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Danube Trout Swim Again in the Bijela Rijeka stream

Removing artificial barriers from the Bijela Rijeka in Plitvice Lakes National Park allows fish and other species to migrate, significantly reducing the risk of floods and droughts.

ZAGREB – We are only one step away from completing the removal of the first artificial barriers from freshwater ecosystems in Croatia, with work remaining on just one of the eight locations on the Bijela Rijeka stream in Plitvice Lakes National Park. The combined flow of the Bijela Rijeka and Crna Rijeka supplies water to Plitvice Lakes, and the last location will be cleared of barriers during the summer after the restoration of a dry-stone bridge. The barrier removal is conducted by experts from Plitvice Lakes National Park and WWF Adria.

Although only 4.5 kilometers long, the Bijela Rijeka stream has been intersected with numerous mills, sawmills, and accumulations over the past 250 years. The park has restored the old flow at three locations where minor interventions were needed and will complete the removal at the fourth location after the dry-stone bridge restoration, while WWF Adria facilitated work with machinery to remove four artificial barriers on the Bijela Rijeka stream. As a result, the Bijela Rijeka now flows through its natural parts without artificial obstructions, allowing native Danube trout to move freely along the entire river. The first trout has already been spotted in the restored flow. By removing barriers at eight locations along the Bijela Rijeka, a total of eight kilometers of the river's flow from the source to Prošćansko Lake has been freed.

"Historically, the Danube trout was the most common species in the waters of the National Park, but overfishing brought its population to the brink of extinction. The remaining individuals were unable to migrate upstream for spawning from Prošćansko Lake for many years due to artificial barriers on the Bijela Rijeka. By removing these barriers, the Bijela Rijeka is returning to its natural state, and the trout will find their way upstream to spawn without hindrance," dr. Kazimir Miculinić explained, expert leader at Plitvice Lakes National Park.

The process that led to the removal of barriers lasted almost six years. Data collection, monitoring, hydrological, hydromorphological, biological, and geodetic research and measurements, and finally the development of the barrier removal project, all preceded the first excavator stroke in early May this year. Removing barriers restores the natural flow dynamics, enables fish and other species to migrate, and significantly reduces the risk of floods and droughts. Rivers naturally perform numerous functions beneficial to individuals and communities, from providing drinking water and food to regulating the effects of climate change. Therefore, barrier removal initiatives, like the one completed at Plitvice Lakes, are extremely important not only for nature but also for people.

"Non-functional barriers built by humans negatively affect the entire living world in and around the water. Their removal is a small contribution to the European Union's strategy to free 25,000 kilometers of rivers from barriers and non-functional dams, and a significantly larger contribution to the nature restoration necessary for strengthening our resilience to climate change," emphasized Dunja Mazzocco Drvar, conservation director at WWF Adria.

In the past two months, the Bijela Rijeka has undergone a significant transformation; its flow is no longer confined to concrete pipes, its sides are no longer controlled by high stone walls, and with the restoration of the dry-stone bridge and removal of the last barrier, it finally returns to its sister, the Crna Rijeka, in a confluence that will no longer be divided by soil, concrete, and stone. Now it flows again in its original form, filling the most beautiful waterfalls and lakes in Croatia, the Plitvice Lakes.
Besides being harmful to nature and its living world, barriers are also dangerous to humans. According to a recently published report by the Dam Removal Europe movement, 82 incidents caused by river barriers have been recorded so far, resulting in the loss of 129 lives.

After successfully removing first barriers in our region from the Vezišnica River in Montenegro in 2021, this is the second barrier removal in the region and the first in Croatia. Plitvice Lakes National Park and WWF are carrying it out with the support of the European Open Rivers Program, a grant-awarding organization dedicated to river restoration.
© Darko Mihalić
Plitvice Lakes - removing barriers from Bijela Rijeka stream

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