. The concept of EWR has typically been used to describe the fraction of available freshwater that is required to sustain critical surface water flows, as suggested by Smakhtin et al. (2004). However, when focusing on groundwater abstraction, the resource available for sustainable abstraction (i.e. the sustainable yield) is limited by a range of environmental considerations addressing both the surface water environments and the groundwater resource itself ( Henriksen et al., 2008 and Navarro and Schmidt, 2012).