Geography

The Mekong River's journey

The Mekong is one of the great rivers of the world – and one of those least controlled by humans. It is subject to great variation in height between the wet and dry seasons. In places you can stand at a point where your feet would be wet in the wet season, and look down ten metres to where the level is during the dry season.

For much of the 20th century the area has been the scene of wars, which meant that there was no money or political structure to develop and control the river.

As you read the following description, you will see the term 'Mekong Basin'. That is the area of land draining into the Mekong River. Look at a map showing the physical relief of the area to help you see how it works.

The Mekong begins 5,000 metres above sea level, in the snow-covered mountains of the Tibetan plateau. It drops to 2,000 metres through bleak gorges to enter the Chinese province of Yunnan, where it traverses some of the grimmest, most inaccessible terrain in the world.

The government of Tibet has adopted a deliberate policy of not interfering with the river, as they realise that it is vital to the other countries through which it flows. They are knowingly limiting their own development by this policy.

For the next 1,200 kilometres the Mekong travels south; the topography is still hostile and the river still isolated from much human interference – though this is changing. China is keen to develop Yunnan, one of the poorest provinces of China, and this will involve harnessing the water of the Mekong for hydroelectricity to power industrial development in the area. A dam has recently been built, and already there are factories polluting the water as it leaves China. This pollution dissipates as the river continues its journey.

Having completed roughly half its passage to the sea, descending 4,500 metres on the way and reaching a width of some 400 metres, the Mekong exits China at Yunnan's southern border. Curving south-west, it constitutes the border between Laos and Myanmar for more than 200 kilometres before reaching the Golden Triangle, the point where the river, joined by a small tributary, brings together the borders of three countries: Thailand, Myanmar and Laos. This junction registers the beginning of what is usually termed the 'Lower Mekong'.

What is the relationship of the Thailand, Myanmar and Laos to the Mekong?

• Of the three countries, Myanmar is least affected by the Mekong's flow, and by any upstream disruption to it.
• Ninety percent of Laos' population is directly dependent on water and agriculture in the Mekong Basin, but as a number of tributaries flow into the Mekong through Laos, so again this country is not greatly affected by upstream development along the Mekong.
• Laos's present uses of the water are mainly for fishing, tourism and transport. But Laos is ideally placed to use the water to generate hydroelectricity and to sell that electricity to the industrialising Thailand.
• Only 36 percent of Thailand's territory is within the Mekong Basin, but that includes its poorest areas. Thailand is looking to use the water to power industrial development in the area, and to enable it to use its neighbours' natural resources. So the Mekong is significant for Thai development.

From the point where the Mekong leaves China, it has only 50 metres left to descend to the sea, which means that it slows down; although there are places where it still flows rapidly through narrows and over rocks.

For a little way beyond the Golden Triangle the Mekong forms the border between Laos and Thailand, but it soon swings east into Laotian territory. Near the ancient Laotian capital of Luang Prabang the river turns south and re-joins the Thai border 250 kilometres later. It continues as the border.

The river now flows smoothly and broadly – up to 1.2 kilometres wide in places – past the Laotian capital of Vientiane, until it flows over the rugged Khone Falls and enters Cambodia, where it is traditionally known as the Thonle Thom. It creates a vast flood plain in Cambodia, until it reaches the Cambodian capital of Phnom Penh.

Nearly all of Cambodia is in the Mekong Basin. Disruption of natural flow upstream would affect Cambodia greatly, as would flood control systems downstream in Vietnam. Cambodia depends on the regular flow of the Mekong for the annual flooding of the Tonlé Sap, a large lake area in Cambodia. During the wet season water actually flows upstream to the Tonlé Sap, as the waters of this tributary cannot enter the fast-flowing Mekong. This regular flood cycle deposits silt for the next season's rice crop, as well as being essential in fish breeding. Changes to this cycle would disrupt Cambodians' lives and economy greatly.

At Phnom Penh the river forks into two streams: the Mekong proper, and the Bassac. The fork creates the apex of the Mekong Delta, a triangular area with its base along part of Vietnam's south-eastern coast. Below the Cambodia–Vietnam border, the Mekong and the Bassac split further and the waters fan out over a richly fertile area of nearly 50,000 square kilometres.

This area, covering only 20 percent of Vietnam's territory but housing over 40 percent of the population, depends on the river floods. The floods dump the silt which is essential for rice growing – the main activity of the area – and also flush out salt which seeps up during the periods of low river flow. A change in the normal flow of the river could bring devastation to Vietnam.

The river finally empties in the South China Sea through numerous mouths; said to be nine, an auspicious number for Vietnamese people. 

Role play: Should the Mekong be dammed?

Roles for participants

The Mekong River Commission was set up in 1992 to coordinate the development of the Mekong River. Full members include Vietnam, Thailand and Laos. Advisory members are China and Tibet, and Myanmar.

The following are typical statements from a range of people living in or involved with the Mekong Basin. The various speakers are responding to the proposed or past building of dams at different points along the river.

The Pla Buk or Giant Catfish is an extraordinarily large fish. It is unique to the Mekong Basin. If we do not preserve it now, it will disappear under development. The Pla Buk must migrate to spawn, and dams will stop the migration. The Pla Buk is of no great economic significance, but it should not be destroyed.

Forestry is a major industry in the area. What will happen to the trees when the area is flooded?

We do not want to damage the river, but industry is necessary for areas of China near the river for us to develop out of poverty. We have no alternative.

This area is the cradle of civilisation, and it is still virtually unexplored archaeologically. Much evidence about human history may be buried here. Once it is flooded for a dam, the evidence will be lost forever.

Fishing is a major industry in this region. Hundreds of thousands of tonnes are fished every year. Most local families supplement their income by fishing. When the dam is built there is a danger that it will suit some species which will increase their numbers, but that will drive away all others. So damage will be done to the variety of fish stocks available.

Our people live in poverty. Infant mortality is increasing. We need to increase people’s standard of living. The development which the dam will bring will achieve this by giving us a product – electricity – that we can sell to other countries which are already developed economically. People who are already developed should not try and stop us from gaining these economic and social benefits as well.

What about us? We people who live in the area will lose our homes, our land, our livelihood.

Dams will improve navigation along the river as it will be possible to travel on the river all year once dams regulate the flow. This will increase business and tourism and will make goods more readily available to people.

Flooding will cause a loss of habitat for some large animals and land-based birds, though water birds will increase greatly.

Tibet will not be affected, because we have the source of the river. We are keen to keep the river as natural as possible and will not develop it or pollute it for others downstream, but that means we are losing potential revenue which could improve the standard of living for our people. We think other countries should pay us some compensation for this.

The dam will hold back destructive flood water and allow plenty for the dry seasons, so areas now unproductive can grow rice through irrigation. This will be a wonderful advantage for many areas.