Given the importance of water as an essential resource as well as a potential threat, climate change impacts on freshwater will affect not only water and flood management per se, but also a number of key policy domains (e.g. energy, agriculture, infrastructure, biodiversity, and health). Despite the ever-expanding scientific basis, reliable information about the nature, magnitude and timing of impacts at the scale needed for practical, site-specific adaptation is generally lacking. Adaptation decisions need to accommodate significant uncertainty.