Rivers and lakes


The most important of the region’s river systems is the Mekong, which is associated with Cambodia’s biodiverse and environmentally critical Tonle Sap Lake. Other important river systems include:

  • The Ayerwaddy (alternatively spelled Irrawaddy), the dominant river system in Myanmar;
  • The Salween, which makes up part of the border of Thailand and Myanmar;
  • The Chaopraya, which flows through central Thailand and is its dominant river system, and
  • The Red River, also called the Hong River in Vietnamese, the most important river system in northern Vietnam.


Like the Mekong, the Salween and Red rivers originate in China, while the Ayerwaddy and the Chaophraya originate in the mountains of Myanmar and Thailand respectively. The Salween has the second largest river basin in the region, after the Mekong.

Rivers are critical not just because of their water but because of the sediment they carry.  Sediment is critical for replenishing flood plains and deltas and re-enriching soils. As the hydrology of the landscape changes so do the sediment flows. If too much sediment enters a river as a consequence of deforestation or environmental degradation its weight may cause it to be deposited too early, silting up parts of the river and further affecting water flows and the ecology of fish. Sediments may also be trapped behind dams and in reservoirs. This means that not enough sediment makes it downstream to be deposited in floodplains and deltas.  This leads to a loss in soil fertility and the subsidence or shrinking of deltas.

Please zoom in and out to see rivers in greater detail. For an overview of rivers and lakes with hydrosheds, please visit the map explorer.

Since 2007, the Mekong and Salween rivers have been listed among the world’s top ten rivers at risk. 1

Threats to the rivers include dams, over-extraction (of water and sand), over-fishing, pollution, transport and shipping, climate change, loss of watershed forests and wetlands, and invasive species.


The Tonle Sap is the region’s most important lake because of the critical role it plays in maintaining the environmental health and biodiversity of the Lower Mekong.

Tourists being transported across Inle Lake, Nyaungshwe Township, Taunggyi, Shan State. Photo: Nyein Chan Naing/EPA

Tourists being transported across Inlay Lake, Nyaungshwe Township, Taunggyi, Shan State. Photo: Nyein Chan Naing/EPA

Other important lakes include Myanmar’s Indawgyi, which is Southeast Asia’s largest lake and one of its most biodiverse; and Inle, another large and biodiverse lake in Myanmar, increasingly important for tourism. 

Read more about the region’s most important river system, the Mekong.


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