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

The same thing is now happening with the water footprint, but with a complication carbon didn't 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 produce data that an external auditor cannot validate, because the methodology applied wasn't the right one for that context.

Most companies that start working with water indicators don't know they have to choose. And those who do know often choose out of habit, without understanding what that decision means once it's time 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 don't know where to start
• You're measuring your water footprint but aren't sure whether the methodology you're using is right for your context
• Your company produces or wants to produce EPDs and you need to know what the EN 15804+A2 standard requires for the water category
• You need to report to GRI 303, CDP, or a lender with ESG criteria and don't 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 don't understand why

What you'll find in this guide:

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

To get up to speed, you can review the ISO 14046 standard and the concept of water footprint in our glossary.

The most common mistake is measuring with the wrong methodology

Many companies that already have an initial water footprint measurement discover it doesn't serve the purpose they needed. The data itself is correct, 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 can't be reused. You have to start over with the right data, the right scope, and the right methodology.

The solution isn't just knowing the theory better. It's having a data capture system granular enough (by facility, by process, by geographic area, by source) to feed both the Water Footprint Network and ISO 14046 without depending 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 the environmental indicators, and ready to feed both ESRS reporting and per-product impact calculations. Without starting from scratch every time a new requirement comes along.

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