Hydropower is a key energy source in almost all world regions. It fuels social and economic development, ensures electricity security, and is a pillar for renewable electricity production. But hydropower and its environmental impacts are vulnerable to climate change. This discussion of model-based climate change impact assessments and underlying modeling assumptions will help decision-makers and scientists analyzing existing studies and identifying the most urgent open questions. Rooted in hydrological uncertainty analysis, this discussion focuses on the importance of local factors and on modeling uncertainties for a critical view on our ability to project future hydropower production in different world regions. (C) 2015 Wiley Periodicals, Inc.