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    1. What We Do
      1. Reducing Impacts
        1. Water
          1. Dams
            1. Examples

A number of dams are planned throughout the Lower Mekong Basin in addition to those already operational or under construction in the Upper Mekong Basin.

Learn more about the Mekong River Basin

Mekong River Basin

Damming the Mekong

The Mekong River, an area of unique environmental splendor, has remained relatively untouched by large dams. Yet expanding populations and developing economies are increasing the demand for hydropower.

If not properly planned and sustainably implemented, these dams will give rise to more than just the water levels of their reservoirs. They will stop up the source of life that flows from this ‘mother of waters’.
A small boat transports a family along the Mekong River.

©

The Mekong’s dramatic seasonal variation is essential to sustaining its abundance of life.
© WWF-Canon / Gerald S. CUBITT

Mekong River Facts

  • Of the Mekong's 1,300 fish species, 600 are long distance migrants that require different habitats throughout the year and their life cycles.
  • The Mekong is the largest inland fishery in the world, producing about 2.6 million tons of fish per year.
  • Of this catch, 70% are long distance migrants.

WWF's solutions

WWF is working with the Mekong River Commission and the Asian Development Bank to improve the environmental performance of new dams.

Our priority is to identify high conservation value parts of the basin, such as the lower mainstream river, and declare them no-go zones for dams development.

Life on the Mekong

The Mekong River provides food, drinking water, irrigation, transport, and energy for the more than 60 million people in China, Myanmar, Laos, Thailand, Cambodia, and Vietnam who live in its basin.

The freshwater fisheries of the Mekong River Basin have a commercial value of US$2 billion and provide 80% of the animal protein consumed by those living there.

The Mekong's natural flooding provides spawning grounds for these fish. And it enriches cropland like the Mekong Delta — where 50% of Vietnam’s staple food crops grow — with fertile sediments and water for irrigation.


Dams get in the way

As the countries of the Mekong Basin develop economically, their demand for energy is growing. Hydropower is seen as both a potential source of this needed energy and as a means for economic growth in and of itself.

But some dams may end up doing more harm than good. Dams on the mainstream of the lower Mekong would be particularly destructive. Serious impacts include:
  • Delta instability: The reduction of sediments as they are trapped by dams would make the Mekong Basin more vulnerable to sea level rise and saline intrusion brought on by climate change.
  • Decreases in fish diversity: Dams in the mainstem will impede migration of fish and other aquatic animals potentially reducing productivity of the fishery by 60%.
  • Damage to livelihoods: Over 75% of rural households in the Lower Mekong Basin are involved in fisheries. Any impact on the ecological balance of the river also threatens the sustainability of the aquatic resources they depend on.

Upper Mekong River dams impact life downstream

Although — for now — the lower Mekong River remains free of large dams, the same cannot be said for its upper reaches.

In 1996, operation of the 126 m high Manwan Dam began. It represented the first of a cascade of 8 hydropower dams planned in Yunnan Province on the mainstream of the Upper Mekong. In 2003, it was followed by the 110 m high Dachaoshan Dam.

Construction is now underway on the Xiaowan dam, which at 292 m high, will be the tallest arch dam in the world. It will span the river over nearly 900 m and create a reservoir that backs up in the narrow gorges for 178 km.

There is little doubt that dams in the upper Mekong are having an impact on downstream hydrology and ecology. Significant reductions in sediments have been measured, stretching as far as southern Laos.

© WWF-Canon / Sayan CHUENUDOMSAVAD

Protecting the Irrawaddy river dolphin's habitat can also insure that fisheries remain intact for human use.

Don Sahong Dam: A mainstream issue

If built, the proposed Don Sahong Dam would be the first dam on the Mekong mainstream in the lower basin area.

Planned for a site less than 2 km upstream of one of the few remaining pods of Irrawaddy river dolphins in the Mekong, the dam would likely spark a decline of its main food source and disrupt its habitat. Such damage would be devastating to a species already on the brink of extinction in this river.

Moreover, the Don Sahong Dam would damage fisheries that are central to people's food security by impeding fish migration. And it could harm the local economy and its developing tourism industry.

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