Mekong River

Factfile

Length: 4,350 km
Sources: Lasagongma Spring, Tibetan plateau
Key Tributaries: Nam Ta, Nam Ou, Nam Soung & Nam Khan (left bank); Nam Mae Kik & Nam Mae Ing (Right Bank)
Basin area: 795,000 km^2

Countries within: Tibet, China, Myanmar, Thailand, Lao PDR, Cambodia & Vietnam
Basin Population: ≈70 million
Discharge: 16,000 m³/s

Physical Geography

The Mekong is one of Asia’s key river systems covering a total area of 795,000 km² with the river itself flowing from its source, Lasagongma Spring, in the Tibetan plateau through 7 Nations before reaching the mouth of this system in the Mekong delta situated in Vietnam.

Formation/Geology

The mekong begins its journey in the same region as another two of Asia’s great rivers the Yangtze and the Huang He within the Sanjiangyuan National Nature Reserve along the Tibetain Plateau. The Mekong then flows through the Three Parallel river area along with the Salween and Yangtze rivers before reaching the border of Thailand, Myanmar and Laos the Mekong then flows eastwards from the tripoint border forming a minor international border between Thailand and Laos before it continues its journey east into Laos for approximately 400 km before once again returning to the border of Thailand and Laos where it continues to flow for approximately 850 km. Once the river has flown this distance acting as the Laos-Thailand border it then flows through Laos into Cambodia where the river continues to flow through cambodia to Vietnam where the Mekong finally reaches the South China Sea at this point the river begins to form one of the Mekong delta. A unique characteristic of the Mekong is also identified within the lower course of the river with three quarters of the total drainage area of the Mekong basin being situated in this region, while the remaining quarter of drainage comes as a combination of both the upper- and middle-course of the river.

Geomorphology

The Mekong is the longest river in Southeast Asia, spanning from its source in eastern Tibet to its mouth in the South China Sea. Much of the upper-course of the river is dominated by the geology of the Yunnan highlands with the river flowing 1,955 km through the narrow steep sided valleys of the region eroding its way through the mountains and plateaus of Southwest China. The river continues its journey meandering throughout southeast asia before reaching the South China Sea in Vietnam, at this the mekong begins to deposit a large portion of the fluvial sediments from within the river forming the basin.

Climate

The Mekong basin spans a large area of Southeast Asia as a result there is a large level of variation within the catchment area, as seen in average precipitation and temperatures that are seen in the Mekong basin. The flow of the Mekong is mainly supported by the precipitation that occurs in the lower course of the basin, with the monsoon climate of the region being most prevalent in the basin from May or June as a result of the southernly monsoon this continues for a number of months. The southerly monsoon is replaced in November with the northeasterly monsoon winds bringing a dryer climate to the region until May. The upper Mekong basin is dominated by the colder temperature of the Tibetan plateau with more seasonal variation in the region, while temperatures across the lower basin is warm throughout the entire year with average temperatures ranging from highs of 32°C and lows of 23°C.

Ecosystems

The Mekong Basin has high levels of biodiversity being the second most biodiverse region in the world, with many different ecosystems and biomes, throughout the whole catchment spanning across a large proportion of Southeast Asia. The lower Mekong region contains approximately 54 million hectares of forest, supporting a diverse array of habitats with ruch with flora and fauna.

Ecological Setting

The Mekong basin is extremely rich and diverse with the basin being home to 16 of the 200 designated ecoregions of the WWF. The greater Mekong region includes an extremely high level of biodiversity with many different ecoregions with their own unique ecosystems. The region is home to high levels of diversity in both flora and fauna including 20,000 plant species, 430 mammals, 1,200 birds, 800 reptiles and amphibians and an over 850 fish species with the identification of more species with time.

Flora

Flora in the mekong is extremely diverse with an excess of 20,000 plant species identified within this region. These species are mainly located in the lower mekong region where many different forms of habitats with wet evergreen forests, in the indo-malysian region, Semievergreen forest, mixed deciduous forest*, created by the dominant monsoon climate of the region, deciduous dipterocarp woodland, wetlands

*contains small trees, shrubs and bamboo forests

Fauna

Mammals

Irrawaddy dolphin
Murina kontumensis
Myanmar snub-nosed monkey
Daovantein’s limestone rat
Indochinese tiger

Soala
Wild asian elephants
Yellow-cheeked crested gibbon

Amphibians

Odorrana mutschmanni
Samkos bush frog

Birds

Gould’s Sun Bird
Grey Crowned Crocias
Bengal Florican
Collared Laughingthrush

There are two distinct types of evergreen forests: lowland and montane evergreen forests that are home to diverse bird species. In the lowland forests, typical species include cuckoos, bulbuls, flowerpecks, woodpeckers, hornbills and barbets. Upper montane evergreen forests standing at heights of 1,700 meters above sea level are rich in bird species that include flycatchers, babblers, thrushes and warblers. This is also where rare Collared Laughingthrush and Grey-crowned Crocias reside.

Aquatic

With over 1,300 species of fish, the Mekong River is the world’s most productive inland fishery. Providing livelihoods to 60 million people, this fishery accounts for up to 25% of the global inland catch, providing up to 80% of all animal protein into the people of the Mekong River basin. Fisheries in the Mekong River are worth 2.5 billion USD per year to the countries of the Mekong.

Many of the species in the Mekong are endemic. Many are super-sized. Among the species of the Mekong are some of the world's most charismatic fish including four to the world's largest:

Giant freshwater stingray - Himantura chaophraya (up to 600kg)
Mekong giant catfish - Pangasianodon gigas (up to 350kg)
Giant pangasius - Catlocarpio siamensis (up to 300kg)

Endangered species

Beyond fish, the Mekong basin is also home to a tremendous diversity of endangered species such as:

Irrawaddy dolphin - Orcaella brevirostris
Giant Ibis - Pseudibis gigantea
Siamese crocodile - Crocodylus siamensis

Human Geography

The Mekong basin is a region that has experienced a large economic growth over the past 20 years with an average gross domestic product (GDP) increase of 6.5% for the whole mekong basin, while a large portion of the population within the basin remains poor. The GDP increase has occurred due to the abstraction of natural resources within the catchment. This is seen across the basin with water resources of the mekong being used to support fisheries as well as for hydro-electric power, fertile land paired with the basin’s climate has led to the growth of agriculture, logging has increased due to the abundance of forests and mineral extraction is leading to the growth of the mining industry. The main issue associated with the increase in activity across the basin comes from the often unsustainable practices that are implemented in this region to obtain these resources, leading to major environmental issues.

Due to current anthropogenic actions within the basin including the extraction of natural resources through mining and deforestation efforts, the resilience of the ecosystems in the Mekong basin to recover has decreased as such this increases the vulnerability of the catchment. As such, this could potentially lead to a positive feedback loop wherein the environment throughout the basin deteriorates leading to further losses in the ecosystems of the catchment threatening the health of the basin and how the basin will respond to other changes.

Pollution

A major threat to the sustained health of the Mekong basin is pollution, there are many sources of pollution throughout the basin ranging from the industrial and mining activities, agricultural and aquacultural practices to sewage discharge and littering. Pollution has become that much of an issue across the basin that as recently as 2019 severe pollution in southern Vietnam led to the waterways within the Mekong Delta turning black and killing biota within the river. This was as a result of the discharge of untreated wastewater from industry within the delta and further impacted the water resources of those living in the basin with water treatment facilities sourcing drinking water from the polluted waters of the mekong. Agricultural activities such as the over use of fertilisers, pesticides and herbicides have severely impacted the overall health of the fluvial environment with the runoff of these materials into the fluvial environment impacts the biota living within the Mekong. These practices can lead to an increase in eutrophication events throughout the catchment leading to losses in biodiversity throughout the basin. Another key issue for the pollution of the Mekong stems from anthropogenic actions with littering leading to an abundance of plastics and microplastics within the mekong severely impacting not only the health of the wildlife within the river but also the marine environment as this material is discharged into the South China Sea. These plastics also pose a potential to negatively affect human health within the basin with an increased consumption of the microplastics from environmental sources such as river water.

Deforestation

There have been many changes across the Mekong Basin with deforestation occurring in many of the Mekong countries with losses being seen in thailand, laos and cambodia losing <1.5 million hectares, 1 and 2.5 million hectares respectively. This was seen across a small timeframe with the loss of 1.55 million hectares being seen between 1990 and 2005. The only country with positive changes in forest cover is Vietnam where there has been an increase of some 5 million hectares.

Climate Change

The Mekong river basin is a system that is at high risk as a result of climate change with much of the basin being situated in a low-lying region creating a greater level of susceptibility to increases in sea-level, flooding events as well as an increased exposure to severe storms. More contributing factors to the susceptibility of countries within the Mekong basin include increased temperatures, changes in precipitation patterns and a heavy anthropogenic dependence on natural resources meaning that the population of the basin will be vulnerable to climate change. Climate change across the basin further exacerbates pre-existing issues that are seen in the basin, with an increased threat to biodiversity loss and changes to the region’s available natural resources. A prime example of the exacerbation of current issues can be seen with water scarcity across the basin, changes to the climate will further the scarcity issue leading to a reduction in agricultural practices which then impacts both food supply but also the livelihoods of those who work in this industry.

The strain of climate change on the environment, including increased temperatures, changes in precipitation and other aspects of climate change, can also make the region more susceptible to further environmental decay as a result of the human pressure on the catchment. This could potentially lead to an increase in fires across the basin, water quality and quantity issues as well as an increase in the number of invasive species within the basin. These impacts not only affect the overall health of the Mekong basin’s environment and ecosystems but also the humans living within the basin leading to negative impacts on the conditions within the basin in terms of economics and also general living conditions.