Half a croissant, on a plate, with a sign in front of it saying '50c'
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Selfish rivers and doughnuts

Lots and lots of freash water.
  (+21, -5)(+21, -5)
(+21, -5)
  [vote for,

Vast quantities of valuable fresh water is disappearing from our land every day all around the world, after a nano seconds research the chief culprit has been found to be rivers.

Rivers really need to give something back to society, especially the farmers and people how get really hacked off with them during droughts.

So this is where the giant doughnuts come in. So you connect a great big pipe from the river mouth and direct the river water to the centre of the 5km diameter doughnut. As fresh water floats on sea water; hey presto you have 295 million litres of fresh water to make the farmers happy. Most important to for the wheat crops as you can make yet more doughnuts!

Land based reservoirs need to be very strong to hold back tons of water, and cost millions of pounds to build let alone the large amounts of land to be purchased. An off shore reservoir needs only a thin impervious sheet to retain that fresh water.

That’s the concept; just replace the doughnut with a circular floatation ring. (Similar to oil containment booms) with an added curtain wall below. Fresh water is kept apart from the sea water.

Oh and you don’t need to block off the river or take all the water from the river mouth.

During severe storms the whole reservoir can be submerged by 5 to 10meters to avoid damage. This would be done by reducing the air pressure in the boom segments which reduces their buoyancy.

Some problems to overcome: How much will the saltwater and fresh water inter-mix at the halocline layer? Perhaps only the lower 20% say of the reservoir would be ‘slightly salty’. Or would wave and wind action mean it all get s stirred up? In which case an extra impervious sheet would need to be added at the bottom of the reservoir to keep the fresh and salt water apart.

Not bad for use in parts of the Mediterranean, Gulf of California, Middle Eastern Gulf states etc.

WaveyDave, Sep 18 2007


       So the idea is to save all that fresh river water wasted in the oceans? Interesting concept.
GutPunchLullabies, Sep 18 2007

       sp: shellfish
po, Sep 18 2007

       So what would happen to the Netherlands if this caught on in Germany?
zeno, Sep 18 2007

       Whoa. The idea is to dam freshwater at sea by floating it on salt water? I have to say, WaveyDave, that I think this is a bloody brilliant idea.
MaxwellBuchanan, Sep 18 2007

       Who's Doug and how did he get nuts named after himself?
Texticle, Sep 19 2007

       This should be built using waters from the Daling river in China. As the engineers watch anxiously to see if it has worked, they can collectively sing this song: "Doughnut forsake me oh my Daling"
xenzag, Sep 19 2007

       Did it not perhaps occur to you that fresh runoff water has some significant role in the ecology of the ocean?
BunsenHoneydew, Dec 09 2007

       Er, as the fresh water floats, how much are you going to contain in your doughnut? That is, the tendency will be for the salt water to push the fresh water up (and out of the doughnut), rather than the fresh water pushing the salt water down.
phoenix, Dec 10 2007

       good point [phoenix]   

       The column of fresh water would need to be 1.025 times as tall as the seawater column, and hence protrude above surrounding sea level. If the reservoir is 10 meters deep, the donut sides must be at least 25 cm above sea level.   

afinehowdoyoudo, Dec 10 2007

       The difference is that small?
phoenix, Dec 10 2007

       //"Doughnut forsake me oh my Daling"//   

       [xenzag], That pun was truly awful! Brava!
csea, Dec 10 2007

       Not too many rivers I know about are fresh as they discharge into the sea. Most large perrennial rivers are tidal - you'll have to collect your fresh water somewhere upstream of the mixing point - which can be as far as 10-20km from the coast.   

       Maybe in exceptional flooding will they run fresh at the mouth, but mostly not, to my knowledge. <standing by to be corrected>   

       Still a good idea, just gotta pipe the gear a little further. The floating it above the saltwater bit is genious.
Custardguts, Jan 21 2008

       Pure water floats in seawater with about 2.5% showing, pure ice floats with about 14% showing.. we need a new proverb like "the tip of the iceberg"... maybe "top o' the pond" ?   

       In any case, the sides would need to be much higher, or the top completely covered, to prevent waves washing over into the pond. So a big bag (or many smaller ones) might be better than a big donut. Still a stellar idea!
afinehowdoyoudo, Jan 21 2008

       In places which are really short of water, river water tends to get used up or polluted before it reaches the sea. E.g. the mighty Colorado river, whic carved out the Grand Canyon is now nothing more than a trickle when it gets to the sea, just so the residents of Phoenix and LA can have green lawns.
hippo, Jan 21 2008

       Rivers are less salty than the ocean, but the longer the water sits in the reservoir the saltier it would get. Silt that is now distributed over wide areas would settle out and build up, as it does behind dams. Coastal fisheries would be negatively affected. In other words, this idea is only half baked. Bun.
Ford, Jan 26 2008

       I think giant buns would work better.
Arcana, Jan 27 2008

       Aren't doughnuts just fried buns?   

Giblet, Jan 27 2008

       //How does that work?// its murphy's law, or entropy, or chemical potential.. nature abhors a difference in chemical concentrations almost as much as it abhors a vacuum!
afinehowdoyoudo, Jan 28 2008

       This idea is very ambiguous and I don't think it is going to work very well. Anyway, how many fresh water consuming farmers actually live in the ocean? Another thing is that, often enough, some rivers don't even make it into their gulfs during times of drought because people are diverting all of the water upstream for agricultural purposes. Finally, it's best to take advantage of gravity and divert the water when it is at a higher elevation before it gets to sea level, or else you'd be paying a huge penalty in pumping and transport for this.
quantum_flux, Jan 28 2008

       // Are you trying to tell us ...// no, just a roundabout way of saying thats leaks are a fact of life.. especially at sea where there's plenty of wave energy sloshing about & random bits of pointy flotsam
afinehowdoyoudo, Jan 29 2008

       So what are you going to do with this donut of fresh water? Inflatable booms are a temporary measure. They break and get washed over if there is any heavy wind or storms, so you have to use the water fairly quickly. Obviously the people near the river don't need it, they already have fresh water and irrigation. You can't move it anywhere without a rigid container, because a soft boom has no structural integrity, and you are talking about a very heavy mass of water if it's anything over a few thousand gallons. You could pump it to someone, but then you'd be just as well off pumping it straight from the river in the first place.
DanDaMan, Jan 29 2008

       uh,,, what? just soak the giant donut up river where you need it. and truck it to a farm. then he can have a bonanza of water from the donut right when he needs it.
cornpad, Jan 31 2008

       "uh,,, what? just soak the giant donut up river where you need it. and truck it to a farm. then he can have a bonanza of water from the donut right when he needs it." -Cornpad   

       I don't understand your use of the word "soak" in reference to transporting water. And why would we want to send fresh water back up river where it came from? There already is fresh water there. Then once it is up river, we load it onto trucks and send it to farms?   

       So let me get this straight. We collect water at the bottom of a river, we then push that water back up the river to where it came from (I have no idea how you would do that), we then load it onto trucks and drive it all over the nation? And this is a brilliant idea?
DanDaMan, Jan 31 2008

       I think the main problem is with the term "fresh" in fresh water. The dead zones in the Gulf of Mexico are growing alarmingly as a result of the high levels of nitrogen runoff from agrobusiness land. It is thought the sharp increase is related to the increase in corn planting for agrofuel. On the other hand, using nitrogen-rich water for irrigation might reduce the need for more fertilizer. How are you going to pump it? And who needs more doughnuts?
harperolocito, Jan 31 2008

       [quantum_flux], et al.. the idea is essentially a method of storing water when it is available and using it when needed. Storing fresh water at sea could be very cheap & configurable compared to on-land storage, even when subsequent pumping is taken into account. During the spring run-off, large of amounts of fairly pure (albeit silty) water are available, & could be stored inexpensively for use during summer drought by this method.
afinehowdoyoudo, Feb 02 2008

       I would rather store water in an actual reservoir than trying to hold it at sea. The sea is constantly moving around and would quickly wash out all the fresh water with salt water. If the water was not completely separated, it would diffuse together very quickly.
DanDaMan, Feb 03 2008


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