A water footprint is the total volume of freshwater used directly and indirectly by an individual, community, business, or nation. It includes blue water (surface/groundwater), green water (rainwater), and grey water (pollution assimilation).
The water footprint is a comprehensive indicator of freshwater use that accounts for both direct water consumption and indirect (virtual) water use throughout the supply chain of products consumed by an individual, community, business, or nation. Developed by Arjen Hoekstra and colleagues at the University of Twente, the water footprint concept distinguishes three components: blue water footprint (consumption of surface and groundwater resources), green water footprint (consumption of rainwater stored in soil as soil moisture, primarily through crop evapotranspiration), and grey water footprint (the volume of freshwater needed to assimilate pollutant loads to meet water quality standards). The global average water footprint is approximately 1,385 cubic meters per person per year, though this varies enormously by country, from less than 700 in some developing nations to over 2,800 in the United States. Food production accounts for roughly 90 percent of the total water footprint, with animal products having significantly larger footprints than plant-based foods. Corporate water footprint assessment is increasingly used for supply chain risk management, sustainability reporting, and identifying hotspots where water use reduction can be most impactful. The Water Footprint Network has developed standardized accounting methods and a global water footprint assessment standard (ISO 14046) provides guidelines for life cycle-based water footprint assessment.