Fish caught by So Srey Nic, Damre village, Koh Tanot, Cambodia

Strategic Environmental Assessment: impacts of mainstream dams

The goal of the Strategic Environmental Assessment (SEA) is to guide decisions relating to proposed mainstream hydropower projects so that development is equitable and ecologically sustainable. The SEA report found the mainstream dams would devastate the world’s largest inland fishery and contribute to growing inequality.

The main impacts of the proposed hydropower dams are:


Home to 781 known species, the Mekong River is the second-largest fish biodiversity region, with about half the entire river being classified as a Key Biodiversity Area. By altering the river’s structure and flow, the 12 proposed hydropower dams would affect 80% of the Key Biodiversity Area and put more than 100 species at risk. The extinction of some species unique to the Mekong, such as the Irrawaddy Dolphin and the Giant Mekong Catfish, would be highly likely. The significance of this cannot be overstated.

Food security and agriculture

Fish protein is central to human nutrition in the Mekong region. Between 50 and 80% of the animal protein consumed by the 60 million people living in the lower Mekong basin comes from the river’s fisheries. These inland fisheries are among the most intensive in the world, and the food security and livelihoods of those living in the region largely rely on river-dependent natural resources. The construction of the mainstream dams would not only endanger fish species, but their reduced numbers would have grave nutritional consequences for these poor rural communities. Furthermore, 20% of agricultural land along the lower Mekong basin would be lost through inundation or clearing, with the remaining 80% experiencing increased complications.

Livelihoods and culture

Significant changes to the Mekong’s ecosystem would affect the social, cultural and religious structure of communities along the river, especially those adjacent to the reservoirs or immediately downstream of the dams. The 12 mainstream projects proposed for the lower Mekong basin would cause the displacement of more than 100,000 people. Not only would they lose their homes but their source of livelihood, with a further 2 million people at significant risk either directly or indirectly. For some, this will be their fourth forced relocation in 15 years. By changing traditional lifestyles forever, the dams could lead to growing inequality and short-to-medium-term poverty while undermining region-wide efforts to meet national poverty alleviation goals.


There are concerns that these dams are being considered without fully assessing their impact and without a sustainable development framework that addresses the installation issues. What is known, however, is that many of the impacts cannot be avoided or mitigated, and that compensation and adjustment programs for communities affected by hydropower in the lower Mekong basin to date have been inadequate.

With nearly 30 million people estimated to be affected by the mainstream projects, the SEA recommends that decisions on mainstream dams should be deferred for a period of ten years.

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What is Oxfam doing?

  • Oxfam Australia has been working in the Mekong region for more than 20 years. We support a network of local and non-government organisations across the six countries in the region, linking grassroots village work with international and regional organisations.
  • Oxfam is an active member of global campaigning group Save the Mekong coalition
  • We’re ensuring that communities know their rights regarding major development decisions that affect their environment and their access to the Mekong’s vital resources