Nov 23, 2020 at 2:12

3 Answers 3


I believe that the scenario is entirely plausible and is definitely so for story purposes. It should appear sufficiently plausible for the suspension of disbelief for 99% of readers. For the 1% of the most skeptical element there may be issues, however skepticism may not always be based on sound knowledge of what is a specialist topic so it would be difficult to improve in this area. Some things to consider are:

The lack of oceans could well have a profound effect upon civilization beyond the obvious. For example there might not be any significant fossil fuel reserves, or at least none within the habitable region. There might be a lack of sedimentary calcium carbonate based rocks such as chalk and limestone. This would have implications for buildings (no traditional cement) and for iron and steel production (no traditional coke, only expensive charcoal and no easily accessible carbonate flux for steel production). So lower grade expensive iron based products perhaps. The civilization might not have many easy option for exploration very far beyond their immediate vicinity.

I suspect that you do have large land animals – assuming this civilization is some sort of vaguely humanoid being. If so they must have evolved from something so there must be or have been some sort of ape size creatures. If there are other smaller mammals as well, there could be scope for some larger herbivores such as sheep or especially goats or even camels or similar.

What is the role of plate tectonics on this world? Without them erosion would eventually flatten the surface leading to shorter rivers more river meanders > then swamps > then lakes right next to the glaciers. With active plate tectonics this could be much less of a problem; however there might then be the prospect of radical reshaping of the environment. For example if land is pushed up or lava flow blocks a key waterway the entire water distribution on the surface might be refashioned in a different direction.

The wind speeds where the cities are located would not be unmanageable in the open, but cities might still want to protect from the wind for comfort. They might (as well as or instead of) choose to build wind breaks out of trees or embankments. Glacier edges do not sound like a promising location for a city. Unless there is some elevation the most likely location for a glacial lake would be right in front of a glacier. Even if not so glaciers also move and are unstable. Windmills sound like an excellent choice of power source.

Navigation of the area sounds plausible, but is subject to many conflicting considerations. How far apart are the rivers? Walking would work unless they are widely separated. If widely separated and if my understanding is correct - the wind blows from the same direction all (or the vast majority) of the time, the journey would be lopsided easy one way, very hard the other way manually hauling with sails down. This would likely be very expensive indeed. If any draught animals are available even dogs they might be employed to help pull a wagon on the return journey, but the operation would be limited by the return journey not by the out bound.

One potential way round this would be to introduce some variation into the topography. With the correct river flow direction and strength they might be able to be blown up river and sail down river. I could even imagine lowering the sails below the water level going down stream to reduce the wind drag and help prevent the vessel from being blown upstream (so as to anchor the boat into the current).

I would have thought that birds could cope with the winds you describe especially towards the lower end where winds would most likely to encounter life. If all else failed the birds could effortlessly use flight to escape predators and then fly back or even walk back or make use of higher ground and the counter currents of turbulent air in such areas.

  • $\begingroup$ Many good points! I didn't have any special plans for plate tectonics (ice sheets wouldn't affect that, right?), but river changes could make for excellent plot-related emergencies. I was hoping that long-distance land-yacht travel could be done at angles to the winds, with sails tilted like on a sailing ship. $\endgroup$
    – Dalas120
    Nov 23, 2020 at 22:45
  • $\begingroup$ I suspect that ice sheets do have an impact on plate tectonics, especially on the vast scales likely to be encountered on your world, but they are important. Perhaps an oceanic plate might behave a little like a continental plate if it were piled up with miles of ice, but I'm not sure there. Perhaps you could get some cross wind land sailing. It would be worth thinking about the placement of the rivers and winds very carefully. You might even be able to be blown across in one area and return by river or vice versa. From memory winds blow out to the north and south and in from the east and west $\endgroup$
    – Slarty
    Nov 24, 2020 at 9:53
  • $\begingroup$ Consider windwagons or even sail driven rail cars. Conditions seems ideal for this type of transport: constant winds, no forests, flat surfaces. $\endgroup$
    – Zjerzy
    Nov 24, 2020 at 23:39

How long has it been like this? Because glaciers are a seriously limited source of water on a geological scale. Once they melt, it is all gone.

Something might be done with a snowpack and reasons why it only snows there and does not rain below, but something has to explain why there is still enough water from glaciers.

  • $\begingroup$ I'm basing my world off of this paper about proxima centauri, which suggests that the glaciers (covering over half of the planet) would be replenished by evaporation from the dayside. $\endgroup$
    – Dalas120
    Nov 23, 2020 at 2:09
  • $\begingroup$ Glaciers are a limited source of water on Earth, but I don't think that is always true. In this case we have a tidally locked world so the scope for cold traps is huge and the amount of water that can be transported by the atmosphere might be significant. A lot will depend on the exact details of the topology, atmosphere, temperature, eccentricity and water content of the planet. $\endgroup$
    – Slarty
    Nov 23, 2020 at 10:27
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    $\begingroup$ This feels like a comment, less so an answer. $\endgroup$
    – BMF
    Nov 23, 2020 at 11:29

Natural and realistic...

There's two ways to approach this. Based on current understanding, it doesn't appear that the "no rain" aspect is plausible. You already discuss water condensing into the atmosphere. And the paper you linked about Proxima Centauri β also discusses precipitation of H2O. Without doing the math, I'd have to say that the likelihood of no rain would require, at least, a very different atmospheric pressure or composition, either of which would also make life on that planet likely to be rather different than what we're used to on Earth. Even looking at non-Earthlike planets, planets that have atmospheres are generally believed to have precipitation, even if it is not water precipitation.

Since it's tidally locked, it's plausible to have a jet-stream (especially given the wind) that by some mechanism only allows rain on the dark/cold side of the planet. In that event, fresh water may not be readily available on the livable side of the planet (even less so if the livable section is only the ring around the terminator between light/dark sides of the planet - and actually this could also account for the winds given the temperature variations "mingling" in that ring region).

You also note snow, which is precipitation of H2O. While some areas could be deserts (in the technical sense regarding low precipitation), it would be hard to find a convincing reason that the bulk of the planet would not only be a desert, but be absolutely arid.

Alternatively, as humans we don't know what we don't know. There are many mysteries even on Earth still to discover, let alone the functionality of other celestial bodies. Given that, you could find some theoretical method by which this could all occur, or even create one from whole cloth using any current known or theorized planets as a basis.

Aside from the livable terminus ring (which might just be the ticket), an Earthlike planet (at least like current Earth) will have water. Without water being common, the ecosystem would be quite different. If the ecosystem was quite different, the atmosphere would be different. If the ecosystem and atmosphere are different and there's a very tiny amount of water, it would likely not have developed animals (including humans) similar to what we have on Earth.

  • $\begingroup$ A note on that is with regards to fish. The arc of development for fish on a world where water is very limited... it's not impossible, but it might be worth exploring. If there are fish, what are they like? Without millions of years of evolution in massive oceans, I expect they'd not only be very small, but probably without a lot of variety. No assurances of such a thing, but just a note. $\endgroup$ Nov 23, 2020 at 20:44
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    $\begingroup$ My understanding is that if there was a lot of water, all the precipitation would be on the dayside (because heat = hadley cell = lower temperature = rain). But since almost all of the planet's water is trapped in ice sheets, the dayside never gets near 100% humidity, and water only precipitates at the extremely cold nightside. Therefore the dayside would be guaranteed to be arid. That is still rain though - I'll changed the title to be "Hemisphere" instead of "Planet" to be more accurate $\endgroup$
    – Dalas120
    Nov 23, 2020 at 22:13
  • $\begingroup$ @Dalas120 ah, that makes sense. So it’s tidally locked it would have to be outside of what we consider the Goldilocks Zone for habitable planets, else the star side would be too hot. Either it’s much further away, or the star is much weaker than our own. But that means that the cold side would be very, very cold. $\endgroup$ Nov 23, 2020 at 23:21

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