The water footprint of food measures the total volume of fresh water used to produce a food item, from the field or farm to the final consumer. This calculation accounts for the water consumed in every step of the supply chain, including growing, processing, and transportation. The footprint emphasizes water that is consumed—meaning it is evaporated, incorporated into the product, or polluted beyond acceptable standards. Since agriculture accounts for roughly 70% of global freshwater withdrawals, understanding the water footprint of our diets is important for addressing global water scarcity and promoting environmental sustainability.
The Three Components of Water Footprint
The total water footprint is broken down into three distinct components that categorize the source and impact of the water used.
The Green Water Footprint refers to the volume of rainwater stored in the soil and subsequently consumed by the crop through evaporation or incorporation into the plant tissue. Relevant for rain-fed agriculture, this water is often considered the least concerning from a scarcity perspective, as it is derived directly from precipitation.
The Blue Water Footprint is the volume of surface water or groundwater withdrawn for irrigation and other processes, which is then consumed. This component is a sustainability concern because it directly depletes finite freshwater resources like aquifers and rivers, often leading to water stress in limited supply regions.
Finally, the Grey Water Footprint represents the volume of fresh water required to dilute the pollutants generated during production, such as nutrient runoff from fertilizers, to a level that meets established water quality standards. This component indicates water pollution and its impact on the surrounding ecosystem.
Measuring the Water Impact of Different Foods
The measurement of water footprints reveals vast disparities in the resource intensity of different food categories, with animal products generally requiring significantly more water than plant-based staples. Producing one kilogram of beef, for example, has a global average water footprint that can exceed 15,400 liters, largely attributed to the water needed to grow the animal’s feed over its lifetime. This contrasts sharply with low-impact staples like vegetables, which require an average of about 322 liters per kilogram, or cereals, which are highly water-efficient in terms of calories provided.
Even within plant-based foods, water requirements vary considerably depending on farming practices and the specific crop. High-value crops such as almonds can have a notably high water footprint, particularly the blue water component, due to the irrigation required to sustain the trees in arid regions. Rice, another high-impact crop, also contributes significantly to the global blue water footprint, especially in major growing regions that rely heavily on surface water for paddy irrigation.
Hidden Water in the Global Food Supply
The concept of “virtual water” explains how the water footprint of food is embedded in trade, representing the water volume used to produce a commodity that is exported or imported. When a country exports water-intensive products, it is essentially exporting its water resource in virtual form, which can have significant geopolitical and environmental consequences. This transfer means that consumption choices in one part of the world can directly influence water availability and stress in distant production regions.
An importing country, especially one that is water-scarce, may achieve water security by relying on virtual water imports rather than producing all water-intensive goods domestically. However, if the exporting country is also water-stressed, this trade exacerbates local water depletion and environmental strain. Tracing these virtual water flows helps identify where the global food system places the heaviest demand on finite freshwater supplies.
Practical Strategies for Reducing Your Food Water Footprint
Individual consumers can significantly reduce their food water footprint by focusing on three primary areas.
The first effective strategy is minimizing food waste. Nearly one-third of all food produced globally is lost or wasted, representing a substantial loss of embedded water. Planning meals and properly storing food helps ensure that the water and other resources used to grow and process the food were not consumed needlessly.
Another impactful action involves shifting dietary patterns, particularly by reducing the consumption of foods with a high blue and grey water footprint, such as beef and other animal products. Swapping out meat-based meals for less water-intensive alternatives like beans, lentils, or grains, even a few times a week, can lead to a considerable reduction in an individual’s overall water impact.
Finally, consumers can make more informed purchasing decisions by supporting local farms that use sustainable practices. These farms often rely more on green water and have better pollution management, which reduces the strain on local water resources.