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Comment by sporkenfang | Hacker News Reader

Maybe I skimmed the article a bit fast, but I saw no mention of desalination plants, which are the obvious solution (though expensive and as far as I'm aware not implemented yet).

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Desalination is pricy for agriculture because it's a long distance to transport the water. Because of recent technological advances, they are completely reasonable for the coastal cities though. The only reason they don't get built, is to justify the huge capital expenditure, they need 25 year guaranteed contracts, and even though the cost isn't that much ($500/acre foot, $0.45/m^3 or 1000 liters), it's still more than what water costs when it rains.

So, what tends to happen in areas with variable rain, is that when a drought hits, they get constructed, and then it starts raining, there is no reason to use the $500/acre foot water from the Desalination plant, instead of the $10-$125/acre foot [1] from rain. The only places that it is economical to build them is where we are guaranteed that they will be required.

If we could be certain the drought would continue, then yes, we would have desalination plants being built all along the coast (as they are in Singapore, Dubai, etc...). Alternatively, we could just bite the bullet and say we need this type of reliability of water supply and just build them. At that point, we could end all the nonsense about "conservation" in residential areas when there is an agricultural water supply issue. None of the conservation that people are doing in residential areas is going to make a spit of difference to the California water shortage situation - it's purely political posturing.

[1] http://www.ppic.org/content/pubs/report/r_1112ehr.pdf pg 24, footnote. ".... In 2005, under a similar deal, MWDSC did not exercise the options to purchase nearly 130,000 af because there was ample rain, and growers again received just the installment ($10 per af, versus a final purchase price for the water of $125 per af)"

It's already happening, but they're expensive and slow to come online:

http://www.noozhawk.com/article/santa_barbara_desalination_p...

http://www.mercurynews.com/science/ci_25859513/nations-large...

I don't think this will work for the lion's share of the water consumption, irrigation - way to expensive to be able to sell the harvest at competitive prices.

It looks like there are proposals, but who knows how serious that is:

http://www.mercurynews.com/science/ci_25859513/nations-large...

They should build a giant desalination plant somewhere between LA and SF like Santa Maria area which can supply LA, SF and Las Vegas through a pipeline. Each city should try and clean and recycle as much water as possible and the pipelines could keep them topped up

It's not going to be easy to build few of them in less than a year.

It's amazing what you can do when you've run out of water... But you are right, it would/will be a massive undertaking. I wonder if desalination will become water's "fracking", something we only turn to due to high price of what we used before or unavailability of what we used before.

I don't think the price will be near what would be needed to make desalination profitable without subsidies, though. The state could choose to maintain current usage and pay whatever it takes to maintain it, but it'd be at a huge loss. The main user of California water is agriculture, and desalinating water just to use it to grow rice is a good way to burn money.

I've seen complaints that it has a big environmental impact too.

Is it due to the amount of power required? Any sources? (Not that I don't believe you, I'm just curious).

California's power grid is already stressed. Desalination takes a lot of power, so any new plants will probably have to install new power generation as well.

If I were building a desalination plant I'd put the generator on site - why waste money on transmission losses?

Natural gas generators are clean enough that I don't think it would be a big problem putting one by the ocean.

True, but real estate by the ocean seems like it would be at a premium.

They are not on the coast, they are more inland. They just needs some pipes to the coast.

The pipes have to go pretty far into the ocean anyway - they can't discharge right on the beach.

Do you know how much energy is required to evaporate the amounts of water necessary for urban consumption?

Eh? Desalination plants don't work on evaporation. They use reverse osmosis membranes.

And even the old ones that do use evaporation, recapture the energy, so you really only need to evaporate the water once, other than losses.

You can desal with excess renewables that would normally be curtailed (wind, for example), also similar to how the aluminum industry in Iceland is there to use their cheap geothermal power.

Desalination is also currently energy intensive. It is suitable for living needs, like having drinkable water, but would absolutely crush any margins when it comes to growing food.

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