CONTEXT:

The Nam Ou River spans approximately 480km and is a transboundary river basin of both national and international importance, shared by Lao PDR and Vietnam. The Nam Ou Cascade Hydropower Project comprises six run-of-river dams and one storage reservoir and represents the first time that a Chinese company has obtained the rights to develop a cascade along an entire river basin outside of China.

PROJECT IMPACTS:

The Nam Ou dams are expected to cause severe impacts on the biodiversity and ecology of the Nam Ou basin and the wider Mekong River basin. The projects will also have significant impacts on the food sources, livelihoods and cultures of local populations, including ethnic minorities and Indigenous Peoples. Construction of the Nam Ou cascade has disrupted the connectivity of the Nam Ou River system. The majority of the Nam Ou mainstream has been transformed from free-flowing river into a series of reservoirs, with profound implications for the river’s overall productivity and species biodiversity.

IMPACTS ON BIODIVERSITY AND ECOSYSTEM HEALTH

The Nam Ou is recognized as one of the most important tributaries of the Mekong in terms of biodiversity. An estimated 139 species of fish are found in the Nam Ou Basin. At least 35 of these species have been found to be endemic and at least 86 are native to the Mekong Basin. It’s predicted that the projects will have a severe impact on the biodiversity in the Nam Ou basin, in particular for fish species, due to loss of connectivity and conversion of the river ecosystem from free-flowing river to a series of reservoirs.

IMPACTS ON LOCAL AND INDIGENOUS COMMUNITIES

The Nam Ou cascade has displaced thousands of villagers to resettlement sites and reduced their access to fisheries and natural resources important for their livelihoods. Impacts on the river ecosystem will have corresponding social and economic impacts due to loss of agricultural and forest land, reduction in fish catches, increase in demand and prices of fish and non-timber forest products, and pressures on wildlife.

Biodiversity Snapshot

At least 20 species impacted along the Nam Ou cascade are listed as either endangered or critically endangered according to the IUCN Red List, among them:

CRITICALLY ENDANGERED

Asian Box Turtle

White Cheeked Gibbon

Siamese Giant Barb

ENDANGERED

Mekong Freshwater Stingray

Yunnan spiny frog

Francois’s Langur

Sunda Pangolin

Chinese Pangolin

Large Antlered Muntjac

Indochinese Tiger

Fishing Cat

Green Peafowl

Big-headed Turtle

PROJECT IMPACTS

LESSONS

NAM OU CASCADE

Lao PDR

Hydropower cascade spanning the entire Nam Ou River, an important and biodiverse tributary system within the Mekong River Basin

Person fishing on Nam Ou. Fishing and food sources will be significantly impacted

Image by International Rivers

Nam Ou River

Image by Collin Key

Critically endangered Asian Box Turtle

Biodiversity Snapshot

At least 20 species impacted along the Nam Ou cascade are listed as either endangered or critically endangered according to the IUCN Red List, among them:

CRITICALLY ENDANGERED

Asian Box Turtle

White Cheeked Gibbon

Siamese Giant Barb

ENDANGERED

Mekong Freshwater Stingray

Yunnan spiny frog

Francois’s Langur

Sunda Pangolin

Chinese Pangolin

Large Antlered Muntjac

Indochinese Tiger

Fishing Cat

Green Peafowl

Big-headed Turtle

Company: Power China

Impact Category

Indigenous Peoples

Impact Category

Food Security

Impact Category

Free-flowing River

CAPACITY

540 MW (phase 1)

732 MW (phase 2)

COST

$2.73 billion​

STATUS

Phase 1 (operating)
Phase 2 (complete)

Local Community Impact​

65 million people depend on the Mekong river basin for their food and livelihoods. The dam site has displaced thousands of villagers and reduced access to fishing.

1.

It is necessary to carry out robust cumulative impact assessments prior to construction to understand, prevent, and mitigate the often considerable impacts of multiple dams on a single river.

2.

Hydropower dams, especially in cascades, should be designed and operated in a way that best approximates natural flows and minimizes the impacts on freshwater ecosystems through the development and implementation of a robust environmental flows regime.

3.

Fish passages and sediment flushing mechanisms should be integrated into the design of dams and to ensure that migratory fish species are sustained and that important sediments continue to nourish downstream areas.

4.

Proper due diligence should have identified the severe impacts of destroying fish and other aquatic species on the food security and livelihoods of local indigenous and ethnic minority people, and disqualified the project from consideration.

5.

All environmental, social, and cumulative impact assessments should be disclosed to the public and made available for public comment.