# Is desalination going to be the solution to the water crisis? Questions and thoughts **URL:** \ **Category:** In My Humble Opinion\ **Tags:** science-math\ **Created:** [March 4, 2025, 1:53pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110 "2025-03-04T13:53:31Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [March 11, 2025, 6:39pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/41 "2025-03-11T18:39:04Z")
> [@Lucas\_Jackson](#): > > OK, this is going to seem like a stupid question… but why cant we just put it back into the ocean? We generally do. But often after watering it down and usually as far away as possible. It’s too salty and creates massive ecologic/environmental issues. Think large dead zone in the ocean, which is a bad issue. The Dead Sea writ quite large. Even the lower salinity Great Salt Lake has wildlife mainly concentrated where it is lower salt. We can’t really use much of the brine, either - we don’t need that much salt. Dumping on land isn’t much better - instead of piping fresh water, now we’re transporting massive amounts of brine. It can and is still done, particularly in areas with limited availability of fresh water, but it does not scale up very well. ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [March 11, 2025, 6:40pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/42 "2025-03-11T18:40:33Z")
The wildlife where the brine gets dumped doesn’t react well. Off the top of my head, seawater is just under 4% salt, while the brine discharge is more like 8% salt. I mean, _to me_ that doesn’t seem like a real issue on the scale of the whole ocean, but I guess it does mean that we’re deciding there’s going to be a dead spot wherever the pipe exits. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [March 11, 2025, 7:44pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/43 "2025-03-11T19:44:36Z")
Ideally you’d output pure water as the product stream & pure salt / fish shit / sedimenent / etc as the waste stream. To only increase the waste concentration in the open ocean by 10% of ambient, you’d need 10 gallons of pristine seawater to blend with the waste from generating 1 gallon of fresh. For any meaningful throughput that’d require putting a vast network of small outlets athwart a large current. Good luck paying for buying or maintaining that affordably. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 11, 2025, 8:05pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/44 "2025-03-11T20:05:47Z")
> [@Pork\_Rind](#): > > The wildlife where the brine gets dumped doesn’t react well. Off the top of my head, seawater is just under 4% salt, while the brine discharge is more like 8% salt. I mean, _to me_ that doesn’t seem like a real issue on the scale of the whole ocean, Bear in mind, the water is to sea life what our atmosphere is to us. Doubling the amount of salt can seriously interfere with both gilled fish and sea-living mammals adapted to filtering out water with the normal amount of salinity. Stranger ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 11, 2025, 8:09pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/45 "2025-03-11T20:09:39Z")
> [@LSLGuy](#): > > Good luck paying for buying or maintaining that affordably. It’s not that hard. You build a big pipe out to the ocean and let the brine dribble out along the way. Or you can pull in seawater from another location, mix it, and discharge the mixed seawater. It’s not that difficult or that expensive, as desalination plants do it already. Just pipes and pumps. The real trick will be reducing the energy costs. Not the energy requirements, necessarily, but the costs. My position is that we should be building _worse_ desalination systems, but much more cheaply, and power them on solar. You don’t build batteries or complex power systems, just run them during the day and turn them off at night. This requires reducing the capital costs of the plants–which is likely possible if you accept some inefficiency. The magic of desalination is that the storage is cheap–just a lake or aquifer. So cheap that you can average output across an entire year, not to mention a day. It’s very well-matched to solar as long as the plant costs can be kept low. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [March 11, 2025, 8:17pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/46 "2025-03-11T20:17:12Z")
> [@snowthx](#): > > Desalination is expensive, energy intense, and creates a lot of waste. It hasn’t caught on because there are cheaper and more passive ways to make more fresh water available, namely conservation True, but even better is 4th stage water recycling. Practically zero extra waste. Less expensive. Desalinization is foolish. Just purify waste water instead. No matter how cheap it gets, you still have the problem of all that salty waste. > [@TriPolar](#): > > Isn’t it easier to purify contaminated fresh water than to desalinate sea water? Yes, by quite a bit. > [@hajario](#): > > If you have available contaminated fresh water. I live on the coast in an area prone to drought. If you are using water you have waste water. > [@StarvingButStrong](#): > > We’ve got lots of “useless” land, No, we don’t. > [@Al128](#): > > you just need to worry about what do do with the contaminantants That is already handled. If you have waste water, you dump it, after cleaning it- how much you clean it varies. > [@Tamerlane](#): > > Toilet to tap (directly or indirectly through an environmental buffer, like injection into aquifers). I know it makes many people wince, but indirect/direct potable reuse is the same general idea as desalination, only cheaper and less polluting. It’s a better solution overall, though you can certainly use a mix of technologies to meet overall goals. Right. > [@Tamerlane](#): > > California and the southwest, not so much. SoCal has vast amounts of waste water. But remember folks- In CA home water use is 10% of overall water use. 80% is AG, 10% industrial. CA, even SoCal has plenty of water. The water from irrigating almond trees alone is equal to how much is residential use. ---
**Author:** ![snowthx](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snowthx/32/10660_2.png) [@snowthx](https://boards.straightdope.com/u/snowthx)\ **Post date:** [March 11, 2025, 8:24pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/47 "2025-03-11T20:24:19Z")
> [@DrDeth](#): > > But remember folks- In CA home water use is 10% of overall water use. 80% is AG, 10% industrial. CA, even SoCal has plenty of water. The water from irrigating almond trees alone is equal to how much is residential use. Yep. And a large percentage of those almonds are destined for export. A lot of ag water usage is not for growing food for our tables, but exports for profit. Sometimes the farmers’ disingenuous bleating about water supplies and building more dams and water storage leans into the whole “welfare” thing - public works and public risk for private profit. > [@Dr.Strangelove](#): > > The magic of desalination is that the storage is cheap–just a lake or aquifer. So cheap that you can average output across an entire year, not to mention a day. It’s very well-matched to solar as long as the plant costs can be kept low. The problem with this thinking is you need more energy and more infrastructure and more maintenance cost for pumping desal water _uphill_ from the ocean to said storage facilities inland, if they even exist nearby. If you are going thru that expense and investment, why not just pump fresh water from the next watershed over into yours, and save the cost and waste from desal? Not to mention the points about reclaimed water that is already available in the vicinity. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 11, 2025, 8:28pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/48 "2025-03-11T20:28:28Z")
> [@snowthx](#): > > The problem with this thinking is you need more energy and more infrastructure and more maintenance cost for pumping desal water _uphill_ from the ocean to said storage facilities inland, if they even exist nearby. I’m not saying that desalination is the best approach in every situation, and I certainly think that increasing agricultural (and other) efficiency is going to be more cost effective in most cases. But even if desalination only reduces coastal water demands, that means less load on those uphill sources of water, since they no longer have to send so much water downhill. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 11, 2025, 8:36pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/49 "2025-03-11T20:36:34Z")
This thread is kinda weird in that people are acting like desalination is like nuclear fusion, and still 50 years away or something, but it’s already in widespread use. And the brine issue–while it _does_ have to be dealt with–isn’t some insoluble technical problem. Here’s a study about the Carlsbad Desalination Plant in California: > **[Study of brine discharge from desalination plant finds good news and bad news](https://news.ucsc.edu/2019/01/desal-brine.html)** > > Brine discharged from the Carlsbad Desalination Plant raises offshore salinity levels more than permitted, but researchers found no direct local impacts on sea life. > Brine discharged from the Carlsbad Desalination Plant raises offshore salinity levels more than permitted, but researchers found no direct local impacts on sea life So not a big deal. Probably they have to improve their discharge modeling, but it didn’t result in a huge plume of dead sea life or anything. Will desalination, by itself, “solve” the water crisis (_is_ there an actual water crisis)? No. But it will play a role and probably a slowly increasing one. As an aside, water is so intertwined with politics that I expect desalination plants to be built simply to avoid having to solve political problems. Arguably this has happened already. ---
**Author:** ![Pork\_Rind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pork_rind/32/111_2.png) [@Pork\_Rind](https://boards.straightdope.com/u/Pork_Rind)\ **Post date:** [March 11, 2025, 8:47pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/50 "2025-03-11T20:47:22Z")
100% I get that. It just intuitively feels to me like that would dilute back to ambient pretty quickly outside of a localized impact. But I also understand that intuition can be a terrible measure of a thing. ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [March 11, 2025, 8:55pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/51 "2025-03-11T20:55:52Z")
> [@Dr.Strangelove](#): > > So not a big deal. Probably they have to improve their discharge modeling, but it didn’t result in a huge plume of dead sea life or anything. > > Will desalination, by itself, “solve” the water crisis (_is_ there an actual water crisis)? No. But it will play a role and probably a slowly increasing one. Well, it can be a big deal. The OP is about its use as “the” solution to the water crisis. As you note and as several posters have noted in this thread, no, this won’t be “the” solution for aforementioned reasons, including the brine, even if it can be part of a useful mix of technologies. This included discussion of existing plants. Brine hasn’t been a major issue for existing plants because they were designed with it in mind. Not an insoluble issue but also one where we can’t just literally dump it offshore as some have suggested. ---
**Author:** ![hajario](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hajario/32/171_2.png) [@hajario](https://boards.straightdope.com/u/hajario)\ **Post date:** [March 11, 2025, 8:59pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/52 "2025-03-11T20:59:09Z")
> [@Great\_Antibob](#): > > Not an **insoluble** issue but also one where we can’t just literally dump it offshore as some have suggested. HA! …. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [March 11, 2025, 9:00pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/53 "2025-03-11T21:00:05Z")
> [@Jasmine](#): > > The criticism is the expense… It is not only very expensive but the brine leftover (super-salty water) is very dangerous to the environment wherever it is dumped (and it is unavoidable). Not sure anyone has found a cost-effective solution to that problem. ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [March 11, 2025, 9:02pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/54 "2025-03-11T21:02:15Z")
> [@hajario](#): > > HA! Oh geez, I wish I could take credit for that. 🤷‍♂️ ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 11, 2025, 9:10pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/55 "2025-03-11T21:10:15Z")
> [@Great\_Antibob](#): > > Brine hasn’t been a major issue for existing plants because they were designed with it in mind. Well, yeah. Any complex system has to be built with a bunch of things in mind or it won’t work right. “Not poisoning the local environment” is a design requirement for a modern desalination plant and so they’re all designed with that in mind. And they aren’t so expensive as to make the systems uneconomic. Desalination and a few other industries (aluminum smelting, fuel synthesis, battery recycling, etc.) are energy intensive but have great room for innovation, and I expect that those that can figure out how to effectively use cheap-but-intermittent renewables will be very well positioned. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [March 11, 2025, 9:14pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/56 "2025-03-11T21:14:12Z")
> [@Dr.Strangelove](#): > > And they aren’t so expensive as to make the systems uneconomic. As long as a cheaper option exists they are uneconomic. As long as the wells do not run dry or there is a drop to be had from a river why pay for desalinated water? Not to mention the costs of trying to pipe water from the ocean to places like Arizona. Ain’t cheap which is why it is not done often. ---
**Author:** ![Al128](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/al128/32/16541_2.png) [@Al128](https://boards.straightdope.com/u/Al128)\ **Post date:** [March 11, 2025, 9:15pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/57 "2025-03-11T21:15:10Z")
> [@Great\_Antibob](#): > > Brine hasn’t been a major issue for existing plants because they were designed with it in mind. Not an insoluble issue but also one where we can’t just literally dump it offshore as some have suggested. I read similar information, IIRC some solutions are to have “somewhat perforated” brine-pipes, that dribble the higher NaCl content over many 100s of meters of length and also alow seawater to filter into the brine-pipe to reduce its concentration even more … ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 11, 2025, 9:19pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/58 "2025-03-11T21:19:22Z")
It seems pretty obvious that if water is already available, you don’t need to build a desalination pant. You build them where water is expensive because it’s not available. You don’t need to build desal plants in Arizona. But if you build them in LA, it needs less water from the Colorado river, which means Arizona can take more. Arizona can even pay for California to build more desal plants in exchange for a share of more water rights. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [March 11, 2025, 9:24pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/59 "2025-03-11T21:24:58Z")
> [@Dr.Strangelove](#): > > Arizona can even pay for California to build more desal plants in exchange for a share of more water rights. So not going to happen until it becomes a crisis. There is a covenant covering water usage from the Colorado river which, even when written, was promising more water than existed in the river. With recent droughts people have noticed this arrangement is unworkable. Absolutely no state involved has been interested in giving up water rights or promising to pay more to someone else so they get more water. In typical fashion, politicians are kicking the can down the road. It will not be solved till it is a crisis and then it will be a disaster cuz you can’t solve problems like these in a few weeks or months. Farmers loooove their free water. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 11, 2025, 9:30pm UTC](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110/60 "2025-03-11T21:30:05Z")
Well, now you’re arguing that it isn’t necessarily an economic or technical problem, but rather a political problem. Which I agree with. That said, if a crisis is inevitable, and things do eventually happen when a crisis hits, then logically those things will inevitably happen. There will be pain, though. [Previous page](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110.md?page=2) [Next page](https://boards.straightdope.com/t/is-desalination-going-to-be-the-solution-to-the-water-crisis-questions-and-thoughts/1015110.md?page=4)