Comments on the international consensus model for the water scarcity footprint (AWARE) and proposal for an...

Life Cycle Assessment (LCA) provides a structured framework, addressing environmental impacts of human activities. LCA requires consensual and scientifically sound characterisation factors to quantify impacts and allow comparisons. This is the objective of the AWARE model, recently published by an international consortium, which is now the reference for water impact in LCA. Looking back at the shape of the equation, linking human water use and water impact, we discuss the limits of the AWARE model and the associated cut-offs. They imply that all regions in a less than fair ecosystem condition are treated at the same level of severity, regardless of the extent of degradation. From this statement, we propose to define the impact by the ratio between the ecosystem demands and the remaining after human activities (DTR model). We use the marginal and average approaches, common approaches in LCA, to determine the corresponding characterisation factors. Through a sensitivity analysis with respect to parameters used (total water availability, ecosystem demand, human consumption and area of the region), we show that the DTR-based characterisation factors have the same properties than the AWARE-based ones between cut-offs. This article therefore provides a new alternative way of quantifying the impact of water use, in line with the AWARE model features, but without its validity limits and induced thresholds.