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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

#21

Post by reaperman »

bluejekyll wrote: post #10
pacificmint wrote: post #7

Earlier quoted context omitted.

Isn’t that how all locks work? Or at least most? I’ve always assumed the energy cost to pump the water would make it cost prohibitive, but I wonder how it compares to rerouting ships or moving containers over land.

Ok, I’m no civil engineer, but couldn’t you design a siphon system that would only require opening and closing valves to capture the water without any pumping?

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.

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

#22

Post by jillesvangurp »

mattmaroon wrote: post #16

I guess it never occurred to me it was fresh water. Can they not just use salt water?

No, because the salt water is at sea level and the drinking water is at the level the ships need to rise to via the locks. Water flows out from a lake at 26 meters above sea level that is fed by a river that comes from the mountains by gravity.

Making the amounts of water that drains out from there move up requires massive amounts of energy. We're not talking a few little pipes here and there. The pumps and energy generation infrastructure project needed to get that done would probably rival or surpass the Panama canal in complexity, scale, and scope. It would be expensive and take a long time to build. Add to that the complexity of doing that while not shutting down the canal for a few years.

Basically the amount of water needed for the locks is a function of the amount of tonnage that ships through the canal and the altitude that ships needs to rise to. We're talking about pumping millions of tonnes of water up by 26 meters. Think something in the order of hundreds of gwh per day at least. Of course you could continue to rely on rivers for part of that. But still, it might be doable but it wouldn't be cheap.

That and the fact that pumping a lot of salt water would destroy large parts of the ecosystem in Panama is a reason that will likely never happen. The locals might object a bit to that. And they probably also rely on that water for drinking and agriculture.

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

#23

Post by [deleted] »

dumbo-octopus wrote: post #20
namaria wrote: post #17

Earlier quoted context omitted.

The canal is connected to a natural fresh water system. You can't just pump salt water in there without risking a massive ecological disaster.

You could pump water to the highest lock lower than the lake though. But salt water doesn't mix well with things not intended for salt water.

[deleted]

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

#24

Post by perihelions »

pacificmint wrote: post #7
donor20 wrote: post #5

One note - they don’t pump water out and back into the locks from a neighboring storage. They flush the water. Each ship needs like 40 million gallons? Maybe title should be insane wastes of water forces authorities…. :)

Isn’t that how all locks work? Or at least most? I’ve always assumed the energy cost to pump the water would make it cost prohibitive, but I wonder how it compares to rerouting ships or moving containers over land.

Some canal locks pump water back,

- "The hydraulic cylinders enable the water used by the locks to be pumped back. Up to 48,000 cubic metres of water are displaced in a single lockage operation. In periods of low discharge on the Meuse, the screws can pump back the water lost due to the passage of a ship through the lock to the upper canal reach."

https://www.inlandnavigation.eu/power-of-water-and-wind/

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

#25

Post by londons_explore »

stkdump wrote: post #15
donor20 wrote: post #5

One note - they don’t pump water out and back into the locks from a neighboring storage. They flush the water. Each ship needs like 40 million gallons? Maybe title should be insane wastes of water forces authorities…. :)

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.

And remember each ship goes up as well as down - so you can theoretically recoup all the energy you used pumping.

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

#26

Post by jacquesm »

scythe wrote: post #13
jgord wrote: post #2

I was amazed to hear they relied on large amount of fresh water supply to refill the lochs for each ships passage.

Panama is very rainy on average. The average rainfall in Colón is 3.4 meters (136 inches) per year. Ciudad de Panamá is a little drier with 1.9 meters (75 inches). For comparison, New Orleans, the continental US's wettest city, gets 1.6 meters (64 inches). But it can vary, and unfortunately, January is the beginning of the dry season, which ends in May.

Not only is it rainy, when it rains it rains. I've been soaked through on 5 meters of exposure between a building and a cab.

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

#28

Post by charlieyu1 »

stkdump wrote: post #15
donor20 wrote: post #5

One note - they don’t pump water out and back into the locks from a neighboring storage. They flush the water. Each ship needs like 40 million gallons? Maybe title should be insane wastes of water forces authorities…. :)

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.

But if it is not pumped back it is free electricity

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

#29

Post by olliej »

bluejekyll wrote: post #10
pacificmint wrote: post #7

Earlier quoted context omitted.

Isn’t that how all locks work? Or at least most? I’ve always assumed the energy cost to pump the water would make it cost prohibitive, but I wonder how it compares to rerouting ships or moving containers over land.

Ok, I’m no civil engineer, but couldn’t you design a siphon system that would only require opening and closing valves to capture the water without any pumping?

Siphoning only works if the destination is lower than the source, otherwise you're looking at free energy, which would definitely be a win for everyone :D

Suez is (was? lets ignore geopolitics instead of physics for now) so successful because it's lock free (ha! tech joke on HN, I'm rocking this :D). The Panama canal was made by creating a massive artificial lake above "sea level" rather than digging a path down to sea level through mountains. Historically this worked, but alas enough corporations profit enough by offloading the costs of their industries onto everyone else as a form of socialism we call subsidized global warming.

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

#30

Post by jorisboris »

paranoidrobot wrote: post #8
pacificmint wrote: post #7

Earlier quoted context omitted.

Isn’t that how all locks work? Or at least most? I’ve always assumed the energy cost to pump the water would make it cost prohibitive, but I wonder how it compares to rerouting ships or moving containers over land.

Also relevant: Gatun Lake that these locks are fed from/part of is freshwater. This makes recovering water from the locks problematic, since you can't feed it seawater.

This looks to me as the correct problem indeed. Inevitably you'll start pumping up salt water eventually.
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