Assess and prioritise barriers for ecological restoration of the River Unac.
The River Unac springs beneath Mount Šator at an altitude of 876 m. Its total length is approximately 66 kilometres and it is fed by around ten tributaries and springs. During summer, certain sections dry up due to reduced inflow from surrounding forest streams, leaving behind small lakes rich in fish. In these areas, the river flows underground, re-emerging at Crno Vrelo approximately 3 kilometres before joining the Una River. The final section flows through the narrowest canyon, reaching depths of up to 350 metres, and is protected as part of Una National Park.
However, upstream of the canyon, migratory routes and spawning grounds for native fish species are threatened by small barriers, historically built for mills and irrigation. Most of these barriers are now defunct. Habitats are further compromised by concrete channels constructed for flood control and a larger dam upstream for the timber industry.
| Project status | Live |
|---|---|
| Project type | Barrier identification and prioritisation |
| Country | Bosnia and Herzegovina |
| River | Unac |
| Focal species | Salmo trutta fario and grayling (Thymallus thymallus) |
| Organisation | Udruga Dinarica |
| Website | Dinarica.org |
The River Unac and its riparian habitats are ecologically important, especially in the Dinaric Karst region. Although the water is typically clear and cold, certain sections suffer from degraded quality due to reduced summer flow and outdated barriers. These barriers threaten habitats for native fish like brown trout (Salmo trutta fario) and rainbow trout (Oncorhynchus mykiss), disrupting migration and spawning. Flow regulation from small dams, flood control structures, and a large upstream dam further fragments habitats.
Removing these barriers is essential for restoring migratory routes, reconnecting fish with historic spawning areas, and aiding the recovery of endangered species. Barrier removal would also enhance biodiversity by improving habitat connectivity and supporting riparian species. Additionally, restoring natural flow patterns would improve sediment transport and water quality. These efforts contribute to the overall ecological health of the river and support progress toward achieving Good Ecological Status under the EU Water Framework Directive.
This project addresses a critical gap in the ecological management of the River Unac, where numerous outdated and abandoned barriers fragment aquatic habitats, obstruct migratory pathways for native fish species, and contribute to the overall degradation of water quality. Despite the clear environmental impact, there is currently no comprehensive assessment of these barriers, leaving a significant knowledge void that undermines effective conservation and restoration strategies.
This initiative aims to systematically identify, assess, and prioritise these barriers for potential removal or mitigation, thereby laying the groundwork for future ecological restoration efforts. In addition to tackling the physical barriers within the river system, the project also confronts challenges posed by outdated, incomplete, or entirely missing data regarding river flow dynamics and fish species distribution. By collecting and updating this crucial information, the project will support evidence-based decision-making and enhance the capacity of stakeholders to restore the River Unac’s ecological integrity and biodiversity.
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