An Overview Of Water Scarcity Footprinting in SimaPro
The latest SimaPro update, version 8.0.4, adds a water impact assessment method that completes an already extensive set of water footprinting methods. This article gives a brief overview of the water footprinting methods that are available in SimaPro, notes some considerations when choosing a method, and shows SimaPro features that can help with interpretation.
Water scarcity footprint methods
To allow for spatially differentiated water scarcity impact assessment, SimaPro 8 features regionalised water flows from the ecoinvent v3 database and several water scarcity footprint methods. Spatial differentiation allows users to determine water scarcity impacts based on local conditions where the water was extracted.
The SimaPro 8.04 update includes the latest inventory datasets from ecoinvent, version 3.1. In this update, water flows are specified by origin (at the country level or regional level), and by source (groundwater, rivers, or lakes) or application (for example cooling). In SimaPro 8, all water scarcity footprint methods and several multi-impact methods that include a water scarcity category also feature spatial differentiation at the country level or regional level.
Choosing Impact Assessment Methods
If you need a simple indicator of water scarcity impact, it is recommended to choose a midpoint method. The ReCiPe Midpoint methods and BEES+ method contain an aggregate of the water use and hence do not give an indication of water scarcity. Four different freshwater scarcity indicator methods are available in SimaPro: Pfister et al. 2009; Boulay et al. 2011; Hoekstra 2012; and Berger et al. 2014. The Ecological Scarcity 2013 method and ILCD 2011 Midpoint methods also include scarcity indicators.
The available water scarcity methods differ in the data sources they use and the scarcity equation they apply: either a withdrawal-to-availability ratio or a consumption-to-availability ratio. Not all methods consider absolute freshwater shortage. Berger et al. 2014 decided to give the highest possible factor in semiarid and arid basins instead of the calculated scarcity factor. This prevents strange results in case water is used in such areas.
If you need to understand the damages of water use to human health, ecosystem quality or resource depletion, an endpoint method is the better choice. The methods developed by Boulay et al. 2011 and Motoshita et al. 2010 measure only impacts on human health, but are very comprehensive. The methods by Pfister et al. 2009 and Pfister et al. 2010 measure water use impacts in all three areas of protection and are consistent with the impact assessment methods Ecoindicator 99 and ReCiPe, respectively.
Water Scarcity Footprint Results Interpretation
SimaPro 8 has features that help you assess the completeness of your water footprint results. The ‘checks’ tab shows whether important water flows have been omitted from your method. You can also assess which flows and processes contribute most to the water footprint.
Although water scarcity footprinting at country or region level as implemented in SimaPro gives much more accurate results than when using global average factors (which is the case when using ecoinvent 2.2 processes), it may still deviate from characterisation at the watershed level. For example, the water scarcity impact factor for the whole of the United States deviates considerably from the factors for the main maize growing areas in the country. Unfortunately, it is not feasible for the background database to provide this level of detail in SimaPro. However, for foreground modelling, there are tools to calculate crop irrigation requirements and to look up water use and scarcity factors for the different watersheds in the world. This information can be added to an LCA model in SimaPro and combined with the background data.
If you need more information on this topic or if you have difficulty in selecting the most suitable water footprint method, please contact me.
Tommie worked for PRé as a Technical Consultant from 2012 until 2015. As a part of the Consultancy Team, he worked with databases and methods. Tommie collaborated in projects such as Prosuite and improving the ReCiPe method.