Introduction: How to Water the Desert

Picture of How to Water the Desert

Here’s how to bring fresh water to all of those arid places you keep hearing about on the news.  This solution is simple and cheap enough that it could be built from parts from any hardware store and affordable in any country with a drought problem.  Basically, you use the sun’s energy to both pump water from the sea and convert it into freshwater.  It seems like most of the world’s water has salt in it, so we should use some of that.

Say you have a large otherwise useless plot of land, like the Sahara. By using the Thermosiphon principle you could pipe water from the ocean to the places that need it.  Here’s how it works:

Step 1: The General Idea

Picture of The General Idea

Hot air rises, the same goes for all fluids, such as water.  Given an extensively long pipe from the ocean to where ever needs water; you can coax that water to move through the pipe using heat.  If your desert is at a higher elevation than sea level, by applying heat to a portion of the pipe, the water inside becomes less dense and elevates.  The colder water prior to the heated portion of pipe, not wanting to create a vacuum, then rushes in to fill the pipe left by the heated water.  So as long as you have heat, water moves up and through the pipe.  (Just use check valves to prevent the water from descending at night.)

Hypothetically, you could pump seawater an infinite distance, given an infinitely long heat source.  Next comes that infinitely long heat source cheap enough to drag across the entire Outback, which could be constructed from soda cans and glass panes.

Step 2: Heat Source

Picture of Heat Source

Say your pipe was in a really hot, sunny place, like a desert, then you could easily use solar power to achieve water flow without using pumps.  A solar trough could cheaply be used to generate the heat necessary for this pumping.  Here’s how a solar trough works:  take a shiny half cylinder and face it generally towards the sun.  The parabolic shape reflects and focuses the sun’s rays towards a center point, in this case, our pipe.  (Here's the Wikipedia article)  This system is in use all over the world for industrial uses such as heat exchangers and can achieve extremely high temperatures.

Step 3: Modifications to a Solar Trough

Picture of Modifications to a Solar Trough

Generally, these systems rotate to follow the sun, but that’s expensive, and poor countries need fresh water.  One way to make this hotter is to combine the greenhouse effect in order to trap our solar heat in the trough.  Ever get in your car on a hot day and wish you could somehow utilize the heat difference between outside and inside?  By laying a sheet of glass atop the trough, we can trap that heat, making our trough more efficient.  Remember, we don’t need to boil the water, just attain higher temperature than the water before it necessary to generate flow. 

Another solution might be to distort the shape of the glass into a lens.  By making the glass get thicker towards the middle, we can further focus the suns rays and trap heat.   Just like roasting ants with a magnifying glass!

While this will not be as efficient as a rotating trough, the longer you extend such a trough, say for a mile or more, then the more thermal energy will be transferred into the water.

Step 4: Converting to Freshwater

Picture of Converting to Freshwater

Once the water reaches its final destination, you need to remove the salt.  The ancient and cheapest solution is to use a solar trough.  For example, if one were to stretch out a trough such as this picture of a solar still over some miles, the freshwater generated could be considerable enough for agriculture.

Here’s how this proposition works:  There is a reservoir of saltwater in the bottom of the still.  As the Sun beats down on the still, the rays generate heat which is once again trapped inside the glass.  As the saltwater in the reservoir heats up, the still becomes humid inside and freshwater condenses on the ceiling of the still.  Being as this still is slanted, the beads of moisture roll down the ceiling and eventually drop off into our reservoir of freshwater.

In this solution, we crisscross the incoming seawater from our heat-pump pipe across the roof of the still.  This accomplishes two things:  One, the incoming water is cooler than the still, thereby giving our heated moisture somewhere to condense(picture a cold glass of water on a hot day.)  The second is that it preheats the incoming seawater (via the sun) before dumping the seawater into the trough, which we want to be really hot. 

Step 5: Testing the System

I'm going to do some measuring to see the relationship between heat input and elevation of water through the pipes.  Commenter bbiorn informed me that coffee makers work on the same principle as this system, called Thermosiphon.

Apparently, a system similar has been proposed here.

I propose using copper tubes, slightly angled from a tub of water, and a propane tank underneath the tube for heat.  I'll prime the tube and install a check valve to keep water in the pipe prior to flow.

I'll probably blow myself up or burn down my back yard, but I'm heading to the hardware store now.

Step 6: Final Thoughts

Once we have a constant supply of fresh water into our desert, we can start growing some groundcover.  Apparently once you have a bunch of plants in an area, clouds are invited and rain becomes more common place.  Check out this thesis, ADRECS, and this one, Desert Rose. Growing plants in the desert causes the soil to become enriched because the plants deposit nitrates from the air into the soil and the plants decompose further enriching the soil.  Eventually, the soil is good for growing everything.

Even before you get to that stage, you have sun, dirt, and freshwater to grow plants.  Drip irrigation or a rotating irrigator could work here.  Still don’t feel like using pumps or fossil fuels for this project?  This thing (picture of Ox) runs on the plants grown and can be used for moving that rotating and pumping water through that irrigator (pic of irrigator).   

Use this invention if you live somewhere such as a small island with no fresh water, Yemen, the Sonora Desert, Australia…  You’re otherwise useless land now has value!


TudorS1 (author)2015-07-19

It is possible to boil water to the desert. If you use diagonal valves in the pipes the pressure of the expanding/heated water will push the water through the tubes.

And it is possible to heat the water in a cheap way..start with making the surface the color black...and there is a good suggestion in the book, without solar. See image. The pipes..well feel free to make the content of the book real. It does descibe a cheap way to make pipes....but..the question is still, if it is fantasy or real:).

Then again, it is always true that things need maintenance. Maintenance also means jobs.

Prof. A. Z. O_Trope (author)2015-01-11

Unfortunately, you can only "pump" water a few inches this way, at best. Yes, warmer water will rise to the top of a column of water. But in a pipe open at both ends, once the overpressure created by the water above the source exceeds the total pressure at the source (~ 1 atm.), water will stop rising. When you do the math, even very cold water at the source vs. nearly boiling water at the top of the pipe will only allow the water to rise a few inches.

(If your source pipe was insulated and could extend to great depth, and you could heat ALL of the water in the pipe, you could do somewhat better, but heating water at the inlet of the pipe would be costly and difficult enough to outweigh any benefit.)

The other error here is the usual one with solar & wind power. Yes, the energy itself can be regarded as "free," but you need land upon which to place the collectors, and even more important, you need to BUILD the collectors, and that costs money (capital investment). Even solar troughs are not free, nor are long pipes, especially (as others have mentioned), pipes that will not corrode in hot seawater. And once the facilities are built, they will need MAINTENANCE -- they will get dusty, they will corrode, microbes & insects & birds & animals will do various things to reduce their efficiency, etc., etc.

There are some viable concepts in ocean-thermal and solar-powered water pumping and desalination, but this is not one of them.

TUYUQ (author)2012-11-03

no one really tested it, and people saying it wont work.
I live in Jordan, we are the 4th poorest countries on fresh water in the world, and we have only 2400 meters of sea exposed to us, and beside that shore, there is a 45 degrees Celsius (85% of the year) desert which is useless and has no life what so ever. if this is feasible it will change this country for ever.

wagon173 (author)TUYUQ2012-11-19

I agree man! I'm in afghanistan right now and these guys here could sure use it too! I'm not sure where they stand statistically, but it hasn't rained since I got here in april! People are always quick to shoot an idea down, and it's few and far between that someone offers encouragement or advice or help. I say go for it! You may have a nobel prize in your future if it works! And if it don't, at least you'll know what not to do the next time you try! :)

TUYUQ (author)wagon1732012-11-21

for the good luck I am studying civil engineering :) I think with some tweaking and compromises this could work, I'll push it to my teacher thats for sure.

mvillalpando (author)TUYUQ2014-02-16

This idea can work, in sections, or fractals. If one were to incorporate Leonardo Da Vince's water pump instrument you may be able to do it in layers, or stages. See this link

TUYUQ (author)mvillalpando2014-02-16

I think taking the scale into perspective, the friction loss will be significant.
anyway I did study the salinity effects on the pipes in the parabolic through pipes and it will ruin the pipes in a very short time... however, I'm interested in this: , I think it could lead to something if we were able to proliferate it on a membrane or something and filter the saline water through it.

tokymaru (author)2010-11-07

i don't think water would rise above the surface of your source enough to flow through the pipe, though steam might.
the salt water alone would wreak havoc on the pipes, zinc would work out better, but maintenance would still be exhaustive and costly.
one break or leak in the line and you water source is gone at least until its fixed and flow is restored.
while it was a good thought, i don't think it would work out.

diy_bloke (author)tokymaru2013-10-22

you are right. the warmer water with a bit lower density may rise a tiny bit above the level of the sea water but if you need to go over some height, the water will just be pushed back in the pipe

diy_bloke (author)2013-10-22

nice idea but it doesnt sound very effective to me. Obviouly all that energu turned int heat in order to elevate the water, better be used for a regular pump

wagon173 (author)2012-12-10

It seems that you could definitely route a pipe line up hwy 15 to keep the amount of water fighting elevation to a minimum. Depending on if it works and how well, you could possibly construct a reservoir on top of one of the mountains or hills to provide water in the event of pipe maintenance. If it were possible, I'd try to make the heated portion out of 316 stainless and the rest out of a very thick schedule pvc to help offset the cost of the stainless steel. Working with plastic and marine grade stainless would also keep maintenance costs to a minimum in the long run. That's my two cents. This is a very interesting project though. When I get back to the US I may play around with a few ideas and let you know what I come up with. Once again, good luck!

scienceguy614 (author)2010-05-03

Another idea would be to make the pipe in an upside down U shape and create a little vacuum force at the end opposite of the water and after the water passes the very top, the gravaty pulling it down would created the water to follow and it keeps on going becuase the water is pulling more water along with it.
Try this: go to your sink, fill it up with water, next get a tube and dip one end in the water and have the other end go to the toilet or a bucket or something. Next, with the end thats going to the toilet or bucket, suck on it to create a vacuum force and then take your mouth of and have it point to the toilet or bucket. the water will keep going untll there's either nomore water or the tube is in air.

zombiefire (author)2010-04-07


buteman (author)2010-02-05

Coffee machines do not work on the thermosyphon system they use what is called a bubble pump system. Also the link you have shown as thermosyphon does indeed show how a thermosyphon works. Unfortunately your idea is NOT a thermosyphon as you can see that the thermosyphon is circulating water and most importantly all the circulation takes place below the water surface.
Sadly it will not lift water above the water surface by the method you propose.

lemonie (author)2009-12-06

You need to publish something you have actually done. Theory is good in a Forum Topic.
(Any thoughts as to why no one has done this yet?)


buteman (author)lemonie2010-01-23

I agree. As it happens I don't believe it will work - it would be wonderful to be proved wrong!

The coffee maker works because the water in the bottom is boiled, the bubbles of steam rise up the tube with some water. The average density of the 2 is low so the steam lifts some water with it.
The diagram Postonic has drawn does not show the water at the bottom being heated at all.
The top of the pipe is open so no vacuum would be formed to lift the water out of the sea to continue the process.
If, in the pi;e, you had 2 non-return valves one below the point you heat and one above it then, if you cycle between heating and cooling the water between the 2 valves you would get a ( very ) small intermittent flow of water. The amount would equate to the difference between the volume of the water at the lower temperature and it's highest temperature less the difference in the volume of that bit of pipe at the 2 different temperatures. As far as I know it would not be easy to find some pipe which would allow this positive output.
As I said I really hope this is wrong.

lemonie (author)buteman2010-01-23

You're right there.
As I asked before: "Any thoughts as to why no one has done this yet?"


ironsmiter (author)2009-12-07

Am I the only one imagining a 30 story tall bic lighter, and miles of pipe....

And then the people at the other end of the pipe getting mad cause it's HOT water, and all they really wanted was a cold beer?

Alpha2904 (author)ironsmiter2010-01-03



Mr. Squiggles (author)2009-12-06

 Might I just say that doing this would be BAD by actually doing this you would be messing with nature which won't work out well. If you introduce water to the desert think about what you're doing to the ecosystem there. We've already done enough to the planet. why take it one step further?

Oroka (author)Mr. Squiggles2009-12-09

 The Sahara was once lush tundra, and only like 7000 year ago too.  Desert is wasted land, if you can make it useful, do it.

Mr. Squiggles (author)Oroka2009-12-10

 But it transformed to desert naturally and besides there are entire ecosystems adapted specifically to that "wasted land" watering the Sahara it is just as bad as chopping down the amazon. Either way you are destroying the natural processes.
Other than this the irrigated areas would attract animals which humans will eventually try to exterminate.
The sahara is also an important source of nutrients for the rest of the planet. If you were to convert it into farmland the sand would not be blown around by the wind at such high levels and slowly starve other ecosystems worldwide.

Oroka (author)Mr. Squiggles2009-12-11

.Nature and Natural are two different things.  The earth would benefit from a new massive region of usable land.  Sure, things will re balance a bit, but things change, as long as we plan well, and use the new land wisely, it should be done.  Humans should be the Sheppards of the Earth, we are still learning what not to do, the time will come when we are one with nature.  A well maintained garden is just as nice, or nicer than a wild field.

Nature is a cruel and uncaring partner.  Wild, unpredictable, and always trying to kill everything.  99% of species that existed are extinct, and pretty much all of that has nothing to do with humans (a few percent at most).

ac1D (author)Mr. Squiggles2009-12-07

one answer: survive.

Mr. Squiggles (author)ac1D2009-12-07

Or, you know, move to a place that's actually inhabitable.

Oroka (author)2009-12-09

 I cant see massive ammounts of water being moved with this... but there is potential.  First, I would use solar collectors to boil the water, then allow the steam to flow, which down the line could be used (at a high enough pressure), to power generators.

Infact, why not just use a nuclear reactor?  Sea water could be boiled, creating clean water, powering generators, creating electricity.  Even better, geo-thermal.  Pump in pressurized salt water, it comes up hot and is allowed to expand, generators, clean water.... we are on the verge of being able to drill geothermal wells almost anywhere... why not to move water to the desert.

ronanry (author)2009-12-08


have you try to send your idea (concept) to someone highly placed in the "green party" of your country ? (sorry for my english, i'm french)

baudeagle (author)2009-12-07

Here is one another item to consider.  How would the contaminates within the water affect your system?  Salt, microscopic organisms, calcium, etc.

How about building a small scale model of this first and then take the lessons learned from this and apply it to a slightly bigger model. Repeat this procedure until you can be confident that your full scale design would work. 

Postonic (author)baudeagle2009-12-07

I'm going to test out the thermosiphon principle in my backyard using thin metal pipe, a check valve and my grill.  I'm confident that the solar trough is well tested, as is a solar still.  Whether or not a solar trough can generate enough heat to substantially raise water will be my second test.  I'll keep this documented on page 5.

As far as contaminates, solar stills supposedly remove most contaminates.  However, as cheaply as I plan on building this, contaminates will probably end my system and cause leaks.

baudeagle (author)Postonic2009-12-07

You may be interested to learn that the flaking of calcium deposits inside of boilers have lead to some terrible explosions.  The same thing could happen to the inside of a pipe.

The testing that you are describing is very dangerous.

Super heated / pressurized steam is nothing to mess around with.  I would recommend taking a couple of classes in thermodynamics before even considering this experiment.  I would also recommend some guidance from a person that is knowledgeable about pressure and steam.  They would think of items that you probably have not even considered.  It would be well worth the time and effort to consult an expert rather than getting a finger blown off or an eye blasted out.

Also read up on a pressure relief valve,   This should be installed on any type of pressurized system.

You should also familiarize yourself with flash boiling.

lieuwe (author)baudeagle2009-12-08

 dude, seriously, that doesn't apply here, that kind off flaking needs some time to accumulate(more than a week) and even then it needs to close off both ends with some distance in-between, which wouldn't happen(first block prevents the second one from forming), and flash boiling only happens in certain circumstances, either with distilled water and really clean equipment, or in closed off spaces... it's like saying that making tea is dangerous...

fegundez1 (author)2009-12-07

I would say that there would be the same problems with this idea as most easy type fix's... not enough profit! look at so many automotive and power  inventions that are bought and shelved by large companies just to keep up profit, and lets not forget the target for our friends the fundamentalists!

Postonic (author)fegundez12009-12-07

I think profit is the one reason this actually could be feasible.  If properly implemented in currently useless terrain, the value of one's property could skyrocket. 
Acres of desert in Saudi Arabia or the Outback are relatively cheap, as is this system, but combine both and the value would be much higher than either the land or the system by themselves.
Mark Twain "Buy land, they're not making it anymore."... fixed

zieak (author)Postonic2009-12-08

I have to take issue with your assertion that desert is wasteland.  It is a part of the biosphere... I guess it might be the same as saying here's a solution to removing all those pesky trees from your rainforest.  Changing the desert to arable land requires more than water.  Good soil is more than just sand.  Not that i disapprove of eliminating drought - that's a noble cause.

Postonic (author)Postonic2009-12-07

This would also be more economically viable on an island that has limited fresh water.  It's a lot cheaper than using fossil fuels for desalination.

lemonie (author)fegundez12009-12-07

The problem with this theory is it won't work. Nothing to do with imaginary conspiracies at all.


fegundez1 (author)lemonie2009-12-07

Imaginary? I'm not sure what part of the world you get your news from

lemonie (author)fegundez12009-12-07

OK give me your news on a viable project on these lines which mysteriously never got done even though it was scientifically and economically-solid?


bbiorn (author)2009-12-06

An example of this theory in practice is a coffee maker.  Water is heated and expelled  at the end of the tube that is higher than the water source.

wolty (author)2009-12-06

Well, I think the idea in and of itself might just work with some major modifications... maybe as a steam engine of sorts...
First of the entire part of the pipe that goes across land would of course have to be black and maybe even have some mirrors directing sun onto the pipe to achieve maximum heat.
Furthermore the part in the ocean would have to be pretty far down to sufficiently cool.
Then I suppose some major calculations would be necessary to find the right size for holes on the land and sea end of the pipe to allow it to release some amount of water in the desert while using some of it to recycle more of the cold water up from the ocean end.
And to start the entire thing of I suppose you'd need some pretty big pumps to load the entire pipe with water the first time around...

I might be wrong but this is how I imagine it would have to be done.

jtobako (author)2009-12-06

Convection will bring warm water to the surface, but won't act as a pump to bring it ABOVE the surface of the body of water.

How much will a mile of trough cost?  5250 feet of supports, reflectors, piping, glass/plastic...and upkeep for when the piping breaks or leaks or when bad weather hits it or someone wants to use the land under it for a road or steal some of it for scrap prices...considering that a desert is HUNDREDS of square miles and you would have to water a significant portion of it?

Kiteman (author)2009-12-06

Convection currents (very probably) would not lift water out of the sea.

As Lemonie says, this is probably better as a forum topic, where you could discuss methods and technologies, maybe even get yourself sorted to produce a working prototype before publishing an actual Instructable.

If you could make it work, and you established your rights to the idea, you'd make a fortune!

wyrm (author)2009-12-06

Great graphics! Have you tested this to see if it actually works?

Kanein Encanto (author)2009-12-06

Is it just me, or does this sound like it doesn't quite jive? I mean wouldn't this just end up setting up circulation within the pipe, not so much water flowing out the far end? As the warmed water rose beyond the heat source wouldn't it cool and just circulate back?

Shame I don't have a small copper pipe to try the idea out with and see... :p

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