Safely harvesting water from the caverns

dwarf-fortress

I just began my first glacial embark, and realizing that I have no water is proving to be a challenge for my crops. I was able to breach the first cavern and wall it off, then I was able to dig to an area adjacent to the cavern lake. Now I want to harvest this water from the lake to build a dependable water source for my fort.

I'm going to be using a water source that is connected to edge tiles to ensure that I have an unlimited source of water. This makes it free game for Forgotten Beasts to spawn. So I need to make some way to pump water where FB's can't break down my stuff.

Now first, are there such things as creatures that could swim under water? If I build in such a way:

~~~~~~~~~~ <- lake
####~##############
####~#Screw> ÷÷~~~~ -> To rest of fortress     
####~##Pump#~######
####~#######~######
###~~~~~~~~~~######
###################

Would my pump stack still be in danger of being broken?

Best Answer

Forgotten beasts, besides being building destroyers, appear to also be amphibious. This means that, without some way to block them from entering, they can, given enough will (as without anything to gather their attention such as a dwarf, they will moan around the caverns), destroy any one of the pumps.

The best way to block the passage of any creature and still let water flow through is with carved Fortifications, as those behave like walls, in that they can't be destroyed. However, they only stop the passage of creatures while they are at a fluid level less than [7/7] (which seems to be a bug). The setup you could employ would be the following:

           ########
           #  ÷÷~~~
~~~~~~~~~~┼╬~~#####
###################

The first construction is a retracting bridge, the second is a fortification and on top is the pump. The bridge is linked to a lever, that you first activate in order to keep the bridge closed. As soon as the bridge opens, water comes through the fortification. Pumps can generally pump water faster than what natural flow can replenish so the fortification's water level will remain below [7/7] until you stop pumping and close the bridge.

This is how you would, with some degree of safety, operate a pump on the caverns. However, and as I stated earlier, without threat, Forgotten beasts are generally peaceful against buildings.

However, you are in a glacier. This means you have possibly tens of levels of ice sitting right above you. Why not use it to make water? Turns out you can do just that, by caving in a level of ice into a reservoir of the same size below. The temperature difference between the ice layer and the rock layer makes that the collapsed ice turns to drinkable water. The process is explained in greater depth in the wiki

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