Water is a fluid found all over the world. It flows from mountain springs, forming the world's oceans, lakes, rivers, and brooks. Water falls as rain and snow, and freezes into ice. Water is home to a variety of aquatic creatures. Many creatures can swim in deep water. Air-breathing creatures that are submerged in water can drown in it. Water comes in two varieties: freshwater, which makes up almost all inland water, and saltwater, which fills the seas. In this version, some brooks and murky pools can be saltwater even if the fortress site is partially mountainous. It is not known if this is a bug. To tell the difference, attempt to set up a drinking zone including some of the water in question. If there are zero tiles of water source available, the water is saltwater.
Water is displayed with the symbols
~, sometimes colored different blues, and white, showing ripples. Water can also take on other colors indicating contaminants such as blood, ichor, or goo. (The game can be configured to show the depth instead).
Dark-colored water symbols indicate the water is one Z-level below the camera level. Water has 7 depth levels per tile, with 1 being a shallow puddle, and 7 filling the tile completely. Dwarves can safely walk through water up to a depth of 3 - at depth 4 or higher, a dwarf will cancel jobs due to "Dangerous terrain" and begin to gain swimming experience. At depth 7, any dwarf that does not have sufficient Swimming skill will drown.
Interestingly, water can slow falls with deep enough water and short enough falls. If the water is deep enough relative to the height of the fall, dwarves can be less injured or even completely uninjured (from a 4 level drop to a 3 level deep pool, for example)
Evaporation occurs when water or magma is at a depth of 1/7. Simply having 2/7 standing water is enough to prevent evaporation. Water or magma at 1/7 depth will even evaporate if it is on top of 7/7 depth water as shown in the example bellow.
Murky pools are an exception. In hot or scorching environments a murky pool can evaporate even when it is completely full. Murky pools also generate water to simulate seasonal accumulation from rainfall. This sometimes makes it possible for a murky pool to replenish itself even when it has been completely drained.
Many environments get cold enough for water to freeze in winter. When this happens, any water that is exposed above ground will freeze into ice. However, water a single tile away that is in an underground tunnel will not freeze. When ice walls thaw, they always leave a 7/7 water tile regardless of how much water may have been present when the ice formed.
When outdoor water freezes or thaws it does so instantly. Any dwarf swimming in water when it freezes will die, and any dwarf standing on a frozen pond will fall into it when it thaws, most probably leading to drowning.
Mining ice can produce chunks of ice. Taking these chunks into a stone layer will cause it eventually melt, turning it into a "water" item (much like those hauled in buckets) which can't be used for anything. Bug:360Caving in an ice wall into a stone layer will cause it to instantly melt into water (provided it does not become exposed to the outdoors), which can be used to get water near the surface in a glacier biome without having to use a pump stack to pump water up from a cavern pool.
Water and magma are both fluids which are constantly trying to flow into adjacent tiles until they have filled all available space or until they run out of fluid. Fluids technically move in 9 directions: down, and to the sides. Fluids cannot move diagonally up or down. Fluids at a depth of 1/7 no longer attempt to move unless they can move down. Fluids under pressure can appear to travel upward until the pressure equalizes, though in reality they are moving downward and/or sideways relative to their source.
If the flow is strong enough, it can move objects such as dwarves, pets, stones, weapons or corpses.
 Sourced Water
Water that comes from rivers, brooks, oceans, aquifers or springs is considered to be sourced water. Any sourced water is an endless supply of water that can never run dry, although it can freeze for part of the year in colder biomes.
When using sourced water you should strongly consider installing floodgates and be aware of how pressure works or you could easily end up flooding your fortress and having a lot more fun than anticipated.
 Salt Water
Dwarves can not use salt water directly; while healthy dwarves will usually prefer to drink booze, wounded dwarves can only be given water to drink.
To check to see if water is salty, use themenu to see if the game shows the pond/pool as a water source. If the "water source (x)" is (0), then the source is salty. If not, then your dwarves will drink it.
A screw pump can be used to desalinate water, but if the fresh water produced ever contacts salty water, the "saltiness" will conduct through the entire body of water making the reservoir permanently salty. Note that once a tile is marked as salty, it cannot be reverted without external tools.
There is a myth that desalinated water turns salty if it ever touches natural stone. This myth has been debunked, any cistern will work, except those dug into a beach, which may spontaneously turn salty, although constructed cisterns on the beach are fine.
The old 40d method of using a well to desalinate water still works in v0.31. Dwarves will drink water from a well over salt water, give it to sick dwarves and use it to clean wounds. You cannot designate the well as a water source, but the dwarves will still use it.
 Stagnant Water
Water taken from a murky pool or wetlands biome will be stagnant, just as water taken from near the ocean will be salty, and just like saltiness, stagnation will spread through any connected bodies of water. So if a river is joined to a murky pool, the river will immediately and permanently become stagnant. Dwarves get an unhappy thought if they have to drink stagnant water, and a doctor cleaning a wound with stagnant water will likely cause an infection.
Pumping stagnant water will make it clean, provided the reservoir has never held stagnant water. Moving water only via flow or with gravity won't clean it; pumping is required.
 Water laced with mud
If a water source is only one z-level deep and its floor is covered by "a pile of mud" (like most underground pools), then any water taken from it will be "water laced with mud". Drinking water laced with mud will give your dwarves an unhappy thought. It might also cause infection if used to clean a wound.
Unlike stagnant water, merely moving the water with flow or gravity will take care of the problem, since it only occurs if the water source tile contains "a pile of mud", and water coming into contact with a clean floor only creates "a dusting of mud".
Contaminants that get into water currently can do very strange things. A pool of blood that gets covered by water will be pushed out of the water as the water flows creating more pools of blood at the edge of the water. Overflowing a large reservoir that contains contaminants of blood will generate a large amount of blood very quickly. This behavior is thought to be a bug.
 Getting Rid of Unwanted Water
Water will flow off the edge of the map, endlessly, which is one way to get rid of large amounts of water (evaporation works better with small amounts). Underground, there are at least two ways to accomplish this. One is to channel your excess water into a dry cavern that is open to the map edge, as the water will flow out (depending on slopes and such). The other, probably easier method, is to mine to the map edge (since you cannot mine the map edge itself, just up to it), then smooth the edge and then carve fortifications into it. Water will flow through the fortifications and off the edge of the map. Make sure your exit flow is equal to or, for safety, greater than your input. One approach that may not work well is to dump your excess water into an underground lake that is open to the map edge, as such lakes have some sort of equilibrium built into them, and your excess water can cause the lake to flood.
Draining lakes and oceans from underneath can be a finicky task, but there's a bit of dwarven magic for it: build a retractable bridge on the level beneath the sea bottom, with ramps directly underneath it. Link this to a lever to control the flow as you desire. Now evacuate the dwarves and wall off the area above the bridge. Then, with the bridge in place, designate ramps around the bridge leading up - breaking through to the sea bottom. Now how can the dwarves dig these squares out? Yep, from beneath the bridge. In this way they get the water flow started without ever getting their little feet wet. This is a great way to set up channels one square in from the map edge near a water source, so that you can properly wall off the baddies from getting into the fort.
[MATERIAL:WATER] - reconstructed from data extracted from memory [STATE_COLOR:ALL_SOLID:WHITE] [STATE_NAME_ADJ:ALL_SOLID:ice] [STATE_COLOR:LIQUID:CLEAR] [STATE_NAME_ADJ:LIQUID:water] [STATE_COLOR:GAS:CLEAR] [STATE_NAME_ADJ:GAS:steam] [STATE_NAME_ADJ:SOLID_POWDER:snow] [STATE_NAME_ADJ:SOLID_PASTE:slush] [BASIC_COLOR:1:0] [BUILD_COLOR:3:0:0] [TILE_COLOR:7:7:1] [SPEC_HEAT:4181] [MELTING_POINT:10000] [BOILING_POINT:10180] [SOLID_DENSITY:920] [LIQUID_DENSITY:1000]