Tonlé Sap

File:Cambodia, Tonle Sap IMG 3324.JPG

Tonlé Sap Lake is located in the northwest of the lower Mekong plain, formed by the collision and collapse of the Indian Plate and the Eurasian Plate.{{cite journal |title= Wrench-Slip Reversals and Structural Inversions: Cenozoic Slide-Rule Tectonics in Sundaland|journal= Indonesian Journal on Geoscience|volume= 1|issue= 1|pages= 35–52|publisher= Institute for Environment and Development University Kebangsaan Malaysia |date= 28 April 2014|last1= Tjia|first1= H. D.|doi= 10.17014/ijog.v1i1.174|doi-broken-date= 1 November 2024|doi-access= free}} The lower Mekong plain used to be a bay, and the sea level rose rapidly at the end of the last glacial period. About {{convert|4.5|m|ft}} high, cores from this period found near Angkor contain tidal deposits, as well as salt marshes and mangrove swamp deposits,{{cite journal |author1=T. Tamura |author2=Y. Saito |author3=S. Sotham |author4=B. Bunnarin |author5=K. Meng |author6=S. Im |author7=S. Choup |author8=F. Akiba |year=2009 |title=Initiation of the Mekong River Delta at 8 ka: Evidence from the sedimentary succession in the Cambodian lowland |journal=Quaternary Science Reviews |volume=28 |issue=3–4 |pages=327–344 |doi=10.1016/j.quascirev.2008.10.010|bibcode=2009QSRv...28..327T }} deposited in caves about 7,900-7,300 years ago The sediments of Lake Sap also show signs of marine influence.{{cite journal |author=D. Penny |year=2006 |title=The Holocene history and development of the Tonle Sap, Cambodia |journal=Quaternary Science Reviews |volume=25 |issue=3–4 |pages=310–322 |doi=10.1016/j.quascirev.2005.03.012|bibcode=2006QSRv...25..310P }} The current river morphology of the Mekong Delta was developed over the past 6,000 years,{{cite web |website=Mekong River Commission|year=2010 |title=State of the Basin Report, 2010|location=Vientiane|url=http://www.mrcmekong.org/assets/Publications/basin-reports/MRC-SOB-report-2010full-report.pdf }} while the remaining waters in the northwest corner of the lower Mekong plain formed the Tonlé Sap.{{cite journal |author1=Mary Beth Day、D. A. Hodell、Mark Brenner、J. H. Curtis |title=Mid to Late Holocene (5-3 ka) Origin of the Modern Tonle Sap Lake System, Cambodia |date=1 December 2008 |journal= AGU Fall Meeting Abstracts |volume=2008 |bibcode=2008AGUFM.H53C1062D |url=https://www.researchgate.net/publication/241364742 |accessdate=4 April 2022}}

The Tonlé Sap drainage basin is bordered to the southwest by the Cardamom Mountains, with heights of more than {{convert|1700|m|ft}}, and to the north are the Piandan Mountains with an average height of {{convert|500|m|ft}}. The basin covers an area of {{convert|86000|km2|sqmi}}. The {{convert|120|km|mi}}-long Tonlé Sap River connects the Tonlé Sap Lake with the Mekong River and contributes 9% of the flow of the Mekong River.{{cite book |url=http://www.mrcmekong.org/mekong-basin/hydrology/ | title=Hydrology | website= Mekong River Commission |access-date=18 May 2015}} The size and water volume of the lake varies greatly throughout the year, with a minimum area of about {{convert|2,500|–|3,000|km2|sqmi}} and a volume of about {{convert|1|km3|mi3}} in the dry season, and the water body expands in the rainy season, increasing the depth to {{convert|9|-|14|m|ft}}.{{cite book |editor=britannica |title=Tonle Sap |url=https://www.britannica.com/place/Tonle-Sap |accessdate=19 April 2022}} The maximum area is {{convert|16,000|km2|sqmi}}, and the volume is about {{convert|80|km3|mi3}}.

About 34% of the water in the Tonlé Sap comes from the rivers that enter the lake, about 53.5% from the Mekong River, and 12.5% from precipitation. May to October is the rainy season in the lower Mekong plain, and November to March is the dry season. The annual rainfall is {{convert|1000|to|4000|mm|in}}. Almost all the precipitation is in the rainy season.{{cite book|last1=McElwee|first1=Pamela|last2=Horowitz|first2=Michael M|title=Environment and Society in the Lower Mekong Basin: A Landscaping Review|date=1999|publisher=Institute for Development Anthropology, SUNY|location=Binghamton|url=http://www.mekonginfo.org/assets/midocs/0001784-environment-environment-and-society-in-the-lower-mekong-basin-a-landscaping-review-volume-i.pdf|access-date=4 January 2018|archive-date=27 September 2021|archive-url=https://web.archive.org/web/20210927120307/http://www.mekonginfo.org/assets/midocs/0001784-environment-environment-and-society-in-the-lower-mekong-basin-a-landscaping-review-volume-i.pdf|url-status=dead}} At the end of the dry season, the Tonlé Sap Lake has a typical depth of {{convert|1|m|ft}}. As the monsoon rain begins, the water level of the river begins to rise, eventually reversing the flow of the river. The water level of the Tonlé Sap increases by about {{convert|10|m|ft}}, the flow of the Mekong gradually decreases at the end of the rainy season, and the flow of the Tonlé Sap then reverses and begins to replenish the flow of the Mekong.{{cite web |url=http://www.wepa-db.net/policies/state/cambodia/overview1_4.htm |title=Cambodia; 1.4. Hydrology| website=Water Environment Partnership in Asia (WEPA) |access-date=12 May 2015}}

The extreme hydrodynamic complexity of the Tonlé Sap Lake, both in time and space, makes it impossible to measure specific flow, and water level rather than velocity and volume determines the movement of water as it shapes the landscape.{{cite journal|url=http://www.mekonginfo.org/assets/midocs/0001968-inland-waters-overview-of-the-hydrology-of-the-mekong-basin.pdf|title=Overview of the Hydrology of the Mekong Basin|journal=Annual Flood Report|publisher=Mekong River Commission|location=Vientiane|date=November 2005|issn=1728-3248|access-date=9 March 2021|archive-date=13 July 2018|archive-url=https://web.archive.org/web/20180713003412/http://www.mekonginfo.org/assets/midocs/0001968-inland-waters-overview-of-the-hydrology-of-the-mekong-basin.pdf|url-status=dead}} 72% of the modern sediments deposited in the Tonlé Sap come from the Mekong River, while only 28% come from the catchments upstream of the lake. Sediment-bound phosphorus acts as the basis of the food chain through phytoplankton, and internal nutrient cycling plays a crucial role in the productivity of the floodplain and, therefore, the long-term sustainability of the lake's entire ecosystem.{{cite journal|last=Kummu|first=Matti|author2=Dan Penny |author3=Juha Sarkkula |author4=Jorma Koponen |title=Sediment: Curse or Blessing for Tonle Sap Lake?|journal=Royal Swedish Academy of Sciences|date=May 2008|volume=37|issue=3|pages=158–162|doi=10.1579/0044-7447(2008)37[158:scobft]2.0.co;2|pmid=18595269|s2cid=22970198 }}

File:Tonle Sap - dopływ.JPG

The land cover of the Tonlé Sap Lake Basin is 55% of the forest land and 45% of the agricultural land. The lake is surrounded by freshwater mangroves known as "flood forests", accounting for 3% of the basin area, and the floodplain is surrounded by low hills and covered with evergreen or deciduous seasonal tropical plants. The forest is dominated by Dipterocarpaceae, Leguminosae, Lacelandaceae, and in some places Pinaceae, Rohan pineaceae or bamboo. As the distance from the lake becomes farther and farther away, the forest gradually turns into a thicket, and finally into a meadow.{{cite web|url=http://treeseedfa.org/doc/Monographs/5Introduction.pdf|title=A. Flora of Cambodia|website=Cambodia Tree Seed Project|access-date=4 January 2018|archive-date=24 June 2022|archive-url=https://web.archive.org/web/20220624092120/http://treeseedfa.org/doc/Monographs/5Introduction.pdf|url-status=dead}} In areas with higher quality soils or higher altitudes, deciduous mixed forests and semi-evergreen forests occur.{{cite web|url=http://www.encyclopedia.com/doc/1O7-semievergrenssnltrpclfrst.html | title= Semi-evergreen Seasonal Tropical Forest |website=Encyclopedia.com |access-date=26 May 2015}} This diversity of vegetation types underlies the species diversity of the Tonle Sap ecosystem, with interlocking forests, grasslands and swamps providing refuge for local wildlife.{{cite web|url=http://cambodia.panda.org/where_we_work/dry_forests/dry_forest_ecology/|title=Dry Forest Ecology|website=World Wide Fund For Nature|access-date=20 May 2015|url-status=dead|archive-url=https://web.archive.org/web/20150521050949/http://cambodia.panda.org/where_we_work/dry_forests/dry_forest_ecology/|archive-date=21 May 2015}}

The lake is home to at least 149 species of fish, 11 of which are globally endangered, and the lake area is also home to 6 near-threatened species, including spotted-billed, great bald, bengal, black-bellied, and Grey-headed fish eagle and Far Eastern reed, in addition to supporting reptile populations including the endangered Siamese crocodile and numerous freshwater snakes, and although much of the Lake District has been turned into farmland, 200 species of higher plants are still recorded.{{cite journal|last1=Campbell|first1=Ian C|last2=Poole|first2=Colin|last3=Giesen|first3=Wim|last4=Valbo-Jorgensen|first4=John|title=Species diversity and ecology of Tonle Sap Great Lake, Cambodia|journal=Aquatic Sciences|date=October 2006|volume=68|issue=3|pages=355–373|doi=10.1007/s00027-006-0855-0|bibcode=2006AqSci..68..355C |s2cid=28804535}} The Mekong giant catfish, which lives in the Tonlé Sap Lake, is one of the largest freshwater fish in the world. A fisherman caught a Mekong giant catfish weighing nearly 648 pounds in May 2004, but its population has been declining since the mid-1970s. It is currently illegal for fishermen to catch and retain Mekong giant catfish, and only a few are used for scientific research.{{cite news|last=Sullivan|first=Michael|title=Tonle Sap: The Flowing Heart of Cambodia|url=https://www.npr.org/templates/story/story.php?storyId=5039980|date=7 December 2005|access-date= 9 March 2021|work=NPR|format=Audio}}

As a natural flood reservoir for the entire Mekong River system, Tonlé Sap Lake regulates floods in the lower reaches of Phnom Penh during the rainy season, and is also an important supplement to the dry season flow of the Mekong Delta.{{cite book|last1=Chadwick|first1=M T|last2=Juntopas|first2=M|last3=Sithirith|first3=M|title=Sustaining Tonle Sap: An Assessment of Development Challenges Facing the Great Lake|date=2008|publisher=The Sustainable Mekong Research Network|location=Bangkok|isbn=9789186125066}} In 1997, UNESCO designated the Tonle Sap as a biosphere reserve, but scientists have been concerned that high dams built in southern China and Laos will affect the strength and flow of countercurrents into the Tonlé Sap, reducing the number of fish in the lake. Tonle Sap habitat for nesting, breeding, spawning, and foraging in the floodplain, which will adversely affect fish productivity and overall biodiversity in the Tonle Sap.{{cite web|url=https://en.unesco.org/news/unesco-conducts-consultations-core-areas-tonle-sap-biosphere-reserve-strengthen-conservation | title=UNESCO conducts consultations at core areas of the Tonle Sap Biosphere Reserve to strengthen conservation and sustainable livelihoods|date=2 February 2021|website= UNESCO Phnom Penh| access-date=9 March 2021}}{{cite book|title=Impacts on the Tonle Sap Ecosystem|date=June 2010|publisher=Mekong River Commission|chapter-url=http://www.probeinternational.org/Impacts-on-the-Tonle-Sap-Ecosystem%28June-10%29.pdf|access-date=4 January 2018|chapter=Technical Note 10}}

Forest loss hotspots are located in low floodplain areas where protected areas are located, significant farmland expansion is mainly in the intersection between the lower and upper floodplains, population growth, fuelwood gathering and logging are the main causes of forest loss, intensification of agricultural activities and upstream hydropower development reduces buffers to natural habitats and increases the risk of forest loss.{{cite journal |author1=Aifang Chen, Anping Chen, Olli Varis & Deliang Chen |title=Large net forest loss in Cambodia's Tonle Sap Lake protected areas during 1992–2019 |journal=Ambio |date=8 February 2022 |volume=51 |issue=8 |pages=1889–1903 |doi=10.1007/s13280-022-01704-4 |pmid=35133565 |pmc=9200915 |bibcode=2022Ambio..51.1889C |s2cid=246636436 }} By the 2030s, hydropower development may lead to large-scale changes in habitat, with the area of coastal forests likely to decrease by 82%, while the area of rain-fed habitats may increase by 10–13%.{{cite journal |url=http://ir.canterbury.ac.nz/handle/10092/8913|title=Impacts of Hydrological Alterations in the Mekong Basin to the Tonle Sap Ecosystem|last1=Arias|first1=Mauricio Eduardo|website=University of Canterbury|year=2013 |location=Christchurch NZ |doi=10.26021/1497 |access-date=15 July 2015}} In July 2020, under the influence of the El Niño phenomenon and the impoundment of dams in the tributaries of the Mekong River, the water level of the Tonle Sap Lake hit a record low for the same period in the past 60 years.{{cite news |title=Ủy hội sông Mekong báo động về mực nước Biển Hồ Campuchia |url=https://www.vietnamplus.vn/uy-hoi-song-mekong-bao-dong-ve-muc-nuoc-bien-ho-campuchia/655740.vnp |accessdate=5 April 2022 |agency=越通社 |date=5 August 2020}}

File:Dwellings on Tonlé Sap.JPG

The Tonlé Sap Lake District has always been a vital fishing and agricultural production area for Cambodia, and it has largely maintained Angkor, the largest pre-industrial settlement complex in history.{{cite journal|last1=Thung|first1=Heng L|title=Geohydrology and the Decline of Angkor|journal=Journal of the Siam Society|date=1994|volume=82|issue=1|pages=9–14|url=http://www.khamkoo.com/uploads/9/0/0/4/9004485/the_journal_of_the_siam_society_vol._lxxxii_part_1-2_1994.pdf|access-date=4 January 2018|archive-date=29 June 2016|archive-url=https://web.archive.org/web/20160629010703/http://www.khamkoo.com/uploads/9/0/0/4/9004485/the_journal_of_the_siam_society_vol._lxxxii_part_1-2_1994.pdf|url-status=dead}} While many fish left lakes and ponds to spawn in flooded forests at the onset of floods, the inflow of Mekong floods brought large numbers of fry, which found shelter and food in flooded forests and floodplains.

The approximately 1.2 million people who live in the Tonlé Sap Lake area, which accounts for about 60% of Cambodia's annual freshwater catch of over 400,000 tons, account for 60% of the country's population's protein intake.{{cite web|website=Wildlife Conservation Society|title=The Tonle Sap Lake and Floodplain |url=https://cambodia.wcs.org/Saving-Wild-Places/Tonle-Sap-Lake-Floodplain.aspx|access-date=9 March 2021}}{{cite web|last=Regional Office for Asia and Pacific|title=Tonle Sap Fisheries|url=http://www.fao.org/docrep/004/ab561e/ab561e07.htm|website=FAO|access-date=30 April 2013}} Most fish are eaten fresh, and savory and fermented fish paste Prahoc is usually marinated from the least popular fish or leftover fish that cannot be sold fresh.{{cite book |url=http://www.fao.org/docrep/005/y4586e/y4586e04.htm | title=CASE STUDY No. 3: TRADITIONAL USE AND AVAILABILITY OF AQUATIC BIODIVERSITY IN RICE-BASED ECOSYSTEMS | publisher= Food and Agriculture Organization of the United Nations |access-date=18 May 2015}} For more than a century, the most productive lake areas have been privatized through a government-lease system of fishing grounds, providing more than $2 million in tax revenue annually.{{cite web|last1=Van Zalinge|first1=Nicolaas|title=Data Requirements for Fisheries Management in the Tonle Sap|url=http://www.fao.org/docrep/005/ad070e/ad070e0a.htm|website=FAO Regional Office for Asia and the Pacific|publisher=UN FAO|access-date=4 January 2018}}

File:Floating_school_at_Tonle_Sap.jpg

Since Buddhism is against killing, fishermen tend to limit their catch to what they can feed their families. They do not kill the fish with their own hands but wait for the fish to die naturally after they leave the water. At the end of the rice season, people restore canoes that have been in use for hundreds of years or build new canoes when they can't be repaired in temples along the river, in preparation for the boating competition of the water festival. After two days of racing all the canoes come together to celebrate the Naga, the water serpent, who supposedly spit out the lake into the sea at the end of the rainy season,{{cite AV media |people=Didier Fassio (director) |date=2002 |title=Children of the Seven-Headed Snake: The Sacred Waters of Cambodia|url=https://emro.libraries.psu.edu/record/index.php?id=1061 |access-date=9 March 2021 |format=Video |publisher=Ampersand}} while bringing fish into the Mekong through the Tonlé Sap River.

The area is home to many Cambodians of Vietnamese origin who live in floating villages on boats by the lake.{{cite news |date=18 October 2020 |title=Quyên góp gây quỹ ủng hộ người gốc Việt trên Biển Hồ Campuchia |url=https://www.vietnamplus.vn/quyen-gop-gay-quy-ung-ho-nguoi-goc-viet-tren-bien-ho-campuchia/669948.vnp |accessdate=20 March 2022 |agency=vietnamplus}} Most of the fishermen of Tonlé Sap Lake are of Vietnamese origin. They have lived in Cambodia for a long time and are the main suppliers of the country's fishery market. They had to flee to Vietnam during the Khmer Rouge reigning era from 1975 to 1979. Only returned after the downfall of the regime and continued to fish in the Tonle Sap.{{cite news|last1=Seiff|first1=Abby|title=When There Are No More Fish|url=https://www.eater.com/2017/12/29/16823664/tonle-sap-drought-cambodia|access-date=4 January 2018|work=Eater|date=29 December 2017}}

{{Portal|Cambodia|Lakes}}

{{Columns-list|colwidth=30em|

• Battle of Tonlé Sap
• Climate change in Cambodia
• Mekong River Commission
• Hydropower in the Mekong River Basin
• List of rivers of Cambodia
• Mekong Delta
• 2007 Tonlé Sap dragon boat accident

}}

{{Reflist}}

• Kuenzer, C. (2013): "Field Note: Threatening Tonle Sap: Challenges for Southeast-Asia’s largest Freshwater Lake." In: Pacific Geographies 40, pp. 29–31.
• Milton Osborne, The Mekong, Turbulent Past, Uncertain Future (Atlantic Monthly Press, 2000) {{ISBN|0-87113-806-9}}

{{Commons}}

• {{usurped|1=[https://web.archive.org/web/20120428152611/http://www.mekong.waterandfood.org/ CPWF-Mekong]}}
• {{usurped|1=[https://web.archive.org/web/20071016045954/http://www.3spn.org/ 3S Rivers Protection Network]}}
• [http://www.usyd.edu.au/mekong/ Australian Mekong Resource Centre]
• [http://www.cnmc.gov.kh/ Cambodia National Mekong Committee]
• [http://www.ensp.umd.edu/Academics/399C_18.Mekong.doc THE STRATEGIC SIGNIFICANCE OF THE MEKONG By: Osborne, Milton]{{dead link|date=February 2024|bot=medic}}
• [https://www.washingtonpost.com/wp-dyn/articles/A35167-2004Dec29.html Washington Post]
• {{usurped|1=[https://web.archive.org/web/20050521025435/http://earthtrends.wri.org/pdf_library/country_profiles/Coa_cou_116.pdf Country Profile]}}
• {{usurped|1=[https://web.archive.org/web/20200809095057/http://www.journalsonline.tandf.co.uk/openurl.asp?genre=issue&issn=0790-0627&volume=22&issue=3 International Journal of Water Resources Development – Tonle Sap Special Issue]}}
• {{usurped|1=[https://web.archive.org/web/20031209061304/http://www.eia.fi/wup-fin/ Tonle Sap Modelling project (WUP-FIN) under Mekong River Commission]}}
• [http://www.mekong-protected-areas.org/cambodia/pa-map.htm Protected areas in Cambodia] {{Webarchive|url=https://web.archive.org/web/20110927190625/http://www.mekong-protected-areas.org/cambodia/pa-map.htm |date=27 September 2011 }}

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Category:Lakes of Cambodia

Category:Biosphere reserves of Cambodia

Category:Shrunken lakes

Category:Tributaries of the Mekong River

Category:Freshwater ecoregions