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Measures and management challenges

Already in the first RBMPs, several European countries planned measures to improve the ecological conditions of rivers impacted by barriers. The planning of measures in the second RBMPs indicated substantial further effort to improve longitudinal continuity in river basin districts. The most common measures planned in this respect include the building of fish ladders and bypass channels, the removal of artificial structures such as barriers, the setting of ecological flows and measures for sediment management.

The implementation of such measures is closely linked to the environmental objective of the WFD to restore continuity for migrating species in regulated rivers. A number of other EU policies are also supporting the restoration of river continuity and the rehabilitation of surface waters that are impacted by barriers, including the Birds and Habitats Directives (2009/147/EC and 92/43/EEC), the new EU Biodiversity Strategy for 2030 (EC, 2020) and the Eel Regulation (Council Regulation (EC) No 1100/2007). The new EU Biodiversity Strategy 2030 has actually included a specific commitment to restore at least 25 000 km of free-flowing rivers by 2030 through the removal of primarily obsolete barriers and the restoration of floodplains and wetlands (EC, 2020).

Overall, due to the very high number of barriers present on rivers in Europe, there is a need for prioritisation of measures to restore continuity. Some national and regional strategies for restoring continuity are in place to ensure a phased approach in dealing with the issue of barriers. Examples include the Benelux treaty on free fish migration (adopted in 1996), continuity restoration initiatives in the international river basins of the Rhine[3] and the Danube (Shepherd, 2012) as well as national programmes and priority networks for river continuity restoration in specific countries such as France, Austria, Germany and Finland (Kampa et al, 2017; Ollikainen & Vilhunen, 2019).

[3] http://www.salmoncomeback.org/

The implementation of measures is affected by significant gaps in knowledge concerning barriers, their abundance, distribution in the European river networks (especially of small barriers) and their ecological effects. Recent AMBER study (see above) might have summarised many of the needed basic information. Also, knowledge still needs to be solidified on the effects of some of the key measures. For instance, barrier removal is increasingly viewed as a necessary management measure to reinstate natural connectivity. However, we so far have little knowledge to make predictions about the geomorphological and biological trajectory of a river system once a barrier has been removed (Birnie-Gauvin et al., 2017). Also, knowledge is lacking on measures to mitigate impacts on downstream migration of fish at hydropower turbines especially in large rivers.

An additional implementation challenge arises from the large number of barriers with an unknown or obsolete use. Funding measures to make barriers with obsolete use passable is a challenge, because of the lack of a specific water use sector assigned to these modifications in the rivers.

In parallel to planning measures for dealing with the impacts of existing barriers, new barriers and dams are built elsewhere in Europe driven by policies for energy production, transport, flood protection and securing water supply (e.g. new hydropower plants in the Balkans, see WWF (2019))[4]. In this respect, a much closer coordination of river basin management planning under the WFD and the planning of new river infrastructure to serve sectoral development is essential to safeguard river continuity.

[4] WWF, 2019. Hydropower pressure on European. The story in numbers.