At the moment I'm sort of managing with the pump out + smooth method. "Sort of" because my thralls dug into and through the second aquifer level before I had fully secured the first, so three drowned. But this sort of works, if in an ellaborate and risky way. It works mostly because it is a stone aquifer, of course (doing this in a sand aquifer would be harder in some respects and easier in others. I think I might manage it with walls).
I dug some holes IŽll have to patch with grates first, though. That's what killed my three dudes. They fall into the water, get stunned, and drown.
EDIT:" Ablel kaddasitah, gem setter, has drowned." OOPS, there goes another one.
Pic sort of related
(http://guncarryinglibrarian.files.wordpress.com/2008/08/achievement.jpg)
I think I might favor the ice method, but requires doing it in the open, and despite my haunted location for some reason does NOT have undead (I have some inner suspicion that all of them are spawned in the underground river), I AM harrased in winter by dark gnomes, which are pathetic, but enough to scare my workers away, and I am not about to dedicate part of my workforce for defense. If only that glassmaker hadnt gone berserk and killed two of my war dogs :/...
!WARNING! Mistakes were found in this arrangement, I'm revising it and posting an updated version on page 2, please do not use this version for piercing multiple aquifers. All mistakes were my own, and all credit is due Tanelorn for the original idea on how to pierce multiple aquifer layers in a minimal amount of space.
It's possible to drill down through any number of aquifer layers, if you're careful, without needing any extra space on each level. You'll need some wood and glass if you have access to it, to make mechanisms. Without glass, you'll need at least enough stone to make the mechanisms for four screw pumps and (possibly) some gears. To begin with, I should say this idea isn't mine, I tweaked it a bit to make it work for what I needed, but the basic idea came from someone else (unfortunately I can't remember who it was, or I'd give credit where credit is due). (Edit: Found it, the original idea came from Tanelorn.)
X = up/down stairway
H = Channel
* = Gearbox
@> = pump, with water pumping in the direction of the arrow/caret
- | = horizontal axles
WWW = water wheel
. = empty square
o = Damp Stone
~ = Water filled square
To start with you need to cut a stairway down into the aquifer, then channel out the a square on each side of the stairway from above, like this...
.....
..H..
.HXH.
..H..
.....
These four channels will allow you to pump out water from around the stairs, giving your miners a place to stand while working on the aquifer level. Before you get to that though, you need a place to pump the water to, and a power source. The way I usually do it is to place the pumps like this...
.......
....^..
.<@H@..
..HXH..
..@H@>.
..v....
.......
Then cut a channel in front of each pump, allowing the water to drop back into the aquifer.
....H..
....^..
H<@H@..
..HXH..
..@H@>H
..v....
..H....
Now you just need a power source, I attach one waterwheel to each pump, and use the flow of the aquifer into the drainage channels to run the wheels, which, admittedly, is a bit excessive dwarfish, but the extra power can be useful running whatever you need later on, and it saves on gearboxes, which depending on what sort of terrain you have access to, may be hard to manufacture.
I usually lay them out like this...
...........
..WWW......
...|..H..W.
...|..^--W.
..H<@H@..W.
....HXH....
.W..@H@>H..
.W--v..|...
.W..H..|...
......WWW..
...........
When you're ready to go, just channel out the tile separating each water wheel from the pumps drainage channel, like so.
...........
..WWWH.....
...|..H..W.
...|..^--W.
..H<@H@..W.
.H..HXH..H.
.W..@H@>H..
.W--v..|...
.W..H..|...
.....HWWW..
...........
If one of the pumps doesn't quite kick in, just run it manually for a few cycles, once the whole system is going the waterwheels should keep moving on their own.
Ok, deep breath. So the setup is a bit complex, but once you have your waterwheels in place, you can start drilling. Please be sure to save first! I haven't lost a miner doing this, yet, and if you do each step exactly this way you shouldn't either, but it's seemed close a few times, so be careful about it.
Once you're ready to start drilling, drop down to the aquifer level, and you'll see this...
ooooooooooo
oo~~~~ooooo
oooooo~oo~o
ooooooooo~o
oo~oo.ooo~o
o~oo.X.oo~o
o~ooo.oo~oo
o~ooooooooo
o~oo~oooooo
ooooo~~~~oo
ooooooooooo
The tiles just on either side of the stairs might have 1-3 water in them, and will fluctuate around there as the pumps above drain the water coming in from the aquifer away, but they should be safe to work on. If you didn't use an up/down stairway, cut a down stairway now to get a look at the next level. Every aquifer level you cut through will be the same, except the last one. On the last level you just need to wall in the 4 squares next to the stairs and then continue down at least one level before you cut out to the sides. If you don't notice you're on the last aquifer level you may inadvertently flood the level below, making it more difficult to proceed, so always check first.
Assuming there is another aquifer layer below, begin by channeling eight tiles away, as follows:
ooooooooooo
oo~~~~ooooo
oooooo~oo~o
ooooHHooo~o
oo~oo.oHo~o
o~oH.X.Ho~o
o~oHo.oo~oo
o~oooHHoooo
o~oo~oooooo
ooooo~~~~oo
ooooooooooo
Now dig out the 4 tiles that are diagonal from the stairs, like so..
ooooooooooo
oo~~~~ooooo
oooooo~oo~o
ooooHHooo~o
oo~o...Ho~o
o~oH.X.Ho~o
o~oH...o~oo
o~oooHHoooo
o~oo~oooooo
ooooo~~~~oo
ooooooooooo
And channel out 4 more tiles, extending the trenches you've already dug like so...
ooooooooooo
oo~~~~ooooo
oooooo~oo~o
oooHHHoHo~o
oo~o...Ho~o
o~oH.X.Ho~o
o~oH...o~oo
o~oHoHHHooo
o~oo~oooooo
ooooo~~~~oo
ooooooooooo
Now this next part seems to be the mildly dangerous one. One at a time, digg out the 4 remaining tiles bordering the central stairs area. This will give you access to the square immediately below where each pump drains, so go ahead and cut a channel down to the next aquifer layer, when you're done, you should have this.
ooooooooooo
oo~~~~ooooo
ooooooHoo~o
oooHHH.Ho~o
ooH....Ho~o
o~oH.X.Ho~o
o~oH....Hoo
o~oH.HHHooo
o~ooHoooooo
ooooo~~~~oo
ooooooooooo
You'll get a rush of water each time, and if you have multiple miners working below one may be accidentally swept into the aquifer, so take your time and do each tile individually. Once you have the channels cut though, the center section should no longer be receiving water from the aquifer, since aquifer tiles don't fill nearby tiles with water diagonally.
To pierce another aquifer level, just disassemble the pumps above, cut a channel through the floor at the end of each axle, then build 4 gearboxes over the channels, and reassemble the pumps on the first aquifer level. With the pumps in place on the aquifer level just channel out the 4 tiles around the stairs, feeding the pumps. When you're done, you should have the following...
Waterwheel Level: Aquifer level:
........... ooooooooooo
..WWWH..... oo~~~~ooooo
...|..H..W. ooooooHoo~o
...|..*--W. oooHHH^Ho~o
..H*.H...W. ooH<@H@Ho~o
.H..HXH..H. o~oHHXHHo~o
.W...H.*H.. o~oH@H@>Hoo
.W--*..|... o~oHvHHHooo
.W..H..|... o~ooHoooooo
.....HWWW.. ooooo~~~~oo
........... ooooooooooo
From there, just repeat everything one level down. You'll need to add a vertical axle for each pump if you have more than two aquifer levels to punch through.
Again.. on the last aquifer level, just wall in the 4 squares around the stairs and leave at least one dry level between you and the aquifer.
Well, found where I screwed up, I left out one step towards the end, and I missed one issue in testing it all. When I was doing the testing I tried it on a couple single aquifer maps first, using these exact steps, and had no problems. Afterwards, I tested it on a single larger fort with multiple aquifer levels, but I used a different arrangement for the waterwheels, because I had a handy nearby river, and it was just easier to set up a few waterwheels and run it all to a gearbox.
To move down through multiple levels, the waterwheels will have to be moved, and power run to the pumps via gearboxes. The easiest arrangement for the gearboxes is just to place them directly over the input hatches, adjacent to the stairs. 3 gearboxes in any arrangement will transmit power to all four pumps.
Second goof on my part, the bit I left out at the end: When drilling through multiple layers, before moving the pumps down to a new level, build walls above all of the unneeded channels, like this...
ooooooooooo
ooooooHoooo
ooo###.#ooo
ooH....#ooo
ooo#.X.#ooo
ooo#....Hoo
ooo#.###ooo
ooooHoooooo
ooooooooooo
And when you remove the screw pumps on each level, before moving them to the next level, wall in the channels they were feeding into as well.
ooooooooooo
oooooo#oooo
ooo###.#ooo
oo#..H.#ooo
ooo#HXH#ooo
ooo#.H..#oo
ooo#.###ooo
oooo#oooooo
ooooooooooo
This prevents any waterflow from the aquifer(s) above making their way down into the work area and overloading the pumps.
Alright I guess we'll have to start a new one; it shouldn't be too bad because we already have all the pump pieces and a pretty good mechanic. Where do I put the water wheels though/do I need to get my power from somewhere else?
Well, you can run the whole thing off one waterwheel honestly, it supplies more than enough power, as long as you have a few mechanisms for gearboxes, for the first floor, just put the gears directly over any three of the input channels, like this: (I guess this would also work with axles between the pumps, need to double check that though, and you'll need the gears anyways once you move down to the next level)
.........
.....H...
.....^...
.H<@*@...
...*XH...
...@*@>H.
...v.....
...H.....
.........
Then run sufficient power to any of the pumps and all of them will start. For example, a setup like this should work:
.........
.........
.H@>HH...
.HWWWH...
...|.....
...|.H...
...|.^...
.H<@*@...
...*XH...
...@*@>H.
...v.....
...H.....
.........
As long as the channels under and around the waterwheel can't flow into the area you're digging, you'll be fine, it was that extra flow that was pulling miners out of position after the first level.
To run power down to the next level, after dismantling your pumps, you'll need to cut at least one channel at the end of the axle leading from the waterwheel, under the spot the input side of that pump was on. Testing out various arrangements now to see what uses the least power.
Multiple Aquifer Pierce II: Electric Boogaloo
All credit for this idea is due Tanelorn, I've just done my best to spread the idea around and make it common knowledge (along with a bit of testing and a few tweaks).
It's possible to drill down through any number of aquifer layers, if you're careful, without needing any extra space on each level.
You'll need a good bit of wood. At the minimum you'll need enough for one waterwheel and 6 axle segments plus 1 additional axle segment per aquifer level. I'd suggest assuming the worst and keeping more wood on hand for extra axle segments.
At least one unit of stone would be useful, though not necessary, for making a mechanism for a gear assembly and you'll need enough Wood, Stone, Glass, or Metal to build the components for 5 screw pumps (If you have no stone, you'll need enough for 6 screw pumps, one of which will be used to transfer power to a vertical axle in place of the usual gear assembly.)
Lastly, you'll need some material to build 16 walls per level of the aquifer, this can be stone, wood, glass, whatever works, and depending on what sorts of material your aquifers run through, you may be able to recover some of this from the stone left behind as you mine. (but don't count on it).
So in the end you'll need:
12+ wood
5 Blocks (6 if you have no stone)
5 Enormous Corkscrews (Again, 6 if you have no stone)
5 Pipes (Also 6 without stone)
16 Miscellaneous material per aquifer level, for walls.
And if you do have stone, one Stone Mechanism.
Examples provided below use the following:
X = Up/down stairway
H = Channel
* = Gearbox
@> = Pump, with water pumping in the direction of the arrow/caret
- | = Horizontal axles
WWW = Water wheel
. = Empty square
+ = Constructed floor
o = Damp stone
~ = Water filled square
Part I: Preparing to mine and powering the pumps
The first step is to dig out an up/down stairway into the aquifer, channel out the 4 squares on each side of the stairs from above, like this:
.........
.........
.........
.........
.........
.........
.........
....H....
...HXH...
....H....
.........
.........
.........
These four channels will allow you to pump out water from around the stairs, giving your miners a place to work from safely on the aquifer level. Before you can begin though, you'll need a power source and a place to pump the water to without flooding your fortress. First, place 4 screw pumps around the stairs in a spiral, like this:
.........
.........
.........
.........
.........
.........
.....^...
..<@H@...
...HXH...
...@H@>..
...v.....
.........
.........
Then cut a channel in front of each pump, allowing you to pump water back into the aquifer...
.........
.........
.........
.........
.........
.....H...
.....^...
.H<@H@...
...HXH...
...@H@>H.
...v.....
...H.....
.........
Now you just need a power source. Originally I attached one waterwheel to each pump, and used the flow of the aquifer into the drainage channels to run the wheels, but there were problems piercing multiple aquifer levels using that arrangement. Any power source will do, as long a it supplies sufficient power, but for the purposes of this guide I'm going to use a single waterwheel/screw pump generator nearby. The first step in preparing for this is to cut a channel for the waterwheel like so:
.........
.........
.........
..HHH....
.........
.....H...
.....^...
.H<@H@...
...HXH...
...@H@>H.
...v.....
...H.....
.........
Then extend one end of the channel by one tile, and add a hook at each end, like this:
.........
.........
.H..H....
.HHHH....
.........
.....H...
.....^...
.H<@H@...
...HXH...
...@H@>H.
...v.....
...H.....
.........
The hooks will be the input and output tiles for a screw pump driving the waterwheel shortly. (And yes, this is a cheap perpetual motion exploit. For those that find that undwarvenly, well, privately I agree with you. You'll need a nearby river, a windmill farm, or sufficient dwarven labor to provide an alternate supply of power if you choose not to use this trick, and I leave the details of that to you.)
Before you build the waterwheel, you'll need to place the screw pump to support it:
.........
.........
.H<@H....
.HHHH....
.........
.....H...
.....^...
.H<@H@...
...HXH...
...@H@>H.
...v.....
...H.....
.........
Then you can add the waterwheel and a three tile horizontal axle connecting it to the first screw pump.
.........
.........
.H<@H....
.HWWW....
...|.....
...|.H...
...|.^...
.H<@H@...
...HXH...
...@H@>H.
...v.....
...H.....
.........
Don't worry if the waterwheel/screw pump kicks on and you start getting some 1/7 or 2/7 water moving around, that's normal, and the aquifer channels will prevent it from flooding, though it's going to get a bit muddy around each screw pump regardless of what you do.
If the pumps don't quite kick in, just run the pump adjacent to the waterwheel manually for a few cycles, and the whole system should kick on. Once you have the waterwheel going, everything should keep moving on it's own.
To power the other three screw pumps, just build three single tile horizontal axles over the "input" channels adjacent to the stairs. These axles won't interfere with the pumps picking up water from below, and they'll transfer power between each of the pumps. When placing a horizontal axle running north/south between two pumps, be sure to to change it's orientation by hitting (s) before placing it. When you're done, you should have something like this, with all four pumps working.
.........
.........
.H<@H....
.HWWW....
...|.....
...|.H...
...|.^...
.H<@-@...
...|XH...
...@-@>H.
...v.....
...H.....
.........
More to follow in Part II: The First Aquifer Level...
Part II: The First Aquifer Level
Time to start digging very, very carefully. Now that all four pumps are running you should see something like this on the first aquifer level:
ooooooooo
ooooooooo
o~oo~oooo
o~~~~oooo
ooooooooo
ooooo~ooo
ooooooooo
o~oo.oooo
ooo.X.ooo
oooo.oo~o
ooooooooo
ooo~ooooo
ooooooooo
The squares I've marked as being open space may show flickering water from time to time, but as long as the pumps are running above, should stay at 1/7 - 2/7 depth, and shouldn't interrupt your miners while they're working. The first step in mining through this aquifer level is to channel 8 tiles away around the work area, like this:
ooooooooo
ooooooooo
o~oo~oooo
o~~~~oooo
ooooooooo
ooooo~ooo
oooHHoooo
o~oo.oHoo
ooH.X.Hoo
ooHo.oo~o
ooooHHooo
ooo~ooooo
ooooooooo
Once that's done, you can safely mine out the 4 diagonal tiles adjacent to the stairs:
ooooooooo
ooooooooo
o~oo~oooo
o~~~~oooo
ooooooooo
ooooo~ooo
oooHHoooo
o~o...Hoo
ooH.X.Hoo
ooH...o~o
ooooHHooo
ooo~ooooo
ooooooooo
And channel out 4 more tiles, extending the trenches you've already dug like so...
ooooooooo
ooooooooo
o~oo~oooo
o~~~~oooo
ooooooooo
ooooo~ooo
ooHHHoHoo
o~o...Hoo
ooH.X.Hoo
ooH...o~o
ooHoHHHoo
ooo~ooooo
ooooooooo
Now this next part seems to be the mildly dangerous one. One at a time, digg out the remaining tiles bordering the central stairs area and immediately channel out the square behind each, the square below where each pump drains. With these squares cut away you'll get a fairly blinding wash of mist, but you'll have finished making this level of the aquifer water tight. At this point you should have:
ooooooooo
ooooooooo
o~oo~oooo
o~~~~oooo
ooooooooo
oooooHooo
ooHHH.Hoo
oH....Hoo
ooH.X.Hoo
ooH....Ho
ooH.HHHoo
oooHooooo
ooooooooo
With the aquifer level now watertight, the cleared space around the stairs should begin drying slowly. Now that the pumps are no longer needed, dismantle the 4 pumps adjacent to the stairs above, as well as the horizontal axles between them, and cut a single channel at the end of the axle leading to the waterwheel (where the light square on the screw pump was prior to dismantling it). Place a gear assembly over this channel and you should end up with something like this:
.........
.........
.H<@H....
.HWWW....
...|.....
...|.H...
...|.....
.H.*H....
...HXH...
....H..H.
.........
...H.....
.........
If you have no stone whatsoever you can use a screw pump instead of a gear assembly, in either case you may have to floor over one of the channels adjacent to the stairs to give your dwarves a place to work. If you are using a screw pump to transfer power, be careful placing it, if it's in the same position as the original pump but reversed in direction, you'll flood the level below. If it's in the same position but reversed and you've floored over the tile at it's exit, it will begin flooding the level ABOVE the aquifer. The safest position is to place it at the end of the axle, running in the same direction, with no open input or output, preventing it from doing anything but transferring power to the pumps below.
.........
.........
.H<@H....
.HWWW....
...|.....
...|.H...
...|.....
.H.@H....
...VXH...
....H..H.
.........
...H.....
.........
On the first aquifer level, begin by walling off the 12 channeled tiles nearest the stairs, like so:
ooooooooo
ooooooooo
o~oo~oooo
o~~~~oooo
ooooooooo
oooooHooo
oo###.#oo
oH....#oo
oo#.X.#oo
oo#....Ho
oo#.###oo
oooHooooo
ooooooooo
Next, cut 4 channels adjacent to the stairs, north, south, east and west, and rebuild 4 screw pumps in the same positions as they were originally in on the level above:
ooooooooo
ooooooooo
o~oo~oooo
o~~~~oooo
ooooooooo
oooooHooo
oo###^#oo
oH<@H@#oo
oo#HXH#oo
oo#@H@>Ho
oo#v###oo
oooHooooo
ooooooooo
At this point, only one of the pumps should be running, so build 3 horizontal axles connecting the other pumps, again, in the same positions as you used previously.
ooooooooo
ooooooooo
o~oo~oooo
o~~~~oooo
ooooooooo
oooooHooo
oo###^#oo
oH<@-@#oo
oo#|XH#oo
oo#@-@>Ho
oo#v###oo
oooHooooo
ooooooooo
Congrats, you're ready to move on to the next aquifer level now. Cut a set of stairs down into the next level and you should have the following on each level:
Above Aquifer 1 Aquifer 2
......... ooooooooo ooooooooo
......... ooooooooo ooooooooo
.H<@H.... o~oo~oooo ooooooooo
.HWWW.... o~~~~oooo ooooooooo
...|..... ooooooooo ooooooooo
...|.H... oooooHooo ooooo~ooo
...|..... oo###^#oo oo~~~o~oo
.H.*H.... oH<@-@#oo o~oo.o~oo
...HXH... oo#|XH#oo oo~.X.~oo
....H..H. oo#@-@>Ho oo~o.oo~o
......... oo#v###oo oo~o~~~oo
...H..... oooHooooo ooo~ooooo
......... ooooooooo ooooooooo
More to come in Part III: Deeper Aquifer Levels...
Part III: Deeper Aquifer Levels
The aquifer levels after the first follow the same basic design, but require a little more care. Starting from this:
ooooooooo
ooooo~ooo
oo~~~o~oo
o~oo.o~oo
oo~.X.~oo
oo~o.oo~o
oo~o~~~oo
ooo~ooooo
ooooooooo
Cut out the same 8 channels, extending out from the clear areas near the stairs, in the same pattern used on the first level. At this point, the pumps will be struggling to keep up, and your dwarves may repeatedly postpone their work due to dangerous terrain, don't worry though, this part should be safe, just nerve wracking.
ooooooooo
ooooo~ooo
oo~HHo~oo
o~oo.oHoo
ooH.X.Hoo
ooHo.oo~o
oo~oHH~oo
ooo~ooooo
ooooooooo
Once that's done, mine out the 4 tiles diagonal from the stairs. Then one at a time channel out one more tile at the end of each trench. Channeling these 4 tiles is particularly delicate, be sure that all 12 walls are in place on the level above, and do each tile individually or you may lose a dwarf in on of the open channels. For safety, designate 4 ramps on the level below, one on each side of the staircase and adjacent to it, to the north, south, east and west. If a dwarf is swept into one of the open channels, the ramps should allow the dwarf to walk back up out of the aquifer without excessive injury. ((First two tests this worked great, but the third time the currents are inexplicably stronger, preventing the dwarves from working, trying different scenarios/designs now to determine why.)) When you're finished, you should have the following (/ represent Ramps):
ooooooooo
ooooo~ooo
ooHHHoHoo
o~o./.Hoo
ooH/X/Hoo
ooH./.o~o
ooHoHHHoo
ooo~ooooo
ooooooooo
Again, use the same basic steps as the level above, mine out each tile bordering the central stairs area and immediately channel the tile behind it. Once this is complete you're safe, and you can begin moving down the pumps from above. At this point you should have the following:
ooooooooo
oooooHooo
ooHHH.Hoo
oH../.Hoo
ooH/X/Hoo
ooH./..Ho
ooH.HHHoo
oooHooooo
ooooooooo
Follow all the same steps for moving the pumps down, with a few changes. First, after the pumps are removed on the previous aquifer level, wall in the "output tile" they were pumping into, or you'll get too much water flowing into the next level you're attempting to dig out, and may lose miners. Second, where you placed a gear assembly on the level above the aquifer, simply build a vertical axle on each level of the aquifer. In the end, you should have the following on the first aquifer level (where the \ represents a vertical axle):
ooooooooo
ooooooooo
o~oo~oooo
o~~~~oooo
ooooooooo
ooooo#ooo
oo###.#oo
o#.\/.#oo
oo#/X/#oo
oo#./..#o
oo#.###oo
ooo#ooooo
ooooooooo
And this on the second...
ooooooooo
oooooHooo
oo###^#oo
oH<@-@#oo
oo#|X/#oo
oo#@-@>Ho
oo#v###oo
oooHooooo
ooooooooo
Simply repeat these steps for each level of the Aquifer. On the last level of the aquifer, you can simply wall off the 4 squares adjacent to the stairs, and proceed down, digging out at least one extra level under the aquifer before spreading out. (If you begin digging out directly under the aquifer, you may flood everything below, so leave that level untouched.)
I just have one last problem. When I reach a non-aquifer tile, it still manages to get slowly flooded because although the pumps work very well, they still allow tiny amounts of water to squeeze by and after 7 of those amounts make it they flood my new stairwell. Obviously if I know where the last aquifer level is in advance I can hold off building my stairwell until the walls are done, but this is not realistically possible unless I've already messed up an aquifer building. What can I do to prevent/unflood?
Hmmm... well, the easiest way would probably just be to carve out the bottom aquifer level like each of the other levels (instead of just walling off the 4 tiles adjacent to the stairs). Then at the end, instead of digging a channel on each tile N/S/E/W of the stairs, just build a pump and pump out the stairwell.
Since room is a bit tight on each aquifer level you may have to cut out on channel adjacent to the stairs and use that to pump them out just long enough to build a wall, like this:
Aquifer Dry(ish)
ooooooooo ooooooooo
oooooHooo ooooo~ooo
oo###.#oo oo~~~o~oo
oH....#oo o~oooo~oo
oo#.X.#oo oo~oXo~oo
oo#.H@>Ho oo~o#oo~o
oo#.###oo oo~o~~~oo
oooHooooo ooo~ooooo
ooooooooo ooooooooo
To prevent this sort of thing, I should probably look at maybe carving the stairs down to the next level later in the process. Since you can't really build on the first non-aquifer level anyways (you just get flooded from above), I guess there's really not much of a downside for cutting out the full pattern on the last aquifer level as well.
Ah! Got it, a bit of dinner and some coffee and some TV (and maybe some loafing around building my fort) it was obvious.
Immediately after breaching each new aquifer level you'll have the following:
ooooooooo
ooooo~ooo
oo~~~o~oo
o~oo.o~oo
oo~.X.~oo
oo~o.oo~o
oo~o~~~oo
ooo~ooooo
ooooooooo
With the pumps running, and before digging out any channels or stairs into the level below, build four walls adjacent to the stairs, like this:
ooooooooo
ooooo~ooo
oo~~~o~oo
o~oo#o~oo
oo~#X#~oo
oo~o#oo~o
oo~o~~~oo
ooo~ooooo
ooooooooo
The wall construction may be suspended a couple times because of momentary blips in the water depth, but be persistent and your dwarves will eventually finish all four. Once those are in place, you should only have 1 or 2 water lingering on the stairs, and no more flowing in from the sides. Designate the stairwell on the next level and wait just a moment. If it fills to 7/7 you know the next level is an aquifer, and you need to remove the walls, then proceed with the usual steps. If it stays at 1/7 or 2/7, then the next level is the first dry level, simply leave your walls in place, and continue down. Viola.