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[archangelomega]

Hey, this is my first post. Ive been lurking the forums for a few months now and have been playing DF alot.. Still not very good at it though.

Im Trying to drain an ocean so that i can build a fortress there and then let the sea build back up around it. At the moment i have made a corridor into an aquifer about 2 z-levels under the waters surfice and it is draining out slowly. but the main problem is im getting about 0-3 fps and theres about 5-6 z-levels of sea. Any advice on how to drain it quicker would be very appreciated.

I also have a small question..

referring to the diagram below, Would the pressure of the sea drain upwards into the aquifer? Or would it balance someway with out the ocean draining or raising in height?

=======########
========#######
========##Ocean#
========#######
#Aquifer#=#######
====#===#######
====#======#===
====#######===

= - Stone
# - Water

[silhouette]

good luck with all the lag...

[DiscoPony]

This would probably be a good read  http://www.bay12games.com/forum/index.php?topic=43574.15

It covers pretty much everything you need to know, I think.  To sum it up, though, any attempt to drain an ocean will bring your computer to its knees.  Water pathing is very CPU heavy and there's really nothing that can be done about it.  Also, I think that water can only drain down into an aquifer, not up, but I haven't actually tried it myself, so I could very well be wrong

Another option would be to pump magma in and then just carve out a dome underwater, but it might not be as much fun.  Anyway, good luck with your project, you've got me wanting to try it myself now 

[petersohn]

I don't think water would drain upwards. As soon as it reaches below the level of your channel, the draining will stop. If you want to drain something upwards, you should either use pump or drain into a chasm.

[XSI]

This will most likely not work, I would expect the aquifer to just fill the tunnel with more water, without draining anything.

You can always try though, I've never tried to drain an ocean into an aquifer with that method, I don't know for sure.

[Malicus]

I tried this a little earlier today, and the ocean DID appear to be draining -- but there wasn't quite enough space (due to water appearing at critical points while I was digging the drain) it seems, because the ocean refilled too quickly to be drained with my setup.  Then again, I didn't REALLY want to sacrifice a miner, so I pierced the ocean at the top (which means that water pressure wasn't doing much to ensure that maximum drainage was happening).

Also, I used a cave-in to pierce the floor of the aquifer.  It's a quite annoying and dangerous dwarven way to drain the ocean, though, since piercing an aquifer from the bottom introduces all sorts of problems.  Maybe if you pierced it from the top and then let the water back out...

[Quietust]

If you were trying to drain the ocean into an aquifer and the entire ocean didn't instantly vanish, then it wasn't actually draining - the water you saw swirling around on the surface was just what had been displaced from your digging. When you actually do drain an ocean into an aquifer, you'll know it immediately because the game will grind to a complete halt (or at least slow down to about 1 frame per 30 seconds or so) as the entire ocean instantly drains away.

[edit] See this thread for a more detailed description of what it's like to really drain an ocean.

[Malicus]

No, it wasn't swirling around.  I kept seeing 1s (above the ramp leading further down) in my tunnel one z-level BELOW sea level.  Below that was 7s.  Still, I'll have to try it again later.

Edit: I tried it again, but the ocean on my embark site was only two z-levels deep (and most of it was only one z-level).  I should have looked for deeper.  However, the water entered the aquifer from below, and it still instantly drained the top z-level where the water was two z-levels deep.  Due to the small amount of water drained, I didn't notice the slowdown when it happened.  I'll try to get more conclusive results next try.

Edit 2: I'm trying with a deeper ocean.  I dug a ramp 2 z-levels below an aquifer such that it started leaking water, then I sacrificed a miner to pierce the ocean from below with another ramp.  ...my CPU is still working on this.  I don't think that miner has even died yet.  I supose I can't get anything really conclusive out of this until it finally works through all that water so I can see it myself.

I think it's working, though, since when I alt-tabbed to DF and the window finally showed up, I saw a bright blue 7, a dark blue 7, and a period representing open space right next to each other, suggesting serious drainage.

Edit 3:  It's still going, but now I've lost the entire top z-level of the ocean, and there is most definitely not that much mined out down there.  I believe it's safe to conclude that you CAN, in fact, drain the ocean upward into the bottom of an aquifer.  And what I saw in my first experiment?  It was what an infinite source of unpressurized water being drained into an infinite capacity drain SHOULD look like.

Edit 4: ...wait, crud.  I found something that invalidated my experiment.  I screwed up.  Time to try AGAIN.

Edit 5: Okay, I tried it again elsewhere, this time making sure that the aquifer was not channeled from above in the same tunnel where the ocean flows in.  The aquifer is on the same z-level as the lowest z-level of ocean.  I dug a ramp under the aquifer so that it would leak, then I sacrificed a miner to dig a ramp under the ocean.  The ocean flooded the tunnel immediately, but it did not drain.  That's probably as expected.  Then I dug a channel into the aquifer from above, making sure that the ocean water had no way to reach it from above this time.

I then engineered a single floor tile cave-in above this channel to knock out the floor below the aquifer that I couldn't get to (but which it was leaking through).  When I had a dwarf pull the lever to trigger the cave-in, the game ground to a halt for a while, and when it allowed me to pause and look around, the ocean had begun draining as it did in the struck-out section above (where I did something stupid).  Therefore, an ocean CAN be drained into an aquifer from below, provided you also have access to the top of the aquifer and said aquifer is only one z-level thick (not counting the leaky z-level below it).

[archangelomega]

Thankyou all for your help and, especially Malicus, for spending time answearing my question. I am now trying to think of a good way to use all of this newly gatherd information, but currently have got no ideas for an oceanic megastructure apart from building the fort and letting the ocean fill back around it... But that doesnt seem Dwarven enough.