Photo: Pixabay/tuproyecto

As countries worldwide scramble to wean themselves off fossil fuels, hydropower is being seen as a greener alternative. The trouble with damming rivers, however, is that often dams cause great environmental harm.

A case in point is the Mekong river in Southeast Asia, which has turned into a shadow of its former mighty self as a result of numerous hydroelectric dams constructed in recent years throughout much of its length from China to Cambodia. No country along its course has been left unaffected.

“Development projects, such as dam construction on the Mekong River and [its] tributaries to support a booming hydropower industry, are bringing great change to ecological, agricultural and cultural systems in this region,” Prof. Kenneth Olson, an American environmental scientist, has warned.

And the Mekong is hardly alone among the world’s rivers undergoing dramatic changes because of wanton damming. More than 260,000 kilometres of river from the Amazon in South America to the Congo in Africa to the Irrawaddy in Asia could soon be impacted by planned hydroelectric developments, scientists at McGill University in Canada warn.

The harm to local wildlife and biodiversity could be colossal, according to experts at the World Wildlife Fund for Nature (WWF), who contributed to the research. The researchers have reached this conclusion after examining a dataset of more than 3,700 potential hydropower projects worldwide to calculate their future impacts on rivers and riverine environments.

“It was sobering to learn that many of today’s remaining free-flowing rivers are at risk of being permanently transformed by new energy infrastructures,” says Prof. Bernhard Lehner, at McGill University’s Global HydroLab who created maps of rivers facing the dangers of damming.

The experts say that even as all that damming could cause irreparable harm to rivers, the new hydrolectric plants on them would contribute relatively little to keep climate change in check. All told, the new dams would generate less than 2% of the renewable energy needed by 2050 to keep global temperature increase below the target 1.5 Celcius limit.

As a result, they recommend evaluating the wisdom of damming fragile rivers for hydropower and suggest other renewable alternatives such as solar and wind in their place.

“It is true that hydropower is a source of renewable energy with relatively low carbon emissions,” says Günther Grill, a post-doctoral fellow at McGill who was an author of the study. “However, hydropower projects can permanently and irreversibly impact river and floodplain dynamics and functions, often in tropical wilderness areas with high biodiversity,” he stresses.

In short, the environmental costs of these projects would far outweigh their economic benefits. “When it comes to river health, climate change and biodiversity loss, we can no longer afford to think of these as separate issues,” says Michele Thieme, a freshwater scientist at World Wildlife Fund and lead author of the study.

“Rivers are powerful agents for keeping wildlife and communities healthy, especially in a warming climate, yet their ability to support life is threatened by hydropower dams in many parts of the world,” Thieme explains. “The best policy solutions will be those that balance renewable energy needs with the many benefits of thriving freshwater ecosystems.”

Apart from ecosystems, local communities would suffer too. Hundreds of millions of people worldwide depend on free-flowing rivers for their livelihoods from fishing to irrigation. Once these rivers are dammed, many riverside communities could face severe consequences, as has happened along the Mekong.

This does not mean, however, that no hydroelectric plants should be constructed anywhere ever. The key is to build dams in ways that can mitigate their environmental impacts to the greatest possible extent.

The solutions, the experts say, include siting dams in locations where they have fewer impacts on nature and local communities, restoring rivers by removing ageing dams, and offsetting the negative impacts of dams on one river by better protecting another, similar river.

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