A water footprint shows the extent of water use in relation to consumption by people. The water footprint of an individual, community, or business is defined as the total volume of fresh water used to produce the goods and services consumed by the individual or community or produced by the business. Water use is measured in water volume consumed (evaporated) and/or polluted per unit of time. A water footprint can be calculated for any well-defined group of consumers (e.g., an individual, family, village, city, province, state, or nation) or producers (e.g., a public organization, private enterprise, or economic sector), for a single process (such as growing rice) or for any product or service.
Traditionally, water use has been approached from the production side, by quantifying the following three columns of water use: water withdrawals in the agricultural, industrial, and domestic sector. While this does provide valuable data, it is a limited way of looking at water use in a globalised world, in which products are not always consumed in their country of origin. International trade of agricultural and industrial products in effect creates a global flow of virtual water, or embodied water (akin to the concept of embodied energy).
In 2002, the water footprint concept was introduced in order to have a consumption-based indicator of water use, that could provide useful information in addition to the traditional production-sector-based indicators of water use. It is analogous to the ecological footprint concept introduced in the 1990s. The water footprint is a geographically explicit indicator, not only showing volumes of water use and pollution, but also the locations.Definition taken from the Hoekstra, A.Y. and Chapagain, A.K. (2008) Globalization of water: Sharing the planet's freshwater resources, Blackwell Publishing, Oxford, UK. The global issue of water footprinting underscores the importance of fair and sustainable resource management. Due to increasing water shortages, climate change, and environmental concerns, transitioning towards a fair impact of water use is critical. The water footprint concept offers detailed insights for adequate and equitable water resource management. It advocates for a balanced and sustainable water-use approach, aiming to tackle global challenges. This approach is essential for responsible and equitable water resource utilization globally. Thus, it gives a grasp on how economic choices and processes influence the availability of adequate water resources and other ecological realities across the globe (and vice versa).
Definition and measures There are many different aspects to water footprint and therefore different definitions and measures to describe them. Blue water footprint refers to groundwater or surface water usage, green water footprint refers to rainwater, and grey water footprint refers to the amount of water needed to dilute pollutants.
Water footprint may be quantified physically simply as a volume (in units of litres or cubic metres). Other metrics, often termed water intensity (water consumption intensity or water footprint intensity), are derived as the quotient of volume and a unit of production, for example: volume per energy (in cubic metres per watt-hour) in the energy generation sector, volume per area (in cubic metres per square kilometre) in the agriculture sector, volume per mass (in cubic metres per tonne) in the manufacturing sector, etc.
Blue water footprint A blue water footprint refers to the volume of water that has been sourced from surface or groundwater resources (lakes, rivers, wetlands and aquifers) and has either evaporated (for example while irrigating crops), or been incorporated into a product or taken from one body of water and returned to another, or returned at a different time. Irrigated agriculture, industry and domestic water use can each have a blue water footprint.
Green water footprint A green water footprint refers to the amount of water from precipitation that, after having been stored in the root zone of the soil (green water), is either lost by evapotranspiration or incorporated by plants. It is particularly relevant for agricultural, horticultural and forestry products.
Grey water footprint A grey water footprint refers to the volume of water that is required to dilute pollutants (industrial discharges, seepage from tailing ponds at mining operations, untreated municipal wastewater, or nonpoint source pollution such as agricultural runoff or urban runoff) to such an extent that the quality of the water meets agreed water quality standards. It is calculated as:
where L is the pollutant load (as mass flux), cmax the maximum allowable concentration and cnat the natural concentration of the pollutant in the receiving water body (both expressed in mass/volume).
Calculation for different factors The water footprint of a process is expressed as volumetric flow rate of water. That of a product is the whole footprint (sum) of processes in its complete supply chain divided by the number of product units. For consumers, businesses and geographic area, water footprint is indicated as volume of water per time, in particular:
That of a consumer is the sum of footprint of all consumed products. That of a community or a nation is the sum for all of its members resp. inhabitants. That of a business is the footprint of all produced goods. That of a geographically delineated area is the footprint of all processes undertaken in this area. The virtual change in water of an area is the net import of virtual water Vi, net, defined as the difference of the gross import Vi of virtual water from its gross export Ve. The water footprint of national consumption WFarea,nat results from this as the sum of the water footprint of national area and its virtual change in water.
History The concept of a water footprint was coined in 2002, by Arjen Hoekstra, Professor in water management at the University of Twente, Netherlands, and co-founder and scientific director of the Water Footprint Network, whilst working at the UNESCO-IHE Institute for Water Education, as a metric to measure the amount of water consumed and polluted to produce goods and services along their full supply chain.Jayne M. Godfrey, Keryn Chalmers. 2012 Water Accounting: International Approaches to Policy and Decision-making. Edward Elgar Publishing. page222Hoekstra, A.Y. (2003) (ed) Virtual water trade: Proceedings of the International Expert Meeting on Virtual Water Trade, IHE Delft, the Netherlands Water footprint is one of a family of ecological footprint indicators, which also includes carbon footprint and land footprint. The water footprint concept is further related to the idea of virtual water trade introduced in the early 1990s by Professor John Allan (2008 Stockholm Water Prize Laureate). The most elaborate publications on how to estimate water footprints are a 2004 report on the Water footprint of nations from UNESCO-IHE, the 2008 book Globalization of Water,Globalization of Water, A.Y. Hoekstra and A.K. Chapagain, Blackwell, 2008 and the 2011 manual The water footprint assessment manual: Setting the global standard. Cooperation between global leading institutions in the field has led to the establishment of the Water Footprint Network in 2008.
Water Footprint Network (WFN)
The Water Footprint Network is an international learning community (a non-profit foundation under Dutch law) which serves as a platform for sharing knowledge, tools and innovations among governments, businesses and communities concerned about growing water scarcity and increasing water pollution levels, and their impacts on people and nature. The network consists of around 100 partners from all sectors – producers, investors, suppliers and regulators – as well as non-governmental organisations and academics. It describes its mission as follows: To provide science-based, practical solutions and strategic insights that empower companies, governments, individuals and small-scale producers to transform the way we use and share fresh water within earth's limits.
International standard In February 2011, the Water Footprint Network, in a global collaborative effort of environmental organizations, companies, research institutions and the UN, launched the Global Water Footprint Standard. In July 2014, the International Organization for Standardization issued ISO 14046:2014, Environmental management—Water footprint—Principles, requirements and guidelines, to provide practical guidance to practitioners from various backgrounds, such as large companies, public authorities, non-governmental organizations, academic and research groups as well as small and medium enterprises, for carrying out a water footprint assessment. The ISO standard is based on life-cycle assessment (LCA) principles and can be applied for different sorts of assessment of products and companies.
Life-cycle assessment of water use Life-cycle assessment (LCA) is a systematic, phased approach to assessing the environmental aspects and potential impacts that are associated with a product, process or service. "Life cycle" refers to the major activities connected with the product's life-span, from its manufacture, use, and maintenance, to its final disposal, and also including the acquisition of raw material required to manufacture the product. Thus a method for assessing the environmental impacts of freshwater consumption was developed. It specifically looks at the damage to three areas of protection: human health, ecosystem quality, and resources. The consideration of water consumption is crucial where water-intensive products (for example agricultural goods) are concerned that need to therefore undergo a life-cycle assessment. In addition, regional assessments are equally as necessary as the impact of water use depends on its location. In short, LCA is important as it identifies the impact of water use in certain products, consumers, companies, nations, etc. which can help reduce the amount of water used.
Water positive The Water Positive initiative can be defined as the concept where an entity, such as a company, community, or individual, goes beyond simply conserving water and actively contributes to the sustainable management and restoration of water resources. A commercial or residential development is considered water positive when it generates more water than it consumes. This involves implementing practices and technologies that reduce water consumption, improve water quality, and enhance water availability. The goal of being water positive is to leave a positive impact on water ecosystem and ensure that more water is conserved and restored than is used or depleted.
Water availability
Globally, about 4 percent of precipitation falling on land each year (about ), is used by rain-fed agriculture and about half is subject to evaporation and transpiration in forests and other natural or quasi-natural landscapes. The remainder, which goes to groundwater replenishment and surface runoff, is sometimes called "total actual renewable freshwater resources". Its magnitude was in 2012 estimated at /year.Frenken, K. and V. Gillet. 2012. Irrigation water requirement and water withdrawal by country. AQUASTAT, FAO. It represents water that can be used either in-stream or after withdrawal from surface and groundwater sources. Of this remainder, about were withdrawn in 2007, of which , or 69 percent, were used by agriculture, and , or 19 percent, by other industry. Most agricultural use of withdrawn water is for irrigation, which uses about 5.1 percent of total actual renewable freshwater resources. World water use has been growing rapidly in the last hundred years."Looming water crisis simply a management problem" by Jonathan Chenoweth, New Scientist 28 Aug., 2008, pp. 28-32.
By sector
Agricultural sector