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A drought has forced authorities to further slash traffic in Panama Canal

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Re: A drought has forced authorities to further slash traffic in Panama Canal

#121

Post by dumbo-octopus »

aziaziazi wrote: post #114
dumbo-octopus wrote: post #110

Earlier quoted context omitted.

Unless of course it prevented the draining of millions of gallons of freshwater. No matter what there is some amount of mixing with the sea. The question is at which lock should that happen. Currently it's at lock 1, everyone here is arguing it'd be absolutely impossible for it to happen at any other lock, without providing any justification.

Here’s a document “salinity intrusion in the Panama Canal”: https://apps.dtic.mil/sti/pdfs/ADA378475.pdf Graphs at page 32 and onward shows that you could (in theory) pump salt water in one more lock upward in both sides. It will make the last lock before lake at 0.5ppt (Atlantic) and 1.32ppt (Pacific). Fresh water is 0-0.5ppt.

So you could cut water by half while still keeping the last lock "fresh", and so long as the incoming flow is more than 2.5x the mixing rate, you could do the same on the pacific side.

Re: A drought has forced authorities to further slash traffic in Panama Canal

#122

Post by Veserv »

ok_dad wrote: post #33
stkdump wrote: post #15

Earlier quoted context omitted.

I had to check if that realistic. 40 million gallons at 85 feet is 11MWh of potential energy. At 70% efficiency it would take 16MWh to pump that. That has to be a small amount of energy compared to what ships take for traveling the detour.

It would take a long time to pump that amount of water out of the lock that you’re lowering, and over time you’ll be pumping saltwater into a freshwater system, which isn’t good. You’d have to do filtering or something, at great expense. Currently it takes a short time to drain the lock, so ships transit faster. It’s pretty fun to do that transit, but I was amazed that the pilot let me conn the ship the whole time in…

The Panama Canal Authority derives ~3 G$ in fees over ~14 K crossings per year for a average cost of ~200 K$ per crossing.

40 M gallons is ~150 K*m^3. Modern bulk desalination turns seawater into potable fresh water at ~0.40 $/m^3, so only ~60 K$. The cost of filtering out any incidental saltwater mixing should be a tiny fraction of that cost.

Even at full desalination it would only constitute ~30% cost increase. Given the minimal amount of filtering that should be required for incidental mixture, it is hard to call that a great expense except in relation to rainwater.

Re: A drought has forced authorities to further slash traffic in Panama Canal

#123

Post by reaperman »

bluejekyll wrote: post #120
reaperman wrote: post #21

Earlier quoted context omitted.

Siphons only really "work" if the final position of the water is lower than the starting position. Siphon effect allows the water to pass through an intermediate higher elevation without continuous external pumping energy, but on average the water must still be going downhill to utilize the siphon effect.

Omg, I wasn’t thinking. The surface of the target liquid needs to be lower than the source. I was thinking of a pipe coming in lower than the lake, but that wouldn’t work.

If it makes you feel better I have a degree in chemical engineering, and a few months ago made the exact same mistake as you for an automatic watering system where I put a reservoir of water in the cabinet below a plant and wondered why water was traveling from the planter into the reservoir and overflowing and spilling all over the cabinet and floor.

Some days we're just dumb, even if most days we're pretty smart.

Re: A drought has forced authorities to further slash traffic in Panama Canal

#124

Post by bluejekyll »

reaperman wrote: post #123
bluejekyll wrote: post #120

Earlier quoted context omitted.

Omg, I wasn’t thinking. The surface of the target liquid needs to be lower than the source. I was thinking of a pipe coming in lower than the lake, but that wouldn’t work.

If it makes you feel better I have a degree in chemical engineering, and a few months ago made the exact same mistake as you for an automatic watering system where I put a reservoir of water in the cabinet below a plant and wondered why water was traveling from the planter into the reservoir and overflowing and spilling all over the cabinet and floor. Some days we're just dumb, even if most days we're pretty smart.

That made me smile. Thanks ;)

Re: A drought has forced authorities to further slash traffic in Panama Canal

#125

Post by ok_dad »

Veserv wrote: post #122
ok_dad wrote: post #33

Earlier quoted context omitted.

It would take a long time to pump that amount of water out of the lock that you’re lowering, and over time you’ll be pumping saltwater into a freshwater system, which isn’t good. You’d have to do filtering or something, at great expense. Currently it takes a short time to drain the lock, so ships transit faster. It’s pretty fun to do that transit, but I was amazed that the pilot let me conn the ship the whole time in…

The Panama Canal Authority derives ~3 G$ in fees over ~14 K crossings per year for a average cost of ~200 K$ per crossing. 40 M gallons is ~150 K*m^3. Modern bulk desalination turns seawater into potable fresh water at ~0.40 $/m^3, so only ~60 K$. The cost of filtering out any incidental saltwater mixing should be a tiny fraction of that cost. Even at full desalination it would only constitute ~30% cost increase. Giv…

30% is a large increase to a canal that we use for a huge portion of our consumer goods, I think. I do agree that they soups build desalination plants now, so they can use them in twenty years when they’re finished and the drought is even worse!

Re: A drought has forced authorities to further slash traffic in Panama Canal

#126

Post by Veserv »

ok_dad wrote: post #125
Veserv wrote: post #122

Earlier quoted context omitted.

The Panama Canal Authority derives ~3 G$ in fees over ~14 K crossings per year for a average cost of ~200 K$ per crossing. 40 M gallons is ~150 K*m^3. Modern bulk desalination turns seawater into potable fresh water at ~0.40 $/m^3, so only ~60 K$. The cost of filtering out any incidental saltwater mixing should be a tiny fraction of that cost. Even at full desalination it would only constitute ~30% cost increase. Giv…

30% is a large increase to a canal that we use for a huge portion of our consumer goods, I think. I do agree that they soups build desalination plants now, so they can use them in twenty years when they’re finished and the drought is even worse!

A Neopanamax vessel is allowed to transport 120,000 metric tons of cargo [1]. ~60 K$ would only amount to 0.50 $/t of extra cost. That is only low single-digit percentage increased shipping cost [2].

And again, that is the cost of desalinating 100% seawater, not the proportionally cheaper cost of desalinating whatever single-digit to maybe low double-digit percent you would actually get from incidental mixture during reclamation.

[1] https://en.m.wikipedia.org/wiki/Panamax

[2] https://unctad.org/system/files/official-document/rmt2022_en...

Re: A drought has forced authorities to further slash traffic in Panama Canal

#127

Post by ok_dad »

Veserv wrote: post #126
ok_dad wrote: post #125

Earlier quoted context omitted.

30% is a large increase to a canal that we use for a huge portion of our consumer goods, I think. I do agree that they soups build desalination plants now, so they can use them in twenty years when they’re finished and the drought is even worse!

A Neopanamax vessel is allowed to transport 120,000 metric tons of cargo [1]. ~60 K$ would only amount to 0.50 $/t of extra cost. That is only low single-digit percentage increased shipping cost [2]. And again, that is the cost of desalinating 100% seawater, not the proportionally cheaper cost of desalinating whatever single-digit to maybe low double-digit percent you would actually get from incidental mixture during…

Good points, I hope the canal authority gets on that! It seems a no brainier to set up even a small desalination plant to make up for droughts.
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