Water Footprint

The water footprint of an agricultural product measures the volume of freshwater appropriated to produce it, including water consumed and water needed to account for pollution. It covers relevant stages of the production chain and is commonly expressed as water volume per unit of product, such as cubic metres per tonne. Unlike simple water withdrawal, it distinguishes the source and purpose of water use.

Components of the footprint

The total product water footprint combines three components, each capturing a different form of freshwater appropriation.

• The green water footprint is rainwater stored in the soil and consumed by the crop, mainly through evapotranspiration.
• The blue water footprint is surface water or groundwater consumed during cultivation and processing, including irrigation water that is evaporated or incorporated into the product.
• The grey water footprint is the volume of freshwater theoretically required to assimilate pollutants so that specified water-quality standards are met.

Scope and calculation

A product footprint is obtained by aggregating the relevant process water footprints across its production chain and relating them to the quantity produced.

• For crops, it reflects climatic conditions, crop water requirements, irrigation, yield and pollutant loads from inputs such as fertilisers.
• Processing water and allocation among multiple products may also be included when the assessment covers the complete supply chain.
• It measures both direct water use at the farm and indirect water use embodied in inputs and processing within the chosen system boundary.

How the measure should be interpreted

A water footprint is a volumetric accounting indicator, not a complete measure of environmental damage.

• The same volume can have different consequences depending on local water scarcity, season and the condition of the river basin or aquifer.
• Sustainability assessment must therefore compare blue water use with available water and grey water requirements with local pollution-assimilation capacity.
• Separating the three components allows rain-fed production, irrigation dependence and water pollution to be evaluated rather than hidden within one aggregate figure.

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