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40d:Aquifer
| This article is about an older version of DF. |
An aquifer is a subterranean layer of water-bearing rock or soil. Attempts to mine through them will result in the mined-out squares immediately filling with water, effectively halting excavation at or below their level. This, in conjunction with the fact that they are often located in areas rich in loam, and sand, makes it difficult to find great quantities of stone in areas with aquifers, making for more challenging gameplay.
Aquifers often follow the landscape, higher levels below hills, and dropping to lower levels in valleys.
Be aware that a single aquifer layer will have water on that level plus the next level down, occupying 2 levels altogether. A two-layer aquifer will occupy those two plus the next level down, totaling 3 levels, and so on. That lowest level is leaking from above, not from the sides, but the water is still there and presents most of the same hazards for mining.
Where they are found
Aquifers are found in soil layers and some porous rock layers. They often span several rock layers.
Layers which CAN contain aquifers:
- sandy clay loam
- silty clay loam
- loam
- sandy loam
- silt loam
- loamy sand
- silt
- sand
- yellow sand
- white sand
- black sand
- red sand
- peat
- pelagic clay
- Calcareous ooze
- siliceous ooze
- sandstone
- conglomerate
- Puddingstone
Layers which CAN'T contain aquifers
Dealing with aquifers
Rule #1 - Never dig "up" to find an aquifer, unless you are prepared for the subsequent flood. There will be no "damp stone" warning when digging up into an aquifer!
The challenges presented by an aquifer may be circumvented in several ways. Firstly, much more of your equipment will likely be made from wood, especially early on, so it may help to be in a heavily forested area. Once you've established your fortress a bit, you will also be able to trade for stone and metals if you run short.
It is also worth noting that it sometimes possible to find some amount of stone above the aquifer. It may help to create exploratory shafts searching for pockets of stone. Be aware that mining along the level immediately below the aquifer will result in patches of 'damp stone,' which will flood if mined out; these squares will flash with water when designating mining areas.
The speed method
For multilayer aquifers, if your miners dig fast enough more than one aquifer layer can be pierced. As of version .40c, one aquifer can drain into another. This allows work to be done from a layer down, but does not successfully pierce through all aquifer layers completely.
The ore method
On maps where the aquifer is not held in a layer of soil, but instead is held in a sedimentary layer such as sandstone, it may be possible to tunnel down through deposits of ore such as magnetite. For this to work you have to find a spot where there is coincidentally an ore deposit on each Z-level you need to dig through. This is only possible through tiresome trial and error, or through the use of a utility like reveal.exe.
The magma/obsidian method
If you have access to a supply of magma, you can create your own obsidian caissons. The water from the aquifer is not pressurized, so it is safe to dig channels in aquifer; then you cover them with magma to create patches of obsidian, and stop the flow of magma with more water. You can now dig inside the patch without it flooding, but leave borders! Don't remove all the obsidian.
The outcome when magma meets water seems to depend somewhat on the height of the magma and water and greatly on the number of magma and water squares. In equal numbers open water usually seems to win, advancing against the magma when an obsidian square is dug away, but aquifers seem a little less potent. One thing that works is to keep digging out obsidian until the water square is exhausted.
Unlike normal exploratory mining, once you have created an obsidian barrier against the aquifer on one level, you cannot dig that out, even though it is not "damp stone". If you do, you will have breached the aquifer again, and must either seal that leak or pump the water out. If you must go down through multiple levels, each level will shrink the area because of these borders, so be sure to channel larger areas than you think you need. (On the bright side, the "level below an aquifer" is gone once you fill that level with obsidian - but only directly under what you created.)
The magma vent method
Magma vents have a dry area around it that may allow you to get past the aquifer with minimal effort. Just outside the magma is always a layer of obsidian, which is one of the many stones unable to hold aquifer water. Just beyond this obsidian will be a layer of the surrounding soil or rock which has been dried by the magma vent. Depending on the exact layout of your magma vent, you may be able to dig straight down next to it, or you may have to dig around a bit to find a workable path.
Tips:
- With a visible magma shaft, any tile that is not touching the magma on its Z-level (by edge or corner) is safe from magma, even if there is magma directly above it.
- Any tile which is not marked as damp is safe from the aquifer, even if there is a damp tile next to it. (This is not true if you have used the magma/obsidian method, above!)
- To find the water-safe tiles, you can dig down staircases on the floor above, which reveal the tile below. These can later be covered up by constructed floors, if you want.
- Warning: Do not dig up staircases on the aquifer layer until you know the tile is safe from water. Digging an up staircase creates an open tile, which can fill with water and render adjacent squares unsafe.
- The dried tiles are the same type as the surrounding aquifer, so an aquifer-filled sand layer can be used for gathering sand, if it touches the magma vent.
The pump method
It is possible to pump the water out of an aquifer; though the supply is apparently unlimited it can be pumped out faster than the water seeps in, allowing for a fairly safe area on the z level. This method is somewhat dangerous since problems with your pumps can lead to drowning, however, it allows a larger area to be cleared than most methods and can be done anywhere. It's possible to build walls on the levels with aquifers to stop water. It's also easier to plan around a series of pumps than hoping you'll hit rock on the way down. There is an example of how to get through an aquifer with pumps here: http://mkv25.net/dfma/movie-120-aquifercmv Note that this method will not work with the current version, as it is no longer possible to pump an infinite amount of water into one tile. It can be modified, however, by placing channels behind the pumps so that the water drains back into the aquifer. It is also no longer possible to operate the pumps with a waterwheel built in the aquifer. This can be resolved by hooking up your pumps to another source of power, or by setting the pumps to be manually operated. The latter option will require quite a few dwarfs with nothing better to do but operate pumps.
> Waterwheels will start generating power in aquifer tiles if the water is disturbed via another channel into the 'pool' or a manually-started pump for a few moments, as the 'motion' has started. it can then be used as additional power for the pumps.
It is possible to expand this method to breach multiple z-levels. Just make sure your room on the next level down has a minimum of room allowed for this design. For areas larger than the design, break up the room into smaller areas (6x6 is reasonably workable) and pump them out one at a time from at least three sides (into another section when necessary, you only need one dry at a time), and building walls on the outer edges. As you pump out additional sections, you can connect them, digging through the dividing dirt walls and building a wall between the two sections you've already built to complete the water-proofing. As a note, pumps can't pump if you build a wall in the space they're pumping from(though floor-grates work fine), which is why it is necessary to either pump from all four sides, or to dig out the space to rewall.
The ice method
There is a simple method of getting past an aquifer although it is restricted to a small shaft down, and not possible on all maps. You will need:
- 9 pieces of material suitable for crafting Walls and floors.
- 1 Carpenter or Mason (depending on your wall's building material of choice)
- 1 Miner (using multiple miners runs the danger of one miner digging a channel on the floor another is standing on!*)[Fixed in .33f]
- A map which freezes
Steps:
- Dig channels in a 5x5 square.
- Dig stairs on the outside of the square to allow access to the next level.
- Carefully dig channels underneath all the other channels and build another stair down.
- Continue down in this way until you're right above the water table.
- Dig channels around a central square.
- Wait for the water to freeze.
- The outer-most blocks of ice on the aquifer level will prevent the inner block from being damp.
- Dig a central set of stairs which will allow you to go through the aquifer level and access the levels below.
- If the map will warm up, make sure to surround the stairwell on the aquifer level with walls.
- This system can be expanded to allow for a bigger stairwell.
Diagram:
- C - channel
- G - grate
- W - wall
- X - up/down stairs
- > - down stair
- < - up stair
- I - Ice/water
- F - Floor
Surface level:
CCCCC CCCCC CCCCC> CCCCC CCCCC
Intermediate levels:
CCCCC CCCCC CCCCCX CCCCC CCCCC
Aquifer level + 1:
CCCCC CCCCC CC>CF< CCCCC CCCCC
Aquifer level:
IIIII IWWWI IWXWI IWWWI IIIII
The cave-in method
If you cause the soil layers above the aquifer to cave-in on the aquifer layer, the caved-in layers above the aquifer will become mineable. Note that you must cave in entire blocks, not just floors.
showcase on 2 levels with aquifer: User:Rhenaya/HowtoDualAquifer
Differing biomes
If your local area has more than one biome, you may be able to dig down in one biome to bridge under an aquifer in another. This won't work if the aquifer is present in all biomes, of course, but it may be useful in the case of a surprise aquifer that was not marked on the region selection screen.
Changes in elevation
Aquifers can follow the surface terrain, staying X-number of levels below the surface, instead of existing on one flat level. By digging a tunnel straight into a lower hillside (and letting the water pour out initially), you can access an area "below" the same aquifer present in an upper level. Treat the flowing water as above, by smoothing, pumping, or letting it flow somewhere.
In a sufficiently steep mountain, the higher elevations may have no aquifer, even if the entire region appears to have one on the Embark screen.
In areas with extreme changes in elevation, be they hills or cliffs, it's possible that the areas above and below the aquifer will be accessible by directly digging into the hillside or cliff. In locations like this, one can build a fortress that enjoys the benefits of having an aquifer with little or none of the hassle of getting through the aquifer to access stone. To find areas like this, look for high elevation cliffs on the embark screen.
Caves
If your embark location happens to contain a cave, it may provide a pre-made path through the aquifer, as the cave's walls will not leak water (unless they are dug away).
Cheating
There are also different 3rd party utilities that can get you through aquifers in a variety of creative and painless ways - if that's okay by you, go for it. Try Tweak, among others.
Advantages of aquifers
It's worth noting that the presence of an aquifer, while challenging, does offer some slight advantages. Firstly, much of the area underground but above the aquifer will be sand, clay, or loam, all of which can be planted in without requiring any kind of irrigation or flooding, allowing farming to get under way quicker and with less stress. Additionally, the presence of water 3-4 z-levels below ground anywhere on the map makes placing wells a simpler task, as well as ensuring easy access to subterranean water supplies. Also, just as water will flow endlessly out of an aquifer if there is a way out, it will flow endlessly into an aquifer given time. If you dig a channel into an aquifer, water that runs into the channel will disappear without ever causing it to overflow. You can power water wheels from one aquifer draining into another.
General tips
- Tunnels dug directly below an aquifer will flood. Go down another level before you ruin all that hard work you spent getting through in the first place.
- Smoothing an aquifer wall will make it stop leaking water. This is especially useful when you are trying to get through with a pump. A tunnel directly below a smoothed aquifer tile will not flood. Digging through the smoothed wall tile will cause it to leak water again until you have completely dug out the tile.
- An aquifer wall will not leak water diagonally; it will only add water to tiles directly north/south/east/west.
- On an ocean island, the aquifer is not potable (unlike aquifers on real-life oceanic islands), so you cannot create drinking water zones from the aquifer.
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