The author, who holds a PhD from Caltech, proposes taking advantage of the decreasing cost of solar power to enable a new age of clean water abundance in California, sustainably, with the potential for massive revenues and profits at all steps in the value chain. Even if the author's calculations are off by a factor of two, the proposal looks like it could work. At a minimum, it merits serious consideration. The status quo will not solve our pressing environmental problems.

The main challenge an innovative large-scale project like this one would face, I think, is a regulatory bureaucracy which to me often seems like it was designed for the technologies and infrastructure of the 20th century, not for those of the 21st century. I shudder to think of, say, inspectors who are highly trained on narrow technical matters, but who lack a fundamental, multi-disciplinary, big-picture view of the entire project, deciding whether to approve individual tiny little parts of it.

"A Saudi Arabian company grows alfalfa on farmland in Arizona and California and sends it overseas to feed the country's cows. These legal farming operations extract groundwater in Arizona and water from the Colorado River across the border in California, experts say." source: https://www.maxwell.syr.edu/news/article/koch-discusses-saud...

Maybe if we stop exporting Colorado water packed in alfalfa and other agri-products, we would have enough water ?

Exporting water through alfalfa to Saudi Arabia who indeed banned alfalfa fields in their country because it was consuming just too much water, is one of the problem we should fix before installing PV and batteries in the desert, and dump concentrated brine somewhere.

If I understand correctly, it is his plan for extracting value from the brine which represents the biggest unknown/the most need for development, while also being the thing that makes it all make sense. I've never heard of any of the existing worlds desal plants doing this, so either it must be harder than he supposes or else he must think that every single person in charge of a desal plant the world over is an idiot.

Don't get me wrong, I realize that sometimes people miss obvious things. And sometimes, there really is a $100 bill on the ground, despite what the apocryphal economist would have you believe.

But in this case, areas like that are what I need to be convinced of. While it's maybe true, you don't just get to assert it.

As they say "What can be asserted without evidence can be dismissed without evidence".

General takeaways:

Proponents of the solution seemed to understate challenges and risks associated with:

1. The pipeline itself (i.e., where to build it) 2. The disposal of brine solution into the Gulf of California. 3. Cooperation with Mexico.

That's not to say the challenges couldn't be addressed, but discussion of such challenges is noticeably absent from the original article.

I wonder if you could store the energy as pressure instead of electricity in batteries.

From what I gather[1], the biggest energy draw in reverse osmosis is pressurizing the water to force it through the RO filters. So, while the sun is shining, fill a tank halfway with salty water, then use solar energy to run pumps to pressurize air above the water. When the sun isn't shining, you now have pressurized water you can let through the RO filters.

Compared to a regular RO plant, this requires high-pressure storage tanks and additional pumps. I'm unsure whether that costs less than batteries or not.

Another part of the analysis is that, if you do build the batteries, they can earn extra money with a side gig stabilizing the grid. Occasionally, when grid conditions get very gnarly, you could shut down the RO plant for a few hours and make a quick buck selling your battery power on the market.

Alternatively, you could pump the water uphill during the day and let gravity supply the energy to force it through the RO filters at night. This means you'll have to build a special reservoir for pre-treated salty water somewhere, though, and you need a lot of pressure, so it would need to be at a high elevation.

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[1] Source (kind of old): https://www.oas.org/dsd/publications/unit/oea59e/ch20.htm

I don't mean some grander point about environmentalism or development, I mean that I have specifically examined solar desalination for the Imperial Valley and he's missed a much simpler way to get the water from point A to point B.

See, there's this other basin in nearby Mexico called Laguna de Salada which is basically an empty salt flat about ten meters below sea level. If you flood that by dredging a canal (about 10-20 km and not very high), you only have to transport the desalinated water about five kilometers to get it into the Imperial Valley drainage basin.

There's no need to back up the Colorado and mess up what's left of the delta, plus you can put the rejected brine back into the now Golfo de Salada where it will mix more slowly and (hopefully) less destructively with the seawater to the south. The area will still be something of a dead zone, but it would only replace an existing dead zone.

"Rejected brine is a serious threat to marine ecosystems, causing negative effects on both flora and fauna. This is especially so when the optimal initial high dilution capacity is lacking in the discharge system. Consequently, brine discharge plumes spread over large areas of the sea floor and modify the structure and distribution of benthic communities such as seagrass habitats. ... Rejected brine disposal costs are between 5 and 33% of the whole desalinization process, depending on the characteristics of the brine, its pretreatment level before disposal, disposal method, and volume"

from: Jiménez-Arias, D., Morales-Sierra, S., García-Machado, F.J., García-García, A.L., Luis, J.C., Valdés, F., Sandalio, L.M., Hernández-Suárez, M. & Borges, A.A. 2020, "Rejected brine recycling in hydroponic and thermo-solar evaporation systems for leisure and tourist facilities. Changing waste into raw material", Desalination, vol. 496, pp. 114443.

Take excess water from SE floods and pump it west opportunistically using excess renewables. Bonus because you can use the pumped water as gravity storage.

Yes, it is not cheap, energetically, to pump water. Yes, you have to cross a big mountain range(which increases opportunities for gravity storage).

For some reason, this suggestion always gets a lot of comments from folks living around the great lakes who think we're going to 'steal' 'their' water(just like they 'steal' CA grown produce, I guess?).

Anyway, a national water grid is needed for national food security and can mitigate flooding damage in the SE(probably more important b/c of AGW).

U.S. thermoelectric plants are the largest source of U.S. water withdrawals, accounting for more than 40% of total U.S. water withdrawals in 2015.: https://www.eia.gov/todayinenergy/detail.php?id=50698

https://solarimpulse.com/solutions-explorer/high-efficiency-...

Now I'm no hydrologist, and haven't researched this idea deeply yet, so don't know second and third order effects (i.e. brine disposal mentioned above, and of course the economics of such a venture.) It seems at some point our collective hands may be forced and we may have to do something that doesn't make a profit, yet sustains humanity as a going concern.

Finally, the fact that we haven't "terraformed" in this fashion drought-stricken places like Africa or elsewhere is a pity. But yes, economics, profit, geopolitics, power struggles, I get it.

If the Salton Sea doesn't have a steady input (from snowpack? not familiar with it), doesn't desal mean we're really just expanding the unsustainable use of the Colorado, maybe delaying it another few decades, but ultimately still growing more and using more water than its watershed can naturally sustain -- especially as climate change increases?

I think the fundamental problem here isn't that we need to make more freshwater out of brine, but that the California (and other) water rights are set to levels that cannot realistically be maintained. The law needs to change even if that hurts the grandfathered rightsholders; there just isn't the same amount of water anymore.

    5 MAF/year of 6% salinity brine contains more than 10 million tonnes
    of magnesium, comparable to current global production, not to mention
    other light metals. At spot prices around $5000/T, a mature brine
    extraction industry could net >$50b/year

The title also seems a bit grandiose. "The US Southwest" for most people I think extends at least as far as the I25 corridor up through NM and CO, and for some it might even reach into western TX. The plan described would really have very little impact on the overall water situation here, even if it did actually live up to its claim of effectively freeing up CA's Colorado allocation.

The American southwest has a couple big things going for it -- unlimited sunshine and an extraordinary amount of empty land. You can combine these things to create huge amounts of electricity which can be used to irrigate new farm land, power mines and build new cities.

The status quo of drawing down on the increasingly precarious water supply is not feasible though. Before the unprecedented snowpack of 2022/2023, many regions were facing extreme water rationing.

Shouldn’t the same URL submitted again redirect to mine?

Is there a certain cutoff when someone else can submit the same URL?

(I’m not complaining, I just want to understand what the rules are)

Costs of the PV and desal (relatively cheap but still absurdly expensive in absolute terms at this scale) will be offset by real estate development and hand-wavey mineral extraction from the sea water.

Environmental impacts of desal's salty waste stream is hand-waved away.

I mean, economic math miiight pencil out. But basing the speculative prosperity of an entire region on a bunch of water and energy machines seems... well... fragile? Full of hubris? Seems like a really expensive way of maintaining an otherwise-unsustainable Potemkin vacation village.

But then again, that's basically the story of the american southwest, so, /shrug? (see Cadillac Desert and all the water stories out there...)

https://www.energy.gov/eere/articles/us-department-energy-an...

Here's an alternative proposal based on a sea level canal and tidal power.

The costs of solar and batteries have been dropping for decades. It's 100% believable that this type of thing has been considered, repeatedly, and discarded as economically infeasible, leading to the major players in the field choosing to ignore it for a while—but that the costs have now dropped enough that the economics work out.

But this is California - there may be reasons that are not economic or technical that have prevented anyone from trying to develop or pursue such an idea. The concentrated salt-brine discharge, for example, may be impossible to get environmental approval for at these volumes.

Putting together the solar panels, the battery, the desalination plant, and the brine plant, he's proposing a $42 billion dollar project that has only been economically feasible for a year or two now. I'm not surprised that it hasn't been built yet.

The places without are so dry they cannot drill, condense or truck in salt water, even though they have plenty of solar.

That's a coordination problem with public rights of way issues which is why it wouldn't happen without specific government policy.

For the basics, practical engineering did a good video on desalinization: https://youtu.be/mxqOPdEUNTs

Mathematically, it’s easy to forget that the PV term in enthalpy is a mathematical trick, not a physical thing, and that it mostly does a nice job explaining physical things when P = atmospheric pressure.

If you want to store, say, 100psi water, the energy you care about is P times delta V, so you need some thing that can change its volume easily, cheaply, and reversibly while under pressure. As a practical matter, this means compressed air or maybe springs. So that water “pressure tank” is actually an air pressure tank that happens to have some water in it too.

There’s nothing wrong with storing pressurized air, except that it’s a heck of a lot more dangerous than storing pressurized water due to the fact that it really does have energy stored in it. (There’s a reason that a PVC pipe filled with 80psi water is a common thing in houses and the main danger is that water escapes if it breaks. A pipe full of 80 psi air is quite hazardous.) There are startups that have played with compressed air energy storage. The resulting gizmos are large.

I would expect a RO plant that is optimized for intermittent use without any energy storage at all to end up being a viable alternative to energy storage, but maybe batteries will end up being cheap enough that this isn’t worthwhile.

I'm optimistic we could:

* Build ocean pipelines that disperse brine over much larger volumes of water to minimize impact on wildlife

* Dump the brine water in engineered desert fields where it will evaporate and deposit salt reserves.

In general, we should be aware of the whole lifecycle of a solution, and optimistically believe we can solve each problem with more work.

Casey's proposing we mine the brine for useful minerals. You're right he's glossing over details, but a citation addressing the economics of brine disposal with his proposed processing would add more to the discussion.

If that’s still too much, use 20 gallons.

It’s a matter of spending energy on pumps, but it’s totally doable.

Also, the ocean salt content will not be increased by this, since the desalinated water will eventually make it back to the ocean.

He literally addresses brine in the article.

>flaunt its unequaled excellence by exporting alfalfa to all corners of the globe.

really not sure if this is satir.

"We desperately need to find ways to massively change human nature, rather than using our vast combined expertise to engineer solutions that let human nature work for us rather than against us."

Any solution to a systemic problem that can be articulated as "If people would just..." is doomed to fail. People will not just. People will continue finding ways to convert resources into better lives—for better and for worse.

Posting on articles like this saying "No! We can't keep finding ways to make consumption not harm the ecosystem! We have to force people to live austere, monk-like lifestyles! Only that will truly save us all!"

Like, I'm as frustrated by the idiocy of growing almonds in California as the next guy, but if this solution will actually work the way it claims to, then we may not need to worry about that anymore. And furthermore, it would mean significant improvements for various other parts of the world currently reliant on transporting enormous quantities of fresh water long distances to coastal areas.

https://www.nytimes.com/2023/10/03/climate/arizona-saudi-ara...

With respect, why can't we do both?

IMO we should absolute not be exporting anything farmed with subsidized water while the survivability of just living in the US southwest is uncertain due to current water levels and climate patterns. That seems like the lowest of low-hanging fruit.