Most of our Water Footprint is in Food

The water we use is our water footprint. When we think about our use of water, we think of our domestic use of water in our homes for drinking, food preparation, washing clothes and dishes, bathing , and flushing toilets, watering lawns and gardens or maintaining pools, ponds, hosing off patios and decks, washing cars and similar activities. However, most of our water footprint is the “virtual water” used to produce the food we eat, the products we buy and the energy we use.

Mankind uses a lot of water. According to a group of researchers in the Netherlands who have been studying, quantifying and mapping national water footprints since the beginning of this century, mankind uses 9,087 billion cubic meters of water each year. Most of the water use occurs in agricultural production an estimated 92% when utilization of rainwater is counted.

The first global study on the water footprints of nations was carried out by Hoekstra and Hung in 2002 and Hoekstra and Chapagain continued to refine the methods of assessing national water footprints with a series of studies in the following decade culminating in the “The Water Footprint Assessment Manual” by Arjen Y. Hoekstra, Ashok K. Chapagain, Maite M. Aldaya and Mesfin M. Mekonnen.

According to their methodology a water footprint has three components: green, blue and grey. The blue water footprint refers to consumption of fresh water resources (surface and ground water). The green water footprint is the amount of rainwater consumed, which is particularly relevant in crop production. The grey water footprint is an indicator of the degree of freshwater pollution and is defined as the volume of freshwater that is required to assimilate the load of pollutants based on existing ambient water quality standards.

In a study published in 2011 Drs. Hoekstra and Mekonnen determined that China, India and the United States are the countries with the largest total water footprints within their territory, with total water footprints of 1,207, 1,182 and 1,053 billion cubic meters of water per year, respectively. The researchers estimated that these countries account for 38% of water footprint of global production.

India is the country with the largest blue water footprint within its territory: 243 billion cubic meters per year. Irrigation of wheat is the process that takes the largest share (33%) in India’s blue water footprint, followed by irrigation of rice (24%) and irrigation of sugarcane (16%). China is the country with the largest grey water footprint within its borders: 360 billion cubic meters per year, which is 26% of the global grey water footprint.

The water footprint of the average global citizen was 1,385 m3/year. The average consumer in the United States has a water footprint of 2,842 m3/year, while the average citizens in China and India have water footprints of 1,071 m3/year and 1,089 m3/year respectively. Remember that the largest component of the water footprint of mankind is agriculture. According to the 2011 Hoekstra and Mekonnen study, cereal products account for the largest portion of the water footprint of the average global citizen (27%), followed by meat (22%) and milk products (7%).