Complementary strengths of water footprint and life cycle assessments in analyzing global freshwater appropriation and its local impacts – Recommendations from an Interdisciplinary discussion series

• Assessing water use along supply chains is key in addressing global water challenges. • Water Footprint and Life Cycle Assessment are not in competition with each other. • The methods have strengths and weaknesses in relation to different questions. • Recommendations for application-dependent uses are provided. Considering globally increasing water challenges, the analysis of water use along supply chains is of great relevance and can be tackled by mainly two methodological approaches: Water Footprint Assessment (WFA) and Life Cycle Assessment (LCA). While sharing the same goal of promoting sustainable water use, both methods developed in different contexts and scientific communities. This has led to heated debates on methodological presuppositions that at times has become unconstructive. To build mutual understanding and enable a fruitful cooperation, researchers from both communities have exchanged over the course of two years. This paper summarizes the outcomes of this discussion series by providing i) a description of the development of both approaches and their ways of assessing freshwater consumption and pollution, ii) an application in a case study, and iii) an analysis of strengths and weaknesses in relation to questions decision-makers may have. Our analysis revealed that WFA’s strength lies in its ability to measure freshwater appropriation, water-use efficiency, water scarcity and total pollution levels. This makes WFA particularly useful for crop selection as well as agricultural and river basin water management. With its focus on assessing impacts, LCA is strong in quantifying potential consequences of water use for humans and ecosystems. This makes it particularly useful for assessing complex supply chains and for analysing water-related impacts in combination with other environmental aspects. Rather than being in competition with each other, we emphasize the individual and complementary strengths of both approaches and their joint efforts in addressing the world’s pressing water challenges.