Editing 40d:River

{{quality|Exceptional|09:00, 23 May 2012 (UTC)}}{{av}}
== Surface Rivers ==

'''Rivers''' are found on the surface of world maps. They vary in width and flow rate, some being wider and than others. They often flow through deep canyons or just across the flat surface of a level. On levels with [[cliff]]s, [[waterfall|waterfalls]] may be found.

'''Major rivers, Minor rivers, Streams and Brooks'''''

On the surface of the world you can find four different types of rivers. 

*[[Brook]]s are not visible on the region map. They are the smallest flowing body of [[water]] that can be found ingame, being only 4 tiles wide. Brooks have a special surface, allowing [[dwarves]] and other units to walk on top of them as if they were covered by floor [[grate]]s, and they never contain any dangerous creatures. Brooks are very common - almost every tile around a stream or larger river will have a brook running through it.
*Streams are light blue and often converge with other streams, and have some tributaries of brooks. They tend to be 4-6 tiles wide.
*Minor Rivers are medium blue and usually have tributaries of streams. They are usually between 7 and 10 tiles wide.
*Rivers are dark blue and usually have tributaries of minor rivers. They are often over 10 tiles wide.
*Major Rivers are distinguished by a "=" as opposed to a "-". Some worlds have no Major Rivers so they can be considered quite valuable. Usually they have minor river tributaries and can often feed large [[lake]]s. Major rivers are much wider than regular rivers, potentially exceeding 40 tiles in width. Besides this, the difference (if any) between major and minor rivers has yet to be discovered. However major rivers are believed to lower the fps.

[[File:Watersystems01.jpg|300px|thumb|Different sorts of rivers in action]]

== Underground Rivers ==

An '''underground river''' is, obviously, a river found [[underground]]. They can be located on the embarkation map pre-[[embark]] through use of the [[site finder]], but are usually invisible until revealed by [[exploratory mining]].  When found, the game will pause and special announcement will be seen.

[[Cave spider]]s may occur near underground rivers. They leave small webs strewn around any nearby areas, which can be collected and woven into [[silk]].

It is also possible (but unusual) to find underground rivers or pools which are automatically visible, as they are exposed to the surface (often due to erosion during world generation) - you may even see a few [[tower-cap]]s already growing in the area.  You can tell it's a cave river/pool because of the distinctive aquatic humanoids such as [[Frogman|frogmen]] or [[olm]]s, and the ever-dangerous [[cave crocodile]]s.  An exposed underground river cannot be distinguished from the more typical hidden type during site-selection.

== Other Important Facts ==

*Rivers presumably contain an unlimited amount of water and cannot be drained like muddy pools.  They can, however, be dammed if you can *temporarily* drain part of them to 1/7 or less for long enough to construct [[construction|walls]] or install [[floodgate]]s. Despite being an unlimited source of water, river source tiles will only refill up to the level of the river's source - it will not overflow if you dam it up. This demonstrates one way to drain and dam a river: [http://mkv25.net/dfma/movie-196-draininganddammingamajorriver-i]. Another way to dam a river is to direct a lava flow into it, producing obsidian in the squares where it encounters water.
*Once dammed, a dry riverbed will refill when it rains, similar to a [[murky pool]].
*Riverbed tiles also permit "wet" trees and shrubs to grow near them - if these tiles are removed (e.g. by building a paved road), only "dry" trees and shrubs will grow near them in the future.
*Rivers and streams often contain an abundance of [[fishing|fish]], including highly dangerous dwarf-killing fish such as [[carp]], [[Pike (fish)|pike]], and [[longnose gar]]. Brooks never contain any dangerous fish, only the vermin variety that your fisherdwarves can catch.
*A dammed river will cease to produce additional water once all of its tiles reach 7/7, even if the dam is subsequently opened. Once the water level near the river's source drops below 7/7, though, the river will start producing water again.

== See also ==

* [[Water]]

{{World|Biomes}}

{{Category|Map tiles}}
{{category|Water bodies}}