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When will a basin-scale vision for the Mekong come to reality?

The Mekong basin is being stirred up by dams, both on the mainstream and tributaries, despite the warning that they pose serious threats to an ecologically and agriculturally vital area of the world. Experts say a basin scale vision is crucial for good water governance, but when will it become a reality?

By Thien Y

3S Basin, Cambodia, December 8, 2016

Special to The Mekong Eye

The controversial Lower Se San 2

Srekor village (Srekor commune, Sesan district, Stung Treng province, Cambodia) looks upset in the slanting dim light of the sunset. Located not far from the Lower Sesan II dam, the village is the destination of much hydropower opposition in recent months.

Still under construction, the Lower Sesan II will be the largest-ever dam in Cambodia, with a height of 75 meters, installed capacity of 400 MW, just 1.5 kilometers from the confluence of Se San and Srepok, before the two rivers join in the Great Mekong. The dam, as designed, will submerge 336 square kilometers and displace 5,000 people from many different ethnic groups.

According to the Cambodian government, this $800 million project is expected to be a stable power supply for the five provinces of Stung Treng, Kampong Cham, Kratie, Preah Vihear and Ratanakiri, to help ending the dependence on electricity import from Laos.

The project is a joint venture between Cambodia’s Royal Group (39%), China’s Hydrolancang Energy Group (51%) and Vietnam’s EVN (10%).

However, it is the most controversial among the Mekong tributary dams. According to 2015 up-to-date survey results of NGO Forum, a Phnom Penh-based non governmental organization, more than 90% of people affected by the Lower Sesan II request the government to stop the dam construction and change the site into a world-class protected area, with ecotourism intergration.

The locals said that the compensation and resettlement for affected people is inadequate and lacks transparency; they have not been consulted from the beginning of the project. Most of them do not want to lose the spiritual land that has been attached to them for ages.

The Lower Se San II dam is on progress of construction in Stung Treng, Cambodia (Photo: Savann Oeurn/Oxfam)

The Lower Se San II dam is on progress of construction in Stung Treng, Cambodia (Photo: Savann Oeurn/Oxfam)


According to Vietnam Rivers Network(VRN), the Lower Sesan II dam will be the worst highlight of a series of dams in the 3S basin, causing negative environmental impact as far as the Mekong Delta of Vietnam. But the EIA reports released by the project developer and the Cambodian government has no indication that a transboundary impacts study has been conducted so far.

“The dam construction will make more impacts on the Mekong Delta. The Vietnam’s largest rice bowl will be affected in terms of productivity. The dam will change the natural flow of the Mekong river, causing sediment reduction and flow imbalance in canals and coastal areas in Vietnam. Fundamental nutrients for agriculture in floodplains of Cambodia and the Mekong Delta of Vietnam will go down,” said Dr. Le Anh Tuan, deputy head of the Institute of Climate Change Research at Can Tho University.

A WorldFish report indicates that the environmental effects of the dam are disastrous, threatening to the survival of more than 50 fish species and reducing almost 10 percent of the total fish capacity in the whole basin (about 200,000 tonnes per year).

“In term of fish migration, about 40% of them will swim to the Mekong river upstream and the rest to the tributaries of of the Sesan, Sekong or Srepok rivers. The Lower Sesan II dam will block most of the fish swimming to 3S upstream. The fish ladder is also impossible and ineffective. Experience from Thailand’s Pak Mun dam has proven this,” the 3S Rivers Protection Network coordinator Meach Mean said.


The dilemma of Vietnam

Together with the Mekong mainstream dams, the network of dams in tributaries, including the in 3S basin, also accumulated significant impacts on the the flow, sediment and fish stocks of the whole Mekong basin.

The 3S basin, covering an area of 78.650 square kilometers 3S in the lower Mekong, is shared by Laos (29%), Vietnam (38%) and Cambodia (33%)

The Sekong, Srepok and Sesan rivers are considered the most important tributaries of the Mekong River basin, contributing water and sediment for downstream flood areas, and is the main route for fish migration.

Therefore, the rivers network in the 3S basin play a key role to the hydrology of the Tonle Sap and the Mekong Delta in Vietnam.

A 2009-published study by Adamson showed that although the 3S basin occupies only 10% of the entire Mekong basin, but contributes 23% of the total annual water volume of the Mekong river on average, which is about 3,000 cubic meters per second in dry season and 4,500 cubic meters per second in the rainy season.

Proposed and existing dams in the 3S region: (CCS Institute)


In addition, the 3S basin contributes 15% of alluvial sediment to the Mekong ecosystem. These are considered the key nutrients of the Tonle Sap and the Mekong Delta, two important agricultural production areas of Cambodia and Vietnam.

Dr. Richard Cronin, expert of the Southeast Asia Program of Stimson Center, a Washington-based think tank, believes that in the game of hydropower development in the Mekong basin, the 3S in particular, Vietnam are in a dilemma.

While Vietnam is concerned about the threat from upstream hydropower projects on the Mekong Delta, the dams in the Central Highlands, which is upstream of the Mekong river’s tributaries, also cause transboundary impacts.

The economy of Vietnam has been developing rapidly in the past few years, plus the incentives for high energy consuming industries such as steel and cement production have led to rocketing energy demands in the country.

Besides electricity purchased from China to compensate for the shortfall, hydropower development is inevitable for Vietnam. Hydropower is considered less expensive and does not require high technology as do other energy sources such as nuclear power or renewable energy.

Vietnam has completed the construction of a series of hydropower dams on the mainstream and tributaries of the Se San and Srepok rivers so far, in spite of of the concerns from MRC and Cambodia.

And the consequences came quickly!

In early 2016, the Central Highlands and the Mekong Delta of Vietnam experienced a record breaking drought. Millions of farmers in the Mekong Delta had to face the most severe salinization. In the Central Highlands, 50,000 hectares of crops were damaged, nearly 30,000 households suffered from water shortage.

VRN pointed out the reason, besides climate change, is the development of hydropower on mainstream and tributaries of the Sesan and Srepok rivers. The water resources, fisheries, livelihood of millions of people in the Central Highlands were negatively affected.

According to Nguyen Quang Nhan, a water resource management expert in Hanoi, on a regional scale the Mekong River flows through many countries but it is still a closed basin, leveling off at national borders.

The cross-border nature of the Mekong is only recognized when the river is said to be an opportunity for economic development, but few people show concerns about the fragile ecology of the Mekong basin.

“In order to reach good water resources governance, all the Mekong countries should view it on the basin scale vision. That means the very careful consideration of where to put a dam, where not to, and thus can maintain the ecological functions of the entire Mekong basin. But it is not easy,” Quang admitted.

Indeed, the benefits of the dams may be calculated, but the cost to the environment, livelihood, culture of communities is unvaluable.

Meanwhile hydropower dams have been still being constructed and the cries of millions of people who have to struggle with the dam consequences are still neglected, like a breeze through the ears.


This is part 3 of 3, in the author’s “Sorrow of Dams” series. See part 1 and part 2.

This story was produced by a local journalist with support from The Mekong Eye and Mekong Matters Journalism Network and is published under a pseudonym at the request of the journalist. The journalist and their outlet retain full editorial and copyright control. 

Lead Photo: The cost to the environment, livelihood, culture of communities by 3S dams is invaluable. (Photo: Savann Oeurn/Oxfam)


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