Mekong River Basin: GCSE Geography Case Study

Where is the Mekong and what is its physical character?

The Mekong River rises on the Tibetan Plateau at approximately 5,200 metres above sea level, in the Chinese province of Qinghai. In its upper reaches — known in China as the Lancang River — it cuts through deep gorges in the Hengduan Mountains of Yunnan province. This upper section accounts for roughly half the river's length.

Crossing into Southeast Asia, the river's character changes: it enters lower-gradient terrain, spreading through wide floodplains and then the vast Mekong Delta of southern Vietnam, a low-lying plain covering 40,000 square kilometres that is one of the world's most productive agricultural regions.

The river's flow is dominated by the monsoon. During the dry season (November–April), discharge is low. During the monsoon (May–October), the river swells enormously. In Cambodia, the floodwaters actually reverse the flow of the Tonle Sap tributary, causing it to push back into the Tonle Sap Lake and expand it from 2,500 km² to over 16,000 km². This extraordinary seasonal flooding deposits nutrient-rich sediments that support Cambodia's rice agriculture and one of the world's most productive freshwater fisheries.

Why is the Mekong important to the people who live along it?

The Mekong is more than a geographic feature — it is the economic and cultural foundation of Lower Mekong countries:

Fish is the primary source of protein for tens of millions of people. The Mekong is the world's largest inland fishery by volume, and its productivity depends directly on the flood-pulse cycle that carries nutrients and enables fish to migrate to their breeding grounds.

What has China built upstream?

China began constructing a cascade of large hydroelectric dams on the upper Lancang/Mekong from the 1990s. By 2024 there were eleven completed dams in China's section, with more planned. The largest — Nuozhadu (2012) and Xiaowan (2010) — are among the tallest dams in the world.

These dams serve Chinese energy needs: hydroelectricity powers Yunnan's industrial development and feeds China's national grid. China argues the dams are purely domestic infrastructure on its own section of the river. Lower Mekong countries see it differently.

Impacts of upstream dams identified by researchers:

• Reduced sediment flow: Dams trap sediment. The Mekong Delta has lost roughly half its natural sediment supply, causing delta subsidence — the land is sinking as it is no longer replenished from upstream
• Altered flood pulse: Dams regulate flow, reducing the extreme seasonal flooding that drives the Tonle Sap reversal and fertilises floodplains
• Reduced fish populations: Fish migration is blocked or disrupted; the Mekong's freshwater fish catch has declined sharply
• Dry season flow changes: China can release or withhold water for electricity generation, causing unexpected flow changes downstream

Vocabulary to know:

• Hydroelectric power (HEP) — electricity generated by water flow through turbines
• Sediment load — the material (silt, sand, gravel) carried by a river
• Delta subsidence — sinking of a river delta as it loses sediment supply
• Flood pulse — the seasonal rise and fall of river levels that drives floodplain ecology

What is the Mekong River Commission?

The Mekong River Commission (MRC) was established in 1995 by the four lower Mekong countries (Laos, Thailand, Cambodia, Vietnam) to manage shared water use. China and Myanmar are only dialogue partners, not full members, meaning China's dam-building is not subject to MRC oversight.

The MRC requires member countries to notify each other of planned projects that could affect river flow. However, its enforcement mechanisms are weak: it cannot compel China to limit dam construction or release water. When a 2020 drought reduced the Mekong to record low levels, data from US government satellites showed that China's dams were holding back water. Chinese officials disputed the analysis.

This illustrates a geopolitical tension that is common in international river management: upstream countries control the resource; downstream countries bear the consequences; and international bodies lack binding power over sovereign states.

What are the long-term threats to the Mekong Delta?

The Mekong Delta in southern Vietnam faces a compound threat that geographers consider one of the most serious land-loss crises in Asia:

• Delta subsidence: Loss of upstream sediment, combined with groundwater extraction for agriculture, is causing parts of the delta to sink at 2–3 cm per year
• Sea level rise: As the Indian Ocean warms, sea levels are projected to rise 30–50 cm by 2050 in the delta region
• Saltwater intrusion: As the delta sinks and sea levels rise, salt water is penetrating further upstream into the rice-growing areas, damaging crops
• Population exposure: 17 million people live in the delta; without adaptation, significant areas could be submerged or rendered unusable within decades

Vietnam is investing in dykes, saltwater-tolerant rice varieties and relocation programmes. But the scale of the problem — driven partly by forces outside Vietnam's control — makes adaptation extremely difficult.

Frequently asked questions

How does the Mekong compare with other international river conflicts?

The Mekong shares characteristics with other contested rivers. The Nile is contested between Ethiopia (which is building the Grand Ethiopian Renaissance Dam), Sudan and Egypt. The Indus is shared between India and Pakistan under a 1960 treaty now under pressure. In all cases, the tension is between upstream countries who control construction and downstream countries who depend on flow. What makes the Mekong distinctive is the scale of dam-building, the speed with which it has occurred, and the power asymmetry: China is one of the world's largest economies; Laos and Cambodia are among its smallest.

Is China to blame for the Mekong's problems?

China's dams have contributed to reduced sediment flow and altered the flood pulse. However, the picture is not simple. Lower Mekong countries — especially Laos — are also building dams, with six on the mainstream already completed or under construction. Sand extraction by private companies in Cambodia, Thailand and Vietnam has also removed enormous quantities of river sediment. Overfishing has reduced fish populations independently of dam effects. Climate change is altering monsoon patterns. The Mekong's decline has multiple causes, but Chinese dam construction is the largest single factor that cannot be addressed without Chinese co-operation.

What does the Mekong look like as a GCSE case study?

For GCSE geography, the Mekong works as a case study for: water insecurity and international conflict; the impacts of HEP development; coastal and delta management; and the challenge of sustainable development across low- and middle-income countries. It also illustrates the SEEP framework neatly — social impacts on fishing communities, economic impacts on rice production, environmental impacts on the delta, and political tensions between China and Southeast Asian nations. It pairs well with comparison to the Nile basin or Indus disputes.

What is the future for the Mekong?

Several futures are possible. Optimistic scenarios involve greater co-operation through the MRC, China joining as a full member, and joint management of dam releases. More pessimistic projections foresee continued dam construction, accelerating delta loss and growing food insecurity for tens of millions of people. One factor is climate change: the Tibetan Plateau's glaciers, which feed the Mekong in the dry season, are shrinking, and projections suggest dry-season flows will decline significantly in the second half of this century. Managing the river in that context will require a level of international agreement that has so far proved elusive.

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