Water Footprint: Concept of Blue Water, GreenWater, Grey Water

Water Footprint is a scientific term which means total amount of freshwater used directly and indirectly by an individual, community or a country over a period of time. It is a geographic indicator which shows the amount of water used/polluted by a group along with the location. The consumption of water by the world has been gradually increasing in the last century with the maximum consumption being done for agricultural purposes.

• The concept was introduced by Arjen Y. Hoekstra in 2002 as an excellent indicator to measure water-use.
• There are three components to of water footprint both for direct and indirect usage calculations. These are Green Water footprint, Blue Water footprint and Grey Water footprint. While the first two account for total consumption but the last one measures the amount of freshwater polluted.
• The knowledge of WF helps organization to study their water-use patterns and gauge the eco-friendly nature of their products and make suitable changes/improvements accordingly. It suggests that the water use as well as the water and also the amount of water contaminated during the industrial processes and is rendered unfit for future use.
• A large part about 70% of world’s water consumption happens in irrigation for farming. Thus, WF becomes even more important and thus modelling and measuring water consumption by agriculture will help us devise ways for alternative management and reduction of virtual water component. Virtual water means the total amount of water i.e. the sum total of water use which happened at all stages of product chain. It comprises- green water, blue water and grey water

Green water

It is the purest component and is the water which transpires from the plant.

Blue water

It is the water present on the surface or stored in groundwater reservoirs.

Grey water

It is the water which has been polluted during production process due leaching of various nutrients and pesticides.

Thus regulation of footprint of these types of water becomes imperative for reducing the overall WF of a nation.

Green water footprint

It signifies the volume of rainwater which is consumed in the process of production of various agricultural and forest products. It is a sum of total water lost in evapotranspiration and came down to surface as precipitation and the water which is locked in harvest produce.

Blue-water footprint

It is the volume of both surface and groundwater which has been consumed to produce a final good.

Grey water footprint

It is the indicator of the amount of pollution of freshwater due to production of a product throughout its entire production and supply-chain. It is calculated as the volume of water that is required to dilute pollutants to such an extent that water-quality remains acceptable as per water quality standards.