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Floating Lake

Everyone likes lakes, no-one likes the land use
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Many consider water as a critical resource for humanity and its associated environment. To protect this resource, I am surrounded by water saving technologies: Low-flow showers, flow-restrictors on taps that aerate the water so it looks like there's more than there is & toilets that only flush 3.6 litres*.

This is understandable in Arizona, but Philadelphia nestles between two large rivers, there's plenty of water. Globally also, there is plenty of water, there's no water problem, it's a salt problem**. Now, this doesn't start as a problem, rain is freshwater, extremely fresh in most cases. The problem is that it often falls directly into salt water before we can get to it.

So, how about we pick a nice calm bit of sea with a reasonable rainfall. The equator is a good place to start looking, as rainfall and calm are features of equatorial ocean. The location should be near shore in relatively shallow waters so that some anchoring is feasible. Nearby land, especially mountains can encourage local rainfall also. Here we construct our nice freshwater lake.

Now, freshwater is less dense than seawater so, if you can separate it from the ocean, it floats. Let's start with a large steel floating ring. From the bottom of this we build a large plastic bag. Initially this could be filled with seawater and subsequently desalinated or filled by pipe from a land source. With a little bit of structural reinforcement from a very flexible wire/plastic mesh we should be able to harness the ~2% buoyancy and making a 2.5km deep lake will provide enough lift to raise the rim 50m from the sea surface.

Now you can stock it with freshwater fish, some floating plants to keep evaporation down and you have a nice freshwater lake that will even be able to supply water under pressure to places right on the shoreline.

* You do have to flush them twice, the orange man is right.

** Although I'll admit there are some local variations.

bs0u0155, Jul 31 2020


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Annotation:







       This would be a great idea to have for a very small island that doesn't get enough rainfall to sustain the people there. Get that little offshore freshwater lake going, perhaps guarded by a breakwater and you're in business.   

       Cool idea.
doctorremulac3, Jul 31 2020
  

       //So, how about we pick a nice calm bit of sea//   

       (+) Nice, but 'that' might be a problem. You will need some sort of sea-wall to keep salt spray from sallinating your fresh water lake. Shouldn't be too hard though. A series of buoys with an outwardly facing 'C' shaped clear plastic curtain aughta do the trick.   

       // Nearby land, especially mountains can encourage local rainfall //   

       Dependent on prevailing wind directions, you don't want to be in the rain shadow.
Skewed, Jul 31 2020
  

       //Nice, but 'that' might be a problem. You will need some sort of sea-wall to keep salt spray from sallinating your fresh water lake.//   

       We can live with a little salt, as long as there is influx and some outlet, then you will reach some kind of equilibrium rather than progressive concentration. Also, freshwater plants require ions, Ca2+, Mg2+, Na+ & various micronutrients that are found in seawater. By supplementing fertilizers selectively you can use plant growth to uptake seawater-derived salts. Also, it IS a wall, if it's 20-50m above, that should prevent most contamination.   

       //you don't want to be in the rain shadow.//   

       The opposite, in the norther hemisphere, that would be off the west coasts. Clouds build up against mountains and rain in front of them, we just need a nice west-facing inlet.
bs0u0155, Aug 01 2020
  

       // The opposite //   

       The rain shadow by definition is the side of the mountains that receives little or no rainfall because it's all been squeezed out climbing the mountains on the other side.   

       Not the side of the mountain it falls on.   

       So not the opposite.   

       For your purpose you don't want to be in the rainshadow.   

       Regardless of which hemisphere you're in.
Skewed, Aug 01 2020
  

       //We can live with a little salt, as long as there is influx and some outlet, then you will reach some kind of equilibrium rather than progressive concentration. Also, freshwater plants require ions, Ca2+, Mg2+, Na+ & various micronutrients that are found in seawater. By supplementing fertilizers selectively you can use plant growth to uptake seawater-derived salts. Also, it IS a wall, if it's 20-50m above, that should prevent most contamination.//   

       Huh... allrightythen.   

       That's one really large plastic bag. Origami and heavy lifting/cartage equipment will be needed in the manufacturing process.
wjt, Aug 02 2020
  

       [wjt]; yeah, but I think you would probably fabricate on- site, heat-sealing (or whatever) together from rolls of plastic.
neutrinos_shadow, Aug 02 2020
  

       I would have bunned you for the title alone. +
blissmiss, Aug 02 2020
  

       Just a random thought.   

       But isn't this largely baked by nature already.   

       Icebergs.
Skewed, Aug 03 2020
  

       //But isn't this largely baked by nature already.//   

       True, but it's very difficult to waterski on an iceberg. Seals get in the way.
bs0u0155, Aug 03 2020
  

       True but there's always skiing & snowboarding, & think how much fun [8th] could have with the seals when the cats run out.
Skewed, Aug 03 2020
  

       ^ Not nearly as much.
Only one life a piece you know.
  

       I'm diggin it. [+]
21 Quest, Aug 05 2020
  

       I made a drawing in my notebook of the exact same idea many years ago..... so I'm bound to approve. I actually thought I had posted it here, but there's no sign, so this has saved me the effort! Ha. In my drawing the lake is shaped like a giant child's flotation ring with a duck's head. I may post the drawing if I can find it easily.
xenzag, Aug 05 2020
  

       21...I spotted 21...hey how ya doing? Long time no see.
blissmiss, Aug 05 2020
  


 

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