ABSTRACT
The water footprint is an indicator of freshwater appropriation (in m3/yr), developed as an analogue to the ecological footprint, which is an indicator of use of biologically productive space (in ha). In order to get an idea of what the footprint size means, one will need to compare the water footprint to the available freshwater resources (also expressed in m3/yr), in the same way as one needs to compare the ecological footprint to the available biologically productive space (in ha) (Hoekstra, 2009). In essence, water footprint sustainability assessment is primarily about making this comparison of the human water footprint with what the Earth can sustainably support. When diving into this issue, however, one will discover that there are many different sorts of questions that one can pose and that there are many complexities involved. Sustainability, for instance, has different dimensions (environmental, social, economic), impacts can be formulated at different levels (primary, secondary impacts) and the water footprint has different colours (green, blue, grey). In this chapter we present a guide to water footprint sustainability assessment, which has grown out of the recent past of increased attention to the subject (Box 4.1).
