User:Mtorre2vu/Water footprint

Definition and measures[edit]
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.

Blue water footprint[edit]
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[edit]
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[edit]
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).

Production or consumption
The assessment of total water use in connection to consumption can be approached from both ends of the supply chain. The water footprint of production estimates how much water from local sources is used or polluted in order to provide the goods and services produced in that country. The water footprint of consumption of a country looks at the amount of water used or polluted (locally, or in the case of imported goods, in other countries) in connection with all the goods and services that are consumed by the inhabitants of that country. The water footprint of production and that of consumption, can also be estimated for any administrative unit such as a city, province, river basin or the entire world. Much of the data surrounding water footprint is a combination of the water footprint of production and the water footprint of consumption. For example the global average water footprint for production and consumption combined of an apple is 790 liter/kg.