3 ms·

Water shortages? I thought the canal connected oceans and I thought the oceans were rising?

Cpoll 3y ago
The canal is 25m above sea level at parts.
8note 3y ago
It's sourced from a lake, which allows for moving locks to get between oceans that have different heights. The oceans don't actually touch each other
myself248 3y ago
The canal forms a ladder that raises ships from one ocean, up through a series of locks, into waterways that cross over the middle of the isthmus, then back down the other side. The canal itself it not all at sea level. Locks work by controlling the release of water from a high point to a low point. The water needs to already be at the high point, by tapping a river or something that's fed by rain; locks do not have pumps to supply their own water. To raise a ship, you pull it into the lock, close the doors on the low side, and open a valve that lets water from the high side flow into the lock and float the ship up. Then you open the doors on the high side. To lower a ship, you pull it into the lock from the high side, close the doors on the high side, and open a valve that lets water from the lock flow to the low side. Then open the doors on the low side and pull the ship out. The low side of one lock is the high side of the next one, so that water basically follows the ship and gets lowered with it as it descends the ladder. But the water has to get to the high middle somehow.
- redleader55 3y ago
  Just adding a few small details here: 1. When the canal was built, it was deemed to hard and expensive to dig at the level of the two oceans so they imagined the locks system as a solution for that. Back then, the canal was built with US money in a time of conflict between Panama(which was part of Colombia) and Colombia. Today Panama is an independent country, but they don't have the finances to upgrade the canal. 2. They don't want to bring water from the ocean up the canal is because the canal gets its water from a series of fresh water lakes. Bringing salty water would kill the life in the lakes are around the lakes and cause a lot more problems long term.
  - myself248 3y ago
    Agreed, pumping sea water seems terrible, but it also seems like there'd be no reason to do that. First, at either end of the system there's a chunk of river at sea-level-ish but flowing towards the sea, so the water up at the upstream end where the lower locks are is probably not salty at all. Second, if each lock had its own pumps, doing it in 3 short lifts rather than 1 big lift to the top, then even if the one or two closest to sea-level ended up somewhat brackish, there'd be a dilution effect going up hill, and there would still be fresh water entering the system from the lakes which would tend to flush it downward. I don't think Gatun is at risk. But what would it cost? Okay, bullshit math time. In mixed units just to annoy metric purists: A quick search says each lock cycle is around 50 million gallons, or 153-acre-feet. It takes 3 steps to raise them 85 feet above sea level, in energy terms let's just model it as one big step. It takes almost exactly 1kWh of energy to raise one acre-foot of water by 1 foot, so 153 acre-feet raised by 85 feet is about 13MWh per cycle. Apparently the canal manages about 40 transits per day, which I'm interpreting as each lock cycles once, so that's 521MWh of energy being provided by the rain delivering the water to the upper lakes. Let's say we want to double that to 80 cycles a day. Oh, also, pumps are only about 70% efficient, so we actually need to provide 745MWh of power. Divide that by 24 hours and we end up with a 31MW power plant. That's..... tiny. Nah. Let's do it with solar. Roughly 6 hours peak sun equivalent per day (data for bocas del toro), we need 124MW of panels. The lakes have plenty of storage so there's no need for batteries, just run the pumps only when the sun is shining. Utility-scale solar runs around $1/watt installed. Labor is cheaper in Panama but conditions may be more challenging, I don't have good estimates for either of those so I'll assume they cancel out. Hey, it's napkin math! $124M for the panels, figure the pumps and plumbing aren't cheap either but even if that's 10x the cost, we're probably still in the single-digit billions. If they've been charging ships to use the canal like Egypt charges for the Suez, they should have quite the rainy-day, er, not-rainy-enough-day, fund for such projects. Especially if they raise prices auction-style during times of high demand, and let the high bidder through. That seems like a no-brainer. What am I missing?
    - jodrellblank 3y ago
      I did my own estimate ( https://news.ycombinator.com/item?id=38997124 https://news.ycombinator.com/item?id=38997124 ) via a different method, before reading down to yours, and got ~450MWh of energy needed - which is close enough to your 521MWh that I'm pretty happy. > "Nah. Let's do it with solar." Why not with hydroelectric? Store power by pumping water up to Gatun Lake, generate power while filling the locks as the water falls down...
idlephysicist 3y ago
I was also confused by this, I had always (perhaps naively) assumed that the canal used salt water throughout. I did some searching and found this article. > Gatun Lake, which forms a key stretch of the canal system and provides fresh water for its locks, saw little rain this year, as El Niño triggered a withering drought. https://fortune.com/2023/12/04/panama-canal-dry-backed-up-brutal-drought-shippers-paying-4m-jump-queue/ https://fortune.com/2023/12/04/panama-canal-dry-backed-up-br...
bsdpufferfish 3y ago
The American engineers who designed and built this are long gone. Gatun lake was an artificial construction of the project.
downrightmike 3y ago
They use freshwater from a man made lake, and over the decades, silt has reduced capacity and then they have been in a massive drought for years. they have no real reclamation from the locks back into the lake, so each trip wastes a ton of water. Really, they should just charge enough to reflect reality and then most ship with just go to the west coast

The canal is 25m above sea level at parts.

It's sourced from a lake, which allows for moving locks to get between oceans that have different heights. The oceans don't actually touch each other

myself248 3y ago

The canal forms a ladder that raises ships from one ocean, up through a series of locks, into waterways that cross over the middle of the isthmus, then back down the other side. The canal itself it not all at sea level. Locks work by controlling the release of water from a high point to a low point. The water needs to already be at the high point, by tapping a river or something that's fed by rain; locks do not have pumps to supply their own water. To raise a ship, you pull it into the lock, close the doors on the low side, and open a valve that lets water from the high side flow into the lock and float the ship up. Then you open the doors on the high side. To lower a ship, you pull it into the lock from the high side, close the doors on the high side, and open a valve that lets water from the lock flow to the low side. Then open the doors on the low side and pull the ship out. The low side of one lock is the high side of the next one, so that water basically follows the ship and gets lowered with it as it descends the ladder. But the water has to get to the high middle somehow.

redleader55 3y ago
Just adding a few small details here: 1. When the canal was built, it was deemed to hard and expensive to dig at the level of the two oceans so they imagined the locks system as a solution for that. Back then, the canal was built with US money in a time of conflict between Panama(which was part of Colombia) and Colombia. Today Panama is an independent country, but they don't have the finances to upgrade the canal. 2. They don't want to bring water from the ocean up the canal is because the canal gets its water from a series of fresh water lakes. Bringing salty water would kill the life in the lakes are around the lakes and cause a lot more problems long term.
- myself248 3y ago
  Agreed, pumping sea water seems terrible, but it also seems like there'd be no reason to do that. First, at either end of the system there's a chunk of river at sea-level-ish but flowing towards the sea, so the water up at the upstream end where the lower locks are is probably not salty at all. Second, if each lock had its own pumps, doing it in 3 short lifts rather than 1 big lift to the top, then even if the one or two closest to sea-level ended up somewhat brackish, there'd be a dilution effect going up hill, and there would still be fresh water entering the system from the lakes which would tend to flush it downward. I don't think Gatun is at risk. But what would it cost? Okay, bullshit math time. In mixed units just to annoy metric purists: A quick search says each lock cycle is around 50 million gallons, or 153-acre-feet. It takes 3 steps to raise them 85 feet above sea level, in energy terms let's just model it as one big step. It takes almost exactly 1kWh of energy to raise one acre-foot of water by 1 foot, so 153 acre-feet raised by 85 feet is about 13MWh per cycle. Apparently the canal manages about 40 transits per day, which I'm interpreting as each lock cycles once, so that's 521MWh of energy being provided by the rain delivering the water to the upper lakes. Let's say we want to double that to 80 cycles a day. Oh, also, pumps are only about 70% efficient, so we actually need to provide 745MWh of power. Divide that by 24 hours and we end up with a 31MW power plant. That's..... tiny. Nah. Let's do it with solar. Roughly 6 hours peak sun equivalent per day (data for bocas del toro), we need 124MW of panels. The lakes have plenty of storage so there's no need for batteries, just run the pumps only when the sun is shining. Utility-scale solar runs around $1/watt installed. Labor is cheaper in Panama but conditions may be more challenging, I don't have good estimates for either of those so I'll assume they cancel out. Hey, it's napkin math! $124M for the panels, figure the pumps and plumbing aren't cheap either but even if that's 10x the cost, we're probably still in the single-digit billions. If they've been charging ships to use the canal like Egypt charges for the Suez, they should have quite the rainy-day, er, not-rainy-enough-day, fund for such projects. Especially if they raise prices auction-style during times of high demand, and let the high bidder through. That seems like a no-brainer. What am I missing?
  - jodrellblank 3y ago
    I did my own estimate ( https://news.ycombinator.com/item?id=38997124 https://news.ycombinator.com/item?id=38997124 ) via a different method, before reading down to yours, and got ~450MWh of energy needed - which is close enough to your 521MWh that I'm pretty happy. > "Nah. Let's do it with solar." Why not with hydroelectric? Store power by pumping water up to Gatun Lake, generate power while filling the locks as the water falls down...

idlephysicist 3y ago

I was also confused by this, I had always (perhaps naively) assumed that the canal used salt water throughout. I did some searching and found this article. > Gatun Lake, which forms a key stretch of the canal system and provides fresh water for its locks, saw little rain this year, as El Niño triggered a withering drought. https://fortune.com/2023/12/04/panama-canal-dry-backed-up-brutal-drought-shippers-paying-4m-jump-queue/ https://fortune.com/2023/12/04/panama-canal-dry-backed-up-br...

bsdpufferfish 3y ago

The American engineers who designed and built this are long gone. Gatun lake was an artificial construction of the project.

downrightmike 3y ago

They use freshwater from a man made lake, and over the decades, silt has reduced capacity and then they have been in a massive drought for years. they have no real reclamation from the locks back into the lake, so each trip wastes a ton of water. Really, they should just charge enough to reflect reality and then most ship with just go to the west coast