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Dam downstream disaster

April 2004

How and why is a dam in China affecting millions of people in south-east Asia?

Dam downstream disaster

Giant Chinese dams are threatening the livelihoods of one hundred million people in neighbouring south-east Asian nations that rely on the shared waters of the Mekong river. The governments of Thailand, Laos, Cambodia and Vietnam are increasingly concerned that previously sustainable economic activities along their own lower stretches of this continental river are now threatened by dam-building on its upper course in China.

The Mekong is south-east Asia’s longest river. Its 4,880 km journey takes it from the Tibetan plateau into China’s densely-populated Yunnan province. From there, it crosses into Burma, Thailand, Laos, Cambodia and Vietnam before reaching the sea. These Newly Industrialised Countries (NICs) are all beginning to place heightened demands on a river that only twenty years ago was still regarded as one of the world’s most untouched (The Guardian, 25 March 2004).

The Mekong River Commission - a joint Thai, Lao, Cambodian and Vietnamese government organisation – is concerned that China will retain so much water for itself that it will become impossible to meet the needs of the smaller states along the river’s lower course. The Chinese dam-building strategy includes the Manwan hydroelectric dam which was finished in 1996 and has already been blamed by Thailand for damaging its fishing industry. The Dachaoshan dam is now almost completed and work has started on a third dam, with a further six planned. For the Chinese, the benefits of dam construction are obvious:

  • A more reliable water supply can be provided for its vast population of 1.3 billion. The regime of Mekong in its natural state shows marked seasonal variations with a pronounced dry season ending around May. Dams provide an all-year regulated water supply.
  • Hydrolelectric power equivalent to fifteen major power stations is expected to be drawn from the first three dams.

However, the social, economic and ecological costs for the downstream nations include:

  • Navigational problems for boats as sandbanks emerge from the lowering waters – in Cambodia, river levels are thought to have dropped by 12%.
  • Interruption of fish migration and spawning patterns – in Cambodia, 1.5 million rely on fishing for their living.
  • Bankside agriculture is now threatened that previously relied upon floodwaters and the deposition of alluvial silts.
  • Flash flooding is expected when surplus floodwater is released unpredictably from the Chinese dams during the wet season

The situation will worsen as the downstream nations add their own dams, following recent recommendations about the importance of developing hydroelectric power in the region made by the Asian Development Bank working in partnership with the Norwegian power company Norconsult. Laos, which the Mekong enters first on leaving China, intends to build the Nam Theun dam on one of its major tributaries. This will reduce the flow into neighbouring Cambodia even further!

What are the challenges of managing continental rivers?

Freshwater yields have natural limits. The hydrological cycle on average yields a fixed quantity of water per time period and this overall quantity cannot be altered significantly by human actions (desalinisation of seawater is becoming feasible in some locations but still at a very limited scale). Freshwater resources may be regarded as a natural capital asset, which need to be maintained to ensure that the desired services they provide are sustainable in the long-term. The Global Water Partnership Technical Advisory Committee (TAC) advises that:

"Upstream-downstream user relations need to be carefully regulated. Linkages between upstream and downstream users of water must be recognised and upstream users must recognize the legitimate demands of downstream users to share the available water resources and sustain usability. Excessive consumptive use or pollution of water by upstream users may deprive the downstream users of their legitimate use of the shared resource. This clearly implies that dialogue or conflict resolution mechanisms are needed in order to reconcile the needs of upstream and downstream users."

The Colorado River faced problems of governance very similar to those of the Mekong as it became increasingly industrialised during the Twentieth Century. With its water shared between seven US states and Mexico, the Colorado has been no stranger to controversy. The Hoover Dam was completed in 1935, potentially allowing the equivalent of two years’ entire flow of river water to be stored behind it in Lake Mead! In 1944 an international agreement was reached that saw the US promising Mexico an annual supply of 1.5 million acre feet – a mere tenth of the total discharge of the river in its natural state [see Keith Hilton’s excellent book Process and pattern in physical geography (1985) for further details of Colorado management].

What are China’s growing water needs?

China’s water management programme needs to meet the needs of one fifth of the world’s entire population. Greater demands for fresh water are inevitable throughout China and the rest of the developing world as a result of:

  • Population growth, with the world’s population rising from 1 billion to 6.3 billion since 1830
  • Industrial demands for water – water is a coolant, a lubricant and often a raw material for manufacturing
  • Lifestyle and occupational changes. Personal hygiene will improve as growing numbers receive education and increasing numbers enter professional occupations (such as the new Indian call centres). Rising affluence will lead to more families owning appliances such as dishwashers and washing machines (UK Anglian Water figures currently show a per capita water usage of around 140 litres per day).

Is China beginning to show environmental concerns?

Last year Beijing announced plans to also exploit the Nu River to meet the thirst for energy. From its source in the Himalayas of Tibet, the Nu flows 1,750 miles through Yunnan province - a region rich in ethnic and biological diversity - and on into Burma and northern Thailand, where it is known as the Salween. However, announcements that 13 dams are to be built have brought domestic and foreign resistance. Last year, a coalition of 80 environmental groups sent a protest letter to Beijing, insisting that plans be abandoned. The river is at the heart of a remote area, a United Nations world heritage site that has been called the "Grand Canyon of the Orient". It is home to more than 80 endangered species, including snow leopards and Yunnan snub-nosed antelopes, as well as wild elephants and oxen. The Chinese government actually appears to be listening in this instance and plans have been suspended. It is far from certain, however, how long this delay will last (adapted from The Guardian, 10 April 2004).

In an attempt to meet these growing water demands, as well as to generate power, both China’s Yangtze and the Hwang Ho (Yellow) River are also now experiencing major hydrological and morphological modifications as a result of dam construction:

  • The Yangtze is the world’s third longest river (more than 5,500 km). The Three Gorges Dam, due to be completed along its course in 2009, will be the world’s largest hydropower station and dam, with a 2-kilometre wall and a massive 595-kilometre-long reservoir behind it! There are huge social costs for all communities in this area who have been forced to migrate.
  • The Hwang Ho is a 4,828 km long river which was responsible for the deaths of 3.7 million people in 1931 from flooding and subsequent starvation in an event known as “China’s sorrow”. The Xiaolangdi Multipurpose Dam Project is intended to harness this deadly river. [source: Winchester, S. et al. (2003) Extreme Earth, Collins]

Teachers’ Notes for Geography in the News article “Dam downstream disaster?”


  • River Management
  • Cost-benefit analysis
  • Human modification of physical systems

11-16 curriculum  

Which other major rivers share their waters between neighbouring states? This could be a good opportunity for group map-work. Different groups of students could compare the political geography of drainage basins for the Nile, Amazon, Rhine, etc. A spokesperson for each group may then offer a brief presentation that asks:

  • How large is the drainage basin?
  • Who are the major users?
  • How might water use in one country impact on user groups in neighbouring states?
  • Do the nations involved have a history of co-operation or conflict?

AS/A2  Physical systems

Most AS students need to study at least one river management study in some detail. On some specifications, such as Edexcel Syllabus A, candidates will need to examine the impact of management on river processes and also on the regime of the river. Students could undertake additional research using the web-links included in this article to examine sedimentation behind the dams and the greater incidence of braiding in the lower course (Cambodia) as more sandbanks begin to appear

Edexcel Syllabus B candidates will find that the Mekong case Study is particularly helpful in the following areas of their first AS paper:

  • How have human activities, some of which may be conflicting, influenced river environments? What are some of the consequences that can occur as a result? A study of one intermediate or large drainage basin should be used to provide an overview of channel and catchment activities and potential conflict. A decision making/issues analysis would be appropriate. Contrasting river basins can be used to exemplify the chosen issues e.g. Mekong, Hwang Ho, Yangtze, Colorado, Rhine, Rhone, San Gabriel.
  • How does the management of river systems pose a continuing challenge for people? Drainage basins and rivers can be managed in a variety of ways. Contrast engineering solutions and the lessons learnt, with more environmentally sensitive, holistic and cost effective schemes.

AS/A2 Human systems

For all AS and A2 students, there are strong links to be made with human geography, notably:

  • Forced migrations result from dam-building in China (the Three Gorges project is certainly worth investigating).
  • The rapid growth of NICs is having significant environmental impacts.

Synoptic (decision-making) studies

The wide range of physical and human impacts - and the difficult decision-making involved – also make this is a useful study for synoptic geography. A useful homework assignment could ask the following questions:

1. Outline the reasons why China needs to dam its major rivers.
2. Assess the human and physical costs associated with dam construction:
   (i) within China;
   (ii) in neighbouring countries.
3. How should the Mekong be managed in order to satisfy the needs of all of the countries that lie within its drainage basin?

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