Geographical, environmental and economic factors also have a considerable impact, There is a diversity of situations across OECD federal and unitary states in terms of the institutional organisation of water policy. On the other hand, though some unitary states still retain significant water responsibilities at central government level, with highly centralised water policy making (Korea, Chile, Israel), most OECD unitary states (France, New Zealand, Greece, the Netherlands) have de facto delegated many responsibilities to lower levels of government. These models are not intended as normative in the sense that one would be better than the other, but they highlight different co-ordination challenges raised by a given institutional organisation of water policy even if - within a same “category” - the degree to which governance challenges have an impact on the performance of water policy may vary from one country to another. In addition to outlining the challenges to co-ordination, they could be enriched by adding other dimensions (e.g. capacity gaps, variety of tools in use, etc.),