Water footprint in agriculture: what it is and how to reduce it

According to the FAO, agriculture uses around 70% of the fresh water withdrawn worldwide. This figure places the primary sector at the centre of the conversation about water and sustainability. When a producer knows the volume of blue, green and grey water their fields demand, they have a quantitative indicator to act with the same precision they use to fine-tune fertilisation or irrigation.

Talking about the agricultural water footprint is no longer just an academic matter. It is an economic issue, because excessive consumption drives up the energy bill for pumping. It is a regulatory issue, because the EU Water Framework Directive pursues good status for water bodies and constrains withdrawals in over-exploited basins. And it is a market argument, because many retail chains ask their suppliers for evidence of responsible water use.

What does the agricultural water footprint measure?

The agricultural water footprint combines in a single result the irrigation water withdrawn from wells or canals (blue footprint), the rainfall stored in the soil and consumed by the plant (green footprint) and the water needed to assimilate fertilisers and crop-protection products until quality standards are met (grey footprint).

The weight of each component varies greatly depending on the crop and the production system. An intensively irrigated crop, such as flooded rice, has a very high blue footprint; a rain-fed crop depends almost entirely on the green water from rainfall. This is why the sustainability of a crop is not explained by the type of plant alone, but by the climate, the irrigation system and the efficiency of nutrient use.

Crops with the highest and lowest footprint

In general, irrigated crops in arid areas, such as cotton or rice, have a high blue footprint, while rain-fed crops keep a low blue footprint because they rely on rainfall. The rain-fed olive grove, for example, depends mostly on green water, which reduces its pressure on rivers and aquifers compared with other vegetable oils that require supplementary irrigation.

The exact figures per kilogram vary widely from one study to another and from one region to another, so they should always be taken as context-dependent estimates. The most cited international references are the estimates of the Water Footprint Network (Mekonnen and Hoekstra). The choice of variety, planting density or the incorporation of organic matter into the soil can change these values appreciably.

Strategies to reduce the agricultural water footprint

There are well-established agronomic practices to reduce water consumption without penalising yield:

• Localised irrigation: drip irrigation, as opposed to flooding or sprinkling, takes water directly to the root zone and reduces losses through evaporation.
• Controlled deficit irrigation: applying less water in the phases where water stress does not compromise production, supported by soil-moisture sensors.
• Adapted and drought-tolerant varieties: species that make better use of the available water.
• Cover crops and organic matter: reduce direct soil evaporation and improve infiltration and moisture retention.
• Precision fertigation: applying nutrients dissolved and adjusted to the crop's needs reduces nitrate losses and, with them, the grey footprint.

All these measures can be integrated into a water footprint assessment like the one we describe step by step in our article on how to measure the corporate water footprint.

Benefits for the farm

Reducing the water pumped lowers electricity consumption and, therefore, the farm's energy bill, an increasingly relevant cost. In addition, demonstrating efficient water use makes it easier to access sustainable-production seals and certifications that many buyers already require, and it improves the farm's resilience against droughts and irrigation restrictions. Water sustainability, well planned, is a factor of competitiveness.

The agricultural water footprint, a metric to optimise resources

Measuring the agricultural water footprint rigorously is the first step to optimising resources, reducing costs and protecting the farm against climate variability. Knowing the consumption data makes it possible to decide where to invest with the greatest return.

To complete the picture, you can also read about the blue water footprint, the green water footprint and the virtual water of food.

Frequently asked questions about the water footprint in agriculture

Why does agriculture consume so much water?

Because crop irrigation accounts for most fresh-water withdrawals: according to the FAO, around 70% globally. The rainwater that crops consume (green footprint) is added to that consumption.

Can the agricultural water footprint be offset?

Recharging aquifers or using reclaimed water can offset part of the withdrawal, but the priority is always to avoid unnecessary consumption at source through more efficient irrigation and management.

What role does technology play in efficient irrigation?

Soil-moisture sensors, weather stations and irrigation scheduling based on evapotranspiration make it possible to apply only the water needed, reducing consumption and the energy cost.

To measure and reduce the water footprint of your agricultural activity with traceable data, you can rely on Manglai's water footprint solution.