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  1. Gammer

    Gammer Active Member

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    Effects of Dumping Salt into a Fresh Water Source

    Discussion in 'Research' started by Gammer, Nov 7, 2016.

    Hey all,

    I'm wondering just what would happen to fresh water source like a river and a lake when you dump a great deal salt into it. Would the salt clear out eventually or would it linger? If it lingered how long would it stay in the water?

    In my work in progress a king, facing an inevitable overthrow by a rebellion, decides to to have the last laugh. He dumps all the salt he has gained from trade into all the nearby lakes and rivers in the kingdom. He also dumps the salt into the soil so nothing can grow.

    Fast forward a few generations and when the MC travels to this old kingdom he finds the land dead since very few plants can grow and water so filled with salt it can't be consumed.

    How plausible is that outcome?

    Thanks in advance.
     
  2. Spencer1990

    Spencer1990 Contributor Contributor

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    I'm no scientist, but I think the answer you're looking for would depend LARGELY on how much salt the king dumps into the water and land. I mean, if he literally covers the land in salt, I could buy some long term impact. But a half-pound per five square feet (for example) wouldn't have the kind of long-lasting effects you're looking for.

    And I'm giving you this information as someone who is not a scientist (average reader). I'm sure someone else will chime in and potentially tell me I'm wrong. So take this with a grain of...well...salt. :p
     
  3. EnginEsq

    EnginEsq Member

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    In our world, it depends Unless you're talking salt amounts at the level of an evaporated salt-water sea (e.g. the Great Salt Lake or the Dead Sea) and/or a completely arid climate, a variety of mechanisms will mitigate the salt over time.

    1) some plants absorb salt.
    2) rain pushes salt down into the soil, eventually pushing it deeper than the roots.

    Now, if there are no rains, the salt will stick around, but why bother slating land that has no rain to support corps? If the land is irrigated, then you can use the irrigation water as a substitute for rain to flush the salt. Now if there's a layer of clay that prevents water from percolating (like caliche) the salt won't perc very far, so that might stop it, but clay layers like that don't make for the best farm lands in the first place.

    Salinization of crop lands is a big concern out in the farmlands of the U.S. southwest. I'm sure there's information on the various ways such land gets desalinized on the web.
     
  4. SardonicWriter

    SardonicWriter Member

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    If we're talking about making it so that in the next generations land can grow next to plants,
    then surely the lake ecosystem must have been impacted as well. No plants? Well hell, no fish
    or anything larger than microbial life, I think. Dead Sea type of proportions.

    That's an obscene amount of salt. Unless there's rain to lessen the amount of salt or if any attached
    rivers lead out to oceans then that salt is going to stay there. EnginEsq is clearly more informed on this
    than me, and he also posted faster than me. Shoot.
     
  5. BayView

    BayView Huh. Interesting. Contributor

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    There was definitely a tradition of sowing salt in enemies' lands historically (or at least a legend of it) but that would be the land, not the water.

    For the salt to stay in the water that long, there would have to be little outflow, I would imagine. Rivers flow by nature, so I don't think they'd stay contaminated for that long. Some lakes have a lot of water turnover as well, so they'd probably recover more quickly. But if you had a lake that didn't have a lot of water turnover, it might work.
     
  6. BayView

    BayView Huh. Interesting. Contributor

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    See the range of times at https://en.wikipedia.org/wiki/Lake_retention_time for an idea of how long it takes different lakes to refresh themselves.

    ETA: Interesting that even two lakes in the same system can have very different refresh times - 2.6 years for Lake Erie, 191 years for Lake Superior. I'm guessing that it's because they're different sizes, and I guess because Lake Erie is downstream from Superior, so it not only gets all the water Superior releases but also all the extra water from the surrounding watersheds?

    But the amount of salt it would take to significantly salinize Lake Superior would be ridiculous. Its volume is apparently 12 000 cubic kilometres (!!!), and salt in seawater is approx 35 parts per thousand. So... careful, it's math time... that would be 3.5%? I think? So 420 cubic kilometres of salt. I think.

    ETA2: This is kinda fun! I'm trying to find a way to wrap my head around cubic kilometres - it's not a measure I'm used to. But I think a cubic kilometre would be a billion cubic metres? Is that right? 1000 x 1000 x 1000? I'd guess salt probably weighs roughly as much as water, so lets say a metric tonne for each cubic metre. That would mean 420 billion tonnes of salt. ?????!?! Is that right? Can somebody check my math? I must have missed a decimal somewhere, or something...

    Except salt weighs more than water. Salt sinks. So... shit, it would be even more than 420 billion tonnes of salt? Am I losing my mind?!?
     
    Last edited: Nov 7, 2016
  7. Gammer

    Gammer Active Member

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    Thanks everyone for your input and information so far, this is all really helpful! :)
     
  8. SethLoki

    SethLoki Retired Autodidact Contributor

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    And that's not counting the really...Really...REALLY big spoon you'd need to stir it in!
     
  9. BayView

    BayView Huh. Interesting. Contributor

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    Don't even get me STARTED on the spoon calculations!
     
  10. SethLoki

    SethLoki Retired Autodidact Contributor

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    Okay then. 'There is no spoon'

    :)
     

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