I never heard of these possibilities - and why not? This is the kind of thinking we need. Of course there will be repercussions, but it seems they are manageable with the technology today. The world is so set in how things are done that opportunities like this are overlooked.
When you read history of the 19th century you can clearly see people had this attitude, esp in the US. They would prospect the land to decide where they would build cities and railways, canals and bridges.
Cadillac Desert, while written during a time of peak environmental cynicism (imagine being a water and land use activitist in the 1970s, things looked bleak!) tells the story of the ambition it took to make large parts of the Western united states liveable. It is incredible how much brain power and work was required and how everyone had the mindset of "how" rather than what we have today, which is mostly coming up with reasons why we shouldn't bother trying.
Along those lines, one thing that shocks me about that time is that people in the 20s and 30s also led huge such projects. We trusted young people with only a few years of experience to chase their ambitions.
That's true. It's amazing what those years gave us - the railroads, bridges, dams, huge projects. Just try to get something like that done in today's political climate.
There were some of us who, in the 1970's, started recycling (which my family still does) which was much more complicated then - no picking up curbside. I have no idea how many of us from the '70s are left, but conservation has been on our radar for years, just waiting for the rest of the world to catch up and get their heads on straight.
Great piece again, thank you! Could you add a column to the table listing all depressions: By how many mm would mean sea level go down if they were filled to MSL?
Hi Tomas, I checked for the Caspian which is the widest area. Caspian sea is 371,000km2 vs all Oceans area 361,000,000km2 , so it means each 1/1000 parts aprox. So each 1 meter raise the level of Caspian sea it takes 1mm down MSL. So considering the 28m of depression of Caspian Sea it would reduce worlwide sea level 3mm aprox. Not much actually :)
nearly all of these have been considered in decades past and the projects abandoned. by far the largest reason for abandoning the projects was the belief that over time the water would simply become too salty and then become a stagnant and dead swamp- people prefer a desert over a swamp.
The challenge here, Tomas, is to come up with the engineering proof to measure the amount of energy that would be needed to desalinate the water and the amount of energy needed to pump the salt-rich brine back to the sea, and figure out a scenario where the inflow to our inland sea is sufficient for both. Once you have that equation solved, the scenario becomes a very good hypothetical.
Nov 7, 2023·edited Nov 7, 2023Liked by Tomas Pueyo
This is a really interesting idea Tomas, and good feedback J Rainstar.
In terms of being an option to reduce global warming, it seems to be a subset of "geoengineering" that offers other benefits (potentially with "no regrets"), but with less global risk than some alternatives.
There's a lot of fast-progressing R&D on solar desalination that might make the difference between it being viable or not.
you mean sources that could cover the topic of estimating the volume of brine produced by desalinization, power needed to pump it to the ocean, power needed to desalinate/pressure gradient launched, and power obtained from hydro across a gradient? the source would be engineering textbooks. the technology to do this efficiently is fairly recent so you may have to do some research and calculations because they have not been done yet.
if you mean the various projects having been considered before, its fairly tedious to describe, but each and every such project was once modeled in the terms of using nukes for terraforming back in the 50s.
Yes I know the previous limit in tunneling, not the more recent one you mention on desal.
Yes, what you describe is what I’d be interested in. I assume some of that must be online, but can’t find. Textbooks sounds like a lot of work, I might need an alternative way like talking with people who’ve considered this.
The one thing that sounds weird is that there’s already plenty of endorheic lakes, like Chad or the Caspian Sea.
Or plenty of seas connected to the ocean with net inflow—red and med being 2 examples. Med also has saline outflow, but I must assume some corners of the world only have inflows. I’d be curious to know what they look like.
Yeah but the only economic case is harder to make. This would have to be a fully public investment because it wouldn’t recoup money directly. In what I propose, it would through hydropower.
Qattara region can even be filled with the the flooding of the Nile which is happening on the yearly monsoon between May and August. And it would have fresh water, not from the sea. But it probably would affect to the needs of the Nile Delta, and it can have a side effect
A big ongoing effort has been the Great Green Wall - an effort to build a green belt to stem desertification along the Sahara's southern flank. It hasn't really worked as anticipated but has generated encouraging shifts. Smithsonian story here: > Slowly, the idea of a Great Green Wall has changed into a program centered around indigenous land use techniques, not planting a forest on the edge of a desert. The African Union and the United Nation's Food and Agriculture Organization now refer to it as "Africa’s flagship initiative to combat land degradation, desertification and drought." Incredibly, the Great Green Wall—or some form of it—appears to be working. < https://www.smithsonianmag.com/science-nature/great-green-wall-stop-desertification-not-so-much-180960171/
Very cool! The Great Green Wall always sounded very hard to pull off (it's dry there for a reason), but this type of bottoms-up initiatives do make a lot of sense. I'm glad to read this!
Just remembered this article I read back during the (post-?)hurricane that hit California a month or so ago - You probably DON'T want to include the Salton Sea here.
(Actual paper is linked near the top, but the above link gives a good summary if you're pressed for time)
Major earthquakes on (specifically just slip-strike?) faults can be induced by large bodies of water forming over the fault lines, as it depresses the crust & lubricates the holding points enough to trigger a quake. You pointed out a lot of the potential spots for flooding are situated over faults, so that may be another issue to consider.
Still 100% agree we should be building these megaprojects - the benefits are huge - but some of these like Salton won't be worth the effort if they cause earthquakes in major population centres
(I should point out I have no background in this field & I'm going off of memory from reading it a month back, so I might be off on things)
using solar, and by my estimates and with the right technology, we can evaporate the sea using the sun and dump it into the depression. We will skip all of the math. Just understand that it was done using maximum solar possible efficiency and a totally passive system that will self-clean and self-recharge every day with the tides and the sun, and work year round.
we'll assume a 50% efficiency rate and that 640 acres will ultimately be needed per meter/second of water we wish to funnel into the depression. the depression's possible water holding capacity is approximately 1.213e+12 meters of water. my estimation is that around 100 miles of coastline are truly available and have not been significantly settled. I will assume that most of the desalinization facilities will be located on a single ridgeline of at most one acre deep which is artificially constructed near the beach, to minimize the amount of energy required, and that the fresh water will be pipelined into the depression from a buried collection system. Around 4 meters/second of water will flow.
The cost of the project, ultimately, is likely to be around 10 dollars per square foot, and totals 1,105,600,000- approximately 1.1 billion when all is done and said. This is around 1.25% of egypt's governmental budget, so it's not entirely unsustainable. However, labor costs and the cost of the land may be larger. So, in my estimation, the project is feasible, however.. that's not a lot of water.
Assuming there is no evaporation, it would require 11699 years to fill the depression.
Love this. Back to the other comment, would love to see numbers in a spreadsheet, if you can just plug your math there. It would clarify things. As they stand, I had a hard time following your reasoning:
What do you mean “we can evaporate the sea with solar”? This would not be part of the plan?
And with “ we'll assume a 50% efficiency rate and that 640 acres will ultimately be needed per meter/second of water we wish to funnel into the depression.”?
And with “ my estimation is that around 100 miles of coastline are truly available and have not been significantly settled.”? Which coastline, of the inner land? The med? Why do you need such a massive coastline?
And with “ at most one acre deep ”? Acreage is a surface not a distance…?
“ Around 4 meters/second of water will flow.”: why do you use m/s and not m3/s?
It’s Tulare Lake and it’s refilling. Going to cause immense problems when it does so this summer (due to the huge snowmelt due to the atmospheric rivers that replenished the Sierra snowpack recently) as people have built up in previously flooded land after that lake had drained away.
I am all for megaprojects, but for seaflooding you really need to give consideration to the question of salt.
1. Water contains salt. Seaflooding leads to a net-positive salt flow into the plain.
2. Evaporation and constant flow cause salinity to rise. Long term equilibrium of seaflooding is a saturated salt solution with salt deposits forming on the bed of the lake. Not conductive to life.
3. High saline water level threaten freshwater aquifers in all surrounding areas.
4. If you want more than an evaporation pond for more rainfall, you must therefore desalinate.
5. Desalination costs energy. Seawater desalination energy cost currently stands at [1]
~3kWh/m^3, so ~3kWh/t=3600s*3kW=10 800kJ/t. From 100m of height difference, you only obtain 100m*10000N/t*1t=1000kJ/t. Therefore, you are essentially desalinating a lot of water to vaporize it in a lake. It is better to use it directly in irrigation systems.
Conclusion for me: The plan is only useful if you can accept a salt lake as the final result. Then you get a bit of electricity and more rainfall. So the plan would be very useful for wasteland without important aquifers.
But it’s true of the Dead Sea today. It’s extremely saline because it’s so low. And its salinity is a source of minerals since they’re harvested.
So a slightly different question would be: would Israelis and Jordanians prefer a Dead Sea or a desert in its place? I think the answer is obviously that they prefer the Dead Sea to exist, and hence this would be good.
Also notice that the evaporated water would become humidity that travels to the region. So it’s not all lost, especially with the right orography around.
I appreciate the long-term-support of your articles with replies to comments!
Agreed re Red-Sea-Esque cases! Another consideration are salt deposits, how quickly will the bed of the lake fill out if sustained by seawater, which is much more salty than e.g. the Jordan. This requires some math and assumptions, but my feeling is that for the deeper basins under consideration, this shouldn't matter in human timescales.
Not sure if you have read about this idea for the Salton Sea, though it has more to do with stabilizing it's water level and salinity than flooding it (very fertile agricultural lands surround the Salton Sea so flooding any higher is not really a sensible option).
Tomas, any promising areas in Australia?! It’s prime real estate for renewables, so over time, generating electricity to desalinate and pump the water should be relatively cost effective.
I noticed that map mentioned Lake Eyre, but doesn't that already have water?
I never heard of these possibilities - and why not? This is the kind of thinking we need. Of course there will be repercussions, but it seems they are manageable with the technology today. The world is so set in how things are done that opportunities like this are overlooked.
When you read history of the 19th century you can clearly see people had this attitude, esp in the US. They would prospect the land to decide where they would build cities and railways, canals and bridges.
Now we fear touching anything.
We need to get back to building.
Cadillac Desert, while written during a time of peak environmental cynicism (imagine being a water and land use activitist in the 1970s, things looked bleak!) tells the story of the ambition it took to make large parts of the Western united states liveable. It is incredible how much brain power and work was required and how everyone had the mindset of "how" rather than what we have today, which is mostly coming up with reasons why we shouldn't bother trying.
Along those lines, one thing that shocks me about that time is that people in the 20s and 30s also led huge such projects. We trusted young people with only a few years of experience to chase their ambitions.
That's true. It's amazing what those years gave us - the railroads, bridges, dams, huge projects. Just try to get something like that done in today's political climate.
There were some of us who, in the 1970's, started recycling (which my family still does) which was much more complicated then - no picking up curbside. I have no idea how many of us from the '70s are left, but conservation has been on our radar for years, just waiting for the rest of the world to catch up and get their heads on straight.
Great piece again, thank you! Could you add a column to the table listing all depressions: By how many mm would mean sea level go down if they were filled to MSL?
If somebody calculates it for me, I’ll add it! It shouldn’t be too complex to do
Do we have a master topographer on the plane?
As a master topographer, maybe you can use the https://en-us.topographic-map.com/ , which I always like to check
Honestly not too hard to make an approximation:
- look up amount of sea water in volume
- take the surface of these depressions, and multiply by average depth for the volume
- add up all the volume of these depressions
- substrate from sea water volumes
- look up how much height that corresponds to
Nah, I think I'll just wing it: max 5 cm of MSL.
Hi Tomas, I checked for the Caspian which is the widest area. Caspian sea is 371,000km2 vs all Oceans area 361,000,000km2 , so it means each 1/1000 parts aprox. So each 1 meter raise the level of Caspian sea it takes 1mm down MSL. So considering the 28m of depression of Caspian Sea it would reduce worlwide sea level 3mm aprox. Not much actually :)
If I follow your math, I find 3cm, not mm?
Also note that the more it fills, the bigger it is in surface! Maybe it would end up like 4cm?
Also add several depressions!
Also it’s not just the water on the ground but in the air, evaporated from these new surfaces!
And on the moisture in surrounding areas!
Yes! 3cm! hahahaha
nearly all of these have been considered in decades past and the projects abandoned. by far the largest reason for abandoning the projects was the belief that over time the water would simply become too salty and then become a stagnant and dead swamp- people prefer a desert over a swamp.
The challenge here, Tomas, is to come up with the engineering proof to measure the amount of energy that would be needed to desalinate the water and the amount of energy needed to pump the salt-rich brine back to the sea, and figure out a scenario where the inflow to our inland sea is sufficient for both. Once you have that equation solved, the scenario becomes a very good hypothetical.
This is a really interesting idea Tomas, and good feedback J Rainstar.
In terms of being an option to reduce global warming, it seems to be a subset of "geoengineering" that offers other benefits (potentially with "no regrets"), but with less global risk than some alternatives.
There's a lot of fast-progressing R&D on solar desalination that might make the difference between it being viable or not.
Thanks!
I looked for sources that could cover this but couldn’t find any. Do you know where you found these? Can you point me in the right direction?
you mean sources that could cover the topic of estimating the volume of brine produced by desalinization, power needed to pump it to the ocean, power needed to desalinate/pressure gradient launched, and power obtained from hydro across a gradient? the source would be engineering textbooks. the technology to do this efficiently is fairly recent so you may have to do some research and calculations because they have not been done yet.
if you mean the various projects having been considered before, its fairly tedious to describe, but each and every such project was once modeled in the terms of using nukes for terraforming back in the 50s.
Yes I know the previous limit in tunneling, not the more recent one you mention on desal.
Yes, what you describe is what I’d be interested in. I assume some of that must be online, but can’t find. Textbooks sounds like a lot of work, I might need an alternative way like talking with people who’ve considered this.
The one thing that sounds weird is that there’s already plenty of endorheic lakes, like Chad or the Caspian Sea.
Or plenty of seas connected to the ocean with net inflow—red and med being 2 examples. Med also has saline outflow, but I must assume some corners of the world only have inflows. I’d be curious to know what they look like.
This is key to figure this out though, i agree
why only look at below sealevel? with all the renewable energy and its peak productions, one could easily imagine other projects.
- aral sea
- mega lake chad
and so on.
Yeah but the only economic case is harder to make. This would have to be a fully public investment because it wouldn’t recoup money directly. In what I propose, it would through hydropower.
What you say is step 2!
Qattara region can even be filled with the the flooding of the Nile which is happening on the yearly monsoon between May and August. And it would have fresh water, not from the sea. But it probably would affect to the needs of the Nile Delta, and it can have a side effect
Yes but there’s arguably not enough water for that.
They tried to do this in another depression and failed.
I think it would take a lot of water away from the delta
Seawater is actually not bad. You can just desalinate what you use for agriculture
You can desalinate when it is cost-effective (when energy costs near zero). Not at present times, though.
And desalinization does have environmental impacts.
Many countries already do this, and energy costs are falling further
Aren’t the countries doing this mostly in the ME, imposing costs on others through externalities (burning carbon)?
Yes, many are. They have cheap energy, which in many cases today means cheap oil.
There was a big book decades ago on Macroengineering and the Earth. Bravura ideas, tough to carry out. I guess we'll see. My guess is the Dead Sea will be first. https://www.sciencedirect.com/book/9781898563594/macro-engineering-and-the-earth
Nice! Asking GPT about the most salient ones.
What are the most underrated in your opinion?
A big ongoing effort has been the Great Green Wall - an effort to build a green belt to stem desertification along the Sahara's southern flank. It hasn't really worked as anticipated but has generated encouraging shifts. Smithsonian story here: > Slowly, the idea of a Great Green Wall has changed into a program centered around indigenous land use techniques, not planting a forest on the edge of a desert. The African Union and the United Nation's Food and Agriculture Organization now refer to it as "Africa’s flagship initiative to combat land degradation, desertification and drought." Incredibly, the Great Green Wall—or some form of it—appears to be working. < https://www.smithsonianmag.com/science-nature/great-green-wall-stop-desertification-not-so-much-180960171/
Very cool! The Great Green Wall always sounded very hard to pull off (it's dry there for a reason), but this type of bottoms-up initiatives do make a lot of sense. I'm glad to read this!
Just remembered this article I read back during the (post-?)hurricane that hit California a month or so ago - You probably DON'T want to include the Salton Sea here.
Link: https://newscenter.sdsu.edu/sdsu_newscenter/news_story.aspx?sid=79250
(Actual paper is linked near the top, but the above link gives a good summary if you're pressed for time)
Major earthquakes on (specifically just slip-strike?) faults can be induced by large bodies of water forming over the fault lines, as it depresses the crust & lubricates the holding points enough to trigger a quake. You pointed out a lot of the potential spots for flooding are situated over faults, so that may be another issue to consider.
Still 100% agree we should be building these megaprojects - the benefits are huge - but some of these like Salton won't be worth the effort if they cause earthquakes in major population centres
(I should point out I have no background in this field & I'm going off of memory from reading it a month back, so I might be off on things)
Oh wow I had no idea.
Definitely something we should keep in mind when assessing these projects! Thanks for sharing.
using solar, and by my estimates and with the right technology, we can evaporate the sea using the sun and dump it into the depression. We will skip all of the math. Just understand that it was done using maximum solar possible efficiency and a totally passive system that will self-clean and self-recharge every day with the tides and the sun, and work year round.
we'll assume a 50% efficiency rate and that 640 acres will ultimately be needed per meter/second of water we wish to funnel into the depression. the depression's possible water holding capacity is approximately 1.213e+12 meters of water. my estimation is that around 100 miles of coastline are truly available and have not been significantly settled. I will assume that most of the desalinization facilities will be located on a single ridgeline of at most one acre deep which is artificially constructed near the beach, to minimize the amount of energy required, and that the fresh water will be pipelined into the depression from a buried collection system. Around 4 meters/second of water will flow.
The cost of the project, ultimately, is likely to be around 10 dollars per square foot, and totals 1,105,600,000- approximately 1.1 billion when all is done and said. This is around 1.25% of egypt's governmental budget, so it's not entirely unsustainable. However, labor costs and the cost of the land may be larger. So, in my estimation, the project is feasible, however.. that's not a lot of water.
Assuming there is no evaporation, it would require 11699 years to fill the depression.
Love this. Back to the other comment, would love to see numbers in a spreadsheet, if you can just plug your math there. It would clarify things. As they stand, I had a hard time following your reasoning:
What do you mean “we can evaporate the sea with solar”? This would not be part of the plan?
And with “ we'll assume a 50% efficiency rate and that 640 acres will ultimately be needed per meter/second of water we wish to funnel into the depression.”?
And with “ my estimation is that around 100 miles of coastline are truly available and have not been significantly settled.”? Which coastline, of the inner land? The med? Why do you need such a massive coastline?
And with “ at most one acre deep ”? Acreage is a surface not a distance…?
“ Around 4 meters/second of water will flow.”: why do you use m/s and not m3/s?
I have always loved the word "picayune" and it's amusing that it's such a long word for referring to "tiny" or "insignificant."
Great article, food for thought. Seems like a feasible idea, if presented to the right audience. Thank you for this.
So far lots of people are into it. Let’s see if anybody picks it up!
Interesting how California is dealing with this problem: "strategic retreat" is their euphemism for pack up and move to higher ground
It’s time to push aside this immobilist mindset and get to move again!
Actually on the topic, I was wondering if anyone has made a plan to remake Lake Tule, once California's largest lake.
I haven’t explored redoing freshwater lakes. I might in the future
It’s Tulare Lake and it’s refilling. Going to cause immense problems when it does so this summer (due to the huge snowmelt due to the atmospheric rivers that replenished the Sierra snowpack recently) as people have built up in previously flooded land after that lake had drained away.
Great
I am all for megaprojects, but for seaflooding you really need to give consideration to the question of salt.
1. Water contains salt. Seaflooding leads to a net-positive salt flow into the plain.
2. Evaporation and constant flow cause salinity to rise. Long term equilibrium of seaflooding is a saturated salt solution with salt deposits forming on the bed of the lake. Not conductive to life.
3. High saline water level threaten freshwater aquifers in all surrounding areas.
4. If you want more than an evaporation pond for more rainfall, you must therefore desalinate.
5. Desalination costs energy. Seawater desalination energy cost currently stands at [1]
~3kWh/m^3, so ~3kWh/t=3600s*3kW=10 800kJ/t. From 100m of height difference, you only obtain 100m*10000N/t*1t=1000kJ/t. Therefore, you are essentially desalinating a lot of water to vaporize it in a lake. It is better to use it directly in irrigation systems.
Conclusion for me: The plan is only useful if you can accept a salt lake as the final result. Then you get a bit of electricity and more rainfall. So the plan would be very useful for wasteland without important aquifers.
[1]https://en.wikipedia.org/wiki/Desalination
Yes this is indeed true.
But it’s true of the Dead Sea today. It’s extremely saline because it’s so low. And its salinity is a source of minerals since they’re harvested.
So a slightly different question would be: would Israelis and Jordanians prefer a Dead Sea or a desert in its place? I think the answer is obviously that they prefer the Dead Sea to exist, and hence this would be good.
Also notice that the evaporated water would become humidity that travels to the region. So it’s not all lost, especially with the right orography around.
I appreciate the long-term-support of your articles with replies to comments!
Agreed re Red-Sea-Esque cases! Another consideration are salt deposits, how quickly will the bed of the lake fill out if sustained by seawater, which is much more salty than e.g. the Jordan. This requires some math and assumptions, but my feeling is that for the deeper basins under consideration, this shouldn't matter in human timescales.
Yes my intuition tells me it’s always going to be less salty than the Dead Sea anyway so we should be good.
Great post... I’ve re-stacked with a note
Not sure if you have read about this idea for the Salton Sea, though it has more to do with stabilizing it's water level and salinity than flooding it (very fertile agricultural lands surround the Salton Sea so flooding any higher is not really a sensible option).
https://energycentral.com/c/pip/great-mexicali-energy-and-shipping-canal
The next article in the series covers it!
Tomas, any promising areas in Australia?! It’s prime real estate for renewables, so over time, generating electricity to desalinate and pump the water should be relatively cost effective.
I noticed that map mentioned Lake Eyre, but doesn't that already have water?
Yeah just Lake Eyre. It has water sometimes. But not much. But the depression is not very high, and it’s far from the sea…
I go into the detail in the premium article!
My question is whether flooding the Qattara Depression would add salt to the Nubian Sanstone Aquifer System. How could this be tested?