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Lake Profile

Tonle Sap (Boeng Tonle Chhma)

General Information

Description Tonle Sap is Southeast Asia's largest freshwater lake. Flooding during the rainy season each year reverses the flow of the Tonle Sap River and triples the surface area of the lake. Large areas of grassland and forest are flooded, creating a highly productive area that supports one of the largest freshwater fisheries in the world.
Country Cambodia
Latitude 12° 58' 48" (12.9800)
Longitude 103° 54' 0" (103.9000)
River Basin Mekong


 Tonle Sap global index map (LakeNet Explorer)
 Largest Lakes in the World by Area (LakeNet Explorer 2004)
 Tonle Sap locator map
 Lake Basin Management Initiative (LakeNet Explorer)

Physical Characteristics

Description The surface area of Lake Tonle Sap varies greatly by season. Data sources report surface areas of from 2,569.9 km2 to 30,000 km2. Furthermore, as the main Mekong flood level heightens each year during the southwest monsoon every June or July, the direction of flow of the Tonle Sap River reverses, creating the exceptional water regime with huge changes in the lake water level (from about 1m up to 10 meters) and water volume (from about 2,500 km2 to approximate 11,000 km2) between seasons.
Volume 40.00 km3
Surface Area 13,000.00 km2
Depth Mean depth: 1.0 m
Maximum depth: 10.0 m
Origin River
Type Fresh
Catchment Catchment size: 70,000.00 km2
Catchment/surface area ratio: 5:1


Economic Value Tonle Sap provides 75% of Cambodia's national inland fish production. Fishing and agricultural activities around the lake support 1.2 million Cambodians. Fish from Tonle Sap are thought to be the single main source of protein for the Cambodian people.

Approximately 3 million people live around the lake.

Major Cities

Watershed Management

Description The Tonle Sap Biosphere Reserve management is based on identifying three zones (core areas, buffer zone and transition zone) and identifying different management goals for each. The core areas are set aside for long term protection and conservation.
Issues Fish stocks and catch are dropping, deforestation is widespread and sewage & other waste are polluting the lake, which provides drinking water for thousands. The largest threats to the flooded forests are the clearing of forests to make way for agricultural land, collection of firewood, and collection of wood for fish traps.
Other Issues Erosion
Nutrient pollution

Biodiversity Conservation

Description Tonle Sap is home to more than 200 fish species, 70 of which are of commercial value. 23 snake species, 13 turtle species, a crocodile species, macaque and leopard cat are among the species identified in Tonle Sap Lake. The variety of biodiversity in Tonle Sap is understudied.

69% of the original forest in the Mekong River basin has been lost. The deforestation rate is 16%.

Designations Biosphere Reserve
LakeNet Biodiversity Priority
Ramsar Site
WWF Global 200
Ramsar Site Name Boeng Chhmar and Associated River System and Floodplain
Ramsar Designations 1, 2, 3, 5, 6
Species of Concern There is heavy exploitation of Tonle Sap's endemic watersnake Enhydris longicauda for use as crocodile food (crocodiles are farmed commercially near the lake) and human food. Harvests of homalopsine watersnakes appears to be highly unsustainable; data gathered durin 1999 and 2000 indicate that more than 8,500 watersnakes per day were being harvested and sold during the peak of the wet season.


Community Forestry International
Mekong Wetlands Biodiversity Conservation and Sustainable Use Programme

LakeNet Programs

World Lake Basin Management Initiative
LBMI Regional Experience Sharing & Review Workshop for Asia


Adaptive Learning: Lessons from Southern Lao PDR  Case Study. Final. MRAG Ltd.. 9/17/2004.
Managing Lake Basins for Sustainable Use - Lake Basin Management Initiative Final Report (PDF)  Project Report. Final. English. 2/27/2006.
Tonle Sap  (PDF) Experience Brief. Final. 2/27/2006.
Tonle Sap: World Bank Comments on Experience Brief  Experience Brief. Draft. World Bank. 3/22/2004.


Adaptive Learning: Lessons from Southern Lao PDR
Biodiversity Conservation of the World's Lakes: A Preliminary Framework for Identifying Priorities
Crop Explorer - Global Reservoir and Lake Elevation Monitoring
Crop Explorer - Lake Level Variations from TOPEX/POSEIDON and Jason-1 Altimetry for Tonle Sap
Greater Mekong Subregion Atlas of the Environment
Helsinki University of Technology / WUP-FIN: Tonle Sap Web Page
ILEC Database
ILEC Database
Mekong River Basin & Tonle Sap Lake
Mekong River Basin map & information
River at risk: the Mekong and the water politics of China and Southeast Asia
Tonle Sap Biosphere Reserve
Tonle Sap Environmental Management
Tonle Sap Environmental Management Project, Asian Development Bank
Tonle Sap Modelling Project
Tonle Sap Ramsar Fact Sheet


6/27/2006 - Thai Dam Casts Long Shadow Over Asia Dam Wars
4/7/2005 - Disappearing Lakes, Shrinking Seas
4/23/2004 - Towards a Lake Basin Management Initiative
4/19/2004 - First Great Mekong Atlas Reveals Problems
11/30/2003 - Mekong River Commission countries sign off on two procedures for water use
8/1/2003 - Good report on basin health - so far
5/19/2003 - Project to ease hardship on Southeast Asia's largest lake
5/15/2003 - Managing & conserving natural resources & biodiversity in Cambodia's Tonle Sap
4/29/2003 - For lake's ecology, a murky future
3/10/2003 - Rising water, deeper man-made problems for Tonle Sap river basin
1/7/2003 - Cambodia: downstream culture: life on the Tonle Sap
11/21/2002 - Conservation Initiative to protect resources and livelihoods in Cambodia's Tonle Sap
5/24/2002 - Mermaid myths, travelers help rare Mekong dolphin
1/10/2002 - Mekong Giant Catfish return to the Mun River
12/1/2000 - The harvest and trade from Tonle Sap, Cambodia in Homalopsine watersnakes
6/29/1999 - Cambodian great lake area may have hydrocarbons
2/12/1999 - Fish past frensy thins Cambodian shoals
1/12/1994 - Mekong ecology threatened by siltation, deforestation

Additional Data Sources

Birkett, C., and I. Mason. 1995. A new global lakes database for remote sensing programme studying climatically sensitive large lakes. Journal of Great Lakes Research, 21 (3) 307-318.
Duker, L. and L. Borre. 2001. Biodiversity conservation of the world's lakes: a preliminary framework for identifying priorities. LakeNet Report Series Number 2. Annapolis, Maryland USA.
International Lake Environment Committee, the United Nations Environment Program and Environment Agency, Government of Japan. 1997. World Lakes Database.
TRAFFIC Bulletin. Vol. 18 No. 3. December 2000.

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