Green Water Footprint

The green water footprint quantifies the volume of rainwater stored in the soil as moisture and consumed by crops and vegetation through evapotranspiration. It refers to water that does not run off or recharge aquifers but is used in place, which makes it especially relevant for rainfed agriculture and natural forests.

It is one of the three components of the water footprint, alongside the blue water footprint (surface water and groundwater) and the grey water footprint (water needed to dilute pollution).

Methodological basis

• Defined by the Water Footprint Network to distinguish rainwater from surface water and groundwater.
• Incorporated in ISO 14046 as a water flow within life-cycle water footprint inventories.

Why it matters

• Agriculture: green water is the largest share of the water consumed in global crop production, roughly three times the volume of blue water used, so it is central to food production.
• Ecosystem services: it sustains forests and grasslands, supporting the carbon cycle and biodiversity.
• Water security: making better use of rainfall reduces pressure on blue water sources and improves resilience to drought.

How it is calculated

Conceptually, the green water footprint corresponds to the rainwater that is actually used by the crop:

Green water footprint = effective rainfall used by the crop (evapotranspiration of rainwater)

It is expressed as a volume per unit of product (for example litres per kilogram) or per area (cubic metres per hectare).

Optimisation strategies

• Conservation agriculture: reduced tillage, cover crops and rotations that improve moisture retention.
• Rainwater harvesting: terraces, bunds and micro-catchments that help water infiltrate the soil.
• Suitable crop choice: varieties whose growth cycle matches local rainfall.

Limitations

• Climate variability: shifting rainfall patterns affect how much green water is available.
• Soil degradation: compaction and loss of organic matter reduce water-holding capacity.
• Data needs: monitoring soil moisture relies on remote sensing and field sensors.

Measuring the green water footprint helps optimise the use of rainfall, reduce the blue water footprint and strengthen food security. At Manglai we help companies measure their water footprint and prepare their sustainability reporting. Discover how Manglai can help you.