Both demand and supply side pressures are on the rise, driven by economic development, population growth, deteriorating water quality and climate change. The OECD Environmental Outlook to 2050 highlights that water resources are already over-used or over-allocated in many places. This is the case where current levels of abstraction exceed the sustainable level (“over-use”) or where existing water entitlements (e.g. licenses or permits) to abstract water exceed the sustainable level (“over-allocation").