Water is following the same path that carbon followed five years ago. First the CSRD turned it into a regulatory obligation. Then came the auditors, the value chain customers and the green finance requirements. And then many companies discovered that measuring badly from the start is far more expensive than not having measured at all.

The same is happening with the water footprint, but with a complication that carbon did not have: there are two main methodologies for measuring it, and they are not equivalent.

ISO 14046 and the Water Footprint Network start from different questions, produce different results and serve different purposes. Choosing the wrong one can compromise an Environmental Product Declaration, create inconsistencies in CSRD reporting or generate data that an external auditor cannot validate because the methodology applied was not the right one for that context.

Most companies that start working with water indicators do not realise they have to choose. And those that do realise often choose out of inertia, without understanding what that decision means when the time comes to verify it.

This guide exists precisely to prevent that from happening.

This guide is for you if:

• The CSRD or ESRS E3 has put water on your radar and you do not know where to start
• You are measuring your water footprint but are not sure whether the methodology you are using is the right one for your context
• Your company produces, or wants to produce, EPDs and you need to know what the EN 15804+A2 standard requires in the water section
• You have to report to GRI 303, CDP or a lender with ESG criteria and you do not know which methodology applies to you
• Someone in your value chain (a customer, auditor or certifier) has asked you for water footprint data using a specific methodology and you do not understand why

What you will find in this guide:

• What each methodology actually measures and why their results are not directly comparable
• What blue, green and grey water mean in the Water Footprint Network and when they apply
• How ISO 14046 works within Life Cycle Assessment and what characterisation factors are
• A comparison table covering the dimensions of difference that matter most in practice
• How to know which methodology you need depending on your goal: CSRD reporting, EPD, GRI or CDP
• What data architecture lets you feed both methodologies without duplicating the effort

To get some context, you can review the ISO 14046 standard and the concept of the water footprint in our glossary.

The most common mistake is measuring with the wrong methodology

Many companies that already have a first water footprint measurement discover that it does not serve the purpose they needed. The data is correct in itself, but it was calculated with a volumetric approach when the customer or certifier was asking for a scarcity impact result. Or the other way around.

When that happens, the work cannot be reused. You have to start again with the right data, the right scope and the right methodology.

The solution is not just knowing the theory better. It is having a data capture system granular enough (by site, by process, by geographical area, by source) to feed both the Water Footprint Network and ISO 14046 without relying on parallel projects every time the requirement changes.

At Manglai we help sustainability teams build that foundation: traceable water data, integrated with the rest of their environmental indicators and ready to feed both ESRS reporting and product-level impact calculations. Without starting from scratch every time a new requirement arrives.

Download the free guide and start solving your company's water measurement.