This chapter provides an institutional mapping of who does what across levels of government and of the public authorities involved in water management in the Netherlands. It is structured around key water management functions: flood defence; water quantity and drainage; water quality; sewage management and wastewater treatment; and drinking water supply. The chapter identifies linkages and mismatches in the allocation of roles and responsibilities, and sheds light on the mutual dependency of the “sub-national triangle” composed of provinces, municipalities and regional water authorities. It suggests ways forward for better interconnectedness across water management functions, and with related areas such as environmental protection, land use, agriculture and nature conservation.