The project aims to enable the future removal of six obsolete barriers in the Trebišnjica River Basin to support the recovery of endangered endemic fish species.
The Trebišnjica River, historically known as the largest sinking river in Europe, flows through a complex system of karst fields, underground channels, and surface streams before disappearing into the ground and re-emerging in coastal springs along the Adriatic. This river system is crucial for maintaining the ecological balance of both surface and groundwater-dependent habitats across the wider region.
Over the past decades, the Trebišnjica has been extensively altered by one of the most complex hydropower systems in the Balkans, including multiple large dams, artificial reservoirs, and tunnels spanning over 70 kilometres. These interventions have severely disrupted the river’s natural hydrology, fragmented habitats, and reduced ecological connectivity. Despite this, the remaining segments of the river still host rich biodiversity, including several endemic and endangered fish species, such as Telestes metohiensis and Delminichthys ghetaldii. These species highly depend on unimpeded access between surface waters, sinkholes, and subterranean habitats for spawning and survival.
| Project status | Completed |
|---|---|
| Project type | Dam removal: pre-demolition |
| Country | Bosnia and Herzegovina |
| River | Trebišnjica |
| Focal species | Telestes metohiensis, Delminichthys ghetaldii |
| Organisation | The Association for Protection of Waters of Eastern Herzegovina "Vrelo" |
| Website | Vrelo NGO |
The Trebišnjica River, located in the Dinaric Karst of Eastern Herzegovina, has suffered severe ecological degradation due to decades of hydropower development and the presence of obsolete barriers. These non-functional structures disrupt natural water flow, sediment transport, and migration routes of endemic fish species such as Telestes metohiensis and Delminichthys ghetaldii.
This project builds on previous research and stakeholder engagement under the “Open Karst Rivers of Eastern Herzegovina to Save Endemic Fish” project, financed under Category A1 – Barrier identification and prioritisation, to prepare for the removal of six key barriers, restoring 13 km of critical river and tributary habitat. The initiative represents a unique opportunity to enhance ecological connectivity, improve water quality, and increase the climate resilience of the Trebišnjica River Basin. Strong local support and alignment with EU Water Framework Directive goals make this a strategic pilot for broader river restoration in karst ecosystems of the Western Balkans.
The primary goal of the project “Freeing Trebišnjica” is to restore ecological integrity and connectivity within the Trebišnjica River Basin by enabling the removal of six obsolete river barriers. These structures, which no longer serve any functional purpose, currently disrupt water flow, sediment transport, and the migratory routes of endangered endemic fish species such as Telestes metohiensis and Delminichthys ghetaldii.
To address these challenges, the project’s team will carry out feasibility studies, hydrological assessments, and environmental impact assessments for each barrier. It will also develop detailed technical removal plans and complete all necessary permitting processes. A strong emphasis will be placed on engaging local communities and relevant authorities to build support for the initiative.
The project is expected to restore approximately 13 kilometres of free-flowing river, thereby enhancing aquatic habitats and improving water quality. Additionally, it will strengthen the river’s resilience to climate change and help mitigate localised flood risks. Ultimately, this project will pave the way for full ecological restoration of a critical karst river system and serve as a model for similar efforts across the Western Balkans.
The “Freeing Trebišnjica” project successfully advanced from initial barrier identification to full technical and institutional readiness for river restoration in one of the most complex karst systems in the Balkan region. Building on prior mapping and prioritisation work, the project delivered comprehensive feasibility studies, hydrological and sediment assessments, an Environmental Impact Assessment, and a detailed technical removal plan for priority barriers.
A key achievement was the successful navigation of a complex and previously untested permitting process. Through intensive stakeholder engagement and collaboration with authorities, the project secured formal approval for the removal of four obsolete barriers and confirmation that no construction permit is required. This represents a major milestone for river restoration in the Republic of Srpska.
The project demonstrated clear ecological benefits, including restoring river connectivity, improving conditions for endemic migratory fish, reducing eutrophication, and enhancing natural sediment transport and flood conveyance. While not all initially proposed barriers were approved due to social considerations, the project established a strong foundation for implementation.
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