Water suppliers worldwide are challenged by climate variations, but so far only the qualitative change in boundary conditions has become clear but not yet the degree and impact on the water supply systems. Short-term quality changes in surface waters can, e.g. be caused by extreme rainfalls after dry periods. Longer heat periods without rain can induce middle-term quality changes in surface waters due to lacking dilution. Furthermore, unsustainable management of groundwater can lead to long-term quality changes and to water shortages, especially in times with higher water demand. Depending on the individual situation, the expected effects on the supply system differ widely, so a general adaptation strategy will not suit the individual problems. The purpose of our work is to enable water supply companies to systematically identify potential risks resulting from climate change and other external factors in a water safety plan approach, and to adapt the supply system in a most effective way by taking advantage of ongoing modernization measures and ‘no-regret’-measures. A suitable adaptation strategy should address climate change conditions as well as other external factors like changing water demand and also to take into account possible effects on every part of the supply system.