The Water Network Research ...
Published by Water Network Research, Official research team of The Water Network
The Water Network Research team has consolidated an answer to the above question.
Further input from members is welcome and appreciated.
The term virtual water was first defined in 1998.
It is the volume of water required for making a product and the water used in the production chain.
Virtual water is comprised of 3 different components:
- Green water
- Blue water
- Grey water
Different kinds of ‘coloured water’ (green, blue, grey and black-which is not virtual water) are classified based on where they are found in nature or the level of contamination of wastewater.
Green water is the soil moisture from precipitation, used by plants via transpiration.
It is part of the evapotranspiration flux in the hydrologic cycle.
Blue water is the freshwater: surface and groundwater.
It is stored in lakes, streams groundwater, glaciers and snow.
Grey water is polluted water which was not in contact with faecal matter .
Grey water is the product water of domestic activities: bathing, laundry and dishwashing or polluted water due to pesticides in agriculture and nutrients from fertilizers.
It can be recycled and reused, not for drinking, but for irrigation. Since it was not in contact with human waste, it can be used for watering crops and other plants and is safely reabsorbed into the ground.
Grey water contains soap and fat particles, even hair. If the chemicals content is not too high, majority of plants are able to handle it. However, if grey water is to be used for irrigation it is highly advised that what goes down the drain is heavily regulated.
This water flows through the man-made infrastructure.
Black water is not virtual water and it is sewage water flushed in the toilets.
It was in contact with faecal matter containing harmful bacteria and disease-causing pathogens.
Black water cannot be reused without risking contamination since the waste doesn’t decompose fats enough.
Related documents:
- A quantification of virtual water flows between nations in relation to international crop trade
- Good water, water to “eat”. What is virtual water?
- Virtual water: an effective mechanism for integrated water resources management
- Review and classification of indicators of green water availability and scarcity
- Greywater Management in Low and Middle-Income Countries
- Grey Water Treatment Systems: A Review
1 Comment
Unfortunately your answer for green water does not make sense- plants do not use water via transpiration. They take in water from the soil via absorption and then lose water to the atmosphere through transpiration. Just in case other educators/laymen are trying to understand these terms and find your site.
Published by Jeanine Kenney