How to drain water from the caverns

dwarf-fortress

I have multiple layers of water in a cavern; it is connected to the "rest of the world" (map edge), so if I use the water up somehow, it is replenished by more water from the outside.

I want to get rid of it all – mostly to be able to cut down all the trees, but also as a fun (mega)project by itself.

How can I do it? Will I have to use magma, or would some arrangement of bridges be sufficient?

Best Answer

As you have surmised it is helpful to block off the water sources at the edge of the map before you can drain the caverns. There are a few options available to do that. Magma is certainly one of them. There is also the cave-in method for dealing with aquifers. You can drop natural stone into the water from above with a cave in. This is one of the few cases where I would consider magma to actually be the safer method. If you had just one z-level of water you could also pump the water out while building walls, however your question implies that you have more than one z-level of water to deal with at the edge of the map.

Bridges will not help unless they are both built under the level of the water and are raising--as opposed to retracting--bridges. Even then a bridge would only block off one z-level of inflow. The only advantages using bridges rather than walls to block inflow would have is that bridges are controllable, and take fewer rocks to build. Although if you wanted controllable you could block off the flow, build bridges (or doors or floodgates) behind the blockage and then unblock the flow. You would want to be sure to connect all your gates etc to levers (and be aware that bridges open opposite to doors and floodgates).

Blocking the flow is not necessarily the only way to drain the caverns however. Water flows in from the side of the map with a maximum rate per edge tile. If you can drain the water off faster than that then you can get some space to build a blockage, or even just drain the entire cavern. You might consider the instructions for draining unwanted water given by the wiki.

If you take this method, though, be sure you will have a great enough drainage rate before you connect to the flooded area.

Related Solutions

Getting rid of water on the lower levels

~~Well you can't tunnel off the side of the map because the edge tile is never diggable, so that's out anyway.~~ So it turns out you can turn an edge tile into fortifications which will drain water. First smooth it, then carve fortifications. (Thanks Nakedible!)

However, for those who consider this cheating or who are using a non-infinite water source, the only way is, indeed, a pump stack. This, while time consuming, isn't as terrible as you might think. (You'll probably have to do this later to bring magma up from the deeps, anyway.) The wiki has a description of optimal pump stack construction.

This will allow you to build a stack of mechanically operated pumps without putting extra machinery on each level. You only have to power one of the pumps in the stack. (Assuming that power source provides enough power for the whole stack.) Combine this with the (somewhat cheating) dwarven water-wheel reactor and you have a relatively painless pumping solution.

I like to put two gears between the power source and the pump stack and attach a lever to the gear nearest the pump stack. This allows me to turn the whole thing off if chaos ensues for any reason or I need to do maintenance to the system.

The alternative is of course a genuine water wheel setup or windmill setups, but these options will force you to be more choosy about where you locate the construction. Any axles or gears that lead from your power source to the pump stack consume power!

You might want to try building a smaller pump stack before going for one that spans 50 levels or more. Keep in mind it's very easy to flood your fortress with Fun!

Trouble creating water source

I have not tried the fill pond strategy to make a farm, but rather the "planned flood" technique.

In 2d...

+---!---+             RRRR
|fffffff|             RRRR
|fffffff| +----+______RRRR
|fffffff|X|wwww?__C__CRRRR
|fffffff| +----+      RRRR
+-------+             RRRR

Where:

R is a river (with 1+ layers of water above it, for pressure)
w is water storage, f is farm (7 f to 1 w)
C is a channel from 1 square above
X is a wall to dig out
? is a door/floodgate hooked to a switch somewhere.
! is a door for mud/water containment

To make the water storage:

dig left C, tunnel, and storage room
build door/floodgate at ?, and connect it to a switch
make sure ? is OPEN
Channel out right C
When room is 7 deep, flip switch

Now, the storage room is filled with 7 * w units of water, one unit per bit of farm!

To make your farm muddy:

Channel at X
Run out of door
Lock door until room is full of mud (and possibly fish)

Best Answer

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Getting rid of water on the lower levels

Trouble creating water source

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