Editing Dam (section)

=== By use ===
==== Saddle dam ====
A saddle dam is an auxiliary dam constructed to confine the reservoir created by a primary dam either to permit a higher water elevation and storage or to limit the extent of a reservoir for increased efficiency. An auxiliary dam is constructed in a low spot or "saddle" through which the reservoir would otherwise escape. On occasion, a reservoir is contained by a similar structure called a [[levee|dike]] to prevent inundation of nearby land. Dikes are commonly used for reclamation of arable land from a shallow lake, similar to a [[levee]], which is a wall or embankment built along a river or stream to protect adjacent land from flooding.

==== Weir ====
{{main|Weir}}
A weir (sometimes called an "overflow dam") is a small dam that is often used in a river channel to create an impoundment lake for water abstraction purposes. It can also be used for flow measurement or retardation.

==== Check dam ====
{{main|Check dam}}
A check dam is a small dam designed to reduce flow velocity and control soil [[erosion]]. Conversely, a [[wing dam]] is a structure that only partly restricts a waterway, creating a faster channel that resists the accumulation of sediment.

==== Dry dam ====
{{main|Dry dam}}

A dry dam, also known as a flood retarding structure, is designed to control flooding. It normally holds back no water and allows the channel to flow freely, except during periods of intense flow that would otherwise cause flooding downstream.

==== Diversionary dam ====
{{main|Diversionary dam}}

A diversionary dam is designed to divert all or a portion of the flow of a river from its natural course. The water may be redirected into a canal or tunnel for irrigation and/or hydroelectric power production.

==== Underground dam ====
Underground dams are used to trap [[groundwater]] and store all or most of it below the surface for extended use in a localized area. In some cases, they are also built to prevent saltwater from intruding into a freshwater aquifer. Underground dams are typically constructed in areas where water resources are minimal and need to be efficiently stored, such as in deserts and on islands like the [[Fukuzato Dam]] in [[Okinawa Prefecture|Okinawa]], Japan. They are most common in [[northeastern Africa]] and the arid areas of [[Brazil]] while also being used in the [[southwestern United States]], Mexico, India, Germany, Italy, Greece, France and Japan.<ref>{{cite web |last=Yilmaz |first=Metin |title=Control of Groundwater by Underground Dams |url=http://etd.lib.metu.edu.tr/upload/1259621/index.pdf |publisher=The Middle East Technical University |access-date=7 May 2012 |date=November 2003}}</ref>

There are two types of underground dams: "sub-surface" and a "sand-storage". A sub-surface dam is built across an [[aquifer]] or drainage route from an impervious layer (such as solid bedrock) up to just below the surface. They can be constructed of a variety of materials to include bricks, stones, concrete, steel or PVC. Once built, the water stored behind the dam raises the water table and is then extracted with wells. A sand-storage dam is a weir built in stages across a stream or [[wadi]]. It must be strong, as floods will wash over its crest. Over time, sand accumulates in layers behind the dam, which helps store water and, most importantly, prevent [[evaporation]]. The stored water can be extracted with a well, through the dam body, or by means of a drain pipe.<ref>{{cite journal |last=Onder |first=H |author2=M. Yilmaz |title=Underground Dams—A Tool of Sustainable Development and Management of Ground Resources |journal=European Water |date=November–December 2005 |pages=35–45 |url=http://www.ewra.net/ew/pdf/EW_2005_11-12_05.pdf |access-date=7 May 2012}}</ref>

==== Tailings dam ====
{{main|Tailings dam}}
[[File:Bituminous geomembrane installation on a mine tailings storage facility.jpg|thumb|[[Bituminous Geomembranes (BGMs)|Bituminous geomembrane]]  installation on a mine tailings storage facility.]]

A tailings dam is typically an earth-fill embankment dam used to store [[tailings]], which are produced during [[mining]] operations after separating the valuable fraction from the uneconomic fraction of an [[ore]]. Conventional water retention dams can serve this purpose, but due to cost, a tailings dam is more viable. Unlike water retention dams, a tailings dam is raised in succession throughout the life of the particular mine. Typically, a base or starter dam is constructed, and as it fills with a mixture of tailings and water, it is raised. Material used to raise the dam can include the tailings (depending on their size) along with soil.<ref>{{cite book |last=Blight |first=Geoffrey E. |chapter=Construction of Tailings Dams |title=Case studies on tailings management |year=1998 |publisher=International Council on Metals and the Environment |location=Paris |isbn=978-1-895720-29-7 |pages=9–10 |chapter-url=https://books.google.com/books?id=qG9Bux3RYWMC&q=tailings+dam&pg=PA9 |access-date=10 August 2011}}</ref>

There are three raised tailings dam designs, the "upstream", "downstream", and "centerline", named according to the movement of the crest during raising. The specific design used is dependent upon [[topography]], geology, climate, the type of tailings, and cost. An upstream tailings dam consists of [[trapezoid]]al embankments being constructed on top but toe to crest of another, moving the crest further upstream. This creates a relatively flat downstream side and a jagged upstream side which is supported by tailings [[slurry]] in the impoundment. The downstream design refers to the successive raising of the embankment that positions the fill and crest further downstream. A centerlined dam has sequential embankment dams constructed directly on top of another while fill is placed on the downstream side for support and slurry supports the upstream side.<ref>{{cite web|title=Properties of Tailings Dams |url=http://www.mining.ubc.ca/faculty/meech/MINE290/Tailings%20Dam%20Construction%20Methods.pdf |publisher=NBK Institute of Mining Engineering |access-date=10 August 2011 |url-status=dead |archive-url=https://web.archive.org/web/20111001213037/http://www.mining.ubc.ca/faculty/meech/MINE290/Tailings%20Dam%20Construction%20Methods.pdf |archive-date=1 October 2011 }}http://mining.ubc.ca/files/2013/03/Dirk-van-Zyl.pdf</ref><ref name="taildam">{{cite book |editor-first=Raj K. |editor-last=Singhal |title=Environmental issues and management of waste in energy and mineral production: Proceedings of the Sixth International Conference on Environmental Issues and Management of Waste in Energy and Mineral Production: SWEMP 2000; Calgary, Alberta, Canada, May 30&nbsp;– June 2, 2000 |year=2000 |publisher=Balkema |location=[[Rotterdam]] [u.a.] |isbn=978-90-5809-085-0 |pages=257–260 |url=https://books.google.com/books?id=PqiYy538JFUC&q=tailings+dam&pg=PA257 |access-date=2015-11-09}}</ref>

Because tailings dams often store toxic chemicals from the mining process, modern designs incorporate an impervious [[geomembrane]] liner to prevent seepage.<ref>{{cite report |last1=McLeod|first1=Harvey  |last2=Bjelkevik|first2=Annika |date=2021 |title=TAILINGS DAM DESIGN Technology Update |publisher= ICOLD Committee on Tailings Dams|url= https://www.icoldchile.cl/boletines/181.pdf|doi= |page= 91}}</ref> Water/slurry levels in the tailings pond must be managed for stability and environmental purposes as well.<ref name="taildam" />