What is a Water Footprint?*
Your water footprint G is the amount of water you use in and around your home, school or office throughout the day. It includes the water you use directly (e.g., from a tap). It also includes the water you use indirectly – this is the water it took to produce the food you eat, the products you buy, the energy you consume and even the water you save when you recycle. You may not drink, feel or see this virtual water, G but it makes up the majority of your water footprint. If you examine your lifestyle you can evaluate your water footprint using data that is based on average water use. In fact, water footprints can be calculated for individuals, households, businesses and countries.
Why Do Water Footprints Matter?
Freshwater (non-saline water) is an important and vital resource to ecological and human life, yet as human populations and prosperity grow, so too does our use of freshwater. This is complicated by climate change and the likelihood of a changing water cycle that has already led to periods of "drought and deluge." Water is already scarce in parts of the United States and the rest of world, and a changing water cycle could further constrain our water supplies.
Water footprints help reveal the amount of water being used at an individual level all the way to a national level and in the numerous processes involved in manufacturing and production of our goods and services. An accurate water footprint also takes into account the amount of water contaminated during manufacturing and production because that water is essentially made unusable and, therefore, taken out of the system. While there can never be a perfect water use assessment or audit tool, the water footprint gives everyone – from individual consumers to business managers to public officials – a solid water accounting framework and aids us all in our efforts to be more efficient and conservative with our water use.
What Makes a Blue, Green or Grey Water Footprint?
Water use is measured in terms of the volume of water consumed or evaporated and/or polluted, per unit of time. A water footprint can be split into three elements:
- Blue Water Footprint: refers to the volume of surface water and ground water consumed (i.e. evaporated or incorporated into the product) during production processes;
- Green Water Footprint: refers to the volume of rainwater consumed (i.e. evaporated or incorporated into the product) by the product; and
- Grey Water Footprint: refers to the amount of freshwater required to mix pollutants and maintain water quality according to agreed water quality standards.
[See Water Footprint Network’s National Water Accounting Framework for more.]
Examples of how the blue, green and grey water footprints contribute to an item's total water footprint can be found in the right column of the Water Footprint Network’s Food Gallery.
*The source of all water footprint content comes from the Water Footprint Network (WFN). The concept of water footprints was created by Dr. Arjen Hoekstra, who along with the others at the WFN, developed the framework and established the international organization as the foremost research network in the discipline.