Abstract

Water scarcity stems from the spatial and temporal mismatch between the supply and demand for freshwater. While water may be abundant globally, freshwater of suitable quality is frequently not available locally in the places where there is human demand. A range of indicators has been developed to assess water scarcity and the adequacy of access to water of appropriate quality faced by different human societies. Indicators have also been developed which focus not on the adequacy of water resources but on the measurement of water consumption itself, both direct and indirect consumption, on an individual, national or product basis. Such indicators raise questions about the adequacy of global water resources and whether water resources on a planetary basis are sufficient for all of humanity to achieve a decent quality of life while maintaining the natural environment in an adequate state. Indicators attempting to measure the sustainability of global human water consumption compared to the environment’s ability to cope with that consumption have been proposed but require further development if we are to realistically assess how close humanity is to reaching a global water scarcity threshold that limits future growth.