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[Vanguard Warden]

I wanted to build a sort of artificial underground lakes, with irrigated ground around the edges of the top of the lake for tree-caps and farming. One feature I was hoping to include was a free-standing waterfall. That is, I want water to flow down from a hole in the ceiling to fill the lake, while the excess water flows out a horizontal shaft into an infinite drain, like a bottomless pit or the edge of the map, made narrow enough that the lake will hold water while draining. However, I'm unsure on how water pressure works in this scenario. Here's a diagram I made of the situation:

Code: [Select]

███████████████
~~~~~~> ███████ - Water flows in here and falls.
███████ ███████
███████ ███████
█___       ___█
████~~~~~~~~~~> - Water collects on this level and drains out the side.
███████████████

Would water poured onto the surface of the lake spread out and flood the area, or would it teleport to the end of the slow-flowing drainage pipe?

[inaluct]

I'm not sure about the answer to your main question, but do you actually have a bottomless pit? Because it's impossible to dig one. It's also impossible to dig off of the map.

[Jim Groovester]

It would teleport to the end of the drain, provided it drains into a chasm or bottomless pit. If it doesn't drain into one of those, then it will build up where the water falls onto and flood your fortress.

I don't think water flows off the edge of the map fast enough to accommodate a waterfall.

[Albedo]

I think you're thinking of it wrong.

Water with pressure (like this) will always ~try~ to seek the same level as its source - in this case, the top of the water fall.  That's where the water is coming from, and there are no "pressure killers" between that and the lake.

Drainage does not respond to "excess water".  Think of it like a J-shaped pipe with a pin-hole in the very bottom, at the base of the curve. If you pour water in the tall end, and can drain it fast enough through that pin hole, it never gets a chance to come up the short end.  If not...

If you can drain the lake fast enough, there's no problem - it never backs up enough to get a chance.  But if you don't, then it will build up, and up, to fill that area and up the shaft to be equal to the level of the water fall.

Drainage is the key here.

[Eater of Vermin]

I like my water features.    What I've found is:

If the feed is supplied by a pump, or from the bottom of a large(ish) multi-level reservoir, then the drain channel needs to be a wider than the feed channel.

If the feed is channelled directly from a river,  then you can get away with the drain channel being the same width.   Mind you, if you put a floodgate in the feed channel just before the waterfall, then you will get a surge of "excess water" that's proportionate to how many z-levels the channel drops, if you open it after letting the channel fill thoroughly.  (More z-levels, more "excess" in the surge.)   

And it's best to install floodgates to limit potential damage, so...

...it's always a good idea to make drainage channels wider than the feeds!

[Shoku]

I did some artsy redirections of an underground river in a few forts.
In the last one I had some parts much wider than others to be sorts of flowing lakes for my multi level towercap farm.

I had floodgates at the van by the river and at the end of the towercaps (before my dining hall shower,) and here's how it went-

Draining the forest didn't really work quite right until i shut out flow from the river- the 3 wide hall of intake and the 3 wide hall of output equaled out, at least for the lower level of the farm. (The top level draining actually muddied up my floors even though I had like a four level drop below that to the last stretch of drainway.)

If I let it drain entirely before opening the intake again the "lake" areas wouldn't fill up very effectively but after closing the output until they were full and then opening it they maintained the water level like the lower level of the forest had.


So, if you want to selectively flood it stuff in the first place and can't be bothered to just close the drainage with floodgates you could have two pumps sending water into the intake but then just disable the one once you had muddied everything and turn the other one off until it was down to 1's and 2's of water all while keeping your lake.

[AncientEnemy]

It's also impossible to dig off of the map.

while technically true, you can drain water off the edge of the map underground by smoothing and carving fortifcations into the stone at the very edge.

[Neruz]

It's also impossible to dig off of the map.

while technically true, you can drain water off the edge of the map underground by smoothing and carving fortifcations into the stone at the very edge.

Which, incidentally, seems to drain water far faster than it should, you can actually drain rivers to dam them with this method.

[Albedo]

Buried somewhere on a discussion page of the wiki is an explanation of how putting a staircase next to a floodgate makes it work faster like that.  I may have the details wrong, but the author was convincing.

(Maybe... "damming"? Or "reservoirs"?)

[Vanguard Warden]

I was getting conflicting reports and no real answers here, so I decided to just test it myself, embarking on a brook with 100 tower cap logs and seven multi-talented construction workers. I built a stacked pump-tower three levels tall off the side of a brook, and had it pour into a small single Z-level pit with a drainage pipe dug into the side of it leading to a dead end. Jim Groovester was correct. As I originally theorized, water poured into the pit slowly draining down the pipe until the pit was 7/7, where it began teleporting to the end of the water in the pipe. It continued doing this until the pipe was full up to the dead end, where it finally started to back up and flood the area around the pit. Even when I hooked the drainage pipe to the side of a brook, the water simply started filling up the brook (from 5s to 7s) outward from the pipe instead of backing up and flooding the area around the lake. Water falling into water will always seek a lower level to flow to before it is willing to spread out over another level of water.

[Shoku]

I've flooded hallways that shouldn't have been floodable if that was completely accurate.

I may have had an innordinate input of water as there were probably around 200 tiles of water resting above other water to path through my 3 wide tunnel and then fall for 6 levels.

And people who re-route underground rivers usually say they need two levels below the grates to keep their hallway dry.

[zchris13]

It piles up, then teleports away.

[Vanguard Warden]

In situations like that with ridiculous amounts of water released all at once, it might take a more path of least resistance approach, and not act completely according to theory. For example, people have made highly pressurized fountains that shoot water up in pyramid formation, if their stories were accurate. I'm just talking about free-flowing water pouring into a lake, so there shouldn't be any problem. Also, I don't need to do anything to try to keep hallways dry, as the water will be falling directly into a large body of water. I'm planning a design looking something like this:

First floor:

Spoiler (click to show/hide)

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█████████████████████████
█.......................█
█.......................█
█.......................█
█...≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈...█
█...≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈...█
█...≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈...█
█...≈≈≈...........≈≈≈...█
█...≈≈≈...........≈≈≈...█
█...≈≈≈...........≈≈≈...█
█...≈≈≈...██D██...≈≈≈...█
█...≈≈≈...█XXX█...≈≈≈...█
█...≈≈≈...DXXXD...≈≈≈...█
█...≈≈≈...█XXX█...≈≈≈...█
█...≈≈≈...██D██...≈≈≈...█   . - Floor
█...≈≈≈...........≈≈≈...█   D - Door
█...≈≈≈...........≈≈≈...█   X - Stairwell
█...≈≈≈...........≈≈≈...█   █ - Wall
█...≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈...█   ≈ - Surface of the water a level down.
█...≈≈≈≈≈≈≈WWW≈≈≈≈≈≈≈...█   W - Water falls into the channel from above here.
█...≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈...█
█.......................█
█.......................█
█.......................█
█████████████████████████


One floor down:

Spoiler (click to show/hide)

Code: [Select]

   ███████████████████
   █≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈█
   █≈≈≈≈≈≈≈###≈≈≈≈≈≈≈█   # - Floor grates, down to another chamber.
   █≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈█   ≈ - Water
   █≈≈≈███████████≈≈≈█   █ - Wall
   █≈≈≈█         █≈≈≈█   X - Stairwell
   █≈≈≈█         █≈≈≈█
   █≈≈≈█  █████  █≈≈≈█
   █≈≈≈█  █XXX█  █≈≈≈█
   █≈≈≈█  █XXX█  █≈≈≈█
   █≈≈≈█  █XXX█  █≈≈≈█
   █≈≈≈█  █████  █≈≈≈█
   █≈≈≈█         █≈≈≈█
   █≈≈≈█         █≈≈≈█
   █≈≈≈███████████≈≈≈█
   █≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈█
   █≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈█
   █≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈≈█
   ███████████████████


This pattern will repeat and alternate back and forth, with each chamber's reservoir filling at one end, and dumping into the next reservoir at the other end. At the very end, the water will drain into the bottomless pit at the end of a cave river that I diverted. I'll make the floor in the chambers wet so tower-caps will grow there, possibly by just plugging the drain and letting the chambers flood initially. If all goes as planned I'll wind up with a multi-layered underground tower cap forest, farmable soil, a safe underground water source, and a series of tranquil mist-generating waterfalls. I'd make the whole area round and organic looking, but I'm bad at grid-based curves. Theoretically, this should work just like my test scenario but on a larger scale; The trenches should fill up due to inadequate drainage, and falling water coming from a level up should teleport down the drain into the next chamber's trench rather than spreading over the surface, continuing the cycle until it pops into the chasm at the end.

[zchris13]

tell us these things from the start.
That looks like a plan!

[Jim Groovester]

Jim Groovester was correct.

Music to my ears.

I'd make the whole area round and organic looking, but I'm bad at grid-based curves.

The mouse is very helpful for this sort of thing. I've got four snazzy sort of organic-looking cave rivers I've dug out using this method.