Water shortages? I thought the canal connected oceans and I thought the oceans were rising?
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.
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?
> "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...
Nice! And Dinorwig runs around 72% round-trip efficiency, which is higher than I expect to see here simply on account of scale, but also in the ballpark.
> generate power while filling the locks as the water falls down...
Now that's an interesting one.
There are already lock systems where there's two parallel chains, and the ascending and descending locks operate in lock-step, with the two locks first equalizing water with each other, before the ascending takes water from above and the descending releases water to below. So that doubles the amount of traffic that can be handled by the same amount of water.
Presumably building twice the infrastructure would be cost-prohibitive or they would've done it over the preceding decade, but storing the water's energy could be quite a bit cheaper and smaller.
Edit: Much simpler, takes more space, saves almost as much water: https://en.wikipedia.org/wiki/Panama_Canal_expansion_project...
It ends up being a lot like linking the shafts of all the pumps, with extra steps for control, eh?
Edit: Oh. Yeah. Okay, at each lock, you've got three pumps on a common shaft, with clutches:
(fill turbine)--[clutch]--(lift pump)--[clutch]--(drain turbine)
Whether you're filling or draining, you clutch that turbine to the lift pump, and lift some water upward as the working water flows downward. No electricity needed.
Hmm. Alright, who wants to go pitch a project?
> 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-br...
Gatun lake was an artificial construction of the project.