[fuoqi]

I wonder how much would it cost to build a tunnel as an alternative to the Panama canal to fundamentally resolve the drought issues. 1.8 km is comparable to ~80 km (probably a shorter tunnel will suffice) and dimensions are also similar (at least for the old Panamax).

[eesmith]

Looks like the Norway tunnel is through hard gneiss. That rock formed 100s of millions or a billion years ago. https://en.wikipedia.org/wiki/Sveconorwegian_orogeny Norwegians know how to tunnel through it, like https://en.wikipedia.org/wiki/B%C3%B8mlafjord_Tunnel and https://trid.trb.org/view/512421 .

The Panama Canal famously had to deal with a lot of mud, clay, and unstable rock, causing many landslides during and after construction.

The geology of Panama is quite complex and the isthmus is only 4 million or so years old. "The geology of Panama includes the complex tectonic interplay between the Pacific, Cocos and Nazca plates, the Caribbean Plate and the Panama Microplate" - https://en.wikipedia.org/wiki/Geology_of_Panama

Looks like Panama City is working on a monorail tunnel to go under the Panama Canal for Line 3. https://www.herrenknecht.com/en/references/referencesdetail/... mentions the complex geology for the TBM has "Heterogeneous ground; La Boca Formation: Sandstone, siltstone, tuff, mudstone, pyroclastic rocks; Tucue Formation: Basalts and andesits; Panama Formation: Tuff, sandstone, agglomerate".

That's quite of bit of soft and crumbly rock.