The water footprint of a process is expressed as water volume per unit
of time. When divided over the quantity of product that results from the
process (product units per unit of time), it can also be expressed as water
volume per product unit.
• The water footprint of a product is always expressed as water volume
per product unit. Examples:
– water volume per unit of mass (for products where weight is a good
indicator of quantity)
– water volume per unit of money (for products where value tells more
than weight)
– water volume per piece (for products that are counted per piece
rather than weight)
– water volume per unit of energy (per kcal for food products, or per
joule for electricity or fuels)
• The water footprint of a consumer or business is expressed as water
volume per unit of time. It can be expressed as water volume per monetary
unit when the water footprint per unit of time is divided by income
(for consumers) or turnover (for businesses). The water footprint of a
community of consumers can be expressed in terms of water volume per
unit of time per capita.
• The water footprint within a geographically delineated area is expressed
as water volume per unit of time. It can be expressed in terms of water
volume per monetary unit when divided over the income in the area.