Tonlé Sap

Infobox lake
lake_name = Tonlé Sap
image_lake = Tonlesap.jpg
caption_lake = NASA satellite image
image_bathymetry =
caption_bathymetry =
location =
coords = coord|12|53|N|104|04|E|type:waterbody_region:KH|display=inline,title
type =
inflow =
outflow =
catchment =
basin_countries = Cambodia
length =
width =
area = 2,700 km² (normal)
16,000 km² (monsoon)
depth =
max-depth =
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residence_time =
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cities = The Tonlé Sap (Khmer: ទន្លេសាប;), "i.e.," large body of water (Cambodian meaning "Large Fresh Water River," but more commonly translated as "Great Lake") is a combined lake and river system of huge importance to Cambodia. It is the largest freshwater lake in South East Asia and is an ecological hotspot that was designated as a UNESCO biosphere in 1997.

The Tonlé Sap is unusual for two reasons: 1) its flow changes direction twice a year, and 2) the portion that forms the lake expands and shrinks dramatically with the seasons. From November to May, Cambodia's dry season, the Tonlé Sap drains into the Mekong River at Phnom Penh. In June, however, when the year's heavy rains begin, the Tonlé Sap backs up to form an enormous lake.

For most of the year the lake is fairly small, around one meter deep and with an area of 2,700 square km. During the monsoon season, however, the Tonlé Sap river which connects the lake with the Mekong river reverses its flow. Water is pushed up from the Mekong into the lake, increasing its area to 16,000 square km and its depth to up to nine meters, flooding nearby fields and forests. The floodplain provides a perfect breeding ground for fish.

The pulsing system with the large floodplain, rich biodiversity, and high annual sediment and nutrient fluxes from Mekong makes the Tonlé Sap one of the most productive inland fisheries in the world, supporting over 3 million people and providing over 75% of Cambodia's annual inland fish catch and 60% of the Cambodians' protein intake. At the end of the rainy season, the flow reverses and the fish are carried downriver.

National and local observers often state that the Tonlé Sap Lake is rapidly filling with sediment. However, recent long-term sedimentation studies show that net sedimentation within the lake proper has been in the range of 0.1-0.16 mm/year since ca. 5500 years before present (BP). Thus, there is no threat of the lake filling up with sediment. On the contrary, sediment is not a threat to the lake but an important part of its ecosystem, providing nutrients that drive the floodplain productivity.

The reversal of the Tonlé Sap river's flow also acts as a safety valve to prevent flooding further downstream. During the dry season (December to April) the Tonlé Sap Lake provides around 50% of the flow to the Mekong Delta in Vietnam.

The lake occupies a depression created due to the geological stress induced by the collision of the Indian subcontinent with Asia. In recent years the building of high dams in Southern China and Laos has threatened the strength and volume of the reverse flow into Tonle Sap; a phenomenon that environmentalists have been slow to recognize or raise concern about. Already fish catches are significantly down.

People and culture

The area is home to many ethnic Siamese. Tonlé Sap is home to a large Vietnamese and Cham community, living in floating villages around the lake.

Incidents

Five Singaporeans from the Singapore Dragonboat team, Chee Wei Cheng, Jeremy Goh, Stephen Loh, Reuben Kee and Poh Boon San, drowned on November 23, 2007, while participating in a national dragon boat competition to celebrate the annual Water Festival. Their dragon boat capsized near a pontoon and they were believed to have been caught by strong currents and trapped underneath the pontoon. [http://ap.google.com/article/ALeqM5jqmQIKbzRB6UR5-qxj3QA-Jbrp6wD8T4JQKG0]

References

* Milton Osborne, "The Mekong, Turbulent Past, Uncertain Future" (Atlantic Monthly Press, 2000) ISBN 0871138069

External links and references

* [http://www.tsbr-ed.org Tonle Sap Biosphere Reserve : Environmental Information Database]
* [http://66.102.7.104/search?q=cache:www.ensp.umd.edu/Academics/399C_18.Mekong.doc+Milton+Osborne+mekong+cambodia+fish+protein&hl=en THE STRATEGIC SIGNIFICANCE OF THE MEKONG By: Osborne, Milton]
* [http://www.washingtonpost.com/wp-dyn/articles/A35167-2004Dec29.html Washington Post]
* [http://earthtrends.wri.org/pdf_library/country_profiles/Coa_cou_116.pdf Country Profile]
* [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]
* [http://www.eia.fi/wup-fin Tonle Sap Modelling project (WUP-FIN) under Mekong River Commission]