PJ: I'm having some irrigation trouble
Care to offer any hints & advice ?
I wanna grow those mushroom thingies inside my fortress but I guess I need to make the floor wet. Anyway to do this in a "set & forget" manner?
Tower caps?
You can't entirely set and forget it -- you'll still have to pull a couple of levers a couple of times a year.
The basic principle is pretty simple, but it's a bit tricky to set up. You need:
(0) Running water.
(1) A reservoir.
(2) A big room to be muddied, about five times as big as the reservoir.
(3) A drainage area.
This is what you want to dig and build:
First, the reservoir level -- A and B are floodgates, 1 and 2 are levers, O is a channel, D is door. I've omitted the stairs you need to build to be able to actually get there; put them wherever you like but remember that water... flows... down.
~~~~~~~
~~river~~
~~~~~~~
A
###
###
###BO
D
1#
#2
Second, the mud level -- should be positioned so that the reservoir drains near the center of the room:
O####O
######
######
######
######
O####O
Third, the drainage level -- directly below the mud level:
######
######
######
######
######
######
Once you've got this set up, connect the floodgate A to lever 1 and floodgate B to lever 2. Forbid passage through door D. Then dig a channel between floodgate A and the river. Pull lever 1. Your reservoir will flood.
To irrigate, pull lever 1 again to close the reservoir. Then pull lever 2, letting the reservoir drain into the big room below. Once empty, pull lever 2 again, and lever 1 again to refill the reservoir.
There's a bit "too much" water in the reservoir; the overflow will go into the drainage room below, and partly irrigate it too. This is needed to fully irrigate the room -- cut it too close, and it'll drain out faster than it spreads out, leaving annoying dry spots.
Then wait.
Eventually, the mud will dry out. At this point, irrigate again. It takes a quite a long time -- on the order of a year or so -- so this isn't a frequent chore by any means.
You can also grow dwarf crops here, you know.
Also note the possible defensive uses of hydraulic engineering: if you're clever, you can set up a system that'll trap any invaders in an area that you can then flood. Drown, you pointy-eared tree-huggers! Muhahahaha! etc.
Edit: for extra credit, do the defensive hydraulic engineering with... magma. Only trouble is that in the current version of DF, magma is a non-renewable resource, so you won't be able to use it indefinitely.
