The history of the grey water footprint, or let’s quote the originator of the idea
The water footprint was introduced in 2002 [1] and quickly became a popular tool for assessing anthropogenic impacts associated with human activities. The basic methodological document that describes the water footprint methodology is the Water Footprint Assessment Manual from 2011 [2]. The water footprint consists of three components, depending on the source and type of water use: 1) the blue water footprint represents water consumption from water sources, i.e. taken from rivers, lakes, and aquifers, 2) the green water footprint represents the consumption of water that comes from precipitation and is stored on the surface of the soil or plants or as soil moisture, and is consumed mainly by evapotranspiration, 3) the grey water footprint represents the amount of water needed to assimilate anthropogenic pollution based on the natural background concentration and existing environmental water quality standards.
