However, because not all of this water is accessible for human use, the term water supply is typically used to refer to “the amount of water that is accessible to a demand centre and can be delivered reliably and sustainably with respect to the environment or the finite resource base” (2030 WRG, 2009), and it is water supply that is of primary interest when addressing the risks of water shortage, at least in the short and medium term. For non-OECD countries, this typically involves increasing access to water for basic consumption and sanitation, something that is provided through investment in water supply and delivery. By contrast, in many OECD countries, the vast majority of the population already has access to a reliable water supply, and considerable water infrastructure already exists. Investment in water supply, for instance, is needed to replace ageing infrastructure, meet increasingly stringent water quality controls, and manage extreme weather events (OECD, 2009).