Request for brainstorm: world of rivers

I was just sitting here, waiting for you to post about it.

First, whether or not you have underground lakes (and underground streams and waterfalls) would depend on what sort of ground material your world has. Do they have something like limestone that would dissolve quickly and easily, thus forming deep underground caves? Which case there would have to be underground lakes.

OR... would you have lakes? I would think so. Sooner or later, there's got to be a valley, even if it's small and just at the bottom of a mountain stream. Lakes are usually fed by rivers and sometimes even feed OUT into rivers, so they would be possible and frequent.

What sort of climate? Varying climates? Are we talking a fairly tropical planet, which case there would have to be a pretty good amount of water, or are we talking more of a desert world? Do they have three-fourths water one-fourth land like we do? Less? More?

*loves a good brainstorm*

Does the entire planet have to be that way?

I mean, presumably it has ecosystems and weather patterns, which means an entire planet would likely have varying climates.

Personally I find it to be a stretch to create a livable planet that is so uniform.

There could be glaciers that are steadily melting and providing the water. But at some point, they'd end up creating large bodies of water. But that could be thousands of years off.

I'm sure there's a way it could work.

I think that it would have varying climates, yeah, but I can't give you a scientific reason why I think that.

In a lot of jungles, even when there aren't rivers, the ground itself is just saturated with water.

And what about plants? If the planet, as a rule, doesn't have climates and is more uniform, then depending on the rainfall, the plants might absorb huge amounts of water and just retain it.

I wonder with, with the water you're talking about and NO oceans, if NEW glaciers might be formed, over time...

I think -- and this is recalling ecology stuff I read years ago -- that rainforests have three levels: The roof, the leaves and the upper branches. Then, the ground, with small plants, animals (who drink out of pools), moss, flowers, bushes, etc. Then there's the third level, below ground, with roots and...er....more roots, even. ANd the soil itself sometimes just sops with water.

I remember when I lived on St. Croix -- which was a lot of tropical forest -- that you could scoop a handful of the ground out and your hand-hole would pool with water almost instantly. So there's a lot of water retained.

I wonder if the cloud cover would be thicker than the cloud cover we experience, since there might be a LOT of water in the clouds (then again, there might not be) which might not be heavy enough to fall as rain.

AND THEN...if there's increased cloud cover, that can affect the temperature, which means the environment might be unstable. Somewhere that's tropical might become colder if it's covered in clouds for a year, or longer. If there's a thick cloud cover, that could drop the temperature enough in already chilly conditions to cause the reformation of glaciers (or at least, the replenishment).

MidnightMuse said:

Well that's certainly interesting - a tropical rainforest that's actually chilly ?
hmmm

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Well, logically following that...

There is a tropical rain forest. Lush, soaking wet, everywhere. Eventually, there's also a heavy cloud cover which drops the temperature. Not enough to cause snow, I don't think, but it's constantly overcast and that leads to a colder season. EVENTUALLY (this would take a year, probably longer) it cools off enough that the thriving tropical plants begin to die, or at least dry off. Does that mean that there's potential for a fire?

Either a fire, or just the death of the plants results in a lot of dead matter on the ground, which means the sight of a tropical forest is suddenly, perhaps, a plain, which means increased winds (tornados?) and means that the clouds start moving (forgive me, but my meteorology is more rusty than my ecology). This blows in new weather fronts, causes rain, causes all manner of storms. Does this make a more moderate climate (oak trees, evergreen trees, etc.) to grow? Or do the clouds eventually blow over and the tropical climate eventually resurfaces.

Or does it resurface? Without the plants to absorb the water, does it absorb into the ground and just run off? So does this tropical environment turn into a moderate climate, or would it turn into a grasslands sort of plains? Or might it actuallyturn into a desert, now that the land (and plants) aren't retaining as much water and the evaporation rate isn't as high.

...

What I like about this idea, as I'm extrapolating it (rightly or wrongly) is that you effectively are left with a mobile climate. Meaning that a tropical forest could be trackable, as the years go by, where it literally shifts across a land mass. So you might be born in a house, in the jungle....and die in a house, in the desert.

Some other brainstorming questions to ask:

What sort of lifeforms have evolved on this planet? Are you putting humans there as colonizers or some other sentient race?

Dune was an all desert planet, so what you're describing doesn't seem too far out to me.

There are a few worldbuilding SF how-to books out there which might help you extrapolate. I think one's by Ben Bova.

A desert world, like the world in Dune, is feasibly easier to imagine (except for the breathable atmosphere) than a world with a functional water system and ecology.

Interestingly enough, the book I keep thinking of when discussing this was Alan Dean Foster's Drowning World. Also wonderful was Larry Niven's Ringworld.

If *I* were writing on this world, it would be a group of human beings who landed, who have no particular technology, who are primitive (iron age, I think) wandering sorts.

It would be more fun. For example, if a part of the world goes from being a desert (dry environment) to a jungle (moist environment) would they people know how to handle the increase chance of infection and disease that increased moisture, such as bogs and water in the wounds, entails? Would the PEOPLE in those areas survive? Or would they be as nomadic as the climate and ecological niches?

What if the rivers you're talking about were more like what goes on in the human body?There's no ocean of blood in any human; it all runs to and fro. There could be something to an ecosystem like that, where your rivers act more like arteries, veins and capillaries. Something that moves it all. It could be an interesting plot device as well.

Rivers flow downhill. Somewhere, there has to be a lowest spot where the water will collect. With that little water surface, a great deal of what collects will evaporate, but that means that whatever is left will build up very high mineral concentrations -- think Dead Sea times ten.

If you have a lot of underground lakes, or aquifers (more like a wet sponge than a lake), you're going to get less evaporation. I can't say for certain, but I would be concerned about there being enough evaporation to drive the water cycle.

Another consideration is that large bodies of water moderate the weather. A planet that is mostly land surface will have an extreme climate - think Central Asia times ten -- very cold winters and very hot summers.

I like someone's suggestion of large icecaps. Some of the ice will sublimate, which will increase the amount of water vapor in the air. Also, you can get some seasonal melt around the edges to jump-start your rivers. You would have glaciers in the mountains, too. Those would also contribute to the rivers. The downside is that cold air can't hold as much water vapor as warm air.

In any event, my gut feeling is that you will get an landscape something like Egypt -- vegetation in the river valleys with desert in between.

Have you considered springs and geysers? That might help get those rivers flowing.

Seems to me that you don't get a decent water cycle (evaporation, clouds, rain, rivers...) without oceans. If the water runs into the ground, what puts it back on the mountains so it can be rivers again? If there are no mountains for the water to flow down, what moves the water? Rainforests exist because of oceans, the shape of the continent and location on the planet (specifically in the temperate and equatorial zones). It's interesting that the vast deserts of the world exist primarily in the same regions. But both the arctic and antarctic regions are also considered deserts, because of low rainfall, not temperature.

The above, of course, is based on a planet like Earth, with a tilt to its rotational axis that allows for seasons. If a planet has more or less tilt, things change. If the planet has no tilt, say, then there is little opportunity for thermal changes in the extreme north or south...so I'd think there'd be less to drive weather.

There are other planetary possibilities to consider, too: one that never changes its orientation to it's star, like Mercury (or the moon to Earth), or one whose axis of rotation points at the star (a hot pole and a cold one).

But I have a rough time conceiving of a planet of rivers without mountains and oceans, or at least, lots of large lakes.

MidnightMuse said:

See, I'm wondering if a planet without large bodies of water, ie: lakes and oceans, would have varying climates?

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The climates would vary more without the moderating effects of the oceans as heat reservoirs.

Evaporation can happen without a big water surface.

Depending on seasonality, you could have a very stormy world full of rapidly varying microclimates...not easy for complex organisms unless they had some kind of powerful reef or bioherm or root structures.

Once the bioherm/monster trees were in, then they would alter the climates themselves to some degree and reduce the extremes a bit and offer shelter to smaller creatures.

A good model might be the mixed reefs of the late Paleozoic in terms of the size and structure of the bioherms.

Pthom said:

Seems to me that you don't get a decent water cycle (evaporation, clouds, rain, rivers...) without oceans. If the water runs into the ground, what puts it back on the mountains so it can be rivers again? If there are no mountains for the water to flow down, what moves the water? Rainforests exist because of oceans, the shape of the continent and location on the planet (specifically in the temperate and equatorial zones). It's interesting that the vast deserts of the world exist primarily in the same regions. But both the arctic and antarctic regions are also considered deserts, because of low rainfall, not temperature.

The above, of course, is based on a planet like Earth, with a tilt to its rotational axis that allows for seasons. If a planet has more or less tilt, things change. If the planet has no tilt, say, then there is little opportunity for thermal changes in the extreme north or south...so I'd think there'd be less to drive weather.

There are other planetary possibilities to consider, too: one that never changes its orientation to it's star, like Mercury (or the moon to Earth), or one whose axis of rotation points at the star (a hot pole and a cold one).

But I have a rough time conceiving of a planet of rivers without mountains and oceans, or at least, lots of large lakes.

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Geysers? Volcanos? Mud volcanos?

If you start with an energy balance equation you get this:

Change in(thermal energy + potential energy + kinetic energy) of the water = heat input + work input.

Most rivers flow without heat or work input, that is the right side of the equation is zero. They simply convert potential energy(ie a height difference) to kinetic energy in the form of motion. As far as my basic ecology tells me, rivers keep flowing because solar energy heats water to a gas, transport it back to a higher elevation and precipitates it out where it can keep flowing. Unless your planet is some 1D mobius strip (which would probably cause, uh, other issues), you can't have a river complete a full loop around the globe on itself with just a potential gradient.

So if you look back at the equation you have two options. Either you can have some sort of work input, a massive natural pump, some sort of volcanic wellspring that maybe takes these underground lakes, hyper pressurizes them and shoots them back up in some sort of massive geyser. I don't know if you can have something that does this on a planetary scale, but it would be a pretty interesting tourist attraction for the planet if you could. Or your planet will reach a steady state where the rivers will move at a rate where enough can evaporate off and precipitate in the higher regions to keep them moving. If rivers are wide but shallow, then you would have an interesting world. Though something tells me if the world was full of such rivers it would lose water and dry up within a few thousand years.

Personally, massive geyser sounds much cooler.

JNot all rainforests are tropical, you know. At least people familiar with the Pacific northwest would know.

Regards,
Scott

Popeyesays said:

JNot all rainforests are tropical, you know. At least people familiar with the Pacific northwest would know.

Regards,
Scott

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Well, duh. But the rain forests *I* was discussing *were* tropical. Primarily because the rain forests that I grew up in and around (practically "in," St. Croix is barely contained towns with jungle filling them up) were tropical.

Since this is brainstorming, feel free to talk about non-tropical rainforests.

MidnightMuse said:

...

The people ... have limited supplies and will eventually adapt and technologically simplify their lives. And then I wondered if they wouldn't - eventually - create man-made lakes for recreation anyway, thus altering the ecosystem ... .

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Did they bring excavation equipment with them?

Or maybe some beavers?