10 March 2020 | 2 minutes.

In conversation with Dr. Steven Weiss

Steven Weiss
Freshwater biodiversity expert & Associate Professor at the University of Graz, Austria.

Steven Weiss, Freshwater biodiversity expert & Associate Professor at the University of Graz, Austria.

How do hydropower dams affect freshwater biodiversity?

Depending on the type and size of the plant, hydropower affects biodiversity in many different ways. The number one impact is habitat destruction. Additionally, with many plants being built, the whole river network becomes fragmented and fish aren’t able to move up or/downstream to fulfil their lifecycle needs.

Additionally, certain plants function with what is known as “hydropeaking”, which is highly destructive. Water is released at certain times of the day to meet peak demands for energy. In a matter of minutes, spawning and rearing grounds can go from being several centimeters or a meter or more deep to being completely dry. The fish don’t have time to respond and are left stranded. Although your so-called run-of-the-river plants don’t have hydropeaking, they all accumulate fine sediments, which must be periodically flushed from the reservoir.

Beaver, Austria. Photo: Leopold Kanzler

Which species are at risk should the planned hydropower plants go ahead?

All of Europe’s large iconic species, such as the Atlantic salmon, European eel, the last surviving populations of sturgeon, would be impacted by these plants. In southern Europe, the Balkans in particular, there are many hotspots, as this is where the highest concentration of endemic biodiversity is found – virtually all of the endemic fish species in the Balkans would be threatened with massive reductions should the planned plants go ahead.

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