Proud, wet beaver sits on dam she probably built herself

Dams are a major driver of environmental change, study finds

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Belgian researchers have found that damming rivers could have a significant and unexpected impact on Earth’s carbon cycle and climate.

There are more than 16 million dams in the world, including 70,000 large dams. We are constantly building new dams and reservoirs, primarily for energy production, and within 15 years, 90 per cent of the world’s rivers may be fragmented by dams.

Reservoirs created by damming rivers can act as significant sources or sinks for carbon dioxide, but these structures are not well represented in current climate change models.

Aiming to understand the role of water reservoirs in climate models, researchers at the University of Waterloo and the Université libre de Bruxelles used a method linking physical parameters such as reservoir size with the processes which determine what happens to organic carbon travelling down dammed rivers. This model allowed them to capture the impact of more than 70 per cent of the world’s artificial reservoirs by volume.

“Dams don’t just have local environmental impacts. It’s clear they play a key role in the global carbon cycle and therefore the Earth’s climate,” said Professor Philippe Van Cappellen of the University of Waterloo’s department of earth and environmental sciences, and the study’s co-author.

“For more accurate climate predictions, we need to better understand the impact of reservoirs.”

According to their model, the researchers found that water reservoirs trap nearly a fifth of the organic carbon moving from land to ocean through the world’s rivers. They report their findings in Nature Communications.

“We’re essentially increasing the number of artificial lakes every time we build a dam,” said Taylor Maavara, a PhD student at the University of Waterloo and lead author of the study. “This changes the flow of water and the materials it carries, including nutrients and carbon.”

Previous research carried out by the team found that ongoing dam construction can impede the transport of nutrients such as phosphorus, nitrogen and silicon through river networks. These changes can have impacts around the world on the quality of water delivered downstream.

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