What is virtual water? Virtual water is the total volume of fresh water used directly and indirectly throughout a product’s supply chain, whether it is a T-shirt or a kilogram of coffee. The global scientific community has established a standardized measurement system that serves as an essential technical benchmark.
The concept was coined by geographer John Anthony Allan in 1993 as a way to quantify the total volume of fresh water used to produce a good or service. His groundbreaking contribution transformed our understanding of global water management and trade, earning him the prestigious Stockholm Water Prize in 2008.
This metric, developed by organizations such as the Water Footprint Network and now firmly established as an international benchmark, this metric is one of the most important sustainability indicators in environmental science today. It reveals the water footprint of every product before it reaches the market, tracing its impact from origin all the way to the end consumer.
It is a key technical tool for using this essential resource more efficiently. Integrating it into a company’s economic planning as another factor in the production chain has been crucial to improving the relationship between water and energy, helping to optimize energy resource management and support climate mitigation.
The three colors of water
To ensure this indicator can be applied clearly and rigorously, the scientific community established three complementary technical categories of virtual water based on its source and use.
The first is green water. This is the volume of rainwater stored in the soil that subsequently evaporates or is taken up and transpired by plants as they grow.
The second is blue water. This refers to surface water and groundwater withdrawn from rivers, lakes, and aquifers for use in production processes. When regions with limited blue water resources import water-intensive goods from areas with abundant green water, this can produce system-wide energy savings. This complementary or compensatory strategy reduces the need for other solutions or infrastructure, such as desalination plants, thereby avoiding more complex industrial processes.
The third category is gray water. This is the theoretical volume of fresh water required to dilute the pollutants generated during a production process until established environmental quality standards are met. This indicator makes it possible to quantify the impact on water resources and assess the benefits of measures such as reducing discharges, improving wastewater treatment, and reusing reclaimed water.
Virtual water: the water–energy nexus
Against this backdrop, the relationship between water and energy—and the role of virtual water—is particularly important. Virtual water can be used to quantify the actual amount of water required for production processes and estimate the energy needed to withdraw, treat, or reuse it. By identifying where the greatest water consumption occurs along the value chain, it also reveals opportunities to reduce both water use and the associated energy demand, thereby improving efficiency.
Water withdrawal, treatment, distribution, and wastewater treatment all require significant amounts of electricity. Similarly, power generation and industrial cooling systems require substantial volumes of water. Research published in ScienceDirect -Research on virtual water-embodied energy consumption- highlights the benefits of improving virtual water–embodied energy coupling efficiency in production processes. The study uses mathematical analysis to show that optimizing virtual water use can simultaneously ease pressure on the energy systems that power water withdrawal and processing.
Spain: innovation in irrigation
Given its geography and climate as a peninsula in southern Europe, Spain has extensive experience in water resource management.
Technical reports from Plataforma Tierra indicate that Spain’s average per capita water footprint is influenced by its role as a net exporter of fruit and vegetables to the European market. This flow of virtual water puts the country in a strong position to implement precision technologies that make the best possible use of every cubic meter of water.
How? Spain is modernizing its infrastructure by embracing digital technology in irrigation and industrial processes. The solutions being introduced include soil-moisture sensors and Internet of Things (IoT) devices that determine precisely when crops need to be watered and how much water they require. LabFerrer, for example, has successfully applied these technologies to truffle plantations and woody crops managed by irrigation communities in Catalonia and Aragon, telling farmers exactly when and how much to irrigate. SmartAgrihubs has also implemented this approach for the Guadalmellato irrigation community in Córdoba.
Ultimately, the international adoption of virtual water as a standardized metric has provided an essential analytical foundation for optimizing natural resource management and progressing toward climate neutrality. Working in tandem with technological innovation, this scientific indicator is becoming a key technical pillar of a more efficient, sustainable, and circular development model.
