The ecological importance of the Plitvice Lakes National Park was recognized by UNESCO which protected the Park due to its outstanding values and biodiversity. This includes the natural tufa barriers important for non-vascular plants, animals like the brown bear, grey wolf, and lynx along with many rare and endemic species, and rich flora inhabiting the park's meadows.

Based on the detailed ichthyological research of the water bodies in Plitvice Lakes National Park, the removal of the barriers on Bijela Rijeka is crucial for ensuring the survival of populations of the Danube trout (Salmo labrax Pallas). There are still several pure indigenous Danube trout populations in Plitvice Lakes National Park, including some of the unique haplotypes with ancient diversity, which, according to the experts, indicates long-term isolation and independent evolutionary history of Danube trout in Plitvice Lakes National Park. 

Scientific research has shown that the main threat to the survival of these unique populations is habitat fragmentation by a series of barriers and the presence of invasive species in the watercourses. The research also concludes that populations might disappear if nothing is done within the next 50 years. 

Bijela Rijeka is recognized as the best suitable spawning ground for the Danube trout. Researchers have also conducted viability analysis. All scenarios confirm that optimal spawning conditions can be ensured only by removing barriers to migration, river, and gene continuity (especially on Bijela Rijeka). The ecological status of Bijela Rijeka is considered good (based on the research done in 2019), but it is degraded by human impact (building of barriers). Removal of barriers will positively contribute to improving the hydromorphological conditions and water quality, as well as maintaining a good ecological status. Research in the preparatory phase shows that no negative ecological impacts are to be expected.

All removals will consist of preparatory works and concrete removal of barriers that will be supervised by the Plitvice Lakes National Park and project partners. Removal will consist of the following activities, detailed per barrier:

Barrier 1: removal of the concrete weir on the Crna Rijeka, redirection of the Bijela Rijeka water course in the old river bed by closing the existing culvert, restoration of the old riverbed of the Bijela Rijeka river using the existing natural material (stones) to mimic the natural riverbed
Barrier 2: removal of only the utmost necessary vegetation that grows on the barrier (such as invasive species), partial removal of the small dyke, removal of the concrete structure, restoration of the riverbed using the existing natural material (stones) to mimic the natural riverbed
Barrier 3: restoration of the now cascade-formed riverbed to enable easier migration of fish species by addition of natural stones to enable the creation of lower distance between cascades that are passable for fish
Barrier 4: restoration of the old riverbed by closing the current culverts used for the diversion of water to the mills and redirection of the river into its natural riverbed
Barrier 5: restoration of the old riverbed by diversion of water into the old riverbed by creation of a natural stone structure (linear pile of larger stones mimicking natural structures)
Barrier 6: removal of the existing stone barrier and stone walls, removal of sedimented material, restoration of the riverbed
Barrier 7: removal of the existing stone barrier and stone walls, removal of sedimented material, restoration of the riverbed, creation of a natural stone structure (linear pile of larger stones mimicking natural structures)  to divert water into the restored riverbed
Barrier 8: removal of vegetation, removal of the concrete wall of the barrier, removal of the dyke upstream and downstream of the concrete wall, removal of the culvert and restoration of the riverbed. 

Project outcomes are: 

1. Connectivity of the migration route for Danube trout in Bijela Rijeka habitat is re-established
2. The population of Danube trout shows improvement
3. Dynamic River ecosystem is restored

With the removal of 8 barriers the whole Bijela Rijeka will be free-flowing and passable for fish and other species. In addition, since Bijela Rijeka, together with the downstream Crna Rijeka and Matica flows into Prošćansko Lake, it can be considered that the whole system will have improved hydromophological conditions and have conditions to re-establish migration route for the Black Sea trout (Salmo labrax Pallas – subspecies of brown trout) and other species (e.g. Gammarus balcanicus, Drusus croaticus, Berdeniella keroveci). All together 7,6 km of the river system will be free-flowing.

• Plitvice Lakes National Park
• ORP
• Dam Removal Europe
• local authority
• Municipality Plitvička Jezera
• Faculty of Science Zagreb