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[Redwood Elf]

OK, I've started a fortress game in an area with a water table 2 levels down from the surface. How do I find a diggable path past it? Digging trenches obviously won't work, since if I dig a trench through a diggable area AND water filled area, the water will flow from one to the other, rendering my excavation useless. What is the usual method?

[Doktoro Reichard]

First, have you embarked in a single biome or does your area have more than one? Usually, aquifers are at different heights in different biomes, so you can eventually dig your way out of them easily.

This being said, the best way to "prospect" the existence of an aquifer-bearing tile is to designate downward stairs. This will reveal the lower tile. If the tile indicates that it's Damp, then it has or is near an aquifer.

Also, there is information in the wiki for how to pass through aquifers.

[Koremu]

Is your Aquifer is rock layers, or soil layers?

[neblime]

the wiki certainly has a lot of information about aquifers but I will give a brief summary here:
first off if your embark has multiple biomes try digging down in each of them, you may be able to go around the aquifer.
next, determine if your aquifer is 1 or multiple z levels deep.  If you dig an up/down stair into the first aquifer layer you hit and see stone below it, you probably have a one layer aquifer on your hands (don't worry about the damp stone, water above a tile causes that) in which case my much preferred method is to carve out a pillar of dirt and drop it into the open aquifer to make a dry dirt shaft through, a good pictorial representation of this can be found here.

if you have a multi layer aquifer on your hands there are other alternatives.  The easiest in this case, assuming your embark is cold enough, is to dig out a large square part of the aquifer in spring/summer, and wait until the water freezes then dig out the inside of the square leaving a layer of ice protecting the excavation from the aquifer, then build walls around the edge of the space so that the water doesn't rush back in when it melts.  Excavate the next layer down, making sure it's a smaller square so that the water can't flow in from above, and repeat until you're through the aquifer.  (remember the last layer will need to be at least 5x5 to secure a 3x3 area to wall off for a 1 tile stairway so make sure your initial square is large enough!)
If you happen to have magma, it's quite easy, you can just excavate a square of aquifer and pump magma into it, filling it with obsidian similar to the ice method, and excavating all except the edges.

if ice is not an option, and you have no magma, you're left with using pumps.  The general idea is pump the water out of a level of the aquifer (and back into a different part of the aquifer, as it can absorb infinite water) fast enough that the water level is low enough for long enough for dwarves to wall off the area and stop water flowing in.  In my experience this method is tedious and time consuming, as the walls will experience many job cancellations due to inconsistent water levels,  the wiki has more information on specific methods.

[Redwood Elf]

Well I managed the plug version after accidentally drowning one miner while trenching out the plug drop point...I guess that even with ramps up out of the wet trench, dwarves just aren't sensible enough to dig from the landward side...

[Talvieno]

Sometimes, if you get really lucky, there can be little plugs of land here and there that don't have any aquifer tiles. It's hit-and-miss to find one, though.

And, nope, dwarves and sensible rarely go together. Take nobles, for instance. Sometimes they want a glass window in their underground room.

[greycat]

Take [my] nobles, for instance.

... please!

[Snaake]

I recently reminisced of last autumn, when I assisted in "breaking" aquifers for the single-pick challenge - reawakened thread last year. I checked the wiki but apparently noone has done a writeup of it. I'd quite like to do it myself but probably won't have time before June since I'm trying to graduate nowish. So meanwhile, you can go read this post and the next post, which has some refinements to Stochasty's method (which builds off earlier work by Merendel and others earlier in the thread, and the cave-in methods known by the wiki and the general community). Pages 12-15 have most of the relevant posts (don't think there's almost anything after, may be some before).

Basically, as long as you have at least 2 dry soil layers it's possible to pierce a 2-layer (soil) aquifer with nothing else but 1 pick and miner. And it's a lot easier and less hassle than using pumps (the double-slit method). This is done by doing a mini-chicken run (a term used in the aquifer article on the wiki; a pure chicken run is trying to dig down into the cavern before your miner drowns) in order to drain the upper aquifer level into the lower.

Your miner needs to dig out the stairs in the 2nd layer before the 1st fills with water, so you need to train their mining skill: it has to be something like 8 to have a (10%+ish) chance at success, but embarking with mining 5 and digging the preparations will get you there, or very close, if you use only 1 miner as recommended. And if you're going for a 1-tile pierce, you get 12 attempts, so it's ok to give it a shot before it's guaranteed... 12 skill or more makes it a pretty sure thing. A 3x3 pierce would have 16 attempts, a 5x3 18, 5x5 20 etc. I think, but to be honest you can just do infinite attempts off to the sides of the basic layout and drain to there if you really need to.

This method can be done, and was in fact developed for, reanimating terrifying/otherwise very dangerous biomes (you can wall yourself off underground as soon as you get your dwarves underground, preferably with the wagon wood so you can make an axe later), or a freezing biome (you don't have to open up the aquifer to the surface, so it doesn't freeze), all you need is 2 levels of soil before the aquifer. The 1-layer aquifer pierce is definitely doable if the surface isn't deadly, but I don't think we ever figured out how to pierce a 1-layer aquifer with only 2 layers of soil above while remaining completely safely bunkered. There's still tricks to minimize the exposure time, of course.

If your surface is safe and your aquifer is only 1 deep you can just do the cave-in outlined in the wiki, but I'd like to add that instead of just channeling a 5x5 area of the aquifer, you can also just channel the 3x3 in the middle. Then dig down stairs in the ring around that, and up* stairs into the aquifer. The stairs won't stop the cave-in unless if they're not in the cave-in area, as my screenshots show. This way you won't have to build floors to access the plug after the cave-in.

*(or up/down like I actually did back in September, but up is safer since you won't flood your fort if you dig out the space underneath those stairs)

P.S. Redwood Elf: If by "2 levels down" you mean 1 dry soil and then aquifer, and the aquifer turns out to be 2 soil layers, a modified (surface-exposed) version could work. First just train your miner somewhere to sufficient skill (10+). This training should include a ring (7x7 for a 1-tile pierce) of down stairs on the surface. It can** also include channeling the ring just inside that from the surface (except for 1 tile which should just be dug on the level below, so you leave 1 tile of floor for support), and another ring of stairs, this time up/down (again, 7x7 for a 1-tile pierce) in the 1 dry soil layer. Then make a mini chicken run to pierce a drain from A1 (Aquifer 1, counting from the surface) to A2. Once you've succeeded at this, you can dig out the top aquifer layer and channel a hole in A2, and cave-in a plug from the dry soil layer into A2.

edit:
**The chances of mini chicken run success are improved if you start it with the miner in a shaft, so they don't do the initial dig diagonally from 1 tile to the side, since then they don't have to move said 1 tile over before moving down and digging into A2. Hence you should only do the up/down stairs in the corners + every 2nd tile (on each mini chicken run attempt spot) in the dry soil layer if you want to optimize this aspect, or the miner will likely stand on a neighbouring up/downstair or on an up ramp left from the channel instead of right above what he's digging.

P.S. Now I started thinking about whether a miner can dig a channel on the level below if they're standing on down stairs, which would make the 2-layer aquifer pierce doable even with 0 mining skill. Probably not.

[Hans Lemurson]

If you have access to a lot of wood, my preferred method is to use LOTS AND LOTS OF PUMPS.  You start your dig with 4 holes at the corners of a 4x4 square and 4 pumps arranged in a circle between the holes each pumping from one into another.  Additional pumps will be required to drain the water that these pumps suck out of the holes.  Power can be provided by Water Wheels powered by streams of water pumped from the aquifer and draining back into it (minimal drainage ensures sufficient water level for the wheels).  To transfer power vertically or around corners, you can use additional pumps as a poor man's gearbox.

If you can ensure that power can be transferred downwards reliably to each new level of the dig, you can pierce aquifers of any depth.  I have personally pierced a 7 level aquifer (2 soil, 5 stone) with this method, yielding a 4x4 borehole with a 2x2 central staircase in it.  This was done with Wood as my only building material.

The trickiest part is getting through soil layers where you have to dig out and replace the soil walls with wooden ones.  If you love job cancel-spam, you'll love this method!

[Kumquat]

I figured out a simplified version of the double-slit method detailed in the wiki.

I call it single-slit method, though the 'slit' can be a single channeled-out tile at least on rock layers. Soil layers can require moving the pump around. The start looks like this:

Code: [Select]

######
###XX#
#V%% #
###XX#
######

The following layers look exactly the same, except with constructed/smoothed walls.
Needs just a miner, a pump operator or two, and some engravers to get through an aquiferous rock layer. A grate is needed to smooth walls around the channeled tile. No need for lots of pumps, one is enough.

This gives a nice 2x3 stair stack. A miner can easily and safely dig the tile under the pump and the next pump drain channel.

[Snaake]

Eh, I'm gonna stick with saying that cave-ins are the way to go. You only ever need 1 miner, at least 1 dry soil level above the aquifer, 1 pick, and not even any building materials on top of that. No cancellation spam or constant redesignating/unsuspending wall construction jobs either (just single-stepping once or at most few times), which is a major selling point for me.

If you want to pierce a 2-layer aquifer without surface exposure, you need 2 dry soil levels. If you want to do the same for a 1-level aquifer, it's a simpler dig but you'll need a 3rd dry soil level before the aquifer. If the aquifer is deeper than 2 layers, doing concentric cave-ins will eventually get you through, but starvation and/or lack-of-booze slowdown may become issues in single-pick challenge style embarks.

The only time you need pumps is if the aquifer is immediately below the surface, and I think that's only even possible in swamps/marshes.

[Maolagin]

Eh, I'm gonna stick with saying that cave-ins are the way to go. You only ever need 1 miner, at least 1 dry soil level above the aquifer, 1 pick, and not even any building materials on top of that. No cancellation spam or constant redesignating/unsuspending wall construction jobs either (just single-stepping once or at most few times), which is a major selling point for me.

If you want to pierce a 2-layer aquifer without surface exposure, you need 2 dry soil levels. If you want to do the same for a 1-level aquifer, it's a simpler dig but you'll need a 3rd dry soil level before the aquifer. If the aquifer is deeper than 2 layers, doing concentric cave-ins will eventually get you through, but starvation and/or lack-of-booze slowdown may become issues in single-pick challenge style embarks.

The only time you need pumps is if the aquifer is immediately below the surface, and I think that's only even possible in swamps/marshes.

Seconded! The only actual drawback to caveins is putting your miner in modest danger, but I've not yet lost a miner this way. In principle you can lose the pick into the water, which is catastrophic in single-pick scenarios, but that risk is easy to minimize if you use another mining designation to ensure that your miner immediately walks away from the ledge.

Then again, the tradeoffs change if you're looking at a stone aquifer instead of soil (soil being far more common). From my tests, I don't think a miner of any level can chicken-run through stone[1] but you can smooth it to stop water production. That makes pump methods likely the easier way to go.

[1] At least in DF2012. This means that chicken-running all the way to the first cavern is probably actually impossible. Since the wiki mentions it as a viable option, perhaps it was possible in other versions.

[Snaake]

Eh, I'm gonna stick with saying that cave-ins are the way to go. You only ever need 1 miner, at least 1 dry soil level above the aquifer, 1 pick, and not even any building materials on top of that. No cancellation spam or constant redesignating/unsuspending wall construction jobs either (just single-stepping once or at most few times), which is a major selling point for me.

If you want to pierce a 2-layer aquifer without surface exposure, you need 2 dry soil levels. If you want to do the same for a 1-level aquifer, it's a simpler dig but you'll need a 3rd dry soil level before the aquifer. If the aquifer is deeper than 2 layers, doing concentric cave-ins will eventually get you through, but starvation and/or lack-of-booze slowdown may become issues in single-pick challenge style embarks.

The only time you need pumps is if the aquifer is immediately below the surface, and I think that's only even possible in swamps/marshes.

Seconded! The only actual drawback to caveins is putting your miner in modest danger, but I've not yet lost a miner this way. In principle you can lose the pick into the water, which is catastrophic in single-pick scenarios, but that risk is easy to minimize if you use another mining designation to ensure that your miner immediately walks away from the ledge.

Then again, the tradeoffs change if you're looking at a stone aquifer instead of soil (soil being far more common). From my tests, I don't think a miner of any level can chicken-run through stone[1] but you can smooth it to stop water production. That makes pump methods likely the easier way to go.

[1] At least in DF2012. This means that chicken-running all the way to the first cavern is probably actually impossible. Since the wiki mentions it as a viable option, perhaps it was possible in other versions.

Yea, I'm going to agree with you that it's probably impossible to chicken run through stone aquifers in DF2012. However, I'm going to be bold and say that if there is dry soil for cave-ins and it is thus possible to get through a 1-thick soil aquifer, it should be possible to use a larger initial footprint and concentric caveins to get through thicker aquifers too. Whether you consider it easier or not is a matter of opinion, in the end. I find the hassle with pumps too much to deal with.


edited to remove obsolete sentence fragment.

[Talvieno]

If you bring stone along with you, or you're lucky enough to find some, you can set up a lever attached to a support, build a little constructed overhang to attach the support to (attached the the ground outside the plug) and then safely pull the lever from a distance to drop the plug. No danger to your miner.

[Koremu]

In sufficiently cold areas you can just freeze your way through it by digging an open pit down from the surface.