Playing ‘dam’-inoes

The Mekong River provides food, water and transportation for more than 60 million people in five countries. In recent decades, however, the river has also become an important power source as dams help generate electricity from hydropower.

The push to generate more electricity from hydropower has led to plans for dozens of dams to be built on the Mekong and along its branches by 2030. A recent study by Cambodian and American researchers calls for a review of these proposed sites so that nations dependent on the river can better assess the impacts of the dams.

Catastrophic impacts

“We find that the completion of 78 dams on tributaries, which have not previously been subject to strategic analysis, would have catastrophic impacts on fish productivity and biodiversity,” Princeton ecologist Guy Ziv and his colleagues wrote in their paper.

The Mekong River starts in the Himalayas and flows through five Southeast Asian countries before reaching the South China Sea. Representatives from Cambodia, Lao PDR, Thailand and Vietnam work together to maintain and develop these resources as the Mekong River Commission (MRC). For more than 60 million people who live in the Mekong River Basin (MRB), the river provides livelihoods, food, water and a means of transportation. Fish from the Mekong provide as much as 80 percent of the animal protein eaten by those who live by the river, and nearby rice fields benefit from both the water- and nutrient-rich sediments when the level of the river exceeds its banks.

By 2015, there are expected to be 41 dams along the Mekong River and its branches, generating nearly 100 Terawatt-hours (Twh) of electricity annually. (For comparison, the International Energy Association reported that the Philippines consumed nearly 51 Twh of electricity in 2009.) In their study, Ziv and his fellow researchers noted that dams built along the branches of the Mekong River are not under the jurisdiction of the MRC, which means neighboring nations may not be completely aware of how these dams might impact them.

Scenarios

The researchers modeled several scenarios to determine how fish populations fared in relation to the number of dams built and where they were situated. For example, the 2015 scenario with 41 dams saw nearly 80 fish species considered “vulnerable.” In contrast, one scenario for the year 2030 features 78 dams built on the Mekong or along its tributaries, resulting in more electricity generated, but the corresponding loss of fish migration paths results in 100 fish species being considered “critically endangered.”

Based on their models, Ziv and his colleagues found that the projected locations of the dams, particularly along the branches of the Mekong River, had a greater impact on fish populations than the number of dams being built.

“In recent years construction of hydropower dams has occurred at an unprecedented rate. It is now estimated that 50 percent of all large rivers have been affected by dam construction. Although socioeconomic progress is desirable, sustainable development requires that unnecessary risks to ecosystems and environmental services, such as fish production and biodiversity, be avoided. In the MRB we find that some hydropower projects can and should be avoided,” the researchers concluded.

The study was published ahead of print March 5 in the “Proceedings of the National Academy of Sciences USA.”

E-mail the author at massie@ massie.com.