Population decline and infrastructure: The case of the German water supply system Ø In this paper we have focused population changes and transformations of infrastructure and supply systems. • demographic changes have significant impacts on supply systems and infrastructure. The functional capacity of these systems requires a certain population size and density. • If population size and composition change considerably, there might be adverse economic, social and technological effects on the supply systems. • With respect to water supply systems, demographic growth and shrinkage processes must be regarded as occurring simultaneously; temporal as well as spatial effects have to be considered, along with quantitative and qualitative aspects of demographic changes. Utilities need strong, spatially differentiated data for estimating demographics. • In this case, intra-regional migration and the related strengthening of demographic heterogeneity are the deciding fact