River and habitat continuity interruptions constitute a major pressure and are defined as part of hydromorphological alterations as a Significant Water Management Issue (SWMI) in the Danube River Basin. The assessments undertaken in the course of the elaboration of the 1st Danube River Basin Management Plan (DRBM Plan) in 2009 showed for the Danube and its major tributaries (rivers with catchment areas larger 4.000km2) the presence of more than 900 continuity interruptions, stemming from different infrastructure projects like flood protection, hydropower generation or navigation. In addition to the transversal structures in the main rivers, a large number of barriers are located also in the smaller rivers of the basin.
These structures represent barriers for fish migration and are therefore influencing natural migration patterns of migratory fish species by preventing access to habitats and suitable spawning grounds. Addressing these pressures by implementing suitable measures (like fish migration aids, transformation of weirs into ramps, abandonment of barriers which are not in use any more) constitutes a major challenge for the improvement of the environmental conditions and for the achievement of the objectives of the EU Water Framework Directive.
The workshop: The first day included two theoretical sessions and in the frame of the second day an excursion took place, where participants visited fish migration aids / practical solutions to get more insight knowledge on the spot.
The theoretical sessions were focusing on the following main discussion points:
1. Update Prioritisation Approach River and Habitat Continuity
- Ecological prioritisation approach as included in the 1st Danube River Basin Management Plan
- National approaches on prioritisation of measures on river and habitat continuity
- Proposals for the update of the approach
2. Technical exchange on measures to ensure fish migration
- Guidance, regulations and approaches in place on planning, construction and operation of fish migration aids
- The ICPDR Technical Paper on Fish Migration Aid
In the frame of the second day experts visited the following fish migration aids:
- Hydropower station “Melk” at the River “Danube”
- Fish migration ramp at the estuary of the river “Melk”
- Vertical slot pass at the river “Ybbs”
Outcomes: In the Danube Ministerial Declaration 2010 Ministers and its representatives reconfirmed their commitment to further develop and make full use of the ecological prioritisation approach for measures to restore river and habitat continuity in order to ensure that they are ecologically most efficient. In line with the commitment the proposal for an update of the existing methodology was discussed at the workshop.
The workshop also served as a valuable platform to exchange information on the practical realisation of measures, since it is also of key relevance to ensure that the implemented measures are effective and allow for the migration of relevant fish species. Since effective measures on downstream migration are still to a certain extent an open issue it was also an important topic which was addressed in the frame of the workshop.
This workshop is supported by the EU Grant DRBMP-2012.