A worldwide-regionalised water supply mix (WSmix) for life cycle inventory of water use

Water utilities draw different water sources (surface and groundwater), including increased use of alternative sources (e.g. desalinated water, reused water, inter-basin water transfers) to supply freshwater to different users (domestic, agriculture, etc.). The combination of water sources and technologies (including infrastructures and energy) results in a regional water supply mix (WSmix) for each specific use. Existing Life Cycle Inventory (LCI) databases used in Life Cycle Assessment (LCA), do not include these mixes when modelling processes, leading to a poor representation of water supply systems and related environmental impacts. To fill this gap, this paper proposes a consistent framework for modelling a regional WSmix at worldwide scale. The WSmix framework includes the scope and system boundaries definition as well as a standardisation of terminology and classification of water sources and users. To facilitate implementation of the WSmix, this paper provides a worldwide database of water source mixes per user and a technology matrix linking water sources to water production technologies, including the connection with the local electricity mix. The relevance of including the WSmix in LCI databases for proper water-use impact assessment is demonstrated with an illustrative case study. The paper finally concludes on the need of using the regionalized WSmix in routine LCA, which is just as straightforward as the use of the regionalized electricity supply mix. Besides, the developed WSmix provides interesting insights beyond the LCA scope to support the strategic management of water sources at various scales including the global scale. 2017 Elsevier Ltd. All rights reserved.