Editing Chennai (section)

== Environment ==
=== Geography ===
{{Main|Geography of Chennai}}

[[File:Chennai 80.26884E 13.04434N.jpg|thumb|Satellite image of Chennai]]

Chennai is located on the [[Coastline of Tamil Nadu|southeastern coast]] of India in the northeastern part of Tamil Nadu on a flat coastal plain known as the [[Eastern Coastal Plains]] with an average elevation of {{cvt|6.7|m|ft}} and highest point at {{cvt|60|m|ft}}.<ref>{{cite report|title=Human Development Report, Chennai|publisher=[[Government of Tamil Nadu]]|url=https://spc.tn.gov.in/Exe_Summary_DHDR/Chennai.pdf|archive-url=https://web.archive.org/web/20210708155304/http://www.spc.tn.gov.in/Exe_Summary_DHDR/Chennai.pdf|url-status=dead|archive-date=8 July 2021|page=4|access-date=1 November 2023}}</ref><ref name="highest-point">{{cite journal|last=Pulikesi|first=M|author2=P. Baskaralingam|author3=D. Elango|author4=V.N. Rayudu|author5=V. Ramamurthi|author6=S. Sivanesan|title=Air quality monitoring in Chennai, India, in the summer of 2005|journal=Journal of Hazardous Materials|volume=136|issue=3|pages=589–596|date=25 August 2006|quote=Chennai is fairly low–lying, its highest point being only {{cvt|300|m|ft}} above sea level is a rugged barren hill opposite to the Airport called Pallavapuram Hill.|doi=10.1016/j.jhazmat.2005.12.039|pmid=16442714|bibcode=2006JHzM..136..589P | issn = 0304-3894}}</ref> Chennai's soil is mostly [[clay]], [[shale]] and [[sandstone]].<ref>{{cite web|title=Practices and Practitioners|url=http://www.rainwaterharvesting.org/Urban/Practices-and-practitioners.htm|publisher=Centre for Science and Environment|access-date=28 December 2012|archive-date=27 February 2021|archive-url=https://web.archive.org/web/20210227031943/http://www.rainwaterharvesting.org/Urban/Practices-and-practitioners.htm|url-status=live}}</ref> Clay underlies most of the city with sandy areas found along the river banks and coasts where rainwater [[Surface runoff|runoff]] [[percolation|percolates]] quickly through the soil. Certain areas in South Chennai have a hard rock surface.<ref>{{cite news|url=https://timesofindia.indiatimes.com/city/chennai/quality-of-groundwater-better-this-year/articleshow/7381926.cms|title=Quality of groundwater better this year|newspaper=[[The Times of India]]|access-date=28 December 2012|date=29 January 2011|url-status=live|archive-url=https://web.archive.org/web/20190426110806/https://timesofindia.indiatimes.com/city/chennai/Quality-of-groundwater-better-this-year/articleshow/7381926.cms|archive-date=26 April 2019}}</ref><ref>{{cite news|last=Lakshmi|first=K.|title=Tardy monsoon: Chennai water table rises only marginally|newspaper=[[The Hindu]]|location=Chennai|date=28 August 2012|url=https://www.thehindu.com/news/cities/chennai/tardy-monsoon-chennai-water-table-rises-only-marginally/article3828935.ece|access-date=28 December 2012|url-status=live|archive-url=https://web.archive.org/web/20200922181939/https://www.thehindu.com/news/cities/chennai/tardy-monsoon-chennai-water-table-rises-only-marginally/article3828935.ece|archive-date=22 September 2020}}</ref> As of 2018, the city had a green cover of 14.9 per cent, with a per capita green cover of 8.5 square metres against the [[World Health Organization]] recommendation of nine square metres.<ref>{{cite news|last=Lopez|first=Aloysius Xavier|title=A Rs. 228-cr. project to take city's green cover to 20%|newspaper=[[The Hindu]]|location=Chennai|date=31 August 2018|url=https://www.thehindu.com/news/cities/chennai/a-228-cr-project-to-take-citys-green-cover-to-20/article24824653.ece|access-date=2 September 2018|url-status=live|archive-url=https://web.archive.org/web/20201203112857/https://www.thehindu.com/news/cities/chennai/a-228-cr-project-to-take-citys-green-cover-to-20/article24824653.ece|archive-date=3 December 2020}}</ref>

{{As of|2017}}, water bodies cover an estimated {{cvt|3.2|km2}} area of the city.<ref name="Shrunk">{{cite news|url=https://economictimes.indiatimes.com/news/politics-and-nation/how-chennai-one-of-the-worlds-wettest-major-cities-ran-out-of-water/articleshow/80680182.cms?from=mdr|title=How Chennai, one of the world's wettest major cities, ran out of water|date=4 February 2021|access-date=1 June 2023|newspaper=[[The Times of India]]|archive-date=29 May 2023|archive-url=https://web.archive.org/web/20230529002022/https://economictimes.indiatimes.com/news/politics-and-nation/how-chennai-one-of-the-worlds-wettest-major-cities-ran-out-of-water/articleshow/80680182.cms?from=mdr|url-status=live}}</ref> Two major rivers flow through Chennai, the [[Cooum River]] (or ''Koovam'') through the centre and the [[Adyar River]] to the south.<ref name="River">{{cite news|url=https://timesofindia.indiatimes.com/city/chennai/its-official-chennais-rivers-are-dead/articleshow/97076908.cms|title=It's official: Chennai's rivers are 'dead'|date=18 January 2023|access-date=1 June 2023|newspaper=[[The Times of India]]|archive-date=7 May 2023|archive-url=https://web.archive.org/web/20230507030243/https://timesofindia.indiatimes.com/city/chennai/its-official-chennais-rivers-are-dead/articleshow/97076908.cms|url-status=live}}</ref> A section of the [[Buckingham Canal]] built in 1877–78, runs parallel to the Bay of Bengal coast, linking the two rivers.<ref>{{cite news|url=https://www.dtnext.in/city/2020/08/30/those-were-the-days-buckingham-canal-and-its-sociopolitical-influences|title=Those were the days: Buckingham Canal and its socio-political influences|date=30 August 2023|access-date=1 June 2024|newspaper=[[Daily Thanthi]]|archive-date=28 June 2024|archive-url=https://web.archive.org/web/20240628082601/https://www.dtnext.in/city/2020/08/30/those-were-the-days-buckingham-canal-and-its-sociopolitical-influences|url-status=live}}</ref> [[Kosasthalaiyar River]] traverses through the northern fringes of the city before draining into the Bay of Bengal, at [[Ennore Creek]].<ref name="Ennore">{{cite news|url=https://www.newindianexpress.com/states/tamil-nadu/2024/Jan/06/fishersmull-peoples-plan-for-ennore-creek-restoration-2648396.html|title=Fishers mull 'people's plan' for Ennore creek restoration|newspaper=[[The New Indian Express]]|date=6 January 2024|access-date=10 June 2024|archive-date=28 June 2024|archive-url=https://web.archive.org/web/20240628082552/https://www.newindianexpress.com/states/tamil-nadu/2024/Jan/06/fishersmull-peoples-plan-for-ennore-creek-restoration-2648396.html|url-status=live}}</ref> The [[Otteri Nullah]], an east–west stream, runs through north Chennai and meets the Buckingham Canal at [[Basin Bridge]].<ref>{{cite news|url=https://www.thehindu.com/news/cities/chennai/residents-along-otteri-nullah-complain-of-pollution-health-risk-and-flooding/article67263643.ece|title=Residents along Otteri Nullah complain of pollution, health risk and flooding|date=3 September 2023|newspaper=[[The Hindu]]|access-date=1 December 2023|archive-date=8 December 2023|archive-url=https://web.archive.org/web/20231208112217/https://www.thehindu.com/news/cities/chennai/residents-along-otteri-nullah-complain-of-pollution-health-risk-and-flooding/article67263643.ece|url-status=live}}</ref> The [[Water table|groundwater table]] in Chennai is at {{cvt|4–5|m}} below ground level on average and is replenished mainly by rainwater.<ref>{{cite book|first1=Susheela|last1=Raghavan|first2=Indira|last2=Narayanan|editor=S.Muthiah|title=Madras, Chennai: A 400-year Record of the First City of Modern India, Volume 1|publisher=Palaniappa Brothers|year=2008|page=13|chapter=Chapter 1: Geography|isbn=978-8-18379-468-8|url=https://books.google.com/books?id=tbR_LLkqdI8C|access-date=6 November 2015|archive-date=29 June 2024|archive-url=https://web.archive.org/web/20240629135924/https://books.google.com/books?id=tbR_LLkqdI8C|url-status=live}}</ref> Of the {{cvt|24.87|km}} coastline of the city, {{cvt|3.08|km}} experiences erosion, with sand accretion along the shoreline at the [[Marina beach]] and the area between the [[Ennore Port]] and [[Kosasthalaiyar river]].<ref>{{cite news|last=Lakshmi|first=K.|title=T.N. lost 41% shoreline to erosion: study|newspaper=[[The Hindu]]|date=10 November 2018|url=https://www.thehindu.com/news/national/tamil-nadu/tn-lost-41-shoreline-to-erosion-study/article25458192.ece|access-date=10 November 2018|url-status=live|archive-url=https://web.archive.org/web/20201129180742/https://www.thehindu.com/news/national/tamil-nadu/tn-lost-41-shoreline-to-erosion-study/article25458192.ece|archive-date=29 November 2020}}</ref>

=== Geology ===
Chennai is situated in [[Seismic hazard|Seismic Zone III]], indicating a moderate risk of damage from [[earthquakes]].<ref>{{cite news|last=John|first=Ekatha Ann|title=Disaster body for panel to monitor highrises in Chennai|location=Chennai|date=29 September 2012|url=https://timesofindia.indiatimes.com/city/chennai/disaster-body-for-panel-to-monitor-highrises-in-chennai/articleshow/16596651.cms|newspaper=[[The Times of India]]|access-date=28 December 2022|archive-date=8 December 2023|archive-url=https://web.archive.org/web/20231208112216/https://timesofindia.indiatimes.com/city/chennai/disaster-body-for-panel-to-monitor-highrises-in-chennai/articleshow/16596651.cms|url-status=live}}</ref> Owing to the tectonic zone the city falls in, the city is considered a potential [[geothermal energy]] site. The [[crust (geology)|crust]] has old granite rocks dating back nearly a billion years indicating volcanic activities in the past with expected temperatures of {{cvt|200-300|°C}} at {{cvt|4-5|km}} depth.<ref>{{cite news|last=Yadav|first=Priya|title=Soon, power from ancient rocks|location=Chennai|date=10 January 2013|url=https://timesofindia.indiatimes.com/city/chandigarh/soon-power-from-ancient-rocks/articleshow/17962871.cms|newspaper=[[The Times of India]]|access-date=10 January 2023|archive-date=25 September 2022|archive-url=https://web.archive.org/web/20220925233731/https://timesofindia.indiatimes.com/city/chandigarh/soon-power-from-ancient-rocks/articleshow/17962871.cms|url-status=live}}</ref>

=== Climate ===
Under the [[Köppen climate classification]], Chennai has the dry-summer version of a [[tropical savanna climate]] (''As''),<ref>{{cite book |last1=Elbeltagi |first1=Ahmed |last2=Pande |first2=Chaitanya B. |last3=Moharir |first3=Kanak N. |last4=Pham |first4=Quoc Bao |last5=Singh |first5=Sudhir Kumar |title=Climate Change Impacts on Natural Resources, Ecosystems and Agricultural Systems |date=13 February 2023 |publisher=[[Springer International]] |isbn=978-3-03119-059-9 |page=348}}</ref><ref>{{cite book |last1=Khan |first1=Ansar |last2=Akbari |first2=Hashem |last3=Fiorito |first3=Francesco |last4=Mithun |first4=Sk |last5=Niyogi |first5=Dev |title=Global Heat Island Migration |date=2022 |publisher=Elsevier |isbn=978-0-323-85539-6 |page=160 |url=https://books.google.com/books?id=P7JYEAAAQBAJ&dq=chennai+dry+summer+climate+As+koppen&pg=PA160}}</ref> closely bordering the dry-winter version (''Aw'') due to a February average rainfall of {{cvt|4.7|mm}}. The city lies on the [[thermal equator]] and as it is also located on the coast, there is no extreme variation in seasonal temperature.<ref name="CMDAA">{{cite web|title=About Chennai|url=https://www.cmdachennai.gov.in/pdfs/tenders/ChengalpattuNewTownDevelopmentPlan/TOR.pdf|page=28|access-date=28 December 2022|publisher=[[Chennai Metropolitan Development Authority]]}}</ref> The hottest time of the year is from April to June with an average temperature of {{cvt|35–40|°C}}.<ref>{{cite news|title=Heat may gradually relent over most parts of the State after June 18, says IMD|date=15 June 2023|url=https://www.thehindu.com/news/cities/chennai/heat-may-gradually-relent-over-most-parts-of-the-state-after-june-18-says-imd/article66973265.ece|newspaper=[[The Hindu]]|access-date=28 November 2023|archive-date=8 December 2023|archive-url=https://web.archive.org/web/20231208112216/https://www.thehindu.com/news/cities/chennai/heat-may-gradually-relent-over-most-parts-of-the-state-after-june-18-says-imd/article66973265.ece|url-status=live}}</ref> The highest recorded temperature was {{cvt|45|°C}} on 31 May 2003.<ref name="IMDE">{{cite report|url=https://imdpune.gov.in/library/public/EXTREMES%20OF%20TEMPERATURE%20and%20RAINFALL%20upto%202012.pdf|title=Climatology tables:Extremes till 2012|publisher=[[India Meteorological Department]]|access-date=29 May 2023|archive-date=5 February 2020|archive-url=https://web.archive.org/web/20200205042509/http://imdpune.gov.in/library/public/EXTREMES%20OF%20TEMPERATURE%20and%20RAINFALL%20upto%202012.pdf|url-status=live}}</ref> The coldest time of the year is in December{{ndash}}January, with average temperature of {{cvt|19|–|25|C|F}} and the lowest recorded temperature of {{cvt|13.9|°C|°F}} on 11 December 1895 and 29 January 1905.<ref name="IMDNorm">{{cite report|title=Climatology tables:Normal 1981-2010|url=https://imdpune.gov.in/library/public/1981-2010%20CLIM%20NORMALS%20(STATWISE).pdf|publisher=[[India Meteorological Department]]|page=279|access-date=29 May 2023|archive-date=20 June 2023|archive-url=https://web.archive.org/web/20230620142419/https://imdpune.gov.in/library/public/1981-2010%20CLIM%20NORMALS%20%28STATWISE%29.pdf|url-status=live}}</ref>

Chennai receives most of its rainfall from the [[northeast monsoon]] between October and December while smaller amounts of rain also come from the [[southwest monsoon]] between June and September. The dry season is between January and May, with March having the least average rainfall at {{cvt|3.4|mm}}. The average annual rainfall is about {{cvt|120|cm}}.<ref>{{cite report|title=Ground Water Brochure, Chennai|url=https://cgwb.gov.in/sites/default/files/2022-10/chennai.pdf|access-date=28 December 2022|publisher=Central Ground Water Board, [[Government of India]]|archive-date=13 December 2023|archive-url=https://web.archive.org/web/20231213065623/https://cgwb.gov.in/sites/default/files/2022-10/chennai.pdf|url-status=live}}</ref> The highest annual rainfall recorded was {{cvt|257|cm}} in 2005.<ref>{{cite news|title=Northeast monsoon dumps 57% excess rainfall in Tamil Nadu in 2021|date=31 December 2021|url=https://www.deccanherald.com/india/northeast-monsoon-dumps-57-excess-rainfall-in-tamil-nadu-in-2021-1066547.html|newspaper=[[Deccan Herald]]|access-date=31 December 2022|archive-date=8 December 2023|archive-url=https://web.archive.org/web/20231208112216/https://www.deccanherald.com/india/northeast-monsoon-dumps-57-excess-rainfall-in-tamil-nadu-in-2021-1066547.html|url-status=live}}</ref> Prevailing winds in Chennai are usually southwesterly between April and October and northeasterly during the rest of the year.<ref>{{cite news|url=https://timesofindia.indiatimes.com/city/chennai/easterly-southeasterly-winds-keep-city-cool/articleshow/58454114.cms|title=Easterly, southeasterly winds keep city cool|date=1 May 2007|newspaper=[[The Times of India]]|access-date=28 December 2022|archive-date=8 December 2023|archive-url=https://web.archive.org/web/20231208112216/https://timesofindia.indiatimes.com/city/chennai/easterly-southeasterly-winds-keep-city-cool/articleshow/58454114.cms|url-status=live}}</ref> The city relies on the annual monsoon rains to replenish water reservoirs.<ref>{{cite report|url=https://mausam.imd.gov.in/chennai/mcdata/ne_monsoon_2022.pdf|title=Northeast Monsoon, 2022|publisher=[[India Meteorological Department]]|access-date=19 March 2023|archive-date=8 December 2023|archive-url=https://web.archive.org/web/20231208112218/https://mausam.imd.gov.in/chennai/mcdata/ne_monsoon_2022.pdf|url-status=live}}</ref> [[North Indian Ocean tropical cyclone|Cyclones and depressions]] are common features during the season.<ref>{{cite news|title=NE monsoon sets in, brings in copious rains|url=https://www.rediff.com/news/2005/oct/12imd.htm|url-status=live|archive-url=https://web.archive.org/web/20200926100107/https://www.rediff.com/news/2005/oct/12imd.htm|archive-date=26 September 2020|work=[[Rediff]]|date=12 October 2005|access-date=1 June 2011}}</ref> Water inundation and flooding happen in low-lying areas during the season with significant flooding in [[2015 South India floods#Chennai|2015]] and [[2023 Chennai floods|2023]].<ref>{{cite news|title=Chennai Flooded, 2015 All Over Again! Cyclonic Storm Michaung to blame or infrastructure|url=https://www.timesnownews.com/chennai/chennai-flooded-2015-all-over-again-cyclonic-storm-michaung-to-blame-or-infrastructure-article-105728590|work=Times Now|date=4 December 2023|access-date=5 December 2023|archive-date=4 December 2023|archive-url=https://web.archive.org/web/20231204114100/https://www.timesnownews.com/chennai/chennai-flooded-2015-all-over-again-cyclonic-storm-michaung-to-blame-or-infrastructure-article-105728590|url-status=live}}</ref>

{{#section:Geography of Chennai|weatherbox}}

=== Flora and fauna ===
[[File:GreaterFlamingo-Mudaliarkuppam.jpg|thumb|[[Greater flamingo]]s wintering at Mudaliarkuppam]]

{{Main|Flora and fauna of Chennai}}

A protected [[estuary]] on the Adyar River forms a natural habitat for several species of birds and animals.<ref>{{cite book|author=S. Theodore Baskaran|editor=S. Muthiah|title=Madras, Chennai: A 400-year Record of the First City of Modern India, Volume 1|publisher=Palaniappa Brothers|year=2008|page=55|chapter=Chapter 2: Wildlife|isbn=978-8-18379-468-8|url=https://books.google.com/books?id=tbR_LLkqdI8C|access-date=28 December 2012|archive-date=29 June 2024|archive-url=https://web.archive.org/web/20240629135924/https://books.google.com/books?id=tbR_LLkqdI8C|url-status=live}}</ref> Chennai is also a [[Birding in Chennai|popular city for birding]] with more than 130 recorded species of birds have been recorded in the city.<ref>{{cite book|title=Pictorial Handbook: Birds Of Chennai|last=G. Thirumalai and S. Krishnan|date=July 2005|publisher=Zoological Survey of India|place=Kolkata|url=http://www.vedamsbooks.com/no41408.htm|access-date=8 December 2023|archive-date=18 June 2009|archive-url=https://web.archive.org/web/20090618145534/http://www.vedamsbooks.com/no41408.htm|url-status=live}}</ref> Marshy wetlands such as [[Pallikaranai wetland|Pallikaranai]] and inland lakes also host a number of migratory birds during the monsoon and winter.<ref>{{cite report|url=http://www.tnenvis.nic.in/PDF/WET.pdf|archive-url=https://web.archive.org/web/20120321122516/http://www.tnenvis.nic.in/PDF/WET.pdf|archive-date=21 March 2012|title=Wetlands in Tamil Nadu|publisher=[[Government of Tamil Nadu]]|access-date=12 October 2015}}</ref><ref>{{cite news|url=https://www.thehindu.com/sci-tech/energy-and-environment/chennai-welcomes-migratory-birds-here-is-a-guide-to-begin-bird-watching/article67457419.ece|title=Chennai welcomes migratory birds. Here is a guide to begin bird watching|date=27 February 2024|access-date=1 June 2024|newspaper=[[The Hindu]]|archive-date=28 June 2024|archive-url=https://web.archive.org/web/20240628082552/https://www.thehindu.com/sci-tech/energy-and-environment/chennai-welcomes-migratory-birds-here-is-a-guide-to-begin-bird-watching/article67457419.ece|url-status=live}}</ref> The southern stretch of Chennai's coast from Tiruvanmiyur to Neelangarai are favoured by the endangered [[olive ridley sea turtle]]s to lay eggs every winter.<ref>{{cite news|url=https://www.thehindu.com/news/cities/chennai/good-nesting-season-of-olive-ridley-turtles-ends-along-chennais-coast/article66854180.ece|title=Good nesting season of Olive Ridley turtles ends along Chennai's coast|date=23 May 2023|access-date=1 December 2023|newspaper=[[The Hindu]]|archive-date=8 December 2023|archive-url=https://web.archive.org/web/20231208075300/https://www.thehindu.com/news/cities/chennai/good-nesting-season-of-olive-ridley-turtles-ends-along-chennais-coast/article66854180.ece|url-status=live}}</ref> [[Guindy National Park]] is a protected area within the city limits and wildlife conservation and research activities take place at [[Arignar Anna Zoological Park]].<ref>{{cite news|url=https://www.thehindu.com/news/cities/chennai/wildlife-centre-at-vandalur-zoo-replaces-night-safari/article5314832.ece|title=Wildlife centre at Vandalur zoo replaces safari|newspaper=[[The Hindu]]|access-date=12 October 2015|url-status=live|archive-url=https://web.archive.org/web/20200730145915/https://www.thehindu.com/news/cities/chennai/wildlife-centre-at-vandalur-zoo-replaces-night-safari/article5314832.ece|archive-date=30 July 2020}}</ref> [[Madras Crocodile Bank Trust]] is a [[herpetology]] research station, located {{cvt|40|km}} south of Chennai.<ref>{{cite news|url=https://www.thehindu.com/sci-tech/energy-and-environment/madras-crocodile-bank-trust-and-its-partner-ngos-in-india-working-to-raise-awareness-on-snakebites/article67329345.ece|title=Madras Crocodile Bank Trust and its partner NGOs in India working to raise awareness on snakebites|newspaper=[[The Hindu]]|date=22 September 2013|access-date=29 August 2022|archive-date=27 September 2023|archive-url=https://web.archive.org/web/20230927154926/https://www.thehindu.com/sci-tech/energy-and-environment/madras-crocodile-bank-trust-and-its-partner-ngos-in-india-working-to-raise-awareness-on-snakebites/article67329345.ece|url-status=live}}</ref><ref>{{cite journal|last=Shankar Raman|first=T. R.|author2=R. K. G. Menon|author3=R. Sukumar|title=Ecology and Management of Chital and Blackbuck in Guindy National Park, Madras|journal=Journal of the Bombay Natural History Society|volume=93|issue=2|pages=178–192|year=1996|url=http://blackbuck.files.wordpress.com/2009/10/raman-menon-sukumar-jbnhs.pdf|access-date=21 Jul 2012|archive-date=18 July 2011|archive-url=https://web.archive.org/web/20110718093532/http://blackbuck.files.wordpress.com/2009/10/raman-menon-sukumar-jbnhs.pdf|url-status=live}}</ref> The city's tree cover is estimated to be around {{cvt|64.06|km2}} with 121 recorded species belonging to 94 genera and 42 families. Major species include [[Copper pod]], [[Indian beech]], [[Gulmohar]], [[Samanea saman|Raintree]], [[Neem]], and [[Tropical Almond]].<ref>{{cite news|title=Tree cover in city is only around 15%|newspaper=[[The Hindu]]|location=Chennai|date=11 February 2018|url=https://www.thehindu.com/todays-paper/tp-national/tp-tamilnadu/tree-cover-in-city-is-only-around-15/article22719066.ece|access-date=11 February 2018|url-status=live|archive-url=https://web.archive.org/web/20200730152628/https://www.thehindu.com/todays-paper/tp-national/tp-tamilnadu/tree-cover-in-city-is-only-around-15/article22719066.ece|archive-date=30 July 2020}}</ref> The city's marine and inland water bodies house a number of fresh water and salt water fishes, and marine organisms.<ref>{{cite report|url=https://www.fisheries.tn.gov.in/includes/assets/cms_uploads/pdf/glance/Fisheries_Policy_Note_2022-23_English.pdf|title=Fisheries policy note|publisher=[[Government of Tamil Nadu]]|access-date=29 August 2022|archive-date=25 June 2022|archive-url=https://web.archive.org/web/20220625144534/https://www.fisheries.tn.gov.in/includes/assets/cms_uploads/pdf/glance/Fisheries_Policy_Note_2022-23_English.pdf|url-status=live}}</ref><ref>{{cite journal |url=https://threatenedtaxa.org/index.php/JoTT/article/view/569 |title=Species persistence: a re-look at the freshwater fish fauna of Chennai, India |journal=Journal of Threatened Taxa |date=2010 |doi=10.11609/JoTT.o2519.1334-7 |access-date=1 August 2023 |last1=Knight |first1=J.D. Marcus |last2=Devi |first2=K. Rema |volume=2 |issue=12 |pages=1334–1337 |archive-date=8 December 2023 |archive-url=https://web.archive.org/web/20231208112216/https://threatenedtaxa.org/index.php/JoTT/article/view/569 |url-status=live }}</ref>

=== Environmental issues ===
[[File:Chitlapakkam-lake-chennai-7-r.jpg|thumb|[[Chitlapakkam Lake]] in the southern part of the city]]

Chennai had many lakes spread across the city, but [[urbanization]] has led to the shrinkage of water bodies and wetlands.<ref>{{cite news|url=https://www.thehindu.com/features/kids/vanishing-wetlands/article6860776.ece|title=Vanishing wetlands|newspaper=[[The Hindu]]|access-date=12 October 2015|url-status=live|archive-url=https://web.archive.org/web/20200730150251/https://www.thehindu.com/features/kids/vanishing-wetlands/article6860776.ece|archive-date=30 July 2020}}</ref><ref>{{cite news|last=Lakshmi|first=K.|title=The vanishing waterbodies of Chennai|newspaper=[[The Hindu]]|date=1 April 2018|url=https://www.thehindu.com/news/cities/chennai/the-vanishing-waterbodies-of-chennai/article23404437.ece|access-date=21 October 2018|url-status=live|archive-url=https://web.archive.org/web/20201127175534/https://www.thehindu.com/news/cities/chennai/the-vanishing-waterbodies-of-chennai/article23404437.ece|archive-date=27 November 2020}}</ref> The water bodies have shrunk from an estimated {{cvt|12.6|km2}} in 1893 to {{cvt|3.2|km2}} in 2017.<ref name="Shrunk"/> The number of wetlands in the city has decreased from 650 in 1970 to 27 in 2015.<ref>{{cite news|title=Next time by water|url=https://www.economist.com/asia/2015/12/12/next-time-by-water|newspaper=[[The Economist]]|access-date=11 December 2015|issn=0013-0613|url-status=live|archive-url=https://web.archive.org/web/20201027132431/https://www.economist.com/asia/2015/12/12/next-time-by-water|archive-date=27 October 2020}}</ref> Nearly half of the native plant species in the city's wetlands have disappeared with only 25 per cent of the erstwhile area covered with aquatic plants still viable.<ref>{{cite news|last=K.|first=Lakshmi|title=Indigenous flora in city wetlands under threat|newspaper=[[The Hindu]]|date=20 January 2019|url=https://www.thehindu.com/news/cities/chennai/indigenous-flora-in-city-wetlands-under-threat/article26039519.ece|access-date=3 February 2019|url-status=live|archive-url=https://web.archive.org/web/20210203021114/https://www.thehindu.com/news/cities/chennai/indigenous-flora-in-city-wetlands-under-threat/article26039519.ece|archive-date=3 February 2021}}</ref> The major water bodies including the Adyar, Cooum and Kosathaliyar rivers, and the Buckingham canal are heavily polluted with effluents and waste from domestic and commercial sources.<ref>{{cite news|url=https://www.thehindu.com/news/cities/chennai/chen-society/issues-of-pollution-raised-at-meeting-for-adyar-river-restoration/article6194140.ece|title=Adyar River pollution|newspaper=[[The Hindu]]|access-date=12 October 2015|url-status=live|archive-url=https://web.archive.org/web/20200730140403/https://www.thehindu.com/news/cities/chennai/chen-society/issues-of-pollution-raised-at-meeting-for-adyar-river-restoration/article6194140.ece|archive-date=30 July 2020}}</ref><ref>{{cite news|url=https://timesofindia.indiatimes.com/home/environment/pollution/TNs-Cooum-river-80-dirtier-than-sewage/articleshow/3382689.cms|title=Couvum River pollution|newspaper=[[The Times of India]]|access-date=12 October 2015|url-status=live|archive-url=https://web.archive.org/web/20210310100749/https://timesofindia.indiatimes.com/home/environment/pollution/tns-cooum-river-80-dirtier-than-sewage/articleshow/3382689.cms|archive-date=10 March 2021}}</ref><ref name="River"/> The encroachment of urban development on wetlands has hampered the sustainability of water bodies and was a major contributor to the floods in 2015 and [[2023 Chennai floods|2023]] and [[2019 Chennai water crisis|water scarcity crisis in 2019]].<ref>{{cite news|url=https://www.thehindubusinessline.com/specials/india-file/living-without-water-in-chennai/article28065458.ece|title=Living without water in Chennai|last=V|first=Jinoy Jose P|newspaper=[[The Hindu]]|date=18 June 2019|language=en|access-date=19 June 2019|url-status=live|archive-url=https://web.archive.org/web/20210225161257/https://www.thehindubusinessline.com/specials/india-file/living-without-water-in-chennai/article28065458.ece|archive-date=25 February 2021}}</ref><ref>{{cite news|last1=Nagarajan|last2=Megson|first2=Jody|last3=Wu|first3=Jin|first1=Ganesh|title=How One of the World's Wettest Major Cities Ran Out of Water|url=https://www.bloomberg.com/news/features/2021-02-03/how-a-water-crisis-hit-india-s-chennai-one-of-the-world-s-wettest-cities|access-date=15 February 2021|newspaper=[[Bloomberg News]]|date=3 February 2021|language=en|archive-url=https://web.archive.org/web/20210402180757/https://www.bloomberg.com/news/features/2021-02-03/how-a-water-crisis-hit-india-s-chennai-one-of-the-world-s-wettest-cities|archive-date=2 April 2021}}</ref>

The Chennai River Restoration Trust set up by the government of Tamil Nadu is working on the restoration of the Adyar River.<ref>{{cite news|url=https://timesofindia.indiatimes.com/good-governance/tamil-nadu/Muck-in-Chennai-rivers-may-soon-turn-manure/articleshow/49074041.cms|title=Muck in Chennai rivers to turn into manure|newspaper=[[The Times of India]]|access-date=12 October 2015|url-status=live|archive-url=https://web.archive.org/web/20160102012423/http://timesofindia.indiatimes.com/good-governance/tamil-nadu/Muck-in-Chennai-rivers-may-soon-turn-manure/articleshow/49074041.cms|archive-date=2 January 2016}}</ref> The [[Environmentalist Foundation of India]] is a volunteering group working towards wildlife conservation and habitat restoration.<ref>{{cite news|url=https://www.thehindu.com/news/cities/chennai/more-citizens-initiatives-for-restoring-waterbodies/article7748606.ece|title=More citizens initiative for restoring water bodies|newspaper=[[The Hindu]]|access-date=12 October 2015|url-status=live|archive-url=https://web.archive.org/web/20200730150443/https://www.thehindu.com/news/cities/chennai/more-citizens-initiatives-for-restoring-waterbodies/article7748606.ece|archive-date=30 July 2020}}</ref><ref>{{cite news|url=https://www.thehindu.com/news/cities/chennai/water-security-mission-to-watch-out-for-citys-needs/article7700011.ece|title=Water security mission to watch out for city's needs|newspaper=[[The Hindu]]|access-date=12 October 2015|url-status=live|archive-url=https://web.archive.org/web/20210407180443/https://www.thehindu.com/news/cities/chennai/water-security-mission-to-watch-out-for-citys-needs/article7700011.ece|archive-date=7 April 2021}}</ref>