Hydropower plays an important role within the renewable energy sector and supports the achievement of international energy security targets. Yet this sector is also vulnerable to droughts which affect generation potential, and high flows which can cause structural and operational damage. Here we use river flows calculated using a multi-model ensemble to investigate the potential water risks which current and planned global hydropower generation capacities may face at 1.5 °C and 2.0 °C warmer worlds. We find that the global hydropower sector will have to face diverse, simultaneous, and compound water risks. We estimate that about 65% of current global hydropower installed capacity will be exposed to risk from recurrent high river flows (here understood as the change in the 1-in-100-years flow). Up to 75% of existing hydropower capacity in Europe, North America and MENA is located in areas where droughts are projected to become at least 10% longer when compared to historical conditions. Achieving a 1.5 °C warming target would reduce these risks, compared to a 2.0 °C scenario.