The increasing risk of energy droughts for hydropower in the Yangtze River basin

To achieve carbon neutrality and the United Nations' sustainable development goals, the energy system is transitioning to renewable energy. Hydropower is one of the main forms of renewable energy, but it is significantly affected by the climate anomalies, such as droughts. Here, we define energy droughts as the periods where daily developed hydropower potential (DHP) is below the 20th percentile of its daily climatology at each hydropower plant and analyze the spatiotemporal characteristics over the Yangtze River basin (YRB). Based on the high-resolution hydrological simulations over 67 hydropower plants in the YRB by using the re-calibrated PCRGLOBWB model, we find that there are about 10 energy droughts per year during 2007-2021, the mean duration is 7 days/event, and the DHP is reduced by 26% during energy droughts. Compared with winter, there are more energy droughts in summer, but with shorter durations. The interannual variation of energy droughts is closely associated with El Nin similar to o-Southern Oscillation (ENSO). Affected by strong La Nin similar to a, energy droughts increased during 2008-2009 and 2011-2012. The propagation from meteorological droughts to energy droughts takes up to 4-7 days for most plants, and around 31% of the energy drought and meteorological drought events occur simultaneously. Specifically, the accumulated energy deficit during the extreme energy drought in the summer of 2022 has a return period of 52 years, and the risk will be further increased by 88%+/- 1.2% under the SSP585 scenario in the future. This study suggests the need to understand the change of energy droughts for hydropower management and the urgency for climate change adaptation for a more stable hydropower supply.