Vary me a river: investigating the impacts of climate variability on hydropower and electricity systems planning in Switzerland

Clean and renewable energy systems play a pivotal role in climate change mitigation strategies. Nevertheless, climate change constitutes a threat to current and future supply of clean energy.   In this study, we investigate how climate variability affects hydropower production and electricity systems planning in Switzerland. As the “water tower of Europe”, Switzerland encompasses a wide range of hydro-climatological conditions and showcases a high share of hydropower in its energy mix, making it a relevant case study. Focusing on all hydropower plants with a capacity > 300 kW, we used daily runoff simulations from the PREVAH model, at 500 m resolution spanning 1991-2022, to estimate water availability and hydropower production for each power plant. The climate-impacted hydropower production time series are then given as input to Nexus-e, an integrated electricity systems modeling framework. This enables us to model the future state of the electricity system in Switzerland while considering climate variability. Our method provides an accurate estimation of national hydropower generation and its variations. The integration of climate informed inputs into Nexus-e yields strong impacts on simulated investments in renewable energy and economic indicators such as power prices and imports/exports. Notably, in case of a projected decrease in hydropower generation due to increased drought occurrence, an increase in wind turbine and alpine PV capacity is needed to meet electricity demand. This scenario poses several societal and political questions regarding the implementation of a resilient energy system for Switzerland in the context of increasing changes in the climate system and pressure on ecosystems and biodiversity.