Before discussing the importance of groundwater, it is expedient to clarify some basic definitions. According to article 2 of the Water Framework Directive (2000):

• Groundwater is defined as “all water which is below the surface of the ground in the saturation zone and in direct contact with the ground or subsoil”.
• An aquifer is defined as “a subsurface layer or layers of rock or other geological strata of sufficient porosity and permeability to allow either a significant flow of groundwater or the abstraction of significant quantities of groundwater”.

Water ranges among the most vital natural resources, contributing, inter alia, to human health and wellbeing, economic development and the integrity of ecosystem services (Groundwater Governance, 2013). Groundwater, which amounts to around 98_% of global freshwater in liquid form, constitutes an important part of global water supply, delivering at least 50_% of drinking water (ibid.) and over 40_% of irrigation water (Siebert et al., 2010). It moreover plays an important role as a buffer in dry periods and in regard to climate change adaptation (Groundwater Governance, 2013).

The last decades have witnessed an increased demand for and thus pressure on global water resources, which in the case of groundwater in many instances induced abstraction beyond sustainable levels, as well as increased pollution levels (Groundwater Governance, 2013). As a consequence, while some regions of the world already struggle with physical scarcity, economic scarcity, i.e. inefficient allocation between competing demands, is now an issue nearly everywhere and requires political action and more effective governance of groundwater resources (Titenberg, 2002; Gibbons, 1986). All this is long since known in theory, but the issue of depleting aquifers and adequate resource conservation and protection has so far received relatively little recognition in global debates. Consequently management practices in place are often still far from inducing a sustainable use (Brooks, 2013)