The damming problem of reconnecting Europe's rivers

This article written by Professor Carlos Garcia de Leaniz was originally published by The Conversation.

Rivers are some of the world’s richest ecosystems and yet they are also some of the most threatened. Despite billion-dollar restoration programmes being implemented worldwide, one of the biggest problems rivers face is actually manmade: dams.

Chances are that much of the water you drink, the electricity you use, and the food you eat would not be possible without dams. Dams help us abstract water for domestic and industrial use; facilitate navigation for commerce and trade; provide fishing and leisure opportunities; and may also help prevent the spread of aquatic invasive species. Hydroelectric dams are also essential for meeting Europe’s 20% renewable energy target by 2020, while climate change is putting additional pressure on surface water resources that may also require new dams.

Built by the Ancient Romans, Spain’s Proserpina dam is the second oldest still in use. Gotardo González/FlickrCC BY

Dams provide a lot of benefits to society, certainly, but not so much to the actual waterways. We have been building dams all over the place for the last 5,000 years, relentlessly and unstoppably. These days we are building them taller and larger than ever before. The world’s current biggest dam, the hydroelectric Three Gorges Dam which spans the Yangtze river in China holds back a reservoir stretching 600km in length. And a new structure planned for the vast River Congo’s Inga waterfalls in Africa could surpass this, with the ability to generate twice as much hydroelectricity as its Chinese counterpart.

Our water reservoirs are now so vast, and have displaced so much water, that it has been suggested they have tilted the Earth’s axis, slowed its rotation, and become a major source of greenhouse gas emissions.

Damming figures

But dams don’t last forever. Many, such as the diversion dams that fed the iron foundries of pre-industrial Europe, or the tailings dams that store mining waste, date from a bygone era and are no longer in use. They eventually clog-up with sediments, come to the end of their working life, and begin to crumble – sometimes catastrophically, endangering people and livelihoods.