Suggested by this thread: Fresh water on large navy ships. - Factual Questions - Straight Dope Message Board
The Navy can distill lots of potable water from salt water already. Why can’t this be done on a much bigger scale for thirsty countries anywhere near oceans?
Not cost-effective, most likely. That tends to be the usual answer for this type of thing.
Yep. Desalinization is expensive. Some Arab states have large-scale desalinization plants- Oman, for example, gets most of its potable water that way- but it helps to have massive oil revenues to pay for it.
It’s more expensive than laying mile after mile of pipe to get your fresh water from somewhere else? Or to have little or no potable water at all?
It’s also rough on the environment.
Much better is 4th stage waste water purification. It can be done cheaper than desalinizations, and it is hwaaaay better for the environment.
The problem is, dudes don’t like the thought of drinking waste waster, no matter how pure. Of course, every glass of water we dring today is part recycled waste water, just that it has gone through Natures recying system.
But you don’t need to lay miles of pipe – there are these things called rivers that carry fresh water just fine. Much of California gets its’ water from the Colorado River, for example. The occasional dam, canal, intake filters, etc. are much less expensive than miles of pipe.
It’s used in Australia.
To have little or no potable water at all is free. Building a pipeline might be more expensive than building a desalinization plant, but production costs have got to be much lower (just my WAG).
ETA: If the pipeline has to go over several mountains or half a continent, the cost will of course at some point increase beyond a desalinization plant.
We have not yet reached the point where it is costly enough to obtain water through other methods. Even if we have to either lay pipes or build a dam, that’s still “cheaper” because it involves a one-time expenditure that gets costed out over a long period of time, after which the cost of the water itself is negligible.
Mind you, the West Coast is rapidly approaching the point where we will have to start doing some desalination. Las Vegas and Phoenix are the keys, as they are growing past the availability of water through any reasonably conceivable traditional delivery system.
Most of California does NOT get its water from the Colorado River; indeed a very small portion of the water used by the state comes from that source. Most of the water used by California comes from the storage system called the Sierra Nevada snowpack. 
(which, of course, is then “delivered” to much of the state via the San Joaquin and Sacramento Rivers)
This has a comparison of desalination and other water sources for california: http://www.coastal.ca.gov/desalrpt/dchap1.html
*And see, e.g., *
and Desalination
And this is a good discussion of the kinds of costs involved: http://www.awa.asn.au/Content/NavigationMenu2/AboutWaterandtheWaterIndustry/WaterFacts/FactSheets/Desalination/default.htm
I’m not seeing how they get $1.15 out of that; perhaps it’s the operating cost?
Regardless, the construction number seems high:
Yes, but the OP is talking about “thirsty countries”. One would presume that a country full of rivers, dams and canals is not that thirsty to begin with.
I wouldn’t put too much faith in those figures with the governments “preferred outcome” being the desal plant which Sydney is getting whether we need it or not.
There are thirsty parts of our non-thirsty country. While maybe it’s not California that’s sucking dry the Colorado river, all of the communities in the desert are doing so. I think only a trickle – if that – reach the Sea of Cortéz these days. Henderson (Las Vegas area), for example, prohibits new home construction with front grass! We in Michigan are water rich, and are fighting hard to prevent other states from “stealing” our water.
Wired magazine had an article a few years ago about a state of the art desalination plant in Arizona or New Mexico, but for some reason a treaty with Mexico won’t let it come online. I don’t recall the details all that well. Maybe I’ll go look it up.
Is desalinization even a word?
Er… OED says no. Apparently we mean desalination.
Most of the world’s freshwater is used for agriculture. Approximately 70%. If we used the water more efficiently, drip lines, surge irrigation, grey water-there would be less water stress, decreasing the need for desalination plants.
Another idea is the idea of virtual water. It’s better for many areas to import food that require large amounts of water, than to irrigate extensively.
As to desalination plants, Ashkelon in Israel is the largest in the world.
It looks like the production cost is .52 per cubic meter of water.
Just think of it as dinosaur piss coming out of your taps. 