Mekong River

The Mekong River Overview:

Mekong River Overview (MRC,2011)

The Mekong River is the tenth-largest river in the world, approximately 4,909 km, with drainage areas 795.000 km² from the eastern watershed of the Tibetan Plateau to the Mekong Delta through three provinces of China, continuing into Myanmar, LAO PDR, Thailand, Cambodia and Vietnam before emptying into the South China Sea. There are seven broad physiographic regions featuring diverse topography, drainage patterns and geomorphology including the Tibetan Plateau, Three Rivers Area, Lancang Basin, the Northern Highlands, Khorat Plateau, Tonle Sap Basin, and Mekong Delta. About 60 million people live in the Lower Mekong Basin (LMB) and while continued economic growth has led to a significant improvement in living standards in recent years, yet many of basin's population still live in poverty.

Major Tributaries and Distributaries:  

In the Upper Mekong Basin, large tributaries are Nam Ta, Nam Ou, Nam Soung and Nam Khan which enter on the left bank; the Nam Mae Kok and Nam Mae Ing enter on the right bank. Further downstream, the mainstream is joined by Songkhram and Mun River on the right bank and Nam Ca Dinh, Se Bang Fai and Se Bang Hiang Rivers on the left bank. In the Tonle Sap Basin, the 3S Basin (Se Kong, Se San, and Sre Pok) is the dominant tributary entering from the left bank while the Tonle Sap Lak, an unusual amazing flow direction, drains the Great Lake into the Mekong River during dry season and reverses its flow during the wet season. The Mekong Delta begins near Phnom Penh and end up in southern Vietnam where the largest tributary, the Bassac River, split into a number of smaller distributaries, forming an area known as "Nine Dragons". 

Irrigation:

Agriculture in Mekong River Basin

The irrigation sector is the largest water users in the LMB, consuming an estimated 41.8 billion cubic meters of freshwater resources per year. More than half of this water use takes place in the Vietnam delta, followed by Thailand, Lao PDR and Cambodia. The assessment of irrigation in the LMB recorded almost 15,000 irrigation projects, varying from small to large scale, and from gravity to pump-fed irrigation. Along with their main use for growing rice, paddy fields provides many other benefits, such as providing a habitat for fish and other animals.

Water Quality:

Regular monitoring since 1985 shows that the Mekong River has generally good water quality apart from some areas near urban centers. Water quality of almost all the mainstreams monitoring stations is rated as 'excellent' for the protection of aquatic life, while the situation is different on some tributaries, where the water is classed as 'moderate' quality, may be threatened of impaired. The recent studies also indicate the presence of persistent organic pollutants in sediment and aquatic organisms in Mekong Delta. Water pollution from industrial sources has been identified in Vientiane and Phnom Penh, and more gradually in northeast Thailand and Mekong Delta. The problem is expected to increase over coming years.

Wetland:

Wetland plays a vital role in the lives of the basin inhabitants and socio-economic development of the region. The principle river and its tributaries, backwaters, lakes and swamps  support many unique ecosystems, such as river's deep pools, plains of reeds and mangrove forests. Natural wetlands absorb floodwaters that could be disastrous during wet season, for example Cambodia's Great Lake (Tonle Sap Lake).

Biodiversity:

The Mekong Basin is one of the most richest areas of biodiversity in the world. Its wetland and forest ecosystem provides a ranges of habitats of flora and fauna. The estimation of biota of the greater Mekong region include 20,000 plant species, 430 mammal, 1,200 bird, 800 reptile and amphibian, and 850 fish species. The inland fisheries yield was estimated at 2.6 million tonnes per year in the LMB, which is the world's largest fresh water yield. Many aquatic or semi-aquatic turtles, snakes and lizard are hunted for subsistence or sold for food or medicine.

Transportation:

Transportation in along the Mekong River

Mekong is an essential transportation for many people living in the region and plays an increasingly important role in international trade and tourism. The Mekong river and its main tributaries are navigable during the high-water season (about eight months of the year) with exception of a 14 km section just north of the border between Cambodia and Lao PDR - the impassable Khone Falls. 

Hydropower:

Hydropower station (http://mekongriver.info/hydropower)

The potential of hydropower in the Mekong River Basin is about 53,000 MW consisting of 23,000 MW in the Upper Mekong Basin and 30,000 MW in Lower Mekong Basin. The current stage of the projects are 26 projects in mainstream and 126 projects in the tributaries. There are four operating hydropower in Yunna province of China with capacity of 8,850 MW, and other three projects are under construction. The tributaries in LMB are currently producing 3,225 MW (10% of potential), and 3,209 MW are under construction. The mainstream of the LMB has potential to produce over 13,000 MW of hydropower. Twelve hydropower project   have been proposed. Those proposals are among the largest and most significant developments ever considered by LMB countries in terms of benefits and risks. 

Climate: 

The climate of the Mekong Basin is dominated by the Southwest Monsoon, which generates wet and dry seasons of more or less equal length. The Southwest Monsoon generates the wet season which usually lasts from May until late September or early October. Tropical cyclones occur over much of the area during August and September and even October are the wettest months of the year in delta. The Northeast Monsoon brings lower temperatures from China and causes dry weather in the Lower Mekong Basin from late October until April.  Rainfalls of more than 2,500 mm/year occur in western mountain regions of Lao PDR while less than 1000 mm/year in central regions of Thailand. Estimated mean annual flow of the Mekong River Basin is almost 460 km³ which about 75 percent of total flow is within just four months between July and October. 

Flood: 

Flooding in Mekong River Basin

Annual floods have the potential to cause damage to unprepared communities, spoil crops and endanger food pulses sustain in the world-renowned productivity of the Mekong freshwater fisheries. The average annual cost of the flood in LMB ranges from US$60 to 70 million, while the average annual value of flood benefits is approximately US$ 8-10 billion. The goal and challenge of flood management is to reduce the costs and impacts of flooding while preserving the benefits. 

Drought: 

Unlike floods, droughts have less apparent benefits. Drought can result in food and water shortages, loss of income, and higher levels of disease. Drought are damaging to agriculture, especially rice and can result in a total loss of crops, livestock and fisheries. In response to the threat of drought, efforts are being made to devise strategies that aims to decrease the vulnerability of people in the basin, especially in agricultural communities. 

Integrated Water Resources Management:

IWRM is a process that promotes the coordinated development of water land, and resources, in order to maximize economic and social welfare in a balanced way without compromising the sustainability of the ecosystems. The IWRM-based Basin Development Strategy of the Mekong River Commission enables country members to set out how they will share, utilize, manage and conserve the water and related resources of the Mekong. The strategy provides an integrated basin perspective against which current and future national water resources development plans can be assessed to ensure an acceptable balance between economic, environmental and social outcomes in the LMB, and mutual benefits to the LMB coutries by:

- Defining the scope of opportunities for water resources development (hydropower, irrigation, water supply, flood management) and their associated risks and required action to optimize the opportunities and minimize the risks;

- Defining other related water-related opportunities (fisheries, navigation, environment and ecosystems, watershed management); and

- Proving a coordinated, participatory and transparent process that promotes sustainable development. 

Reference:

MRC, (2011). Planning atlas of the lower Mekong River basin. Mekong River Commission. 

MRC, (2010). State of the basin report of the lower Mekong River basin. 
Mekong River Commission.

by Sophal Try

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