In the Lim River (Bosnia and Herzegovina), a rope with canisters prevents dumped waste from entering the turbines of a downstream hydropower plant. | Photo: Helena Huđek
Question: Ms. Huđek, Mr. Pusch, you were involved in counting instream barriers in river courses throughout Germany and 14 other European countries for AMBER. What was the reason for this?
Martin Pusch: The aim of the project was to create a European atlas of instream barriers. The official number of barriers reported by the EU Member States was 630,000. Knowing from experience that authorities’ statistics are incomplete, we set about recording the true number of structures in 15 countries by conducting surveys along selected river sections. The findings were used to calculate a more realistic, but still conservative figure: there are 1.2 million barriers in Europe’s rivers, including 225,000 in Germany, 179,000 of which were known to the authorities.
Helena Huđek: I documented the barriers encountered along a 20 km stretch of 25 different rivers, respectively, in Germany, the Czech Republic, Hungary and six Balkan countries. We recorded all of the barriers, i.e. the type of barrier, its use, and whether the river still had sufficient water.
What did your exploration reveal?
HH: We discovered many more barriers than we had anticipated. In the Czech Republic in particular, we found lots of small barriers, around one metre in height, that had been self-constructed to make angling or swimming easier. Nobody was aware that these barriers existed.
What impacts do barriers have on river systems?
HH: They fragment the river, making it impossible for fish to pass the barriers. Migratory fish species need to swim upstream in order to spawn, but they are no longer able to reach their spawning grounds…
MP: … and most fish ladders are not effective. They frequently have an insufficient water depth and are often too steep, and fish find it difficult to locate the passage entrance. Dams and weirs also have the effect of interrupting sediment transport. This prevents the formation of new gravel banks in the riverbed, which represent a prerequisite for the successful reproduction of trout, and also for the natural self-purification processes in rivers.
Why were so many barriers built in Europe’s rivers?
MP: The oldest transverse structures, dating back to the Middle Ages, were used to power mills. From the 20th century onwards, these mills were often converted into small hydropower plants . Many more barriers were built to compensate for the effects of river regulation, often carried out during agricultural land improvement operations. Straightening of a stream or river inevitably leads to incision because of the steeper slope, i.e. sediment is transported downstream. As a result, the river becomes deeper, causing unstable banks and bridge foundations. To avoid this, many bottom sills were installed, increasing the number of barriers in the river.
Which current developments are particularly problematic?
HH: In the Balkans, there were 590 weirs for small hydroelectric plants in 2015. There are now more than 1,300, meaning that the number of such plants has more than doubled in five years. There are plans to build a further 3,000 hydroelectric power plants over the next few years. Most of these planned hydroelectric power plants are small, with a capacity of up to ten megawatts, i.e. they do not generate much electricity. And yet they have a disastrous effect because they often redirect the entire river discharge to the turbines via long canals, causing extensive river stretches to run dry. This has a devastating impact on all riverine life. Unfortunately, state subsidies are still granted for the construction of small hydropower structures, also in Germany, incidentally.
Ms. Huđek, how would you describe the general situation you encountered?
HH: Compared to the rivers in Central Europe, there are more unspoiled rivers in the Balkans. However, these river systems are currently being destroyed very quickly by a “wave” of hydroelectric power plant construction. We saw river forest clearances, the straightening of natural river beds, the construction of new barriers, the canalisation of rivers, water pollution, and waste dumped into rivers; we also came across dried-up river beds. In the Balkan region, these problems are spreading like a disease, with pristine rivers vanishing in front of our very eyes.
You and your colleagues propose the removal of as many instream barriers as possible, particularly small ones. Where can barriers be removed most effectively?
MP: Since many transverse structures are actually no longer in use, they could be systematically dismantled. It would also be relatively simple to replace many of the 72,000 or so stream pipings in this country with larger passageway profiles, or to uncover streams again. Such pipe systems exist wherever roads cross streams, or where streams were in the way of other uses. The smooth surface of these pipings scares off fish, as well as other animals such as otters. However, when larger transverse structures are demolished, there is often a need to reverse historic river straightening. This then calls for the complete restoration of the stream or river, to make it longer and shallower again. To do this, riparian areas need to be purchased, watercourses widened and river bends created. The most important example of such a restoration project in Germany is the Lippe River in North Rhine-Westphalia (NRW), which now once again features long channel sections harbouring a variety of fish populations and very interesting dynamic floodplains.
The results of this river inventory were fed directly into the EU Biodiversity Strategy for 2030: the aim is for 25,000 km of Europe’s rivers to be freed from barriers by then. Is it a realistic goal?
MP: It is an ambitious goal because many of the rivers need to be restored to their natural state, but we believe it can be done! We have already identified 27 rivers in Europe, with a total length of 5,500 km, where instream barriers can be removed with relatively little effort.
What costs would be involved?
MP: It would cost around €315 million to restore the 27 rivers mentioned, which equates to 70 cents per citizen, based on the number of EU residents. As a comparison, agriculture costs each EU citizen approximately €100 per year. Even so, the costs of river restoration seem high at first sight. In a new EU project proposal, we therefore suggest how to increase the acceptance of restoration measures among the population. The idea is to make people aware of the benefits they would have if a lot of money was spent on restoring “their” river. Examples of these so-called ecosystem services include the retention of floodwaters, the stabilisation of groundwater levels during dry periods, more effective self-cleaning, and enhanced recreational value for walkers, anglers and swimmers. The aim is for citizens and communities to consider it attractive when “their” freshwaters are restored. A positive example: a restored section of the Ruhr River in Arnsberg (NRW) has become a popular backdrop for newlywed photos!
The interview was conducted by Wiebke Peters.
