40d:Mist

Mist is created by water falling from one Z-level to another. Walking through it generates a happy thought for a dwarf.
Do not confuse with magma mist; this does not create a happy thought for the dwarf.

Generating Mist

AncientEnemy [1] devised a convenient way to generate mist.This method relies on the fact that screwpumps pump water faster than water spreads out.

An example of a simple mist generator.

Simply put, water is dropped from the floor above and then immediately sucked up by the next pump.

• When built underground, evaporation is nonexistent. (Above ground may still suffer heat evaporation, depending on temperature.)
• The walls in the corner of the z=0 level are unnecessary if you instead create a Pond zone in one of the z=1 corner squares.
• The statues in the z=0 level serve two purposes. First, they prevent dwarfs from standing under the water, which would cause job cancellation spam. The second reason is that statues don't get muddy, so you don't have perpetual muddy spots. An alternative to statues is to build paved roads (which don't get muddy) where the statues are, and only fill the pond to 2/7 water (which dwarfs don't mind).
• This system is generally only capable of maintaining a single 7/7 square of water, due to the way water descends z-levels. Any additional water put into the system will quickly overflow into the pump chamber (z=1).
  

A movie [2] best illustrates the operation. For fun, this same configuration can be used with magma [3] as long as magma safe screwpumps are used.

Another technique, should you have a brook or river and a chasm on the same map, is to build an arrangement so that the water is pumped from the river to the chosen location, falls through a three-story hole in the floor, and then follows a path along to the chasm. The two stories between the collection area and the chosen mist area seems to prevent water pressure from causing a flood, and with the chasm being bottomless and the river/brook providing infinite water, there is no danger of running out of either capacity or water, unless the map freezes.