Reference

When using terms from this glossary, please refer to the original source: Hoekstra, A.Y., Chapagain, A.K., Aldaya, M.M. and Mekonnen, M.M. (2011) The water footprint assessment manual: Setting the global standard, Earthscan, London, UK. [Download]

Glossary

Ambient water quality standards - The maximum allowable amount of a substance in rivers, lakes or groundwater, given as a concentration. Ambient water quality standards can also refer to other properties of the water, such as temperature or pH. Standards are set to protect against anticipated adverse effects on human health or welfare, wildlife or the functioning of ecosystems.

Blue water – Fresh surface and groundwater, in other words, the water in freshwater lakes, rivers and aquifers.

Blue water availability – Natural run-off (through groundwater and rivers) minus environmental flow requirements. Blue water availability typically varies within the year and also from year to year.

Blue water footprint – Volume of surface and groundwater consumed as a result of the production of a good or service. Consumption refers to the volume of freshwater used and then evaporated or incorporated into a product. It also includes water abstracted from surface or groundwater in a catchment and returned to another catchment or the sea. It is the amount of water abstracted from groundwater or surface water that does not return to the catchment from which it was withdrawn.

Blue water footprint impact index – An aggregated and weighed measure of the environmental impact of a blue water footprint at catchment level. It is based on two inputs: (i) the blue water footprint of a product, consumer or producer specified by catchment and by month; and (ii) the blue water scarcity by catchment and by month. The index is obtained by multiplying the two matrices and then summing the elements of the resultant matrix. The outcome can be interpreted as a blue water footprint weighed according to the blue water scarcity in the places and periods where the various blue water footprint components occur.

Blue water scarcity – The ratio of blue water footprint to blue water availability. Blue water scarcity varies within the year and from year to year.

Business water footprint – See ‘water footprint of a business’.

Corporate water footprint – See ‘water footprint of a business’.

Critical load – The load of pollutants that will fully consume the assimilation capacity of the receiving water body.

Crop water requirement – The total water needed for evapotranspiration, from planting to harvest for a given crop in a specific climate regime, when adequate soil water is maintained by rainfall and/or irrigation so that it does not limit plant growth and crop yield.

Crop yield – Weight of harvested crop per unit of harvested area.

Dilution factor – The number of times that a polluted effluent volume has to be diluted with ambient water in order to arrive at the maximum acceptable concentration level.

Direct water footprint – The direct water footprint of a consumer or producer (or a group of consumers or producers) refers to the freshwater consumption and pollution that is associated to the water use by the consumer or producer. It is distinct from the indirect water footprint, which refers to the water consumption and pollution that can be associated with the production of the goods and services consumed by the consumer or the inputs used by the producer.

Effective precipitation – The portion of the total precipitation that is retained by the soil so that it is available for crop production.

End-use water footprint of a product – When consumers use a product, there can be a water footprint in the end-use stage. Think about the water pollution that results from the use of soaps in the household. In this case, one can speak about the end-use water footprint of a product. This footprint is strictly spoken not part of the product water footprint, but part of the consumer’s water footprint.

Environmental flow requirements – The quantity, quality and timing of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well-being that depend on these ecosystems.

Environmental green water requirement – The quantity of green water from ands that need to be reserved for nature and biodiversity preservation and for human livelihoods that depend on the ecosystems in the natural areas.

Evapotranspiration – Evaporation from the soil and soil surface where crops are grown, including the transpiration of water that actually passes crops.

External water footprint of national consumption – The part of the water footprint of national consumption that falls outside the nation considered. It refers to the appropriation of water resources in other nations for the production of goods and services that are imported into and consumed within the nation considered.

Geographic sustainability – The geographic sustainability of the green, blue and grey water footprints in a catchment or river basin can be assessed based on a number of environmental, social and economic sustainability criteria.

Global water saving through trade – International trade can save freshwater globally if a water-intensive commodity is traded from an area where it is produced with high water productivity (small water footprint) to an area with lower water productivity (large water footprint).

Green water – The precipitation on land that does not run off or recharge the groundwater but is stored in the soil or temporarily stays on top of the soil or vegetation. Eventually, this part of precipitation evaporates or transpires through plants. Green water can be made productive for crop growth (although not all green water can be taken up by crops, because there will always be evaporation from the soil and because not all periods of the year or areas are suitable for crop growth).

Green water availability – The evapotranspiration of rainwater from land minus evapotranspiration from land reserved for natural vegetation and minus evapotranspiration from land that cannot be made productive.

Green water footprint – Volume of rainwater consumed during the production process. This is particularly relevant for agricultural and forestry products (products based on crops or wood), where it refers to the total rainwater evapotranspiration (from fields and plantations) plus the water incorporated into the harvested crop or wood.

Green water footprint impact index – An aggregated and weighed measure of the environmental impact of a green water footprint at catchment level. It is based on two inputs: (i) the green water footprint of a product, consumer or producer specified by catchment and by month; and (ii) the green water scarcity by catchment and by month. The index is obtained by multiplying the two matrices and then summing the elements of the resultant matrix. The outcome can be interpreted as a green water footprint weighed according to the green water scarcity in the places and periods where the various green water footprint components occur.

Green water scarcity – The ratio of green water footprint to green water availability. Green water scarcity varies within the year and from year to year.

Grey water footprint – The grey water footprint of a product is an indicator of freshwater pollution that can be associated with the production of a product over its full supply chain. It is defined as the volume of freshwater that is required to assimilate the load of pollutants based on natural background concentrations and existing ambient water quality standards. It is calculated as the volume of water that is required to dilute pollutants to such an extent that the quality of the water remains above agreed water quality standards.

Grey water footprint impact index – An aggregated and weighed measure of the environmental impact of a grey water footprint at catchment level. It is based on two inputs: (i) the grey water footprint of a product, consumer or producer specified by catchment and by month; and (ii) the water pollution level by catchment and by month. The index is obtained by multiplying the two matrices and then summing the elements of the resultant matrix. The outcome can be interpreted as a grey water footprint weighed according to the water pollution level in the places and periods where the various grey water footprint components occur.

Hotspot – A hotspot is a specific period of the year (such as the dry period) in a specific (sub)catchment in which the water footprint is unsustainable, for example, because it compromises environmental water needs or water quality standards or because the water allocation and use in the catchment is considered unfair and/or economically inefficient.

Indirect water footprint – The indirect water footprint of a consumer or producer refers to the freshwater consumption and pollution ‘behind’ products being consumed or produced. It is equal to the sum of the water footprints of all products consumed by the consumer or of all (non-water) inputs used by the producer.

Internal water footprint of national consumption – The part of the water footprint of national consumption that falls inside the nation, in other words, the appropriation of domestic water resources for producing goods and services that are consumed domestically.

Irrigation requirement – The quantity of water exclusive of precipitation, in other words, the quantity of irrigation water, required for normal crop production. It includes soil evaporation and some unavoidable losses under the given conditions. It is usually expressed in water-depth units (millimetres) and may be stated in monthly, seasonal or annual terms, or for a crop period.

Maximum acceptable concentration – see ‘ambient water quality standards’.

National water footprint – Is the same as what is more accurately called the ‘water footprint of national consumption’, which is defined as the total amount of fresh water that is used to produce the goods and services consumed by the inhabitants of the nation. Part of this water footprint lies outside the territory of the nation. The term should not be confused with the ‘water footprint within a nation’, which refers to the total freshwater volume consumed or polluted within the territory of the nation.

National water saving through trade – A nation can preserve its domestic freshwater resources by importing a water-intensive product instead of producing it domestically.

Natural concentration – The natural or background concentration in a receiving water body is the concentration in the water body that would occur if there was no human disturbance in the catchment. (It corresponds to the ‘high status’ conditions as defined in the EU Water Framework Directive.)

Operational water footprint of a business – The operational (or direct) water footprint of a business is the volume of freshwater consumed or polluted due to its own operations.

Organizational water footprint – See ‘water footprint of a business’.

Overhead water footprint – The water footprint of a product consists of two elements: the use of freshwater that can immediately be related to the product and the use of freshwater in overhead activities. The latter element is called the ‘overhead water footprint’. The overhead water footprint refers to freshwater use that in the first instance cannot be fully associated with the production of the specific product considered, but refers to freshwater use that associates with supporting activities and materials used in the business, which produces not just this specific product but other products as well. The overhead water footprint of a business has to be distributed over the various business products, which is done based on the relative value per product. The overhead water footprint includes, for example, the freshwater use in the toilets and kitchen of a factory and the freshwater use behind the concrete and steel used in the factory and machineries.

Primary impacts – The term ‘primary impacts’ is used in the context of assessing the sustainability of a water footprint in a geographic area. Primary impacts refer to the effect of the water footprint in a catchment on water flows and water quality.

Production system – The production system of a product consists of all the sequential process steps applied to produce it. A production system can be a linear chain of processes, it can take the shape of a product tree (many inputs ultimately resulting in one output product) or it may rather look like a complex network of interlinked processes that eventually lead one or more products.

Return flow – The part of the water withdrawn for an agricultural, industrial or domestic purpose that returns to the groundwater or surface water in the same catchment as where it was abstracted. This water can potentially be withdrawn and used again.

Secondary impacts – The term ‘secondary impacts’ is used, next to the term ‘primary impacts’, in the context of assessing the sustainability of a water footprint in a geographic area. Secondary impacts refer to the impacts of a water footprint on ultimate ecological, social and economic values such as biodiversity, human health, welfare and security.

Supply-chain water footprint of a business – The supply-chain (or indirect) water footprint of a business is the volume of freshwater consumed or polluted to produce all the goods and services that form the input of production of a business.

Sustainability criteria – Sustainability criteria are generally categorized into three major themes: environmental, social and economic sustainability.

Virtual-water balance – The virtual-water balance of a geographically delineated area (for example, a nation or catchment area) over a certain time period is defined as the net import of virtual water over this period, which is equal to the gross import of virtual water minus the gross export. A positive virtual-water balance implies net inflow of virtual water to the nation from other nations. A negative balance means net outflow of virtual water.

Virtual-water content – The virtual-water content of a product is the freshwater ‘embodied’ in the product, not in real sense, but in virtual sense. It refers to the volume of water consumed or polluted for producing the product, measured over its full production chain. If a nation exports/imports such a product, it exports/imports water in virtual form. The ‘virtual-water content of a product’ is the same as ‘the water footprint of a product’, but the former refers to the water volume embodied in the product alone, while the latter term refers to that volume, but also to which sort of water is being used and to when and where that water is being used. The water footprint of a product is thus a multidimensional indicator, whereas virtual-water content refers to a volume alone.

Virtual-water export – The virtual-water export from a geographically delineated area (for example, a nation or catchment area) is the volume of virtual water associated with the export of goods or services from the area. It is the total volume of freshwater consumed or polluted to produce the products for export.

Virtual-water flow – The virtual-water flow between two geographically delineated areas (for example, two nations) is the volume of virtual water that is being transferred from the one to the another area as a result of product trade.

Virtual-water import – The virtual-water import into a geographically delineated area (for example, a nation or catchment area) is the volume of virtual water associated with the import of goods or services into the area. It is the total volume of freshwater used (in the export areas) to produce the products. Viewed from the perspective of the importing area, this water can be seen as an additional source of water that comes on top of the available water resources within the area itself.

Water abstraction – See ‘water withdrawal’.

Water appropriation – This is a term used in the context of water footprint assessment to refer to both the ‘consumption’ of freshwater for human activities (green and blue water footprint) and the ‘pollution’ of freshwater by human activities (grey water footprint).

Water consumption – The volume of freshwater used and then evaporated or incorporated into a product. It also includes water abstracted from surface or groundwater in a catchment and returned to another catchment or the sea. It is important to distinguish the term ‘water consumption’ from the term ‘water withdrawal’ or ‘water abstraction’.

Water footprint – The water footprint is an indicator of freshwater use that looks at both direct and indirect water use of a consumer or producer. The water footprint of an individual, community or business is defined as the total volume of freshwater used to produce the goods and services consumed by the individual or community or produced by the business. Water use is measured in terms of water volumes consumed (evaporated or incorporated into a product) and/or polluted per unit of time. A water footprint can be calculated for a particular product, for any well-defined group of consumers (for example, an individual, family, village, city, province, state or nation) or producers (for example, a public organization, private enterprise or economic sector). The water footprint is a geographically explicit indicator, showing not only volumes of water use and pollution, but also the locations.

Water footprint accounting – The step in water footprint assessment that refers to collecting factual, empirical data on water footprints with a scope and depth as defined earlier.

Water footprint assessment – Water footprint assessment refers to the full range of activities to: (i) quantify and locate the water footprint of a process, product, producer or consumer or to quantify in space and time the water footprint in a specified geographic area; (ii) assess the environmental, social and economic sustainability of this water footprint; and (iii) formulate a response strategy.

Water footprint impact indices – See ‘blue/green/grey water footprint impact index’.

Water footprint of a business – The water footprint of a business – which can also be called alternatively corporate or organizational water footprint – is defined as the total volume of freshwater that is used directly and indirectly to run and support a business. The water footprint of a business consists of two components: the direct water use by the producer (for producing/manufacturing or for supporting activities) and the indirect water use (the water use in the producer’s supply chain). The ‘water footprint of a business’ is the same as the total ‘water footprint of the business output products’.

Water footprint of a consumer – Is defined as the total volume of freshwater consumed and polluted for the production of the goods and services consumed by the consumer. It is calculated by adding the direct water use by people and their indirect water use. The latter can be found by multiplying all goods and services consumed by their respective water footprint.

Water footprint of national consumption – Is defined as the total amount of fresh water that is used to produce the goods and services consumed by the inhabitants of the nation. The water footprint of national consumption can be assessed in two ways. The bottom-up approach is to consider the sum of all products consumed multiplied with their respective product water footprint. In the top-down approach, the water footprint of national consumption is calculated as the total use of domestic water resources plus the gross virtual water import minus the gross virtual-water export.

Water footprint of national production – Another term for the ‘water footprint within a nation’.

Water footprint of a product – The water footprint of a product (a commodity, good or service) is the total volume of freshwater used to produce the product, summed over the various steps of the production chain. The water footprint of a product refers not only to the total volume of water used; it also refers to where and when the water is used.

Water footprint offsetting – Offsetting the negative impacts of a water footprint is part of water neutrality. Offsetting is a last step, after a prior effort of reducing a water footprint insofar reasonably possible. Compensation can be done by contributing to (for example, by investing in) a more sustainable and equitable use of water in the hydrological units in which the impacts of the remaining water footprint are located.

Water footprint sustainability assessment – The phase in water footprint assessment that aims to evaluate whether a certain water footprint is sustainable from an environmental, social, as well as an economic point of view.

Water footprint within a geographically delineated area – Is defined as the total freshwater consumption and pollution within the boundaries of the area. The area can be for example a hydrological unit such as a catchment area or a river basin or an administrative unit like a municipality, province, state or nation.

Water footprint within a nation – Is defined as the total freshwater volume consumed or polluted within the territory of the nation.

Water neutral – A process, product, consumer, community or business is water neutral when: (i) its water footprint has been reduced where possible, particularly in places with a high degree of water scarcity or pollution; and (ii) when the negative environmental, social and economic externalities of the remaining water footprint have been offset (compensated). In some particular cases, when interference with the water cycle can be completely avoided – for example, by full water recycling and zero waste – ‘water neutral’ means that the water footprint is nullified; in other cases, such as in the case of crop growth, the water footprint cannot be nullified. Therefore ‘water neutral’ does not necessarily mean that the water footprint is brought down to zero, but that it is reduced as much as possible and that the negative economic, social and environmental externalities of the remaining water footprint are fully compensated.

Water pollution level – Degree of pollution of the run-off flow, measured as the fraction of the waste assimilation capacity of runoff actually consumed. A water pollution level of 100 per cent means the waste assimilation capacity of the runoff flow has been fully consumed.

Water productivity – Product units produced per unit of water consumption or pollution. Water productivity (product units/m3) is the inverse of the water footprint (m3/product unit). Blue water productivity refers to the product units obtained per cubic metre of blue water consumed. Green water productivity refers to the product units obtained per cubic metre of green water consumed. Grey water productivity refers to the product units obtained per cubic metre of grey water produced. The term ‘water productivity’ is a similar term as the terms labour productivity or land productivity, but now production is divided over the water input. When water productivity is measured in monetary output instead of physical output per unit of water, one can speak about ‘economic water productivity’.

Water scarcity – See ‘blue water scarcity’ and ‘green water scarcity’.

Water self-sufficiency versus water dependency of a nation - The ‘water self-sufficiency’ of a nation is defined as the ratio of the internal to the total water footprint of national consumption. It denotes the degree to which the nation supplies the water needed for the production of the domestic demand for goods and services. Self-sufficiency is 100 per cent if all the water needed is available and indeed taken from within the nation’s own territory. Water self-sufficiency approaches zero if the demand for goods and services in a nation is largely met with virtual-water imports. Nations with import of virtual water depend, de facto, on the water resources available in other parts of the world. The ‘virtual water import dependency’ of a nation is defined as the ratio of the external to the total water footprint of national consumption.

Water withdrawal – The volume of freshwater abstraction from surface or groundwater. Part of the freshwater withdrawal will evaporate, another part will return to the catchment where it was withdrawn and yet another part may return to another catchment or the sea.




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