Environmental impacts from the same substance or activity may vary across space (e.g. ecosystem, medium, topology, human population) and time (e.g. season, weather). It is also the case that environmental issues interact, so that, for example, water-security policies may need to include policies for the adaptation to, and mitigation of, climate change, as well as the provision and protection of water resources. For example, an economic instrument that affects prices will not be effective if consumers are not aware of prices, or the means by which they can respond to price increases.3 That said, instrument mixes are not always either necessary or efficient (OECD, 2007a).