Environmental adaptation of hydropower facilities requires a holistic approach and systematic monitoring

Sweden is currently carrying out a large nationwide process in which around 2,100 hydropower plants and dams are being reviewed in court to ensure compliance with modern environmental legislation. Two new scientific studies from SLU show that this process could have major implications for ecosystems in our waterways – but that the outcome depends on how much consideration is given to habitats around the facilities and how well mitigation measures are followed up. 

A focus on fish alone is not enough to protect entire ecosystems

In one of the studies, researchers examined 33 legally binding court rulings from the review process. Of these, 22 facilities had their permits revoked and will therefore be removed. The remaining eleven may continue operating, but only if environmental measures are implemented – primarily fish passages solutions to facilitate upstream and downstream movement across the dam. However, the researchers warn that environmental requirements focus too narrowly on fish passage and that habitats in and around the facilities must not be overlooked.

– Many animals and plants, including fish, are negatively affected by hydropower dams. Altered flow regimes, changes in nutrient and sediment transport, and periodically flooded areas affect habitats throughout the entire water system, including regulated lakes, says Josefin Sundin, researcher at the Department of Aquatic Resources at SLU and lead author of the study.

The researchers conclude that environmental adaptation of hydropower can produce positive environmental outcomes, but that important improvements are still needed. According to the researchers, a key shortcoming in the rulings is that monitoring of the efficiency of proposed mitigation measures is often insufficient or entirely absent. Without monitoring, there is a significant risk that solutions that appear effective in theory – but do not work in practice – will continue to be applied over long periods, resulting in wasted resources.  

The researchers also emphasize that authorities can make an important contribution by implementing additional measures in connection with remediated hydropower facilities, allowing multiple environmental objectives to be achieved while adapting hydropower operations.

Long-term monitoring is needed to secure environmental outcomes

The second study is a comprehensive research review involving several Swedish universities and provides an overview of the ecological effects of hydropower. It summarizes decades of research on how flow regulation affects water flow, temperature, and oxygen levels, as well as migration opportunities and habitats for organisms in both aquatic and adjacent terrestrial environments. The researchers also present available mitigation measures and note that although many measures exist, knowledge of their effectiveness is often based on individual case studies.

To strengthen the knowledge base, the researchers propose a so-called programmatic monitoring of mitigation measures. This means that specific measures are monitored using standardized methods across many locations and over long periods, in order to build a robust base of evidence.

– The relicencing of Sweden’s hydropower facilities is a historic opportunity to safeguard ecology in and around our waterways. However, we must ensure that mitigation measures work as intended, and that requires follow-up monitoring. Without systematic and long-term monitoring, we risk investing in costly measures that do not deliver the intended environmental benefits, says Daniel Nyqvist, researcher at the Department of Aquatic Resources at SLU and lead author of the study.

A major advantage of comprehensive and systematic monitoring is that it becomes easier to predict how different mitigation measures will perform. When well-established measures are applied in new locations, the likelihood of achieving the desired outcome increases, while the need for monitoring and associated costs may decrease.

Important knowledge base for the future of hydropower

Both studies are highly relevant in Sweden, where thousands of hydropower plants are currently being assessed against new environmental requirements. At the same time, the findings are also important internationally, as many countries face similar challenges in regulated rivers.

The studies have been published in the scientific journal Knowledge and Management of Aquatic Ecosystems.

Insights from a nation-wide environmental relicensing of hydropower facilities in Sweden: a review of court verdicts from a biological perspective

Balancing hydropower production and ecology – ecological impacts, mitigation measures, and programmatic monitoring