Open data on environmental flows: supporting decision-making to balance climate change impacts, biodiversity loss, and energy transition

Hydropower is a highly efficient, low-carbon source of energy. However, its operation often leaves only a minimal amount of water in rivers—known as environmental flows. In Switzerland, an above-average proportion of aquatic species are listed as endangered, including 65% of fish species. An increase in hydropower production will further intensify competing demands on water resources, particularly regarding environmental flow requirements, where renewable energy generation and ecological needs conflict. Put simply, environmental flows represent a reduction in hydropower production and a minimum threshold for river ecology.

In the past, the reduction of Swiss hydropower production due to environmental flow requirements has been repeatedly overestimated, mainly due to missing data. This lack of information has hindered evidence-based decision-making aimed at balancing energy production, water quality, and biodiversity conservation. The newly developed environmental flow database provides publicly available data, encompassing legal, hydrological, and technical attributes. It covers 252 hydropower plants with an installed capacity of at least 3 MW and is built on a plant-specific structure, which allows for linkage with the Swiss hydropower statistics (WASTA) to handle hydro-energetic questions efficiently.

A publicly available database is critical in the context of climate change, which is altering hydrological conditions and intensifying conflicts over the water resource management. Environmental flows involve not only the tension between energy production and river ecology but also considerations of water quality and other uses, such as drinking water supply, agricultural irrigation, cooling, and the operation of wastewater treatment plants. For sustainable water management, it is crucial to establish a public and reliable database that balances competing interests.

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