A methodology is developed to reveal the dynamics of behavior and interactions among actors (stakeholders) in water supply systems and their effect on the technical network and the ecological and socio-economic environment. An agent-based model is under construction which allows to simulate different scenarios of the actors' behavior and to compare the results with observed phenomena (stylized facts) of Swiss cities. First results further clarify the significance of demand trend analysis. We envision the model in a final stage as being helpful to tackle the task of illuminating the diffusive claims, expectations and interactions of the actors involved. Knowledge about these processes is crucial to uncover bottlenecks hindering the sustainable development of our water supply systems into the future.