Open areas of fluids research:
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The behavior of underground waterfalls (river sources) has not been studied.
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Here's a little test study done by Maw. To summarize it, the waterfall tile creates a 7/7 tile of water on top of it, and it fluid paths just like a pump. Further, it can be collapsed and its water creating potential will be preserved.
Anyone got more info on this? Does he mean that collapsing the 'waterfall' tiles into a lower z-level will cause them to create water there, or will it create water in midair?
Also, what will happen if something crashed through the waterfill tiles? I assume it will just be destroyed, which would a total waste, but I like to be sure
As to your first question:
Collapsing the 'waterfall' tile to a lower z-level will cause them to create water at the new level location. The waterfall creation is tied to the tile, not to the location. Your question was the reason for my testing in the first place (I wanted the latter effect)
As to your second question, please find from a later post in the referred thread:
3) I lose the waterfall source completely (and have to redirect a brook instead)?
Note that you can destroy the waterfall tile by collapsing on it a natural wall (blocking the tile) or a natural floor (not blocking the tile). Collapsing a constructed floor will not have an effect, as falling constructions deconstruct into their source materials.
Thus, 3) will only be the result if you collapse a natural wall or floor onto the waterfall tiles, destroying said tile. It is immaterial if you just collapse with the waterfall tile supported by natural walls underneath, or cause collapses down several z-levels; either way the waterfall source tile is 'covered' and destroyed.
Assumption - given that natural floor destroys the source, I doubt collapsing a wall, then mining the wall would re-reveal the waterfall source tile. You essentially replace the waterfall source tile with the upper floor's floor tile.
Note: Untested - does a falling construction (which deconstructs so no new floor tile), smashing into the waterfall tile with open space underneath cause the waterfall tile to collapse to a new zlevel, or does it destroy the waterfall tile. The reference above is for a natural floor/wall onto the waterfall tile. Simple test to collapse a construction on any floor tile (e.g. a coloured stone) onto some other colour stone. Which do you end up with?