Editing Dam (section)

=== By size ===
There is variability, both worldwide and within individual countries, such as in the United States, in how dams of different sizes are categorized. Dam size influences construction, repair, and [[Dam removal|removal]] costs and affects the dams' potential range and magnitude of environmental disturbances.<ref>{{Cite conference |last1=Carter |first1=Edward F. |last2=Hosko |first2=Mary Ann |last3=Austin |first3=Roger |date=1997 |title=Guidelines for Retirement of Dams and Hydroelectric Facilities |conference=Waterpower '97 |url=https://cedb.asce.org/CEDBsearch/record.jsp?dockey=0106463 |publisher=ASCE |pages=1248–1256}}</ref>

====Large dams====
The [[International Commission on Large Dams]] (ICOLD) defines a "large dam" as "A dam with a height of {{convert|15|m|abbr=on}} or greater from lowest foundation to crest or a dam between {{convert|5|m|abbr=on}} metres and 15 metres impounding more than {{convert|3|e6m3|acre-ft|lk=out}}".<ref>{{cite web |title=Definition of a Large Dam |url=https://www.icold-cigb.org/GB/dams/definition_of_a_large_dam.asp |publisher=International Commission on Large Dams |access-date=23 January 2021}}</ref> "Major dams" are over {{convert|150|m|abbr=on}} in height.<ref>{{cite web|url=http://www.iucn.org/themes/wani/eatlas/html/technotes.html |quote=A large dam is defined by the industry as one higher than 15 meters high and a major dam as higher than 150.5 meters. |work=Watersheds of the World |title=Methodology and Technical Notes |access-date=1 August 2007 |archive-url=https://archive.today/20070704103642/http://www.iucn.org/themes/wani/eatlas/html/technotes.html |archive-date=4 July 2007 |url-status=dead |df=dmy }}</ref> The ''Report of the World Commission on Dams'' also includes in the "large" category, dams which are between {{convert|5|and|15|m|abbr=on}} high with a reservoir capacity of more than {{convert|3|e6m3|acre-ft|lk=out}}.<ref name="urlDams and Development: An Overview">{{cite web|url=http://www.dams.org/report/wcd_overview.htm |title=Dams and Development: An Overview |date=16 November 2000 |quote=Box 1. What is a large dam? |access-date=24 October 2010 |url-status=dead |archive-url=https://web.archive.org/web/20101028045913/http://www.dams.org/report/wcd_overview.htm |archive-date=28 October 2010 }}</ref> [[Hydropower]] dams can be classified as either "high-head" (greater than 30 m in height) or "low-head" (less than 30 m in height).<ref name="Poff Hart 2002">{{Cite journal|last1=Poff|first1=N. Leroy|last2=Hart|first2=David D.|date=2002-08-01|title=How Dams Vary and Why It Matters for the Emerging Science of Dam Removal;... |journal=BioScience|language=en|volume=52|issue=8|pages=659–668|doi=10.1641/0006-3568(2002)052[0659:HDVAWI]2.0.CO;2|issn=0006-3568|doi-access=free}}</ref>

{{as of|2021}}, ICOLD's World Register of Dams contains 58,700 large dam records.<ref name="UNU-2021">{{cite book |last1=Perera |first1=Duminda |display-authors=et al.|title=Ageing Water Storage Infrastructure: An Emerging Global Risk |date=2021 |publisher=United Nations University Institute for Water, Environment and Health |location=Hamilton, Canada |isbn=978-92-808-6105-1 |url=https://inweh.unu.edu/wp-content/uploads/2021/01/Ageing-Water-Storage-Infrastructure-An-Emerging-Global-Risk.pdf |access-date=23 January 2021 |format=Report Series, Issue 11}}</ref>{{RP|6}} The tallest dam in the world is the {{convert|305|m|ft|adj=mid|-high|abbr=on}} [[Jinping-I Dam]] in [[China]].<ref>{{cite web |title=The Jinping-I Double Curvature Arch Dam sets new world record |url=http://en.powerchina.cn/2016-12/28/content_27870606.htm |website=en.powerchina.cn |access-date=16 November 2018 |archive-date=17 November 2018 |archive-url=https://web.archive.org/web/20181117022403/http://en.powerchina.cn/2016-12/28/content_27870606.htm |url-status=dead }}</ref>

==== Small dams ====

[[File:Dam in Europe at Autumn as viewed from FPV drone.webm|thumb|Dam in Europe at Autumn as viewed from FPV drone.]]

As with large dams, small dams have multiple uses, such as, but not limited to, [[hydropower]] production, flood protection, and water storage. Small dams can be particularly useful on farms to capture runoff for later use, for example, during the dry season.<ref>{{Cite journal |last1=Nathan |first1=R. |last2=Lowe |first2=L. |date=2012-01-01 |title=The Hydrologic Impacts of Farm Dams |url=https://www.tandfonline.com/doi/abs/10.7158/13241583.2012.11465405 |journal=Australasian Journal of Water Resources |volume=16 |issue=1 |pages=75–83 |doi=10.7158/13241583.2012.11465405 |issn=1324-1583}} <!-- as of 3 July 2023, doi is still broken --></ref> Small scale dams have the potential to generate benefits without displacing people as well,<ref>{{Cite web|title=Why small-scale hydroelectric plants benefit local communities|date=3 September 2015 |url=https://www.weforum.org/agenda/2015/09/why-small-scale-hydroelectric-plants-benefit-local-communities/|publisher=World Economic Forum|language=en|access-date=2020-05-11}}</ref> and small, decentralised hydroelectric dams can aid rural development in developing countries.<ref>{{Cite journal|last=Faruqui|first=N. I.|title=Small Hydro for Rural Development|date=1994|journal=Canadian Water Resources Journal|language=en|volume=19|issue=3|pages=227–235|doi=10.4296/cwrj1903227|issn=0701-1784|doi-access=free|bibcode=1994CaWRJ..19..227F }}</ref> In the United States alone, there are approximately 2,000,000 or more "small" dams that are not included in the [[United States Army Corps of Engineers|Army Corps of Engineers]] [[National Inventory of Dams|National Inventory of dams]].<ref>{{Cite book|last=Graf|first=WL|title=Sustaining Our Water Resources|publisher=National Academy Press|year=1993|location=Washington DC|pages=11–42|chapter=Landscapes, commodities, and ecosystems: The relationship between policy and science for American rivers}}</ref> Records of small dams are kept by state regulatory agencies and therefore information about small dams is dispersed and uneven in geographic coverage.<ref name="Poff Hart 2002" />

Countries worldwide consider small hydropower plants (SHPs) important for their energy strategies, and there has been a notable increase in interest in SHPs.<ref name="Couto Olden 2018">{{Cite journal|last1=Couto|first1=Thiago BA|last2=Olden|first2=Julian D.|date=2018|title=Global proliferation of small hydropower plants – science and policy|journal=Frontiers in Ecology and the Environment|language=en|volume=16|issue=2|pages=91–100|doi=10.1002/fee.1746|issn=1540-9309|doi-access=free|bibcode=2018FrEE...16...91C }}</ref> Couto and Olden (2018)<ref name="Couto Olden 2018" /> conducted a global study and found 82,891 small hydropower plants (SHPs) operating or under construction. Technical definitions of SHPs, such as their maximum generation capacity, dam height, reservoir area, etc., vary by country.

==== Non-jurisdictional dams ====
A dam is non-jurisdictional when its size (usually "small") excludes it from being subject to certain legal regulations. The technical criteria for categorising a dam as "jurisdictional" or "non-jurisdictional" varies by location. In the United States, each state defines what constitutes a non-jurisdictional dam. In the state of [[Colorado]] a non-jurisdictional dam is defined as a dam creating a [[reservoir]] with a capacity of 100 acre-feet or less and a surface area of 20 acres or less and with a height measured as defined in Rules 4.2.5.1. and 4.2.19 of 10 feet or less.<ref>{{Cite web|title=DWR Dam Safety Non-Jurisdictional Dam |publisher=Colorado Information Marketplace |url=https://data.colorado.gov/Water/DWR-Dam-Safety-Non-Jurisdictional-Dam/6smc-zj6j/data |language=en|access-date=2020-05-11}}</ref> In contrast, the state of [[New Mexico]] defines a jurisdictional dam as 25 feet or greater in height and storing more than 15 acre-feet or a dam that stores 50 acre-feet or greater and is six feet or more in height (section 72-5-32 NMSA), suggesting that dams that do not meet these requirements are non-jurisdictional.<ref>{{Cite journal|date=7 December 2009|title=Evaluation of Non-Jurisdictional Dams|url=https://www.ose.state.nm.us/dams/submittal/EvaluationOfNonJurisdictionalDams.pdf|journal=Office of the State Engineer, Dam Safety Bureau}}</ref> Most US dams, 2.41&nbsp;million of a total of 2.5&nbsp;million dams, are not under the jurisdiction of any public agency (i.e., they are non-jurisdictional), nor are they listed on the [[National Inventory of Dams]] (NID).<ref name="Brewitt Colwyn 2020">{{Cite journal|last1=Brewitt|first1=Peter K.|last2=Colwyn|first2=Chelsea L. M.|date=2020|title=Little dams, big problems: The legal and policy issues of nonjurisdictional dams|journal=WIREs Water|language=en|volume=7|issue=1|pages=e1393|doi=10.1002/wat2.1393|issn=2049-1948|doi-access=free|bibcode=2020WIRWa...7E1393B }}</ref>

Small dams incur risks similar to large dams. However, the absence of regulation (unlike more regulated large dams) and of an inventory of small dams (i.e., those that are non-jurisdictional) can lead to significant risks for both humans and ecosystems.<ref name="Brewitt Colwyn 2020" /> For example, according to the [[National Park Service|US National Park Service]] (NPS), "Non-jurisdictional—means a structure which does not meet the minimum criteria, as listed in the Federal Guidelines for Dam Safety, to be included in dam safety programs. The non-jurisdictional structure does not receive a hazard classification and is not considered for any further requirements or activities under the NPS dam safety program."<ref>{{Cite journal|date=25 May 2010|title=Director's Order #40: Dam Safety & Security Program|url=https://www.nps.gov/subjects/policy/upload/DO_40_5-25-2010.pdf|journal=United States Department of the Interior, National Park Service}}</ref> Small dams can be dangerous individually (i.e., they can fail), but also collectively,<ref>{{Cite journal|last1=Fencl|first1=Jane S.|last2=Mather|first2=Martha E.|last3=Costigan|first3=Katie H.|last4=Daniels|first4=Melinda D.|date=2015-11-05|editor-last=Deng|editor-first=Z. Daniel|title=How Big of an Effect Do Small Dams Have? Using Geomorphological Footprints to Quantify Spatial Impact of Low-Head Dams and Identify Patterns of Across-Dam Variation|journal=PLOS ONE|language=en|volume=10|issue=11|pages=e0141210|doi=10.1371/journal.pone.0141210|issn=1932-6203|pmc=4634923|pmid=26540105|bibcode=2015PLoSO..1041210F|doi-access=free}}</ref> as an aggregation of small dams along a river or within a geographic area can multiply risks. Graham's 1999 study<ref>{{Cite journal|last=Graham|first=W J|date=September 1999|title=A Procedure for Estimating Loss of Life Caused by Dam Failure|url=https://www.usbr.gov/ssle/damsafety/TechDev/DSOTechDev/DSO-99-06.pdf|journal=U.S. Department of the Interior, Bureau of Reclamation}}</ref> of US dam failures resulting in fatalities from 1960 to 1998 concluded that the failure of dams between 6.1 and 15 m high (typical height range of smaller dams<ref name="Pisaniello 2009">{{Cite journal|last=Pisaniello|first=John D.|date=2009|title=How to manage the cumulative flood safety of catchment dams|url=http://www.scielo.org.za/scielo.php?script=sci_abstract&pid=S1816-79502009000400001&lng=en&nrm=iso&tlng=en|journal=Water SA|volume=35|issue=4|pages=361–370|issn=1816-7950}}</ref>) caused 86% of the deaths, and the failure of dams less than 6.1 m high caused 2% of the deaths. Non-jurisdictional dams may pose hazards because their design, construction, maintenance, and surveillance is unregulated.<ref name="Pisaniello 2009" /> Scholars have noted that more research is needed to better understand the environmental impact of small dams<ref name="Couto Olden 2018" /> (e.g., their potential to alter the flow, temperature, sediment<ref>{{Cite journal|last1=Ashley|first1=Jeffrey T. F.|last2=Bushaw-Newton |first2=Karen|last3=Wilhelm|first3=Matt|last4=Boettner|first4=Adam|last5=Drames|first5=Gregg|last6=Velinsky|first6=David J.|date=March 2006|title=The Effects of Small Dam Removal on the Distribution of Sedimentary Contaminants |journal=Environmental Monitoring and Assessment|language=en|volume=114|issue=1–3|pages=287–312|doi=10.1007/s10661-006-4781-3|pmid=16565804|bibcode=2006EMnAs.114..287A |s2cid=46471207|issn=0167-6369}}</ref><ref name="Poff Hart 2002" /> and plant and animal diversity of a river).