Background The ecological functioning of the Ljubljanica River corridor – upstream and downstream of the Ljubljana urban area – towards the confluence with the Sava, and further upstream along the Sava, has been heavily degraded. This section of the river is also a habitat for a fragmented and heavily endangered population of Danube salmon (Hucho hucho), as well as populations of Danube roach (Rutilus pigus) and striped chub (Leuciscus souffia). The Ljubljanica River acts as a corridor, linking the limestone headwater areas and alluvial plain areas of the Sava. Due to its unique character, the Ljubljanica River and its corridor has remained a vital habitat for numerous endangered species, in spite of it being one of the most degraded rivers in Slovenia. Currently, it represents a habitat for 26 different native fish species, including several species listed in the Habitat Directive (Eudontomyzon mariae; Barbus meridionalis; Rhodeus sericeus amarus; Cobitis taenia; Cottus gobio, as well as those mentioned above). The eco-hydrological conditions in the Ljubljanica River corridor influenced the development and also help to maintain the unique habitat conditions in the Ljubljansko Barje wetland area in a fragile ecological equilibrium. Objectives The project aims to improve the coherence of Natura 2000 sites by restoring the functionality of the Ljubljanica River as a corridor linking two sites. It will achieve this by removing barriers to fish migration, enhancing and restoring habitats, improving the water management infrastructure, and putting in place a water monitoring system. The target fish species are Danube roach, Danube salmon and striped chub. Through implementation of the restoration measures, the Ljubljanica River channel will be renewed. By restoring the corridor continuum, the Ljubljanica River corridor will function as a passage or stepping stone that will connect the upstream Ljubljansko Barje Natura 2000 site with floodplain areas that are positioned downstream of the urban area of Ljubljana, and further upstream along the Sava and the Natura 2000 site Sava-Medvode-Kresnice. In this way, a previously unified population of Danube Salmon will be reunited. The project will also carry out an ecohydrological survey and develop hydrological models. The survey will serve as a basis for drafting a management plan, identifying threats at the project site, implementing restoration actions and additional habitat conservation and restoration works. The project also aims to promote relatively simple river restoration measures for improving the ecological status of the river to meet the requirements of the Water Framework Directive. Furthermore, the project aims to raise awareness among the general public, local stakeholders and decision-makers at local and national level. Expected results: Improved ecological status of the heavily degraded Ljubljanica River corridor; Concrete restoration measures, including the construction of two fish passes, the reconstruction of the Ambrožev trg barrier and the restoration of three meanders that will lead to improved habitat conditions for the target fish species; Improved connectivity of fish populations that are now very fragmented; Demonstration of how restoring a river corridor can improve the habitat conditions and migration of organisms, as well as enhancing the natural coherence between Natura 2000 sites and the surrounding landscape; A hydrological model of the Ljubljanica River for water level regulation and adjustment. The operation of a barrier, according to the hydrological model, will help to the re-establish the hydrological functioning of the Ljubljanica River during low to medium flows, which is necessary for the conservation of the Ljubljansko Barje Natura 2000 site; Demonstration of examples of good practice that can be easily applied on various spatial scales and in accordance with a Water Framework Directive implementation strategy.