Water Footprint Calculation?

Hi John,

What’s the best way to calculate the water footprint for any manufactured or grown item?

Hi Grant

To calculate the water footprint of any product you’ll need to consider the various aspects of its production.

A grown crop for example, has a Green Water Footprint so it uses a set amount of water which makes for an easier calculation than a space rocket which has a Blue Water Footprint. However, if you can get the fullest data with figures to me, including raw material extraction to manufacturing processes for some moderately complex product, then I’ll do my very best. Is this for a WOW exhibition? If so, you must mention Grey Water Footprints too.

Green Water Footprint: This refers to the volume of rainwater consumed during the growth of crops or other vegetation used in the product. It’s often associated with agricultural processes.

Blue Water Footprint: This is the volume of freshwater consumed from surface or groundwater sources during the production process. It includes water used in irrigation, industrial processes, and other direct water withdrawals.

Grey Water Footprint: This measures the amount of freshwater required to assimilate pollutants and maintain water quality. It represents the volume of water needed to dilute pollutants to meet specified legal water quality standards.

Here’s a simplified approach to estimating the water footprint of a product:

Identify Key Ingredients/Components:
List all the major components or ingredients of the product.
For each component, identify its source, e.g., agriculture, industry, quarried, wild foraged.

Determine Water Use for Each Component:
For agricultural products, estimate the water used for irrigation (green water footprint) and get rainfall figures.
For industrial processes, consider the water used directly in manufacturing (blue water footprint).

Consider Processing and Manufacturing:
Include water used in processing, manufacturing, cooling, washing, packaging, distribution and any additional industrial activities.

Account for Pollutants:
Assess the water needed to dilute and assimilate pollutants generated during the production process (grey water footprint).

Sum Up Component Footprints:
Add up the water footprints of all components to get the total water footprint of the product.

Express Results:
Express the results in volumetric terms (e.g., cubic meters) or in impact terms (e.g., equivalent to the water required to fill a certain number of Olympic-sized swimming pools).

It’s important to note that water footprint assessment methodologies may vary, and more comprehensive assessments may consider indirect water use, geographical location, and seasonal variations. Specialized tools and databases, such as the Water Footprint Network’s WaterStat or the Water Footprint Assessment Tool, may provide more accurate and detailed assessments for specific products.

By assigning algebraic variables to each component, we can represent the water footprint calculation for a product as follows:


GWGW be the Green Water Footprint,
BWBW be the Blue Water Footprint,
GWiGWi​ be the Green Water Footprint of component ii,
BWiBWi​ be the Blue Water Footprint of component ii,
GWtotGWtot​ be the total Green Water Footprint,
BWtotBWtot​ be the total Blue Water Footprint,
GWprodGWprod​ be the Green Water Footprint for production,
GWprocGWproc​ be the Green Water Footprint for processing,
GWmanuGWmanu​ be the Green Water Footprint for manufacturing,
GWpolGWpol​ be the Green Water Footprint for pollution,
BWprodBWprod​ be the Blue Water Footprint for production,
BWprocBWproc​ be the Blue Water Footprint for processing,
BWmanuBWmanu​ be the Blue Water Footprint for manufacturing,
BWpolBWpol​ be the Blue Water Footprint for pollution.

The algebraic expressions could be formulated as:

Green Water Footprint:

Blue Water Footprint:

These equations only capture the main components of a product’s water footprint, considering both green and blue water. You can further refine the expressions based on the specific components and processes involved in the production of the product.
Always let me know if I can be of any help to you and World of Water.


“I have some really sad news today. The One and Only John C. Jones passed away in January 2024. He was a Mathematician and worked tirelessly for the good of the planet, devoting himself daily to helping business start ups whether at his local library in Chester or globally, online via the BusinessEye forum of the Welsh Government.”

“John was one of those very rare people who could form a very deep friendship but never meet or even talk face to face. Over the years he solved several very difficult math calc. problems for the Hales Turbine project and gave much help and support in hard times.”

“Kind and generous, fun to be with, a great friend who will be missed very much and never forgotten.”

“Without John’s encouraging words, World of Water’s aim for an international water awareness centre might have drifted downstream and out of sight years ago. “Just do a little more each day towards the goal” was his advice. We will John.”