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Difference between revisions of "40d:Aquifer"
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Revision as of 22:34, 18 December 2007
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.
Where they are found
Aquifers are found in soil layers and some porous 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
Layers which CAN'T contain aquifers
Dealing with aquifers
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 above 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 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 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 and magma is chunky, so it is safe to dig channels in aquifer. Though you will have to re-dig a lot of channels due to an element of chance, you can create a pool of magma on the aquifer z-level, and then pinch the pool off from the supply of magma with water. When it cools (which you can hasten with more water) you can dig down through the middle of a 3x3 patch of obsidian without flooding. With larger starting patches, you can dig through multiple levels of aquifer.
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 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
It is possible to expand this meathod 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 nessessary, 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, which is why it is nessessary 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!)
- 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
Intermidiate 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.
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.
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.
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