Introduction to water footprinting

A water footprint is a measure of how much water your business uses and which direct and indirect environmental impacts result from this. It can help you understand and manage your water use and even protect your company from physical, regulatory, and reputation risks. But how does it work and how is it calculated in SimaPro?

The importance of water

Freshwater is a scarce resource; its annual availability is limited and its local demand is growing. Water is unequally distributed, and humanity’s water footprint has exceeded sustainable levels in several areas. Water is a crucial resource for almost every business, from food to clothing to consumer products. As part of a life cycle assessment (LCA) approach, water footprinting has a lot to offer to companies: understanding your water footprint means understanding where the water is being used, where its use can be reduced, and where the risks in the supply chain are. In this article, we will introduce water footprinting and why it is important and explain the differences in water footprinting methods available in SimaPro.

Why does it matter?

Water scarcity is quickly becoming one of the most important sources of stress on the environment and humans, causing an increase in diseases and malnutrition in communities and reducing biodiversity. By itself, this makes water use interesting for companies. Moreover, overuse and pollution of water can cause a large risk for your operations.

Water footprinting is a risk management tool to assess physical risk (future problems with access), regulatory risks (unexpected water-related law or regulation may increase cost), and reputational risks (loss of customers or investors due to opinions about decisions about water resources and communities). Without measuring the water footprint, it is difficult to know if your company may face a water-related risk. Furthermore, as we all know, you can’t manage what you can’t measure.

How is a water footprint calculated?

Most of us are familiar with the carbon footprint. Carbon emissions are a global issue; emissions of carbon (and carbon equivalents) all have the same impact on the atmosphere, no matter where they are emitted. Although this creates great complexity in policies, it is relatively simple to calculate the effect of these emissions with LCA. Each emission has a corresponding impact.

Although a water footprint is similar, measuring the water footprint requires a different approach than carbon – it can be more complicated to calculate. Water is not an emission, but a resource, so we must consider both supply and regionality. The first step in calculating a water footprint is the inventory stage: add up the total volume of water used to produce a good in the supply chain. This provides valuable insight on its own, as it is important to understand how much water a product, process, or company consumes. The next step is impact assessment. What does using this much water mean? And what are the implications and impact of this?

Water quality and water availability are the main considerations that need to be taken into account using impact assessment. Water is unequally distributed, meaning that using water in one area might be worse than using water in another area. In addition, water scarcity is driven by competition – the more water you use, the less there is left for others. Opinions differ on how best to take these considerations into account. Therefore, while there is basically one accepted method for calculating a carbon footprint (IPCC GWP 2013), there are several methods for calculating a water footprint.

What are the different methods?

For guidance on how to calculate a water footprint, ISO published ISO 14046: Water footprint: Principles, requirements, and Guidelines in August 2014. This is an international standard that defines the principles, requirements, and guidelines for conducting an LCA-based water footprint for products, processes, or organizations.

Water footprinting in SimaPro

In SimaPro, 10 methods are available, each with its unique qualities. Some important considerations:

  • Study objectives
  • Audience
  • Acceptable level of uncertainty

First, of course, you must understand the differences between the methods. One good resource for understanding these methods is the SimaPro methods manual. In this article, we will illustrate the differences with some flow charts, although these cannot give an exhaustive overview. After this article points you in a certain direction, I suggest you read more about the methods that sound interesting before making a decision.

Midpoint vs endpoint

As with many life cycle impact assessment (LCIA) methods, there are two different types of water footprinting methods you can choose from midpoint and endpoint methods. Midpoint methods apply a characterization factor to measure impact, while endpoint methods take this one step further and apply an indicator to express actual damages.

In the case of water footprinting methods, the midpoint methods measure local water scarcity and are typically measured in cubic meters of water. This number can be interpreted as the amount of water downstream users are lacking as a function of water consumption. An endpoint method measures damages and is often measured in DALY (Disability-adjusted life year) for human health impact. Some of the methods also include the damages to ecosystems.

Breakdown of midpoint methods

A key difference between the midpoint methods is the scarcity equations used. There are three main scarcity equations:

  • Withdrawal to availability ratio (WTA) measures how much water in an area is withdrawn in the industrial process versus how much is available.
  • Consumption to availability ratio (CTA) is similar to WTA, but takes into account that a lot of water can be withdrawn and then put back into the water source, for instance cooling water. Therefore, this method only includes water that is no longer available as a result of the process.
  • Demand to availability ratio (DTA) includes human and ecosystem demand for water. This method examines the total amount of water available and subtracts the demand to see how much water is available for use.

The demand-to-availability ratio is unique to the newest water footprinting method in SimaPro: the AWARE method (Available WAter Remaining). This method was developed by WULCA (working group under the umbrella of UNEP-SETAC Life Cycle Initiative) in 2016 and was led by a few of the authors of the existing methods (Boulay and Pfister).

Water footprinting in SimaPro: midpoint methods

AWARE offers one generic impact category indicator for water scarcity, without necessarily being located at any specific point on the cause-effect chain of either the human health or the ecosystem quality endpoint indicator. This simplified method is excellent for LCA practitioners who need just one simple indicator.

All of the midpoint methods have m3 as the unit, except one: the Ecological Scarcity 2006 method, which is measured in environmental loading points. Similarly, all the methods (except Hoekstra et al 2012) use the WaterGap model to model water withdrawals and use. However, it is important to note that even though the different methods express their results in the same units, it is not possible to directly compare their results. If you choose a water footprinting method for one of your products, it is good to use it for your other products as well.

Breakdown of endpoint methods

The endpoint methods can also be broken down by what is included. Like the midpoint methods, they use different scarcity equations. As discussed, endpoint methods express their results in actual damages. Some only include human health impact, while the methods by Pfister include impacts on human health, ecosystems, and resources and are also compatible with other existing methods (like Eco-indicator 99 and ReCiPe). The methods that only look at human health impact, however, are more comprehensive because they include more types of water use (domestic and fisheries in addition to agriculture), while Pfister only includes impacts caused by agricultural uses.

Water footprinting in SimaPro: endpoint methods

If you would like more information before choosing any of the methods, check out the descriptions of each method in SimaPro or the publications themselves.

Get started with water footprinting today

We hope this overview has helped demystify the key differences between the available water footprinting methods. With this information, you are better equipped to choose the best water footprinting method for you. Water footprints can give you valuable insights into the environmental impacts associated with water use in your product or process and can help support stakeholders and decision-makers fight against global water scarcity. The field of water footprint is still developing, with new research and best practices continually being developed.

Paula Bernstein

Paula Bernstein worked for PRé from 2013 to February 2018. Her areas of expertise included environmental product performance, LCA databases, and supply chain sustainability measurement. Paula collaborated structurally in LCA and sustainability metrics implementation projects for many industries, such as apparel, food, and building & construction. She also worked closely with the PRé software team to implement databases in PRé’s software package SimaPro.

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