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Comment by bluejekyll | Hacker News Reader

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?

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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.

That made me smile. Thanks ;)

No; at some point you're going to lift the water up. That requires pumping.

Why is that? Britain is covered with a preindustrial canal network with thousands of locks which use nothing but channels doors and gravity. Literally made of wood and operated by hand.

Raising water on the low side to the level on the high side simply requires joining the two sides together.

If sea level is their high side, I don't understand why they can't use this supply forever.

The sea level is the low side. The lake is the high side - which works great until the supply of lake water dries up.

The obvious solution is a sea-level tunnel a hundred miles long. Probably cheap. ;)

There has been proposed canal in Nicaragua. It would be 170 miles long and have locks to reach Lake Nicaragua.

Chinese company got concession to build decade ago, but didn't do anything and then went out of business.

i dunno about tunnel... i am not a digger but I don't think digging 26 meters (highest point of canal) would require tunneling... just dredging.

You'd have to deal with the Chagres (assuming the current drought ends) as well.

The original excavation was done mostly dry and massive by any standards: 27kt of dynamite were used.

I'm also not a digger, but 26 meters of dredging over a 13km distance sounds crazy expensive. You would have to also widen the valley to prevent landslides into the canal.

Sea level is a low side on both ends of the channel.

Some lock flights have pumps to keep the ponds at the top full of water because they are near the highest point in the area so they can't refill naturally fast enough or simply to avoid depleting the upstream water source. See, e.g., https://en.wikipedia.org/wiki/Caen_Hill_Locks

I think the thing you are missing is that raising the low side means that the next boat to use the lock going up has to drain the high water into the low canal. The Panama Canal has system to conserve that water but some water still moves down the locks both for raising and lowering.

The British locks depend on a source of water at the top of the canal. I watched a video recently about Canal Trust rebuilding lock reservoir. The water levels definitely can limit if locks and canals are usable.

The Panama Canal has a reservoir at the top, Gatan Lake, but the water is low. Sea level is never the high side, it is always the low side.

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.

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