Dismantling dams is a new initiative for Europe and the world. Not only do dams very rarely supply the amount of water, or electricity, they were designed for, but rapid silting up of the lakes formed behind them make their useful lifespan severely limited. The world is littered with defunct dams but, they continue to block water flow. It is therefore refreshing to report one example of what happens when defunct dams are removed. The results are also a model for what should be done in other places.

       Artificial barriers have long blocked Europe’s waterways. Three years ago, when construction workers started demolishing a series of dams on the Hiitolanjoki River in Finland, they were greatly surprised to spot a run of salmon. Part of the country’s last wild and landlocked population, the fish were returning to the river after years of absence. For Pauliina Louhi, it was a sign that the ecosystem’s recovery had begun.

       “It was not only adults – there were many salmon juveniles,” Louhi, an ecologist at Natural Resources Institute Finland, a Finnish research organisation, recounts enthusiastically. “They had already been spawning on the lower-most part of the river. When I saw how the site looked after the dam removal, I actually had tears in my eyes.”

       The river used to be a key migration route for the endangered freshwater salmon from Lake Ladoga, in nearby Russia, to Finland. But between 1911 and 1925 the introduction of three dams supplying hydroelectric energy created barriers between the salmon and their spawning grounds. The salmon and other fish, like brown trout, were trapped on the Finnish side of the river.

       Today, however, with the dams removed, the water runs freely once again through newly built rapids surrounded by tall trees. Every time a dam was removed, salmon “embraced” the new part of the river, says Hanna Ollikainen, executive director of the South Karelian Recreation Area Foundation, a civil society organisation, which acquired the dams and is responsible for the environmental and touristic development of the area.

       In 2021, after the first removal, five spawning nests were spotted; in autumn 2022, one year on, baby salmon reached a record-breaking number of 200 fish per acre (0.4 hectares). When the removal of the upmost dam, Ritakoski, was completed in December 2023, they found a free passage to the upper parts of the river and its tributaries.    

       The removal of the three dams was the result of decades of work, which took into consideration not only the health of the river, but also the economic consequence, says Ollikainen. Evaluations concluded that their electricity production had become unprofitable for the power plant owners – especially when the costs of maintenance and mandatory environmental protections, such as fish-ladder introductions, were taken into account, Ollikainen says. So the dams were sold and dismantled.

       The decommissioning of the three Finnish dams is not an isolated case, however. Across Europe, many dams are either approaching the end of their operational life, or the costs of their maintenance are outweighing the benefits they provide. Similarly, in the United States, many are due to be re-licensed, sparking discussions about whether they are still fit to yield services. And it is not just big dams: millions of small barriers block European rivers.      

       Until recently, a comprehensive assessment of the extent of river fragmentation in Europe was lacking. But now it exists, the case for dam removal has been building.

       Rivers in highly industrialised areas, such as in Europe and the U.S., have been heavily modified for centuries, from road-crossings and water extraction for agriculture, to the addition of low barriers such as weirs, culverts, water mills and hydroelectricity. Such barriers have created a series of problems. They not only cause biodiversity loss, impacting fish and microorganisms, but also prevent nutrients and sediments from flowing downstream, hindering fisheries and the livelihoods that depend on them. As dams block sediments behind them, the water downstream also has a highly erosive power. Plus barriers modify the water levels of the river, impacting the recharge of the aquifer that holds underground water.

       Research now shows that at least 1.2 million instream obstacles block river flows in 36 European countries, with about 68% less than 2m (6.6ft) in height. “Even barriers as small as 20cm (8in) may impact or delay the movement of some organisms,” says Carlos Garcia de Leaniz professor in Aquatic Biosciences at Swansea University and coordinator of Amber, a project that created the first atlas of European river barriers.

       Nor is Europe alone in this trend. In fact, the Europe efforts were inspired by the dismantling works already happening in the US, says Fernández Garrido. The US is home to nearly 92,000 dams with an average age of 62 years. The first big dam removal in the US involved the Edwards Dam removal on the Kennebec river in 1999. Built in 1837, when the owner’s licence expired in 1997, the Federal Energy Regulatory Commission didn’t renew it, prioritising the ecological benefits of the river for the first time instead. Today, nearly 2,000 dams have been removed from US rivers.

       It is interesting that one of the biggest proponents of building dams in the U.S. and elsewhere, has now become their biggest detractor. A previous blog documented his complete turnaround and his international activities to remove dams where they no longer serve the purpose for which they were created.

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