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Europe's rivers are broken, but there is a fix

Published: 17 December 2020
Caban Coch Dam, Wales
The AMBER project has estimated there are at least 0.74 barriers per km of stream across Europe.

An international team of researchers, including experts from the University of Southampton, have found that the flow of Europe’s rivers and the movements of animals are impeded by at least 1.2 million instream barriers – with many being obsolete and beyond repair.

The results, published in Nature (https://doi.org/10.1038/s41586-020-3005-2), show that Europe has probably some of the most fragmented rivers in the world, and that small barriers – weirs, culverts and fords less than 2m high - are the main culprits, affecting fish and other wildlife.

A team of scientists at the International Centre for Ecohydraulics Research (ICER), University of Southampton, built on previous work to develop a rapid barrier assessment tool to map the impact of barriers on river networks throughout Europe.

Southampton Professor of Ecological Engineering, Paul Kemp, explains that this project is particularly important as many of the barriers identified were previously not recorded on any database.

“European rivers have suffered from a long-historic legacy of many hundreds of years of river engineering for agriculture, flood prevention, navigation, electricity generation and water supply,” said Professor Kemp.  “This has resulted in a very high density of small barriers that have degraded the ecological status of our rivers so that many fail to meet the basic standards of the EU Water Framework Directive.”

Many barriers the team identified were found to be obsolete or out of use and Professor Kemp and his colleagues believe that removing them provides unprecedented opportunities for restoring river connectivity. Halting current rates of fragmentation (i.e. avoid building new dams) and applying adaptive management to reduce the impact of existing barriers will also support the restoration of river biodiversity.

This research is one of the main outputs of the EU Horizon 2020 project Adaptive Management of Barriers in European Rivers (AMBER) which, for the past four years, has been mapping river barriers across Europe to provide the first pan-European assessment of river fragmentation. Using barrier modelling and extensive field ground-truthing, the study has estimated that there are least 0.74 barriers per km of stream, and produced the first comprehensive barrier inventory, the AMBER Barrier Atlas.

Professor Carlos Garcia de Leaniz at Swansea University who led the project said, “Existing views on river fragmentation tend to consider only the impacts of large dams, but these are relatively rare; what fragments rivers the most are not dams, but hundreds of thousands of small weirs and other low-head structures, many of which can be removed, providing unprecedented opportunities for restoration”.

Dr Jim Kerr, Research Fellow for the AMBER Project at the University of Southampton added: “Our rapid barrier assessment tool provides critical data that feeds into methods to prioritise restoration actions, such as dam or weir removal, by the most cost-effective means while providing the greatest gains for regeneration of lost biodiversity.”

The results of AMBER have already reached policy makers and fed directly into the 2030 Biodiversity Strategy, helping to set a clear target of reconnecting at least 25,000 km of Europe’s rivers by 2030.

AMBER has received funding from the European Union's Horizon 2020 Research and Innovation Programme. The project seeks to apply adaptive management to the operation of dams and other barriers to achieve a more sustainable use of water resources and a more efficient restoration of stream connectivity. The AMBERT team has developed tools and simulations to help water companies and river managers maximize the benefits of barriers and minimize ecological impacts.  

 

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