Reconciling hydropower generation with biodiversity

Raphaël Angeles in front of the Dynamo hydropower plant in Courrendlin, on which he worked to make its exploitation more sustainable. © EPFL / 2025

Raphaël Angeles in front of the Dynamo hydropower plant in Courrendlin, on which he worked to make its exploitation more sustainable. © EPFL / 2025

For his master’s project in environmental science and engineering, EPFL student Raphaël Angeles came up with methods for making hydropower generation more environmentally responsible, taking the Dynamo hydropower plant in Courrendlin, in Jura Canton, as his case study.

Raphaël Angeles jumped into his master’s project with both feet. Equipped with wading boots and a GPS system, he measured the bathymetry, or river-bed topography, of the Birse river that runs through Jura Canton, focusing on the section near the Dynamo hydropower plant in Courrendlin. His research gives an initial snapshot of the current state of the river and its natural habitats and provides quantitative recommendations on how the plant operator and the Canton of Jura can improve the plant’s environmental performance.

The Birse river runs through Jura Canton. © Flickr

Crunching through data supplied by the Canton of Jura, together with figures on the plant’s hydropower generation rates, Angeles found that reducing the plant’s annual production by 10% could lead to a 38% improvement with respect to an ecological index. This could be achieved if the plant used a variable discharge, which, compared to a steady flow rate, allows for more natural, dynamic river conditions. Importantly, such an approach would improve the habitats of brown trout, a species currently under threat, and grayling, an endangered species – although additional research is needed to quantify the benefits to grayling. Angeles’ findings have been published in Sustainability.

Angeles began his research on this section of the Birse during his master’s internship at EcoEng, an environmental engineering firm based in Porrentruy. He wanted to work in the field of ecology and had become interested in the environmental renovation of hydropower plants during his classes with Giovanni De Cesare, operational director of EPFL’s Hydraulic Constructions Platform (PL-LCH) and Angeles’ eventual master’s project supervisor. Jura cantonal officials suggested to Angeles to examine the Dynamo hydropower plant in Courrendlin, which has been in operation since 1899 and is one of Switzerland’s 705 hydropower plants (based on 2024 figures from the Swiss Federal Office of Energy). Hydropower currently accounts for 55% to 60% of the country’s total power generation; small hydropower plants like Dynamo account for approximately 6%.

Developing a hydraulic model

Angeles started by collecting all the data he needed for the 2.5-kilometer stretch of river near the plant. These data included the river’s daily flow rates for the past 20 years, the river’s topography and the plant’s hydropower output. He used this information to develop a hydraulic computer model and an ecological index – the Habitat Suitability Index – that varies based on water velocity and flow depth.

Water velocity and depth play an important role in the quality and sustainability of river habitats as they are key parameters influencing how fish grow in a river from the larva stage into adults. Angeles’ index is calculated largely from these parameters and also reflects the number of brown trout and grayling habitats that exist in the section of the Birse under study. What’s more, the index is designed to account for exceptional circumstances such as droughts – leading to extremely low water levels in the summer – and heavy precipitation. One of Angeles’ first findings was that for brown trout, river conditions near the plant are not ideal.

Angeles then used his model to run environmental and financial optimization scenarios for different river flow rates. His variable flow-rate approach – called a non-proportional flow allocation method – allows for more granular control than that typically employed at hydropower plants. The method can be used at larger plants too, and in other hydraulic applications.

The concrete channel carrying water to the plant. © Flickr

Solar panels as an added bonus

To make up for the decrease in hydropower production at the Dynamo hydropower plant that Angeles’ study calls for, he suggests that the plant operator install solar panels on the concrete channel carrying water to the plant – especially since the channel currently has no environmental value. That could boost annual power generation by 20%, equivalent to the electricity use of around 30 households.

Angeles, now an EPFL graduate, has moved from his native Lausanne to Jura Canton where he works for EcoEng. There, he applies his engineering skills to sustainability endeavors, running hydraulic models to help protect against river floods, working on the environmental renovation of an old hydropower plant and mitigating the risks associated with surface runoff. When he’s not at work, Angeles can be found pursuing his interests in dance, mycology and the mountains.

Swiss biodiversity under serious threat

Most of Switzerland’s run-of-river hydropower plants are operated by private-sector concession holders. In 2011, the Swiss government amended the Federal Water Protection Act to require plant operators to complete their facilities’ environmental renovation by 2030. The federal government provides subsidies to support the renovation work through an environmental certification that allows them to sell power at a higher rate.

Run-of-river hydropower plants have been a feature of the Swiss landscape for over a century. They collect flowing water in a series of small reservoirs, while mobile dams prevent migrating fish and bedload transport across the facility. Switzerland’s efforts to renovate these plants are part of a broader initiative to restore river habitats and help protect biodiversity. Rivers in the country are under threat from canalization, for example, as well as strategies to disconnect them from floodplains. The presence of hydropower plants causes their flow rates to vary widely by hydropeaking. What’s more, river ecosystems are being affected by micropollutants and pesticides.

The Swiss Federal Office for the Environment (FOEN) has reported that nine fish species are considered to have disappeared from Swiss rivers in the past 150 years, including all long-distance migratory fish (salmon, sea trout, allis shad, cuttlefish, European sturgeon, Adriatic sturgeon and river lamprey). The grayling that Angeles studied in his research has been deemed an endangered species, while other species are under threat or potentially under threat. According to the FOEN, the number of grayling fished in Switzerland plunged from 80,000 in 2000 to 30,000 in 2019.

References

Raphaël Angeles, Patrick Della Croce, Federico Ferrario and Giovanni De Cesare, “Ecological Flow Assessment: Balancing Trout and Grayling Habitat Ecology and Hydroelectric Production,” Sustainability, 31 October 2024. https://doi.org/10.3390/su16219473