Rivers, lakes, forests and soil do not exist in separate environments, but are part of ecosystems that interact and support each other. A watershed is the area of land where this interaction takes place. Water from rain, streams and other water bodies run through the land to a common point, such as a bay, a stream channel or a reservoir. A watershed may also be called a catchment or basin.

Flooded forest, Cambodia Flooded forest, Cambodia. Photograph by Bernard Tey. Cropped.
Licensed under Creative Commons Attribution-Non Commercial 2.0.

In the case of the Mekong River, river water flows from the mountains in the Himalayas, down through the basin to the Mekong Delta, and out into the East Vietnam Sea. As it flows, water is also collected from rain run-off, and from the water table beneath the land.

Watersheds are impacted by many factors, through interaction with both natural elements and human activity in the area. The trees and plants in forests not only tap into the water within the soil, but they also affect the quality and composition of the soil itself, filtering rain water and run off as it flows to streams or down into the water table.

Mekong River profile Map showing the course and elevation of the Mekong River through five countries1


Similarly, agricultural land will affect the composition, chemical balance and quality of the soil, which also impacts the quality and amount of water travelling through the watershed.

Landslides, soil erosion, floods, biodiversity loss, and unsustainable water extraction and farming practices are some of the main reasons for watershed degradation, leading to loss of soil fertility, water tables and springs, as well as desertification and sedimentation.2

The Mekong River Commission was established in 1995 when the governments of Cambodia, Laos, Thailand and Vietnam signed the “Mekong Agreement” (Agreement on the Cooperation for the Sustainable Development of the Mekong River Basin).3 It also provides for the other two countries in the Greater Mekong Subregion (China and Myanmar) to join in cooperative efforts on behalf of the life of the river system.

While the agreement does not mention the term “watershed”, it does broadly state its aim as “sustainable development and utilisation of the water and related resources and environment of the Mekong River Basin”.4

The Food and Agriculture Organization of the United Nations (FAO) has also undertaken assessment and review of its member countries’ watershed management policies and practices, both globally and at regional levels. 

Related to watersheds


  • 1. Mekong River Commission. 2011. 1995 Mekong Agreement and Procedures. Phnom Penh, Vientiane: Mekong River Commission, viii. Accessed 29 January 2015. http://www.mrcmekong.org/assets/Publications/policies/MRC-1995-Agreement-n-procedures.pdf.
  • 2. Poudel, Krishna. 2003. “Watershed management in Nepal: Challenges and constraints.” In Preparing for the next generation watershed management programmes and projects: Asia, edited by Moujahed Achouri, Larry Tennyson, Kumar Upadhaya and Roger White, 119-128. Rome: FAO. Accessed 29 January 2015. ftp://ftp.fao.org/docrep/fao/009/a0270e/A0270E00.pdf.
  • 3. The Kingdom of Cambodia, the Lao People’s Democratic Republic, the Kingdom of Thailand and the Socialist Republic of Viet Nam. 1995. Agreement on the Cooperation for the Sustainable Development of the Mekong River Basin. Mekong River Commission. Accessed 24 July 2015. http://www.mrcmekong.org/assets/Publications/policies/agreement-Apr95.pdf.
  • 4. Mekong River Commission. 2011. 1995 Mekong Agreement and Procedures. Phnom Penh, Vientiane: Mekong River Commission. Accessed 29 January 2015. http://www.mrcmekong.org/assets/Publications/policies/MRC-1995-Agreement-n-procedures.pdf.
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